JPH03232570A - Coating method with roller curtain - Google Patents

Abstract

PURPOSE:To prevent the break of a coating curtain by providing a soft auxiliary roll in contact with the surface of a coating roll moving from a doctor blade toward a doctor roll and rotating this auxiliary roll reverse from the coating roll. CONSTITUTION:The coating material T supplied onto the surface of the doctor roll 2 is transferred onto the surface of the coating roll 1 disposed at a prescribed spacing between the roll surfaces by paralleling the axis thereto and the coating material discharged downward from the spacing between the two rolls is scraped by the doctor blade 4 provided in contact with the lower part of the coating roll 1 and is freely dropped like the curtain. A material 7 to be coated is passed below these two rolls and is coated with the free falling curtain of the material. The soft auxiliary roll 3 is disposed in contact with the surface of the coating roll 1 moving from the doctor blade 4 toward the roll 2. This roll 3 is rotated reverse from the rotating direction of the roll 1. Consequently, the striate coating unequalness and the break of the curtain by slipping are eliminated.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a roller curtain coating method.

In the roller curtain coating method, paint is supplied between a paint roll and a doctor roll whose axes are arranged parallel to each other at a predetermined distance between the rolls, and the paint is carried on the paint roll surface and discharged downward from between the two rolls. In this method, the paint is scraped off with a doctor blade placed in contact with the lower part of the coating roll, and allowed to fall freely downward in a curtain-like manner, and the object to be coated is passed under both of the rolls, thereby coating with the free-falling curtain of the paint. The paint roll is a roll that carries paint on its rotating roll surface and continuously supplies the paint to the paint curtain via a doctor blade. The doctor roll usually rotates in the opposite direction to the paint roll, and is a roll that pulls back the paint carried on the paint roll and limits the amount of paint carried downward from between the two rolls to a predetermined amount. be. The amount of paint supplied to the paint curtain is mainly adjusted by the distance between the two rolls and the peripheral speed of rotation.

Roller curtain painting, like other curtain painting methods such as slit type and overflow type, can virtually eliminate paint loss compared to paint painting methods, spray painting methods, dipping painting methods, etc. It has excellent advantages such as extremely large coating capacity and a very good finish on the painted surface, and compared to other curtain coating methods, it allows for more adjustment factors such as the amount of paint supplied, so it can be used for painting a wide variety of products in small quantities. It also has the advantage of being able to respond quickly.

In recent years, home appliances, office equipment, etc. in particular have become extremely diverse depending on their uses and customer requests.
As the variety of products (board width), colors, and types of coatings are diversifying to meet individual requirements, the superiority of the roller curtain coating method, which can relatively easily accommodate the production of a wide variety of products in small quantities, is attracting even more attention. .

[Conventional technology]

In the roller curtain painting method, for example,
As disclosed in Japanese Utility Model Publication No. 1-178972 and Japanese Utility Model Application Publication No. 63-63163, when a paint is supplied between a coating roll and a doctor roll, the paint is supplied directly between these two rolls. Paint pools were forming between the rolls.

However, in the above method, the liquid level of the paint pool bulges under the paint supply nozzle, or the so-called "dancing phenomenon" occurs in which the liquid level undulates over the entire surface, causing uneven coating. As a method for preventing such uneven coating, the present inventor has already proposed a method of supplying the paint onto the coating roll surface or doctor roll surface without forming a paint pool ("Roller Curtain Coating Method"). ” (filed on January 31, 1990).

In the method proposed above, the paint is supplied onto the doctor roll surface and then supported (transferred) onto the coating roll surface.
If the coating is carried out in the form of a coating, the surface of the coating roll must have sufficient wettability for the coating material.

If the wettability is insufficient, a slip phenomenon will occur between the paint and the coating roll surface, and the paint on the doctor roll surface will not be sufficiently transferred to the coating roll surface, eventually causing the paint curtain to break. This slip phenomenon becomes particularly noticeable as the coating roll circumferential speed (strictly speaking, the coating roll circumferential speed relative to the doctor roll circumferential speed) increases, and becomes an obstacle to coating film thickness controllability.

Conventionally, hard rolls such as stainless steel rolls, ceramic rolls, and chrome-plated steel rolls have been used as coating rolls, but the roll surface is mirror-finished to ensure close contact with the cutting edge of the doctor blade.

Such a mirror-like roll surface has poor wettability with paint, and there is a problem in that paint curtain breakage is likely to occur due to poor paint transfer from the doctor roll surface.

Furthermore, if uneven scraping occurs when the paint carried on the coating roll surface is scraped off with a doctor blade, streaks of paint remain on the coating roll surface that has passed through the doctor blade, corresponding to the uneven scraping.

