JP2667032B2 - Roller curtain coating method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a roller curtain coating method.

The roller curtain coating method is a method in which the paint is supplied between a paint roll and a doctor roll, whose axes are arranged in parallel at a predetermined roll surface interval, and the paint is carried on the paint roll surface and discharged downward from between the two rolls. Is scraped off with a doctor blade provided in contact with the lower part of the coating roll, guided downward and freely dropped in a curtain shape, and the object to be coated is passed under the two rolls to be coated with the free falling curtain of the coating material. Is the way. The coating roll is a roll for supporting a coating material on a rotating roll surface and continuously supplying the coating material to a coating curtain via a doctor blade. Doctor roll is usually rotating in the opposite direction to the paint roll, pull back the paint carried on the paint roll,
It is a roll for limiting the amount of the paint, which is carried downward between both rolls, to a predetermined amount. The amount of paint supplied to the paint curtain is adjusted mainly by the interval between the two rolls and the rotational peripheral speed.

Roller curtain coating, like other curtain coating methods such as slit type and overflow type, can eliminate virtually no paint loss compared to brush coating, spray coating, dipping coating, etc. It has excellent advantages such as extremely large capacity and very good finish of the painted surface.Moreover, compared to other curtain painting methods, it can take a lot of adjustment factors such as the amount of paint supply, so it can be applied to small quantity and many kinds of painting. Has the advantage of being able to respond quickly.

In recent years, in particular, home appliances, office equipment, etc. have become extremely diversified in accordance with their uses or customer demands, and the materials used for these, such as pre-coated steel sheets, are also materials, dimensions (thickness, width), coloring, coating, etc. Since the types of films have been diversified according to each request, the superiority of the roller curtain coating method, which can relatively easily cope with the production of small lots of various types, is attracting more attention.

[Conventional technology]

In the roller curtain coating method, for example, as disclosed in Japanese Utility Model Laid-Open No. 61-177892 and Japanese Utility Model Laid-Open No. 63-63163, when supplying paint between a coating roll and a doctor roll, The paint was directly supplied between these two rolls to form a paint pool.

However, in the above-mentioned method, the so-called "dancing phenomenon" in which the liquid level of the paint pool rises below the paint supply nozzle or the whole surface undulates, causing a coating unevenness. The present inventor has already proposed, as a method of preventing such coating unevenness, a method of supplying a coating material on a coating roll surface or a doctor roll surface without forming a paint pool ("Roller curtain coating method"). "Heisei 2
Filed on January 31, 2008).

In the above proposed method, when the paint is supplied on the doctor roll surface and then carried (transferred) on the paint roll surface, the paint roll surface has sufficient wettability to the paint. There is a need. If the wettability is insufficient, a slip phenomenon occurs between the paint and the paint roll surface, and the paint on the doctor roll surface is not sufficiently transferred to the paint roll surface, which eventually causes the paint curtain to break. This slip phenomenon becomes more remarkable as the peripheral speed of the coating roll (strictly speaking, the peripheral speed of the coating roll relative to the peripheral speed of the doctor roll) is increased, and it becomes an obstacle to the controllability of the coating film thickness.

Conventionally, a hard roll such as a chrome-plated steel roll has been used as a coating roll, but the roll surface is mirror-finished to be in close contact with the blade edge of a doctor blade. Such a mirror-finished roll surface has poor wettability to paint, and there is a problem that the paint curtain is likely to be cut due to poor paint transfer from the doctor roll surface.

[Problems to be solved by the invention]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a roller curtain coating method capable of preventing a paint curtain from being cut due to a poor transfer of a paint from a doctor roll to a coating roll, and performing stable coating even when a coating roll peripheral speed is increased.

[Means for solving the problem]

According to the present invention, according to the present invention, the paint supplied on the doctor roll surface is transferred onto a coating roll surface which is arranged in parallel with the axis at a predetermined roll surface interval, and is carried on the coating roll surface. The paint discharged downward from between the two rolls is scraped off by a doctor blade provided in contact with the lower part of the coating roll, freely dropped downward in a curtain shape, and the object to be coated is passed under the two rolls. In the method for coating with a free-fall curtain, a roller curtain coating method is characterized in that a coating roll having a uniform roughened roll surface is used.

[Action]

The roller curtain coating method of the present invention, by making the coating roll surface a uniform rough surface, the wettability to the coating is increased compared to the conventional mirror-finished coating roll, and the coating curtain breaks due to poor transfer to the coating roll. Since this can be prevented, stable coating can be performed even at high peripheral speeds of the coating roll.

The roll surface roughness and uniformity of the coating roll are set in advance by a test according to the viscosity of the paint to be used, the thickness of the dried coating film, the solid content of the paint (NV%), and the like.

In order to obtain a uniform roughness, it is appropriate to roughen the roll surface by shot blasting or laser treatment with an appropriate particle size.

 Hereinafter, the present invention will be described in more detail with reference to Examples.

〔Example〕

Referring to FIG. 1 (a), sectional view, (b) front view, and (c) perspective view, a paint is applied on a doctor roll surface by using a coating roll having a uniform roughened roll surface according to the present invention. An example of the roller curtain coating method to be supplied will be described.

