JP5888269B2 - Application method to substrate - Google Patents

Description

  The present invention relates to a coating method and a coating apparatus for coating a substrate with a multilayer coating solution.

  Conventionally, various coating films are formed on a substrate surface in order to impart performances such as corrosion resistance, workability, aesthetics, and insulation to a continuously running substrate such as a steel plate. In this treatment, a roll coater 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 3-roll coater has become a mainstream coating method because it has excellent controllability of the coating thickness and has a relatively beautiful surface appearance. The 3-roll coater consists of a pickup roll that draws up the coating liquid from the coater pan filled with the coating liquid, a doctor roll that adjusts the amount of the coating liquid drawn up by the pickup roll, and the adjusted coating liquid from the pickup roll to the substrate. It is comprised by the applicator roll which transfers. The direction of rotation of each roll may be a reverse rotation that rotates in the opposite direction or a natural rotation that rotates in the same direction at the close point between the rolls or at the close point, but in general the reverse rotation is compared Since a smooth coating surface can be easily obtained, reverse rotation is often performed between the applicator roll and the substrate. The applicator roll uses a rubber roll in which rubber is lined on a steel roll so as not to damage the surface of the substrate.

In recent years, multilayer coating films may be required in the design of coating films formed on a substrate due to increasing needs for high added value such as high corrosion resistance and high conductivity. As a method for applying a multilayer coating solution for forming a multilayer coating film, there are a curtain coater method in which a coating solution is supplied from a plurality of slits and dropped in a curtain shape, and a die coater method in which a plurality of slits are provided. (Patent Document 1, Patent Document 2)
However, in the case of a curtain coater, since the minimum liquid flow rate at which a curtain can be formed is determined by the coating liquid, it is necessary to increase the transport speed of the base material in order to apply a thin film to the base material in a multilayer state. However, increasing the line speed causes uneven coating due to air entrainment and makes thin film coating difficult.

  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 coater that supplies the coating solution close to the desired film thickness, and a smooth base material such as a glass substrate. However, in the case of a continuously traveling steel plate or the like, it is difficult to make the die coater close because the shape changes in both the width direction and the longitudinal direction. In addition, when applying to a substrate by applying a slot die, the slit width is usually set narrower than that of the substrate in order to eliminate the influence of the edge portion of the substrate. In this case, it is difficult to apply the coating liquid over the entire width, which may cause a deterioration in yield.

  On the other hand, there is a method of applying a multilayer coating solution using a roll coater. When performing the coating treatment of a multilayer coating solution by a roll coater alone, if the second layer coating solution is applied while the first layer coating solution is in an undried state, the first layer is scraped off and a laminated coating film Can not form. Therefore, it is necessary to apply the second-layer coating liquid after the first-layer coating liquid is applied and then through a drying process. However, in that case, the coating process and the drying process are required twice, and the running cost increases.

  Furthermore, in recent years, the production line has been speeded up from the viewpoint of reducing running costs, and due to the speeding up, coating defects due to air entrainment from the upstream side of the base material have occurred more significantly at the meniscus portion between the base material and the roll. There is a high possibility of end. In addition, various types of coating liquids are used to improve the functionality of the steel sheet, but the liquid physical properties are different from each other. The effect of the liquid physical properties, especially when using high-viscosity coating liquids The application conditions are frequently changed to reduce the speed in order to make the coating uniform, and the productivity may be hindered.

Japanese Patent No. 4598493 JP 2004-160274 A

  The present invention has been made in view of such circumstances, and a substrate that can be beautifully applied with a thin film at high speed when a multilayer coating solution is applied to a continuously running substrate using a roll coater. An object is to provide a coating method and a coating apparatus.