When the paint roll surface goes around once and receives paint transfer from the doctor roll again, transfer unevenness occurs corresponding to this streaky unevenness, which causes unevenness in the film thickness of the paint curtain, and eventually causes streaky unevenness in the coating film thickness. It was causing this.

[Problem to be solved by the invention]

The present invention is a roller that prevents paint curtain breakage due to poor paint transfer from the doctor roll to the coating roll, prevents the occurrence of streaky coating unevenness, and enables stable, high-quality coating even when the coating roll circumferential speed is increased. The purpose is to provide a curtain painting method.

[Means to solve the problem]

According to the present invention, the above object is to transfer the paint supplied on the doctor roll surface onto the coating roll surface whose axis is parallel to this and arranged at a predetermined distance between the roller surfaces, and to transfer the coating material onto the coating roll surface. The paint discharged downward from between the two rolls is scraped off with a doctor blade installed in contact with the lower part of the coating roll, and allowed to fall freely downward in a curtain-like manner. In the method of painting with a free-falling curtain, a soft auxiliary roll is placed in contact with the surface of the paint roll moving from the doctor blade to the doctor roll, and this auxiliary roll is rotated in reverse relative to the paint roll. Achieved by the featured roller curtain painting method.

[For production]

The roller curtain coating method of the present invention involves rotating a soft auxiliary roll in reverse relative to the coating roll, which is placed in contact with the coating roll surface that is moving toward the doctor roll after passing through the doctor blade. The streaky unevenness of paint remaining on the surface of the paint roll that has passed through the blade is pressed with an auxiliary roll to smooth it out.
The remaining paint is forcibly rubbed onto the paint roll surface with an auxiliary roll, and the paint roll surface can be uniformly wetted with paint, thereby simultaneously eliminating streak-like paint unevenness and paint curtain breakage caused by slipping.

The present invention will be explained in more detail below using Examples.

〔Example〕

FIG. 1 shows an embodiment of the roller curtain coating method of the present invention.

For comparison, FIG. 5 shows an example of a roller curtain coating method having the same configuration as FIG. 1 except that no auxiliary roll is used.

In both figures, a doctor roll 2 that rotates in reverse relative to the coating roll 1 is arranged on the right side of the coating roll 1. The paint T is supplied onto the roll surface of the doctor roll 2 from the supply port t of the paint supply jig 5, transferred to the roll surface of the coating roll 1 at position Y, carried on the coating roll 1 surface, and moved downward. After being scraped off by a doctor blade 4 provided in contact with the lower part of the coating roll 1 and guided downward to freely fall as a coating curtain 6, a cut plate-like or band-shaped coating is run downward in the direction of the arrow S. It is applied to the surface of the object 7 to be coated to form a coating film.

Usually, the coating roll 1 and the doctor roll 2 are arranged with an interval between the roll surfaces depending on the thickness of the paint curtain to be formed, the coating speed, etc. As the coating roll 1 and the doctor roll 2, - a ceramic roll for boat fishing;
Hard rolls such as stainless steel rolls or chrome-plated steel rolls are used.

In the case of FIG. 5 in which no auxiliary roll is used, the scratched unevenness Po of paint remaining in streaks on the surface of the coating roll 1 that has passed the doctor blade 4 is caused by the paint transfer from the doctor roll 2 to the coating roll 1. As a result, uneven transfer, uneven coating thickness of the paint curtain 6, and final uneven coating thickness (streaky coating unevenness) occur. Furthermore, since the paint wets the surface of the paint roll extremely non-uniformly in the form of scratched unevenness Po, the transfer from the doctor roll 2 becomes extremely unstable and the paint curtain 6 is likely to break.

However, in the example of FIG. 1 using an auxiliary roll in accordance with the present invention, from the doctor blade 4 to the doctor roll 2,
An auxiliary roll 3 is placed in contact with one surface of the coating roll that is moving toward. That is, in the figure, the doctor roll 2 is placed on the right side of the coating roll 1, and the auxiliary roll 3 of the present invention is placed on the left side. The auxiliary roll 3 rotates in reverse relative to the coating roll 1. After all, these three rolls 1°2.3 are all in a relationship in which the adjacent rolls rotate in reverse, as indicated by arrows R1, R2, and R3.

As the auxiliary roll 3, a soft roll such as a rubber roll, a sponge roll, a fur roll, a cloth roll, etc. is used.