The coating roll 1 and the doctor roll 2 having a uniform rough surface 7 are arranged at a predetermined roll surface interval h with their axes parallel. The roll surface interval h is set in relation to a predetermined coating film thickness, the rotation speed of the coating roll and the doctor roll, the traveling speed of the object to be coated, the coating viscosity, the coating specific gravity, the coating specific gravity, and the like. The coating roll 1 and the doctor roll 2 are respectively rotated in directions indicated by arrows by a roll driving device (not shown). The work 6 moves below the two rolls in the direction of the arrow.

A paint supply jig 5 disposed above the paint roll 1 and the doctor roll 2 temporarily stores paint T from a paint supply source (not shown), and determines the opening degree of a discharge port t extending in a width direction at a lower portion. The paint supply can be adjusted. The jig 5 is disposed so that the discharge port t is positioned parallel to the axes of the two rolls 1 and 2 and above the doctor roll 2. The coating material adjusted to a predetermined amount is supplied from the discharge port t as a curtain having a predetermined width w substantially parallel to the roll width W as shown by a on the roll surface of the doctor roll 2.

The paint supplied on the two doctor rolls
Transferred between the coating roll 1 and the coating roll 1 and guided downward by a doctor blade 3 disposed in contact with the lower part of the coating roll, falls freely as a coating curtain d, and is coated on a workpiece 6 such as a strip steel plate. You.

The roll surface roughness of the coating roll 1 is set to a roughness sufficient to prevent a slip phenomenon between the roll surface and the paint, but if it is too rough, it may cause streak-like coating unevenness, Since it becomes difficult to uniformly scrape from the paint, it is set according to the viscosity of the paint to be used, the relationship between the paint film thickness after drying and the paint solid content (NV%), and the like. For example,
Using pre-coat paint, dry coating thickness 10 to 30 μm, NV
When coating with 30 to 50%, the surface roughness of the coating roll is 5
μm or less is appropriate. In this case, the uniformity of the roughness can be evaluated by the uniformity of the distribution of the roughness waveform, as exemplified in the roughness meter chart in FIG. 2, and in the example of FIG. If it is twice, it can be considered that it is practically uniform.

Table 1 summarizes the results of coating the pretreated electrogalvanized steel sheet by using the roller curtain coating apparatus shown in FIG. 1 and changing the surface roughness of the coating roll 1 in various ways. The roughening of the roll surface was performed as follows. That is, JIS
In order to obtain roughness within the range of Ra0.075 to 10 μm based on G5903 and JIS R6001, select conditions such as the number of grinding materials such as steel grids and alumina glass beads, projection time, projection amount, projection distance, etc., and grind Was subjected to a shot blast treatment on a roll surface having a smooth finish. In the case of a corrugated surface having a round bottom with a round bottom, the surface of the roll having the same smooth finish was subjected to laser processing to give a rough surface. The coating conditions are as described in (Note 2) below.

(Note 1) * The larger the value, the better the surface wettability.

(Note 2) Coating conditions Paint: Pre-coat paint (Dainippon Ink Co., Ltd.), Paint viscosity: 40-100 seconds / 25 ° C (Ford cup # 4), Dry coating thickness: 20 μm Wetability test condition JIS K6768 According to. (Wetability test reagent: standard reagent of formamide / ethyl glycol ether) When the coating roll 1 having a uniform and appropriate roughness according to the present invention is used (Examples 1 to 3), the wettability of the roll surface is good. Even in high-speed coating in which the ratio (va / vd) of the peripheral speed (va) of the coating roll 1 to the peripheral speed (vd) of the doctor roll 2 is about 70 or more, no streaky coating unevenness occurs and uniform scraping occurs. The workability was good, and the coating could be performed without causing slip between the coating and the coating roll.

On the other hand, in the case of Comparative Example 1 using a coating roll having a roll surface roughness that is too rough, the wettability of the roll surface is good, but stripe-like coating unevenness occurs and the uniform scraping property is poor,
Good coating could not be performed.

On the other hand, in the case of Comparative Example 2 in which the roll surface was mirror-finished as in the past, the wettability of the coating roll surface was poor,
Even though the peripheral speed ratio was reduced to about 20 or less, a slip phenomenon occurred with the paint and the paint curtain was broken.

〔The invention's effect〕

As described above, according to the roller curtain coating method of the present invention, even if the circumferential speed ratio of the coating roll is increased, the slip phenomenon between the coating roll and the coating can be prevented, and the uniform scraping property is sufficiently ensured. High quality coating without uneven coating can be performed.

[Brief description of the drawings]

FIGS. 1 (a), (b) and (c) are (a) sectional views, (b) front views, and (c) for explaining one embodiment of a roller curtain coating method according to the present invention. ) A perspective view and FIG. 2 are graphs showing roughness meter charts for various roll surface roughnesses. 1: Paint roll, 2: Doctor roll, 3: Doctor blade, 4: Doctor knife, 5: Paint supply jig, 6: Workpiece, 7: One paint roll with uniform rough surface, a: Paint supply Curtain, d: free fall paint curtain.

Claims (1)

(57) [Claims] 1. A paint supplied on a doctor roll surface is transferred onto a coating roll surface having its axis parallel to the coating roll and arranged at a predetermined roll surface interval. The paint discharged to the coating roll is scraped off by a doctor blade provided in contact with the lower part of the coating roll and freely dropped in the form of a curtain, and the object to be coated is passed under the two rolls to be coated with the free falling curtain of the paint. A method for coating a roller curtain, comprising using a coating roll having a uniform rough surface.