JP6070804B2 - Method and apparatus for applying slurry to substrate - Google Patents

Description

  The present invention relates to a method and a coating apparatus for applying a slurry to a traveling substrate.

  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. As this treatment method, 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. It is known that the 3-roll coater is excellent in controllability of the coating film thickness and has a relatively beautiful surface appearance. However, as the number of rolls increases, production costs increase because maintenance and operation management become complicated. For this reason, in order to perform surface treatment simply, a coating treatment method using a one-pair roll squeezing method after applying a slurry as shown in FIG. 1 is now widely used.

  This method is a method of adjusting an excessively supplied coating liquid in advance by the pressing load of the roll, and in some cases, a rubber roll having a groove engraved on the surface is used in order to secure a necessary adhesion amount. The roll rotates in the same direction on the substrate and the contact surface, squeezes excess coating liquid, and adjusts the amount of adhesion.

  As a typical coating defect in roll coating, there is a streak-like appearance defect that occurs in the circumferential direction of the roll, called living (roping). This is known as a defect that occurs when the fluid pressure fluctuation of the liquid meniscus between the rolls and between the roll and the substrate exceeds the effect of stabilizing the surface tension. As it increases, it tends to occur. Therefore, the supply amount of the coating liquid needs to be minimized.

  In addition, when supplying a coating liquid containing solid particles such as slurry, if a slit nozzle or the like is used, nozzle clogging becomes a problem, and it is difficult to uniformly supply in the width direction. For this reason, it supplies with the spray nozzle etc. which arranged in the base-material width direction. However, it is difficult to uniformly supply the coating liquid to the substrate, and the slurry cannot be uniformly supplied in the width direction, and coating unevenness remains even after roll drawing.

  Patent Document 1 discloses a slurry coating method using gas wiping in which a gas fluid is ejected from a slit nozzle in order to suppress these coating unevenness defects and realize uniform coating. Patent Document 2 discloses a method of adjusting the final adhesion amount by gas wiping after adjusting the slurry adhesion amount using a roll coater.

JP-A 63-286521 Japanese Patent No. 3004151

  However, when the final adhesion amount is adjusted by gas injection from a nozzle, the slurry is scattered and it is difficult to maintain a beautiful appearance. Moreover, since the base material after slurry application cannot contact with a conveyance roll until drying is completed, the area | region used as a suspended state exists and a vibration tends to occur. When the final adhesion amount adjustment is performed by gas injection, the nozzle distance fluctuates due to the fluttering of the base material, and the nozzle is unintentionally brought close to the base material and slurry scattering occurs. In addition, when the line speed decreases due to the entry / exit processing of the base material, the gas pressure adjustment cannot catch up and the slurry wiping force becomes excessive, and slurry scattering may occur. Therefore, it is difficult to maintain a beautiful appearance over the entire length.

  Then, an object of this invention is to solve the said subject and to provide the slurry application | coating method and slurry application | coating apparatus which can apply | coat a slurry uniformly with respect to the base material which drive | works.

  The inventors of the present invention have intensively studied to solve the above problems. As a result, it was found that a uniform slurry film free from defects due to slurry scattering, coating unevenness, and the like can be produced by adjusting the amount of adhesion by gas injection from a nozzle and then performing roll drawing.

The present invention has been made based on the above findings, and the gist thereof is as follows.
[1] supplying slurry to the traveling substrate;
After supplying the slurry, a step of injecting a gas to the substrate using a nozzle;
And a step of pressing a roll against the front and back of the substrate after the gas is injected.
[2] The slurry application method according to [1], wherein the roll rotates on the contact surface of the base material so as to be in a direction opposite to a traveling direction of the base material.
[3] The slurry application method according to [1] or [2], wherein after the step of pressing the roll, gas is sprayed onto the substrate using a nozzle.
[4] A slurry application device including a slurry supply device for supplying slurry to the base material along a base material traveling direction and a roll for adjusting the amount of slurry adhesion by pressing against the base material front and back. And a slurry application device having a first nozzle for injecting gas to the substrate between the slurry supply device and the roll.
[5] The slurry applying apparatus according to [4], wherein the roll rotates so as to be opposite in a contact surface with respect to a traveling direction of the base material.
[6] The slurry application according to [4] or [5], further including a second nozzle for injecting gas, wherein the roll is sandwiched between the first nozzle and the second nozzle. apparatus.

  According to the present invention, surplus slurry can be wiped off by injecting gas onto the substrate after the slurry is supplied, and the amount of slurry adhered to the substrate is uniformly adjusted. As a result, it is possible to produce a uniform slurry film free from defects due to slurry scattering and uneven coating.

It is a side view of the coating device which concerns on one conventional embodiment. 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.

  In the present invention, a slurry supplied from a nozzle as shown in FIG. 2 or FIG. 3 is applied to one or both sides of a traveling substrate, that is, a substrate that is continuously passed through a pair of rolls. Method and slurry application apparatus. Referring to FIG. 2, the slurry application device includes a pair of slurry supply nozzles 2 for supplying slurry, a pair of rubber rolls 3, and a pair of gas injection nozzles 4. The gas injection nozzle 4 is disposed between the slurry supply nozzle 2 and the rubber roll 3.

  In the present invention, as a means for supplying the slurry, it is sufficient that the slurry is supplied to the substrate. For example, a spray nozzle is preferably used. The shape of the spray nozzle for supplying the slurry is preferably an orifice diameter of 3 mm or more in order to prevent clogging. The slurry to be supplied is not particularly limited, and examples thereof include magnesium oxide. Further, as the slurry supply amount, since it is throttled later by gas injection and roll, it may be supplied to some extent, and for example, it is preferable that the wet film thickness is 200 μm or more.

  As the roll of the present invention, any slurry may be used as long as the slurry is evenly distributed with respect to the substrate. For example, a rubber roll is preferably used. As the rubber material of the rubber roll, urethane rubber, nitrile rubber, hyperon rubber and the like which are excellent in wear resistance are preferable. The rubber hardness of the rubber roll is preferably from Shore A45 to 85. The roll diameter is preferably about 50 to 400 mm. In order to secure a necessary amount of slurry adhesion, a rubber roll having grooves engraved on the surface may be used.

  As the nozzle of the present invention, a gas injection nozzle for injecting gas is used. As gas injected from a gas injection nozzle, air 100vol%, nitrogen, etc. are mentioned, for example. Among these, air that can be used in atmospheric circulation without fear of lack of oxygen is particularly preferable. Moreover, as gas injection pressure (injection speed), 10-80 kPa is preferable. A slit nozzle etc. are mentioned as a kind of nozzle. When a slit nozzle is used, the slit gap of the nozzle is preferably 0.3 mm or more and 2.0 mm or less. If the slit gap is small, the gas momentum required for slurry wiping cannot be obtained sufficiently and the slurry becomes non-uniform. In addition, if the slit gap is large, the air volume increases, and thus slurry scattering occurs, resulting in an appearance defect. Preferably, it is 0.5 mm or more and 1.5 mm or less.

  Next, a method for applying the slurry of the present invention will be described with reference to FIG.

  The substrate 1 is passed through the direction of the arrow in FIG. The sheet passing speed is preferably 300 m / min or less because scattering tends to occur due to an increase in the slurry wiping amount. First, slurry is applied from the slurry supply nozzle 2 to the front and back of the substrate 1 to be passed.

  Next, gas is injected from the gas injection nozzle 4 to the base material 1 on which the slurry is applied. The surplus slurry is wiped off by the action of the gas injection nozzle 4. The slurry adhesion amount is adjusted uniformly with respect to the width direction of the substrate 1. Next, the base material 1 from which the excess slurry has been wiped off is pressed against the rubber roll 3. The slurry adhered in a uniform amount with respect to the width direction of the base material 1 is squeezed by the pressing load of the rubber roll 3. By narrowing down the rubber roll 3 in this way, the slurry adhering in a uniform amount to the width direction of the substrate 1 is leveled. That is, due to the action of the rubber roll 3, it is possible to avoid slurry scattering that can be generated by gas injection and (spots) defects due to slurry scattering. Further, since the slurry leveled by the gas injection nozzle 4 is squeezed by the rubber roll 3, a slurry film without coating unevenness can be obtained as compared with the case where the slurry having unevenness supplied by the spray nozzle is squeezed.

  In this invention, it is preferable that the gas injection nozzle 4 is arrange | positioned from the rubber roll 3 in the upstream which is 100 mm or more away. When closer than this, the jet flow injected from the gas injection nozzle 4 collides with the slurry reservoir generated on the gas injection nozzle 4 side of the rubber roll 3, and scattering occurs. Moreover, after leveling the slurry with the rubber roll 3, it is preferably dried using a hot air drying furnace or an IH coating / drying apparatus under a temperature rising rate of 150 ° C./second or less. If the rate of temperature increase is faster than this, an uncoated part will occur due to the generation of bubbles due to the sudden boiling of the slurry. Furthermore, it is possible to efficiently flow down the liquid squeezed by the gas injection nozzle 4 by lowering the upstream side of the base material and passing the plate with an inclination. If the inclination is 1 degree or more, it is effective. Preferably it is 3 degrees or more.

  The wet film thickness of the slurry wiped by the gas injection nozzle 4 is 0.8 times or more and 3.0 times or less of the wet film thickness after being wiped by the gas injection nozzle 4 by the rubber roll. It is preferable that By reducing the amount of liquid squeezed by the rubber roll 3, the amount of liquid meniscus between the roll and the substrate is reduced. As a result, the streak pattern generated when the meniscus is disturbed is reduced, and a more beautiful and uniform appearance can be obtained. When the adhesion amount is larger than 3.0 times, the meniscus liquid amount between the roll and the substrate is increased, and a streak pattern is generated. On the other hand, when the adhesion amount is less than 0.8 times, the liquid amount of the meniscus between the roll and the substrate becomes non-uniform in the substrate width direction, and coating unevenness increases. Further, as a preferable condition, the slurry wet film thickness after being wiped off by the gas injection nozzle 4 is 0.9 times or more and 1.5 times or less of the wet film thickness squeezed by the rubber roll.

  In the present invention, the rotation direction of the rubber roll may be the same as that of the base material at the contact surface with the base material, but the appearance of living is suppressed when the direction of rotation in the direction opposite to the base material is suppressed. Becomes more beautiful. Therefore, the reverse direction is preferable. Further, the rotation speed in the reverse direction is 0.8 times or more and 2.0 times or less the sheet passing speed of the base material. When the rotational speed is slower than 0.8 times, the streak defect increases. On the other hand, if it is faster than 2.0 times, the slurry supply becomes insufficient and the occurrence of scumming becomes significant. Furthermore, as a preferable condition, the roll rotation speed is set to 0.9 times or more and 1.4 times or less of the sheet passing speed of the base material. In addition, when rotating in the same direction, the rotation speed is preferably 0.4 to 0.9 times slower than the base material.

As an embodiment of the present invention, as shown in FIG. 3, the rubber roll 3 may be sandwiched between gas injection nozzles 4 and 5. That is, gas is blown by the gas injection nozzle 5 onto the base material 1 after being squeezed by the rubber roll 3. Thereby, the effect of leveling the slurry can be further enhanced. Therefore, even if some streaks are generated on the front and back surfaces of the base material after being drawn by the rubber roll 3, a slurry coating without any coating unevenness can be produced by the action of the gas injection nozzle 5. When leveling the slurry surface with the gas injection nozzle 5, it is preferable not to squeeze it further thinner than the wet film thickness squeezed with the rubber roll 3. That is, it is an extent which does not reduce the amount of slurry adhesion, and specifically, it is preferably an extent which does not generate a slurry pool at a position where gas collides.
When the wet film thickness is further reduced by the gas injection nozzle 5, the gas is injected at a high pressure, so that scattering occurs. This ultimately deteriorates the appearance. The gas pressure of the gas injection nozzle 5 is preferably adjusted to such an extent that liquid cannot be accumulated at a position where the gas collides with the slurry surface. As the gas injection nozzle 5, it is preferable that the slit gap is 0.3 mm or more and 4 mm or less. If the slit gap is small, it is necessary to bring the nozzle close to the substrate in order to obtain a leveling effect, which increases the risk of contact. On the other hand, if the slit gap is large, the air volume increases and slurry scattering occurs. Preferably they are 0.5 mm or more and 2.0 mm or less.

  Examples will be described below.

  Slurry coating was performed on the steel sheet having a plate thickness of 0.3 mm and a plate width of 900 mm under the coating conditions described in Table 1, and the coating appearance after drying was evaluated. In the coating apparatus shown in FIGS. 1 to 3, the slurry supply nozzle 2 was formed by arranging round holes in the width direction at a pitch of 100 mm. The diameter of the hole is 8 mm. A slit nozzle with a slit gap of 1 mm was used for the gas injection nozzles 4 and 5. The material of the roll was a rubber roll in which rubber was lined on a metal roll. The rubber lining thickness is 20 mm, the rubber is urethane rubber, and the hardness is Hs55 °. The roll diameter was 150 mm. Moreover, the rubber roll of the conditions rotated in the same direction on a base material and a contact surface gave the V-groove process of width direction pitch 0.55mm and depth 0.3mm on the surface.

  The slurry used was a mixture of magnesium oxide powder in water with a solid content adjusted to 5% by volume. The substrate passing speed was 100 m / min, and the rotation speed of the rubber roll was appropriately changed. After forming the slurry film, air was blown at 350 ° C. in a hot air drying furnace, and the temperature was raised to 150 ° C. at a temperature rising rate of 10 ° C./sec.

  In Table 1, the final wet film thickness is a value converted from the adhesion amount after drying and the slurry solid content concentration. The wet film thickness A was converted by measuring the amount of adhesion after drying of the MgO film only by gas injection during the slurry application. The wet film thickness B is a value converted from the amount of adhesion after drying when gas injection is stopped and only roll drawing is performed. In addition, about the adhesion amount, it grasped | ascertained compared with the analytical curve created beforehand by measuring the steel plate cut out after drying with a fluorescent X ray. The calibration curve was prepared by measuring the fluorescent X-ray intensity for the sample after forming the MgO film and measuring the difference between the sample mass and the sample mass after wiping the MgO film to confirm the adhesion amount. At this time, the mask diameter is 20 mm, the fluorescent X-ray acceleration voltage is 45 kV, the acceleration current is 50 mA, and the measurement time is 20 seconds.

  Regarding the appearance evaluation, the steel plate after drying was cut out and visually evaluated under a sufficiently bright fluorescent lamp. The case where no streak was produced and a smooth film was obtained was marked as ◎ ++. The streaks were so fine that they could not be visually confirmed, and those having a substantially smooth film were marked as +. The case where slight streaks that were hardly noticed by visual generation were marked as ◎. Although the streak that can be visually confirmed is generated, it is evaluated as ○ for those that are infrequent, and × for those that show clear stripes or slurry spots on almost the entire surface.

  As shown in Table 1, it became possible to apply the slurry smoothly and uniformly to the substrate by gas injection. On the other hand, when the conventional method is applied by roll drawing alone, unevenness in film thickness and spot defects due to slurry scattering occur, and uniform application cannot be achieved.

  In addition, although the steel plate was used as a base material in the said Example, it does not need to be specifically limited to a steel plate, What is necessary is just a base material. The present invention is also applicable to other metal plates such as aluminum, paper, and films.

DESCRIPTION OF SYMBOLS 1 Base material 2 Slurry supply nozzle 3 Rubber roll 4 Gas injection nozzle 5 Gas injection nozzle

Claims (6)

A step of supplying a slurry from a nozzle to a traveling substrate, a step of injecting a gas to the substrate using a nozzle after supplying the slurry, and after the gas is injected, on the front and back of the substrate A step of pressing the roll and adjusting the final adhesion amount of the slurry, and the roll rotates on the contact surface of the base material so as to be opposite to the traveling direction of the base material. rate Ri strip passing 2.0 times der below 0.8 times the speed of the substrate, a slurry method of coating, characterized in Rukoto beveled and lower an upstream the substrate side.   Furthermore, after the process of pressing the said roll, gas is injected with respect to the said base material using a nozzle, The coating method of the slurry of Claim 1 characterized by the above-mentioned. The slurry application method according to claim 1 or 2, wherein the inclination is 1 degree or more. A slurry supply device for supplying a slurry from a nozzle to the base material along a base material traveling direction, and a roll for adjusting the final adhesion amount of the slurry by pressing against the front and back of the base material, the slurry supply device And a first nozzle for injecting gas to the base material between the roll and the roll, the roll is rotated so as to be in the opposite direction on the contact surface with respect to the traveling direction of the base material, rotational speed of the rolls Ri 2.0 times der below 0.8 times the sheet passage speed of the substrate, a slurry application apparatus according to claim Rukoto beveled to lower the substrate side is the upstream . The slurry coating apparatus according to claim 4 , further comprising a second nozzle for injecting gas, wherein the roll is sandwiched between the first nozzle and the second nozzle. The slurry coating apparatus according to claim 4 or 5, wherein the inclination is 1 degree or more.

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