The gist of the present invention is as follows.
[1] Supplying a multilayer coating liquid to a rotating applicator roll by a die coater, and then bringing the applicator roll into contact with a continuously running substrate to transfer the multilayer coating liquid to the substrate. Before the multi-layer coating liquid is transferred to the base material by the applicator roll, the same coating liquid as the coating liquid that forms the lowermost layer on the applicator roll is pre-coated on the base material by the coater. Then, while the pre-coated coating liquid on the substrate is in a liquid state, the applicator roll performs transfer to the substrate while rotating in the direction opposite to the substrate at the contact portion with the substrate, and the bottom layer The method of applying to a base material, characterized in that the temperature of the coating solution for forming is from 40 ° C to 80 ° C.
[2] A multilayer coating solution is supplied to a rotating intermediate roll by a die coater, and then the intermediate roll is rotated in a direction opposite to the applicator roll at a contact portion with the rotating applicator roll. The multi-layer coating liquid is transferred to the applicator roll, and then the multi-layer coating liquid is transferred to the base material by bringing the applicator roll into contact with a continuously running base material. Before the coating solution is transferred to the substrate, the coater is pre-coated with the same coating solution as the coating solution that forms the lowermost layer on the applicator roll, and after the pre-coating, on the substrate. While the pre-coated coating solution is in a liquid state, the applicator roll is And while rotating in the opposite direction performs the transfer to the substrate, the temperature of the coating solution for forming the lowermost layer, the coating method to a substrate, characterized in that at 40 ° C. or higher 80 ° C. or less.
[3] The method according to [1], wherein excess coating liquid applied to the substrate by the precoat and transferred from the substrate to the applicator roll by rotation of the applicator roll is removed from the applicator roll. Application method to the substrate.
[4] The precoating is applied to the base material, transferred from the base material to the applicator roll by the rotation of the applicator roll, and the excess coating liquid transferred from the applicator roll to the intermediate roll by the rotation of the intermediate roll. It removes from an intermediate | middle roll, The coating method to the base material of said [2] characterized by the above-mentioned.
[5] The method for coating a substrate according to any one of [1] to [4], wherein the die coater generates a negative pressure upstream of the coating part.
[6] A die coater that supplies a multilayer coating solution to a rotating applicator roll, the applicator roll that contacts the continuously running substrate and transfers the multilayer coating solution to the substrate, and the applicator roll. Before the multi-layer coating solution is transferred to the substrate, the coating device for the substrate has a coater that pre-coats the same coating solution as the coating solution that forms the lowermost layer on the applicator roll. And the applicator roll is rotated while the applicator roll rotates in a direction opposite to the substrate at the contact portion with the substrate while the pre-coated coating liquid on the substrate is in a liquid state after the pre-coating. It has a function of transferring to the base material, and a temperature control device for controlling the temperature of the coating solution forming the lowermost layer to 40 ° C. or more and 80 ° C. or less is provided in the coating device An apparatus for applying to a base material characterized by that.
[7] The multi-layer coating liquid is transferred to the applicator roll by rotating in a direction opposite to the applicator roll at a contact portion between the die coater that supplies the multilayer coating liquid to the rotating intermediate roll and the rotating applicator roll. The intermediate roll, the applicator roll for transferring the multi-layer coating liquid to the base material in contact with the continuously running base material, and before the multi-layer coating liquid is transferred to the base material by the applicator roll, A coating device for a base material having a coater for pre-coating the same coating liquid as the coating liquid for forming the lowermost layer on the applicator roll on the base material, and the applicator roll is a base material after the pre-coating. While the upper pre-coated coating solution is in a liquid state, the applicator roll is in the contact portion with the substrate. And a temperature control device that controls the temperature of the coating solution forming the lowermost layer to 40 ° C. or more and 80 ° C. or less in the coating device. An apparatus for applying to a base material.
[8] The apparatus according to [6], further comprising a blade that removes from the applicator roll excess coating liquid that has been applied to the base material by the precoat and transferred from the base material to the applicator roll by rotation of the applicator roll. The coating apparatus to the base material of description.
[9] The excess coating liquid applied to the base material by the precoat, transferred from the base material to the applicator roll by the rotation of the applicator roll, and further transferred from the applicator roll to the intermediate roll by the rotation of the intermediate roll. The apparatus for coating a base material according to [7] above, further comprising a blade that is removed from the intermediate roll.
[10] The coating apparatus for a base material according to any one of [6] to [9], wherein a suction device is provided on the upstream side of the coating portion of the slot die.

  According to the present invention, a multilayer coating solution can be beautifully applied to a substrate with a thin film at high speed using a roll coater.

It is a side view of the coating device concerning one embodiment of the present invention. It is a side view of the coating device which concerns on other embodiment of this invention. It is an enlarged view of the slot die coater which concerns on embodiment of this invention. It is a figure shown about the relationship between a coating liquid density | concentration and a coating liquid viscosity. It is a figure shown about the relationship between coating liquid temperature and coating liquid viscosity. It is a figure shown about the relationship between a coating liquid viscosity and the speed ratio of the roping generation limit. It is a figure shown about the relationship between the coating liquid temperature and the speed ratio of the roping generation limit. It is a side view of the coating device which concerns on one conventional embodiment. It is a side view of the coating device which concerns on other conventional embodiment. It is a side view of the coating device which concerns on other conventional embodiment.

Hereinafter, the present invention will be described in detail.
The present invention is a method and a coating apparatus for applying a multilayer coating solution supplied from a die coater to one side or both sides of a substrate that is continuously passed through one or a plurality of rolls.
FIG. 1 is a side view of a coating apparatus according to an embodiment of the present invention, and shows a coating method on a substrate of the present invention. In FIG. 1, 1 is a base material, 2 is a slot die coater, 3 is an intermediate roll, 4 is an applicator roll, 5 is a blade, 6 is a coating liquid recovery tank, 7 is a suction device, 8 is a backup roll, and 9 is an upper layer coating. Liquid supply pump, 10 is an upper layer coating liquid, 11 is an upper layer coating liquid tank, 12 is a lower layer coating liquid supply pump, 13 is a lower layer coating liquid, 14 is a lower layer coating liquid tank, 15 is a heater, 16 is a temperature control device, 17 is a roll, 18 is a pan dish for precoat. According to FIG. 1, the multilayer coating solution is supplied from the slot die coater 2 to the intermediate roll 3, and then transferred to the applicator roll 4 through the intermediate roll 3, and transferred and applied to the substrate. The intermediate roll 3 uses a flat roll whose surface is mirror finished. The intermediate roll 3 rotates in the opposite direction to the applicator roll 4 at the contact portion with the applicator roll 4, and the applicator roll 4 rotates in the opposite direction to the substrate 1 at the contact portion with the substrate 1. In this way, by rotating the rolls in the opposite directions between the rolls or between the applicator roll and the base material, the laminated state of the multi-layer coating liquid is maintained, and the laminated coating is applied on the base material. A film can be formed.

  Further, before the multi-layer coating liquid is transferred to the base material 1 by the applicator roll 4, the same coating liquid as the coating liquid that forms the lowermost layer on the applicator roll 4 can be pre-coated on the base material 1. The roll 17 is installed. Then, after pre-coating, transfer from the applicator roll 4 to the substrate 1 is performed while the pre-coated coating liquid is in a liquid state. The coating liquid for pre-coating the substrate is the same as the coating liquid for forming the lowermost layer on the applicator roll 4 among the multilayer coating liquids supplied to the applicator roll 4 via the intermediate roll 3 by the slot die coater 2. . By performing the pre-coating, it is possible to suppress air entrainment from the upstream side of the travel line of the substrate 1 when performing transfer by the applicator roll 4. In addition, when the pre-coating is performed using the same coating liquid as that of the lowermost layer, the coating liquid used for the pre-coating passes between the applicator roll 4 and the base material 1 and enters between the applicator roll 4 and the base material 1 The coating can be performed stably without hindering the stabilizing effect of the lowermost liquid film. When an upper layer liquid or a coating liquid having a high viscosity is used for the pre-coating, the effect of stabilizing the meniscus of the coating liquid is reduced and streak defects are likely to occur.

  Thus, in this invention, it has a precoat apparatus in the upstream of the running direction of a base material. As shown in FIG. 8, in the case of a conventional coating apparatus that does not have a pre-coating apparatus, when a coating is performed under a high-speed coating condition and in a thin film state, a streak pattern or blur is likely to occur in the line direction. The reason why the streaky pattern is generated is that the air flow accompanying the base material disturbs the meniscus between the base material and the applicator roll. As for the cause of the blurring, when the applied film thickness is very thin, the amount of liquid transferred to the convex portion becomes extremely thin due to the unevenness of the surface of the base material, resulting in liquid breakage. This is because it becomes easier. Therefore, in order to obtain a uniform film thickness without generating a streak pattern, the air accompanying the substrate may be prevented from affecting the meniscus between the applicator roll and the substrate. In the present invention, by providing a precoat roll, the coating liquid applied to the base material flows into the gap between the applicator roll and the base material, and functions to effectively block the air accompanying the base material. As a result, a streak pattern is not generated. In addition, pre-coating with a pre-coating roll makes it possible to contact the applicator roll in a state where a coating film is formed on the surface of the steel sheet, so there is no scumming and uniform coating is possible. Become.

  The effect of coating liquid applied by pre-coating on film thickness uniformity and film thickness reduction was investigated. The upper limit of the thickness of the liquid film to be precoated is limited by the entrainment of air (bubbles). Since the speed of the precoat roll also increases in proportion to the line speed, when the speed is increased, air is entrained in the meniscus between the roll and the base material or air accompanying the surface of the roll. It tends to occur. Bubbles are more likely to be caught in the meniscus as both the substrate and the roll become faster. Then, it was found that the amount of the bubble wound into the meniscus is proportional to the thickness of the liquid film. As a result of changing the thickness of the precoat liquid film and examining the presence or absence of entrainment of bubbles, it was found that there was no entrainment of bubbles if the thickness of the precoat liquid film was 30 μm or less. Therefore, the thickness of the precoat liquid film is preferably 30 μm or less. Furthermore, since the amount of bubbles involved depends on the physical properties of the coating solution, the thickness of the precoat liquid film is more preferably 15 μm or less in consideration of the coating solution that changes over time due to evaporation or the like.

  When performing pre-coating, for example, when only one roll for pre-coating is used, it is difficult but possible to reduce the thickness of the pre-coating liquid film while maintaining the thickness at 30 μm or less. On the other hand, if there are two or more rolls, it is possible to achieve both uniformity in film thickness and reduction in film thickness. Furthermore, the three-roll method having three rolls has higher film thickness controllability and is more desirable than the two-roll method having two rolls. However, the cost of the 3-roll method is high. Further, the thickness of the precoat liquid film is not related to the final film thickness, and even if there is film thickness non-uniformity of the degree of roping, it does not affect the effect of the present invention. For the above reasons, the two-roll method is preferred for precoating. In addition to the three-roll method using three rolls and the two-roll method using two rolls, a film thickness of 30 μm or less can usually be obtained without particularly controlling the film thickness. It is more reliable to preset the film thickness to be 30 μm or less.

  As for the rotation direction of the precoat roll, in the case of FIG. 1, the rotation direction between the roll that draws the coating liquid from the precoat pan and the roll that transfers the coating liquid to the substrate is the same direction. However, the present invention is not limited to this, and the rotation direction may be the reverse direction. In the present invention, a rubber roll having a smooth surface is used as the precoat roll. However, a groove roll having an uneven surface formed on the roll surface may be used. Furthermore, the coating liquid for pre-coating is not limited to the system for drawing up from the pan dish for pre-coating, and a system for coating the coating liquid from the nozzles may be adopted.

  Supply of the coating liquid to the slot die coater 2 is performed by the upper layer coating liquid supply pump 9 and the lower layer coating liquid supply pump 12 from the upper layer coating liquid tank 11 and the lower layer coating liquid tank 14. The lower layer coating solution tank 14 is provided with a heater 15 for heating the coating solution, and the temperature of the coating solution is set to 40 ° C. or more and 80 ° C. or less by controlling the heating amount of the heater outside the heater 15. A temperature control device 16 for controlling the temperature is installed.

  In addition, the lower layer coating solution in the precoat pan 18 is precoated on the substrate in advance via the two rolls 17. The roll 17 is a rubber roll or metal roll lined with rubber, and the surface is polished in a smooth state. In addition, a heater 15 for heating the coating solution is installed in the precoat pan 18, and the temperature of the coating solution is set to 40 ° C. or higher by controlling the heating amount of the heater outside the heater 15. A temperature control device 16 is installed to control the temperature below ℃.

  Thus, high-speed coating becomes possible by controlling the temperature of the lower layer coating solution to 40 ° C. or more and 80 ° C. or less. Details will be described later.

  Moreover, in order to remove the excess coating liquid applied to the base material by pre-coating, transferred from the base material to the applicator roll by the rotation of the applicator roll, and further transferred from the applicator roll to the intermediate roll by the rotation of the intermediate roll. In addition, a blade 5 is installed on the intermediate roll 3. This is because when the coating liquid remaining on the intermediate roll 3 is supplied again to the coating section of the slot die coater 2, the meniscus shape of the coating liquid is disturbed and stable coating is hindered, and the coating film thickness is not uniform. Because it becomes. In addition to the intermediate roll 3, a blade can be installed on the applicator roll 4. Any blade may be used as long as the coating liquid can be scraped off. The material of the blade may be metal or rubber as long as uniform scraping can be performed.

  In FIG. 1, the intermediate roll 3 is a flat metal roll having a mirror-finished surface. When the substrate 1 is a metal plate such as a steel plate, the applicator roll 4 can be a rubber roll lined with rubber. By using a rubber roll, the influence of eccentricity can be absorbed by elastic deformation, and unevenness in appearance and change in the amount of adhesion can be reduced. The rubber lining thickness is preferably about 5 to 40 mm. The rubber hardness is preferably about 40Hs to 80Hs. Although it is a method that is often used to apply the base material 1 in a state of being wound around the backup roll 8, double-sided simultaneous application that does not require a backup roll in which a roll coater is arranged on both sides of the base material 1 is used. It can also be applied to.

  In FIG. 2, other embodiment of the coating method to the base material of this invention is shown. In FIG. 2, the intermediate roll 3 is not provided, and the other symbols are the same as those in FIG. According to FIG. 2, a multilayer coating solution is supplied from the slot die coater 2 to the applicator roll 4, and then transferred and applied to the substrate 1. Further, the applicator roll 4 rotates in the direction opposite to the base material 1 at the contact portion with the base material 1.

  In addition, a blade 5 is installed on the applicator roll 4 in order to remove excess coating liquid applied to the base material 1 by pre-coating and transferred from the base material 1 to the applicator roll 4 by the rotation of the applicator roll 4. ing.

  In addition, before the multi-layer coating liquid is transferred to the base material 1 by the applicator roll 4, the same coating liquid as the coating liquid that forms the lowermost layer on the applicator roll 4 can be pre-coated on the base material 1. The roll 17 is installed. Then, after pre-coating, transfer from the applicator roll 4 to the substrate 1 is performed while the pre-coated coating liquid is in a liquid state.

  In addition, a heater 15 for heating the coating solution is provided in each of the lower coating solution tank 14 and the precoat pan pan 18, and the heater 15 is applied to the outside by controlling the heating amount of the heater. A temperature control device 16 for controlling the temperature of the liquid to 40 ° C. or more and 80 ° C. or less is installed.

  When the amount of the base material to be applied is small, it can be stably applied by the method shown in FIG. 2, but when the base material is large and continuous application is required, the applicator roll is worn out and has a non-uniform shape. In some cases, coating defects may occur. Therefore, when mass production in continuous operation is performed, the method of FIG. 1 is preferable.

FIG. 3 is an enlarged view of the slot die coater 2. For example, when two layers of coating liquid are applied to a substrate, the slot die coater 2 includes two coating liquid supply units 2a and 2b for supplying each liquid as shown in FIG. A suction device (suction) 7 for generating a negative pressure can be provided upstream of the section. The rotation of the intermediate roll or applicator roll causes an air flow to accompany the coating liquid supply unit. Therefore, if there is no suction mechanism, the probability of air entrainment occurring in the liquid film increases, which may result in coating defects. Thus, the negative pressure is generated by the suction device 7 to solve the above problem, stably maintain the meniscus shape of the supplied coating liquid, and a gap several times as large as the film thickness formed on the substrate. Can be ensured, and the effect of gap variation due to substrate thickness variation can be mitigated and stable coating can be achieved.
The supply of the coating liquid to the slot die coater can be performed by, for example, a pump that can stably discharge a constant flow rate. At that time, the application liquid is stably supplied onto the intermediate roll or applicator roll by adjusting the negative pressure of the suction device, the gap between the intermediate roll or applicator roll to which the application liquid is supplied and the tip of the slot die coater, etc. be able to.

  Next, using the coating apparatus shown in FIG. 1, a basic investigation was performed on the uniform coating conditions between the slot die coater capable of forming a multilayer liquid film and the intermediate roll. The length of the opening at the nozzle exit of the slot die coater was set to 50 μm for both the upper layer and the lower layer, and the gap between the tip of the slot die coater and the intermediate roll was set to 50 μm. The coating liquid was supplied to the slot die coater using a metering pump, and the coating liquid was supplied from separate coating liquid tanks for the upper layer and the lower layer. A suction device was installed upstream of the slot die coater, and a collection tank for collecting the coating solution sucked by the suction device was installed. An aqueous coating solution was used as the coating solution.

  FIG. 4 shows the relationship between the concentration and viscosity of the coating solution, and FIG. 5 shows the relationship between the temperature and viscosity of the coating solution. In FIG. 4, the temperature of the coating solution is 20 ° C., and in FIG. 5, the concentration of the coating solution is 20%. The viscosity of the coating solution is adjusted by adding a dilution chemical to the coating solution, and the temperature of the coating solution is controlled by a heater installed in the lower coating solution tank and a temperature control device installed outside. Controlled. From FIG. 4, it can be seen that the viscosity of the coating solution increases as the concentration of the coating solution increases. FIG. 5 shows that the viscosity of the coating solution decreases as the temperature of the coating solution increases.

  Based on these results, the temperature and concentration of the coating solution, the rotational speed of the intermediate roll (hereinafter sometimes referred to as the peripheral speed), the rotational speed of the applicator roll, and the line speed of the base material are changed. The appearance change on the roll and the substrate surface was confirmed. A galvanized steel sheet having a thickness of 0.6 mm was used as the substrate. First, an investigation was conducted on conditions of good appearance between the viscosity of the coating solution and the roll. The concentration of the coating solution was changed in the range of 1% to 20%, and the appearance change between the intermediate roll and the applicator roll was confirmed. The speed of the substrate was the same as the peripheral speed of the applicator roll. Further, the coating thicknesses of the upper layer and the lower layer were set to 20 μm, respectively. As a typical coating defect, a streak pattern in the circumferential direction of a roll called roping is transferred to a steel sheet, resulting in uneven film thickness and deterioration in appearance. Roping tends to occur more easily as the viscosity of the coating liquid is higher and as the rotational speed of the roll is higher. Appearance change was determined by checking the presence or absence of this roping and determining that there was no roping.