By bringing such a soft auxiliary roll 3 into contact with the coating roll surface moving from the doctor blade 4 toward the doctor roll 2 and rotating it in reverse, the surface of the coating roll 1 that has passed the doctor blade 4 can be scraped off. The remaining unevenness P is pressed and smoothed. At the same time, since both rolls rotate in reverse, the remaining paint is forcibly rubbed onto one surface of the coating roll, and the coating material Q is evenly applied to the surface of the coating roll moving from the auxiliary roll 3 to the doctor roll 2. Wet it. That is, in FIG. 1, the area a from the contact area Y'' between the coating roll 1 and the auxiliary roll 3 to the opposing point Y between the coating roll 1 and the doctor roll 2 is uniformly wetted with the paint Q, and the opposing point Paint transfer with Y is also a problem (it can be done).

Furthermore, by supplying a small amount of the same paint as that to be coated to the contact area Y' between the auxiliary roll 3 and the coating roll 1, the surface of the coating roll 1 moving from the auxiliary roll 1 to the doctor roll 2 is coated. Wetting can be further improved.

The paint can be supplied to the contact area Y° in the form of a curtain 11 from a thin slit-shaped paint supply port 10 disposed directly above the contact area Y'', as shown in FIG. 2, for example.

As another method, as shown in FIG.
The paint may be made into a thin film and supplied onto the roll surface of the auxiliary roll 3 (F in the figure), and may be transferred by pressing it against the roll surface of the coating roll 1 in the contact area Y°.

In addition, as shown in FIG. 4, a roll whose surface is made of a soft porous material such as sponge is used as an auxiliary roll
The coating material 14 may be supplied to the porous roll surface by dropping it little by little from the coating material supply port 13 to impregnate the surface of the porous roll.

〔Effect of the invention〕

As explained above, in the roller curtain coating method of the present invention, a soft auxiliary roll is placed in contact with the surface of the coating roll that is moving toward the doctor roll after passing through the doctor blade, and the roller curtain coating method is reversed with respect to the coating roll. By rotating, the auxiliary roll presses and smooths any streaks of paint remaining on the coating roll surface that has passed through the doctor blade, and the auxiliary roll forcibly rubs the remaining paint onto the coating roll surface for painting. Since the roll surface can be uniformly wetted with paint, it simultaneously eliminates streak-like coating unevenness and paint curtain breakage caused by slippage, and enables stable, high-quality coating even when the coating roll peripheral speed is increased. can.

[Brief explanation of drawings]

1 to 4 are side views showing an example of an apparatus for carrying out the roller curtain coating method using an auxiliary roll according to the present invention, and FIG. It is a side view which shows the comparative example when carrying out a method. 1: Painting rotor 2: Doctor roll, 3: Auxiliary roll, 4: Doctor blade, 4°: Doctor knife, 5: Paint supply jig, 6: Free fall curtain of paint, 7: Object to be painted, 10: Thin Slit-shaped paint supply port, 11: Paint supplied in a curtain shape from the paint supply port 10, 12: Extrusion coater 13: Paint supply port, 14: Paint dripped from the paint supply port 13, P, P
”: Uneven scraping (streaky residual paint) Q: Paint roll 1
Paint that evenly wets the roll surface, R1: Rotating direction of the coating roll, R2: Rotating direction of the doctor roll, R3: Rotating direction of the auxiliary roll, S: Traveling direction of the object to be coated, T: Inside the paint supply jig 5 t: paint supply port of paint supply jig 5;

Claims (1)

[Scope of Claims] 1. The paint supplied on the doctor roll surface is transferred onto the paint roll surface whose axis is parallel to this and is arranged at a predetermined distance between the roll surfaces, and the paint is carried on the paint roll surface and both of the above rolls are transferred. The paint discharged downward from between the rolls is scraped off with a doctor blade installed in contact with the bottom of the coating roll, and allowed to fall freely downward in a curtain-like manner.The object to be coated is allowed to pass under both of the rolls, allowing the paint to fall freely. A method for coating with a curtain, characterized in that a soft auxiliary roll is placed in contact with the surface of the coating roll moving from the doctor blade to the doctor roll, and this auxiliary roll is rotated in reverse relative to the coating roll. How to paint roller curtains. 2. The method according to claim 1, characterized in that a small amount of the paint used for the coating is also supplied to the contact area between the auxiliary roll and the coating roll. 3. The method according to claim 2, characterized in that the paint is supplied directly to the contact area from a paint supply port located directly above the contact area. 4. The method according to claim 2, wherein the coating material is supplied to the contact area by supplying a small amount of the coating material for the coating onto the roll surface of the auxiliary roll using an extrusion coater. 5. As the auxiliary roll, at least a roll surface made of a porous material is used, and the porous material portion is impregnated with the paint used for the painting to supply the paint to the contact area. 3. A method according to claim 2, characterized in that: