JPH0720572B2 - Continuous coating method for steel sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention is directed to continuously coating a paint, particularly a paint containing an additive having a large specific gravity, on a steel sheet for a long time with a uniform paint composition. The present invention relates to a continuous coating method for steel sheets.

[Prior Art] In order to impart corrosion resistance and durability to steel sheets, and also from the viewpoint of aesthetics, paint is generally applied and baked. For coating, it is necessary to use only boil oil that has been used for a long time and various synthetic resins such as epoxy resin, polyester resin, acrylic resin and vinyl chloride resin that have been widely used in recent years as coating film-forming substances. Recently, a paint containing an additive having a large specific gravity such as a conductive metal powder such as stainless steel powder has been used in order to improve the weldability during processing.

A roll coater is mainly used to continuously paint the steel sheet.

Hereinafter, various conventional coating methods using a roll coater will be outlined with reference to the drawings.

FIG. 7 is a bottom feed system, FIG. 8 is a top feed system, and FIG. 9 is a top feed bottom coat system.

The bottom feed method shown in FIG. 7 is generally an epoxy resin type,
This method is said to be suitable for low-viscosity paints such as polyester resin-based and acrylic resin-based paints. In this system, the pick-up roll 1 and a metering roll 2 ', which is close to the pick-up roll 1 and can adjust the gap, are provided as a gap structure.
Is provided and the lower peripheral surface of the pick-up roll 1 is immersed in the paint 6 in the paint tank 5, and the rotation of the pick-up roll 1 causes it to adhere to the peripheral surface of the pick-up roll 2 '(not rotating). The paint 6 having a predetermined amount of adhesion through a predetermined gap is brought into contact with the pick-up roll 1 almost horizontally, and is transferred to the peripheral surface of the applicator roll 3 rotating in the same direction as the pick-up roll 1 and goes through the upper side. The steel sheet 7 transferred and brought into reverse travel by the back-up roll 4 is brought into contact with the applicator roll 3 to continuously coat the steel sheet 7.

The top feed method shown in FIG. 8 is generally said to be suitable for high viscosity paints such as vinyl chloride resin sol paints. In this system, the rolls are arranged in substantially the same manner as in the bottom feed system except that the metering roll 2'which is a gap forming member is arranged at a substantially horizontal position on the opposite side of the pick-up roll 1 from the applicator roll 3. The paint 6 is supplied and stored in a paint reservoir formed by the peripheral surfaces of the pick-up roll 1 and the metering roll 2'and the rolls are rotated as shown in FIG. 6 is transferred and the steel plate 7 is painted. With this top feed method, a pick-up roll 1
In order to make it easier for one paint 6 to pass through the gap between the and the metering roll 2 ', the metering roll 2'is also rotated, and after passing the gap, the knife 6 causes the paint 6 attached to its peripheral surface to move downward. The paint receiver 8 installed is scraped off.

The top feed bottom coating method of FIG. 9 is generally said to be suitable for containing an additive having a large specific gravity.
In this system, the coating tank 5 is constructed by using a part of the peripheral surface of the pick-up roll 1 as one side wall, the applicator roll 3 is vertically arranged below the pick-up roll 1, and its lower end peripheral surface contacts the steel plate 7. Let them do it. Then, while the paint 6 is stirred by the stirrer 10 in the paint tank 5, the rolls are rotated as shown in FIG. 9 to transfer the paint 6 to coat the steel sheet 7.

[Problems to be solved by the invention]

However, when the paint 6 contains an additive having a large specific gravity, each method has the following problems.

That is, in the bottom feed system, this additive gradually settles to the bottom of the paint tank 5. Therefore, as time passes, the amount of the additive in the paint 6 applied to the steel plate 7 via the pick-up roll 1 and the applicator roll 3 decreases, and eventually,
There is a problem in that a coated steel sheet cannot be produced because the content of additives in the coating film is small and the desired effect cannot be obtained. Further, even during the transfer from the paint tank 5 to the steel plate 7, the paint 6 adheres to the peripheral surface of the pick-up roll 1 and is drawn up from the paint tank 5 to the meter ring 2 '. In addition, the additive flows irregularly downward in the paint layer formed on the peripheral surface of the applicator roll 3 due to its large specific gravity (in the case of stainless steel powder, the specific gravity is 7 to 8), and accordingly does not flow down. However, there is a problem in that the distribution of the additives present in the paint is not uniform.