  FIG. 6 shows the relationship between the coating liquid viscosity and the speed ratio of the roping occurrence limit between rolls when the peripheral speed of the intermediate roll is 50 mpm. In FIG. 6, the coating solution concentration was 20%, and the temperature of the coating solution was changed from 20 ° C. to 80 ° C. The speed ratio at the limit of occurrence of roping was defined as a value represented by V2 / V1, where V1 is the rotation speed of the intermediate roll and V2 is the rotation speed of the applicator roll. FIG. 6 shows that as the viscosity of the coating solution increases, the speed ratio at the roping occurrence limit decreases, indicating that the applicator roll is likely to roping at a lower speed. From the results shown in FIG. 6, when the viscosity is low, for example, when the viscosity is about 1.2 mPa · s, the appearance is good even if the rotation speed of the applicator roll is increased to about 4.8 times the rotation speed of the intermediate roll. It became clear that On the other hand, when the viscosity is 10 mPa · s, it becomes clear that the rotation speed of the applicator roll can be increased only to about 1.1 times the rotation speed of the intermediate roll, and a high-viscosity coating liquid was used. In some cases, it became clear that uniform application at high speed becomes difficult.

  Next, the change of the coating appearance was confirmed by changing the temperature of the coating solution. The other conditions were the same as described above, and the lower layer coating solution and the precoat coating solution were heated to a predetermined temperature to confirm the appearance change between the intermediate roll and the applicator roll. The results are shown in FIG. In FIG. 7, the concentration of the coating solution was 20%, and a coating solution having a viscosity of 10 mPa · s at 20 ° C. was used. As shown in FIG. 7, by setting the temperature of the lower layer coating solution and the precoat coating solution to 40 ° C. or higher, the rotation speed of the applicator roll is determined from the limit speed of roping, even when a high concentration coating liquid is used. As a result, it became clear that it was possible to achieve a high speed coating of 100 mpm or more. When the coating solution temperature is less than 40 ° C., the coating solution has a high viscosity, the roping occurrence limit speed is low, and the rotation speed of the applicator roll is less than twice the viewpoint speed of the intermediate roll. Become. On the other hand, when the temperature of the coating liquid exceeded 80 ° C., the liquid film dried immediately after coating, resulting in insufficient leveling of the coating film, resulting in uneven adhesion amount.

  As described above, in the present invention, the temperature of the multilayer coating solution is set to 40 ° C. or more and 80 ° C. or less. By setting the coating liquid viscosity to 40 ° C or higher and 80 ° C or lower, the speed ratio between the intermediate roll and the applicator roll can be increased to 2.0 times or more, and the multilayer coating is applied to the steel sheet at high speed and in a thin film state. Is possible.

  The viscosity range of the coating solution in the present invention is preferably 4 mPa · s or less at 40 ° C. or higher. When the pressure exceeds 4 mPa · s, the meniscus between the intermediate roll and the applicator roll becomes unstable when the speed ratio between the intermediate roll and the applicator roll is increased as the viscosity increases. May occur, resulting in poor appearance. When the viscosity of the coating liquid is increased, the viscosity of the coating liquid increases, so that it may be difficult to reduce the viscosity even if the temperature of the coating liquid is increased. In addition, when the dilution rate of the coating solution is increased, particularly in the case of an aqueous coating solution, the surface tension of the coating solution increases with dilution, so that the wettability to the steel sheet is deteriorated. Therefore, the concentration range of the coating solution is preferably 5% or more and 30% or less. Although it does not prescribe | regulate especially as surface tension of a coating liquid, in order to ensure the wettability to a steel plate, 50 dyn / cm or less is preferable.

  Further, it is desirable that the peripheral speed of the applicator roll is 1.0 to 1.4 times the traveling speed of the substrate. In the same way as between the intermediate roll and the applicator roll between the applicator roll and the base material, the lower the applicator roll peripheral speed with respect to the line speed, the more the roping appears, and the applicator roll peripheral speed becomes faster. Is 1.0 or more, the liquid film state becomes uniform and a good appearance is obtained. However, if the peripheral speed of the applicator roll is excessively increased, the appearance deteriorates. The reason for this is that if the peripheral speed of the applicator roll is increased too much, roping that occurs between the intermediate roll and the applicator roll cannot be avoided. In other words, considering only the gap between the applicator roll and the steel plate, a faster applicator roll peripheral speed gives a better appearance, but roping tends to occur between the intermediate roll and the applicator roll, and if roping occurs, the applicator It is transferred as it is from the roll to the substrate. In order to avoid roping between the intermediate roll and the applicator roll, the intermediate roll peripheral speed may be increased as described above. However, if the applicator roll peripheral speed is excessively high, the intermediate roll peripheral speed must be very high. I must. In addition, if the applicator roll peripheral speed exceeds 1.4 times the line speed, the liquid pool of the coating liquid between the base material and the applicator roll is likely to vibrate, and uneven coating tends to occur. It must be less than 1.4 times the speed.

  Using the apparatus shown in FIG. 1, coating was performed under the coating conditions shown in Table 1 on a coil of a galvanized steel sheet having a thickness of 0.6 mm and a width of 1200 mm to form a liquid film on the galvanized steel sheet. . Next, the appearance of the roll surface and the base material being applied were evaluated, and the appearance of the coating after drying was evaluated and the amount of adhesion was confirmed.

  In the coating apparatus of FIG. 1, the slot die coater 2 includes a coating liquid supply unit (not shown) for two-layer coating and a suction device 7. The material of each roll is a surface-flat metal roll in which the intermediate roll 3 is applied with hard chrome plating, and the applicator roll 4 is a rubber roll in which rubber is lined. The rubber lining thickness is 20 mm, the rubber is urethane rubber, and the hardness is Hs55 °. The roll diameter of each roll is 150 mm for both the intermediate roll 3 and the applicator roll 4. The heater 15 was installed in the lower layer coating solution tank 14 and the precoat pan 18 to change the temperature of the lower layer coating solution and the coating solution for precoat coating. The film thickness of the coating solution was adjusted in the range of 15 μm to 30 μm for each of the upper layer and the lower layer.

  In addition, as a comparative example, the case of changing the film thickness of the upper layer and the lower layer and changing the peripheral speed of the roll is performed. Appearance was evaluated and the amount of adhesion was confirmed.

  The used coating solution has a viscosity of 10 mPa · s and a surface tension of 40 dyn / cm at a temperature of 20 ° C. The viscosity coefficient is the value at a liquid temperature of 20 ° C. The liquid film thickness was adjusted to 10 μm for the two layers by changing the ratio of the upper and lower coating liquid thicknesses on the intermediate roll 3 in FIG. 1 and on the applicator roll 4 in FIG. In addition, the precoater used the same specification as an applicator roll by the 1 roll rotated in the direction opposite to a base material.

  Regarding the appearance evaluation, the case where a smooth film was obtained without streaking was marked as ◎, and the case where clear streak-like unevenness was observed on the entire surface was marked as x.

  The appearance after drying is determined by visual observation under a sufficiently bright fluorescent lamp, and it is marked ◎ for those that do not generate streaks and a smooth film is obtained, and those that appear streaky on almost the entire surface X.

The amount of adhesion after drying (g / m ² ) was measured by taking a sample for measurement from the center in the width direction and 100 mm on both edges of the coated steel sheet, punching out to a diameter of 40 mm, and using a fluorescent X-ray analyzer for each. It calculated by measuring the intensity | strength of a liquid film component and converting into an adhesion amount from the analytical curve created beforehand. The total adhesion amount shown in Table 1 is an average value of the adhesion amount at each position in the width direction.

  The results obtained as described above are shown in Table 1 together with the conditions.

  As shown in Table 1, in the present invention example, by installing a precoat roll and controlling the temperature of the coating solution in the range of 40 ° C. to 80 ° C., even in the case of using a highly viscous coating solution, in a multilayer state, High-speed, uniform application in a thin film state became possible. On the other hand, in the comparative example, the meniscus part between the intermediate roll and the applicator roll becomes unstable, air bubbles are generated due to air mixing when the precoat is not used, appearance defects occur, and uniform application in a multilayer state is It was difficult.

  In addition, although the galvanized steel plate was used as a base material in the said Example, it is not limited to a steel plate especially, It applies to other metal plates, such as aluminum, paper, and a film.

  In addition, as a conventional method, as shown in FIGS. 8, 9, and 10, when a precoater is not installed, a slot die coater alone, a curtain coater alone is applied to a steel plate having the same specifications as in the above embodiment, after drying. The appearance of the coating was evaluated.

  The applicator roll and intermediate roll of the roll coater shown in FIG. 8 have the same specifications as the applicator roll and intermediate roll of Example 1. As a result, in the case of the roll coater shown in FIG. 8, entrainment of air occurs between the applicator roll and the base material under the condition of a high speed coating speed of 200 mpm, and the surface of the base material after the coating has spots. Many patterns occurred. It was impossible to apply a high-viscosity coating liquid beautifully at high speed as in the present invention example.

  In the case of the slot die coater shown in FIG. 9, in each solution, the slit coating outlet-steel plate gap cannot be brought close to 100 μm or less due to the problem of the steel plate thickness accuracy, and the thickness before drying is more than 60 μm for stable application. It became a film. In addition, when an attempt was made to reduce the thickness and the amount of the supplied liquid was reduced while the gap was kept as it was, a sag due to liquid breakage occurred. Further, when the gap was made closer, blurring and streak patterns were generated due to the gap fluctuation accompanying the board thickness fluctuation.

  In the case of the curtain coater shown in FIG. 10, it is necessary to make the liquid film thickness about 100 μm in order to stably form the curtain-shaped coating film, and when the amount of the supply liquid is reduced for thinning, Curtain formation became unstable, and the liquid was cut off, resulting in an appearance defect.

  As described above, when a conventional roll coater, a slot die coater, or a curtain coater is applied as a conventional method, roping occurs and the formation of a blur or curtain liquid film becomes impossible, and a multi-layer coating liquid can be stably applied at high speed. I couldn't.

DESCRIPTION OF SYMBOLS 1 Base material 2 Slot die coater 2a, 2b Coating liquid supply part 2c Suction 3 Intermediate roll 4 Applicator roll 5 Blade 6 Coating liquid collection tank 7 Suction device 8 Backup roll 9 Upper layer coating liquid supply pump 10 Upper layer coating liquid 11 For upper layer coating liquid Tank 12 Lower layer coating solution supply pump 13 Lower layer coating solution 14 Lower layer coating solution tank 15 Heater 16 Temperature controller 17 Roll 18 Precoat pan 19 Curtain die

Claims (5)

A method for applying to a substrate having a line speed of 100 mpm or more,
A multi-layer coating solution is supplied to the rotating applicator roll by the die coater.
Next, in transferring the multi-layer coating liquid to the substrate by contacting the applicator roll with a continuously running substrate,
Before the multi-layer coating solution is transferred to the substrate by the applicator roll, the substrate is precoated with the same precoat coating solution as the lower layer coating solution that forms the lowermost layer on the applicator roll by the coater.
After the pre- coating, while the pre- coated pre- coat coating solution on the substrate is in a liquid state, the applicator roll performs transfer to the substrate while rotating in the opposite direction to the substrate at the contact portion with the substrate. ,
The method of applying to a substrate, wherein the temperature of the lower layer coating solution and the precoat coating solution is 40 ° C or higher and 80 ° C or lower. A method for applying to a substrate having a line speed of 100 mpm or more,
A multi-layer coating solution is supplied to the rotating intermediate roll by a die coater.
Next, the intermediate roll is rotated in a direction opposite to the applicator roll at a contact portion with the rotating applicator roll, and the multilayer coating liquid is transferred to the applicator roll by the intermediate roll,
Next, in transferring the multilayer coating liquid to the substrate by contacting the applicator roll with a continuously running substrate,
Before the multi-layer coating solution is transferred to the substrate by the applicator roll, the substrate is precoated with the same precoat coating solution as the lower layer coating solution that forms the lowermost layer on the applicator roll by the coater.
After the pre- coating, while the pre- coated pre- coat coating solution on the substrate is in a liquid state, the applicator roll performs transfer to the substrate while rotating in the opposite direction to the substrate at the contact portion with the substrate. ,
The method of applying to a substrate, wherein the temperature of the lower layer coating solution and the precoat coating solution is 40 ° C or higher and 80 ° C or lower.   The excess coating liquid applied to the substrate by the precoat and transferred from the substrate to the applicator roll by rotation of the applicator roll is removed from the applicator roll. Application method.   It is applied to the base material by the precoat, transferred from the base material to the applicator roll by the rotation of the applicator roll, and further, the excess coating liquid transferred from the applicator roll to the intermediate roll by the rotation of the intermediate roll is transferred from the intermediate roll. It removes, The coating method to the base material of Claim 2 characterized by the above-mentioned.   The said die coater produces | generates a negative pressure upstream of an application part, The coating method to the base material as described in any one of Claims 1-4 characterized by the above-mentioned.

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