Further, in the top feed method, the additive 6 settles in the direction of the paint reservoir and the paint 6 having a large amount of the additive is first supplied to the steel plate 7, and thereafter the paint 6 having a small amount of the additive is supplied.
Is supplied to the steel plate 7, and the paint layer formed on the peripheral surface of the pick-up roll 1 and the peripheral surface of the applicator roll 3 is added during the transfer from the paint reservoir to the steel plate 7. There is a problem in that the material flows irregularly due to its large specific gravity, and accordingly, the distribution of the additive present in the coating material 6 is not uniform without flowing down.

Furthermore, in the top feed bottom coat method, a stirrer
Although the amount of sedimentation of the additive in the paint 6 is small due to stirring at 10, the paint 6 adheres to each roll peripheral surface and is transferred downward because the pick-up roll 1 and the applicator roll 3 are vertically aligned. During this time, the additive flows irregularly downward in the paint layer due to its large specific gravity, and the paint 6 also flows down irregularly, so that the distribution of the additive in the coating film is not uniform. However, there is a problem that it is difficult to control the thickness of the coating film.

[Means for solving problems]

The object of the present invention is to solve the above-mentioned problems of the prior art and continuously coat a steel sheet with a uniform coating composition for a long time even when using a coating containing an additive having a large specific gravity. Another object of the present invention is to provide a continuous coating method for a steel sheet as a means capable of forming a coating film having a uniform composition.

That is, according to the present invention, the side wall of the side wall constituted by the pick-up roll and the gap-positioning member provided in proximity to the pick-up roll so that the gap can be adjusted is supplied and adhered to the peripheral surface of the pick-up roll to form a gap-forming member. When the paint that has passed through the gap is continuously coated on the steel plate running in contact with the applicator roll through the upper surface of the applicator roll provided in contact with the pickup roll in a substantially horizontal direction, the pickup roll and the gap constituent are A paint tank is formed as one side wall, and the paint filled up to a level higher than the gap between the pick-up roll and the gap forming member in the paint tank is rotated along a plane perpendicular to the roll axis of the pick-up roll. A stirrer for rotating flow that stirs and stirs and a stirrer for parallel flow that stirs and stirs a parallel flow almost along the length of the pick-up roll. Those relates to a continuous coating method of the steel sheet, characterized in that allowed to pass through the gap between the machine and by the composite stirring cowpea while evenly stirring Te pickup roll and the gap structure.

Hereinafter, the method of the present invention will be described in detail with reference to the drawings. First
FIG. 3 is an explanatory view showing an example of an implementation state of the method of the present invention, FIG. 2 is a side sectional view showing an example of a stirrer for causing a rotary flow, and FIG.
The figure shows one embodiment of a stirrer that causes a parallel flow, and FIGS. 4 to 6 are graphs showing the results of the examples for each item.

[Description of configuration]

In the method of the present invention, the rolls and the gap forming members are arranged in the same manner as in the top feed system, and a coating tank is newly constructed as described below to perform continuous coating while performing two-way compound stirring.

That is, as shown in FIG. 1, the gap forming body 2 is shown in the vicinity of the pick-up roll 1 so that the gap can be adjusted. A plate-shaped body may be provided) to form a side wall with the two objects, and an applicator roll 3 is provided on one side of the side wall so as to be in contact with the pick-up roll 1 substantially horizontally, and further the pick-up roll of the applicator roll 3 is provided. A back-up roll 4 is provided on the peripheral surface on the side opposite to 1 so that the steel plate 7 is inverted and comes into contact with the peripheral surface. As shown in FIG. 1, the pick-up roll 1 described above is used.
And a gap forming body 2 as one side wall to form a paint tank 5. The paint tank 5 is filled with paint 6 to a position higher than the position of the gap between the pick-up roll 1 and the gap forming body 2. Combined stirring consisting of two types of stirring is performed.

One is a stirring that causes a rotary flow almost along a plane perpendicular to the roll axis of the pick-up roll 1 (hence this is also a vertical plane), and a stirrer 11 for a rotary flow is used as shown in FIG. . As the agitator 11 for this rotary flow, for example, as shown in FIG.
Use the one in which 1b is fixed parallel to the cylinder axis. As shown in FIG. 1, the stirrer 11 for rotary flow is used with its cylinder axis substantially parallel to the roll axis of the pick-up roll 1. The rotation direction is preferably rotation from the bottom dead center to the pick-up roll 1 side, but there is no problem in stirring effect even if it is rotated to the opposite side, or it may be reversed periodically.

The other stirring that constitutes the composite stirring is stirring that causes a parallel flow that flows substantially along the length direction of the pick-up roll 1, and a stirrer 12 for parallel flow is used as shown in FIG. As the stirrer 12 for the parallel flow, for example, a propeller stirrer may be used, and a flow may be generated from one side wall formed by the pick-up roll 1 and the gap forming body 2 toward the opposite side wall. In FIG. 1 and in the enlarged view of FIG. 3, a wide stirring plate 12b which is substantially along the plane perpendicular to the roll axis of the pick-up roll 1 is slidable on a guide rod 12a positioned parallel to the pick-up roll 1. The stirring plate 12b is slid along the guide bar 12a while being periodically inverted in the paint 6 to cause a parallel flow of the paint 6 along the length direction of the pick-up roll 1. Of. It is preferable to form holes 12ba in the stirring plate 12b as shown in FIG. 3 in order to prevent waviness and foaming during stirring.

These two types of stirrers are rotary flow stirrers as shown in FIG.
It is preferable that 11 is installed at a position close to the bottom, and that the parallel flow agitator 12 is installed above the rotary flow agitator 11 to agitate.

In this way, the paint is mixed with the pick-up roll 1 and the gap forming body 2 while being stirred by the composite stirring composed of two kinds of stirring.
After that, the steel sheet 7 is continuously coated in the same manner as in the conventional case. After coating, baking is performed according to the conventional technique.

〔effect〕

According to the method of the present invention, since the coating material 6 is stirred by the above-mentioned composite stirring, even if the coating material 6 contains an additive having a large specific gravity, the additive can be transferred to the bottom of the coating material tank 5 by the rotating flow. The sedimentation is prevented, and the additive which is scraped up and rotated along the vertical plane is further stirred in the horizontal direction by the parallel flow so that it is more uniformly distributed in the coating material 6. The coating 6 thus homogenized is adjusted to a predetermined amount by the gap between the pick-up roll 1 and the gap forming body 2 and applied to the steel sheet 7 via the applicator roll 3. However, the applicator roll 3 or the back-up roll Four
Is disposed almost horizontally with the pick-up roll 1 and is transferred on the upper peripheral surface thereof, so that the additive does not flow in the paint 6 even during the transfer, and therefore the thickness of the paint 6 is not uneven. In this way, the steel sheet 7 can be continuously coated with a uniform coating composition and a uniform thickness over a long period of time.

[Examples, Comparative Examples 1 and 2] Hereinafter, the method of the present invention will be specifically described with reference to Examples and Comparative Examples.

As a base plate, stainless steel strip (SUS 304, 0.4 mm thickness x 1010 mm
(Width) coil and a coating type chromate was used to perform pretreatment for coating with a total chromium amount of 40 mg / m ² (one side).

The pretreated steel strip was continuously coated and baked for 30 minutes as follows.

First, an undercoat paint (epoxy resin paint containing an anticorrosion pigment, paint viscosity is # 4 for 80 seconds with a cup) was applied and baked at a steel strip temperature of 200 ° C. to form a paint film having a thickness of 4 μm.

Then use 100 parts by weight of silicon-modified polyester resin-based paint as the top coat paint, and add 100 parts by weight of stainless steel powder to apply it by the various methods described below and bake it at a steel strip temperature of 230 ° C. A coating film having a thickness of 11 to 13 μm was formed. The line speed of each of the above coatings was 40 m / min.

The various coating methods are as follows.

Example: A method of the invention similar to that of FIG. 1 using the stirrer of FIGS. 2 and 3.

Comparative Example 1: The same method as in the above Example except that the stirrer shown in FIG. 3 was not used.

Comparative Example 2: The same method as in the above Example except that the stirrer shown in FIG. 2 was not used.

Comparative Example 3: The same method as in the above Example except that no stirrer was used.

Comparative Example 4: Conventional bottom feed method similar to that shown in FIG.

For each of the above methods, the degree of settling of the stainless steel powder in the coating tank during the top coating, the distribution state of the stainless steel powder in the coating film of the obtained coated steel strip, and the weldability were investigated.

The above survey and evaluation were carried out in the following manner, and the results are shown in FIGS. 4 to 6 for each item.

(1) Sedimentation degree of stainless steel powder After the lapse of a predetermined time, the bottom and inner walls of the paint tank 5 were scooped up with a spoon, and at the end of painting, the paint in the paint pan was allowed to flow out to examine the sedimentation degree of the stainless steel powder at each time. .

◎: No settling ○: Slightly settled △: Significantly settled ×: Significantly settled (2) Distribution state of stainless steel powder in the coating film Examining the content of the stainless steel powder in the coating part after a lapse of a predetermined time with a cross-section microscope did.

⊚: Sufficiently contained and uniformly distributed ◯: Almost completely contained and uniformly distributed Δ: Almost fully contained but unevenly distributed ×: Almost no contained (3) Weldability With a self-propelled seam welder, the coating speed after a lapse of a predetermined time, welding speed 2.5m / min, welding current 4KA
Welded under the conditions.

◎: Good weldability ○: Nugget is formed but tensile shear force is insufficient △: Slightly energized ×: No energization at all From Figures 4 to 6, According to the method of the invention, additives having a large specific gravity such as stainless steel powder do not settle in the paint tank even when continuously applied over a long period of time, and the additives in the paint film of the resulting coated steel sheet are It can be seen that the content is sufficient and the particles are evenly distributed, and the desired effects such as improvement of weldability are sufficiently exhibited. Further, it is understood that such an effect is not effective not only in the conventional roll coater technique but also in lacking either one of the rotary flow and the parallel flow constituting the composite stirring in the method of the present invention.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an example of an implementation state of the method of the present invention, and FIG. 2 is a side sectional view showing an example of a stirrer for causing a rotary flow,
FIG. 3 is a diagram showing one mode of a stirrer for causing a parallel flow, FIGS. 4 to 6 are graphs showing the results of the examples for each item, and FIG. 7 is a bottom feed system, FIG. Is a top feed system, and FIG. 9 is a top feed bottom coat system. 1 …… Pickup roll 2 …… Gap structure 2 ′ …… Meter ring roll 3 …… Applicator roll 4 …… Backup roll 5 …… Paint tank 6 …… Paint 7 …… Steel plate 8 …… Paint receiver 9 …… Knife doctor 10 …… Stirrer 11 …… Rotating flow stirrer 11a …… Cylinder body 11b …… Stirring blade 12 …… Parallel flow stirrer 12a …… Guide rod 12b …… Stirrer 12ba …… Hole

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Naoto Mori, 1st 7th Takatani Shinmachi, Ichikawa-shi, Chiba Ichikawa Research Institute, Nisshin Steel Co., Ltd. (72) 1st, 7th Takatani Shinmachi, Ichikawa, Chiba Nisshin Steel Co., Ltd. Ichikawa Laboratory

Claims (3)

[Claims] Claim: What is claimed is: 1. A pick-up roll and a gap-constituting member provided on the side wall of the pick-up roll in close proximity to the pick-up roll so that the gap can be adjusted. When the paint that has passed through the gap is continuously coated on the steel plate running in contact with the applicator roll through the upper surface of the applicator roll provided in contact with the pickup roll in a substantially horizontal direction, the pickup roll and the gap constituent are A paint tank is formed as one side wall, and the paint filled up to a level higher than the gap between the pick-up roll and the gap forming member in the paint tank is rotated along a plane perpendicular to the roll axis of the pick-up roll. A stirrer for rotating flow that stirs and stirs and a stirrer for parallel flow that stirs and stirs a parallel flow substantially along the length of the pick-up roll. Continuous method of coating a steel sheet, characterized in that allowed to pass through the gap between the composite stirring evenly stir Te cowpea the pickup roll and the gap arrangement according. 2. The continuous coating method for a steel sheet according to claim 1, wherein a paint containing an additive having a large specific gravity is used as the paint. 3. A method for continuously coating a steel sheet according to claim 2, wherein a paint containing stainless steel powder as an additive having a large specific gravity is used.