JPH06254479A - Painting method using painting roll - Google Patents

Abstract

PURPOSE:To provide a roll coating method capable of always stably forming a homogenous film with constant thickness throughout a period of painting work with good workability. CONSTITUTION:When a strip material 6 is continuously painted by roll coating using a painting roll 2 of which at least the surface layer is constituted of an elastomer, a membrane composed of a resin or metal preventing the swelling of the elastomer due to a coating soln. or the solvent thereof is formed on the surface of the pointing roll 2 before performing painting.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous coating method for a belt-shaped body using a coating roll, and in particular, a uniform coating film having a constant thickness can be stably formed from beginning to end of the coating work. The present invention relates to a coating method made possible.

[0002]

2. Description of the Related Art Conventionally, a "roll coating method" has been used as a means for applying a coating liquid such as a paint or a functional material to a continuously running strip (steel plate, resin film, paper, etc.). Has been commonly used. 1 and 2, a pickup roll 1 and an applicator roll (coating roll) 2 are used, and the coating liquid in a coating liquid pan 4 is fed along a backup roll 5. It is a schematic explanatory drawing of a typical "roll coating method by 2 rolls" of the system of applying to the to-be-coated body 6 which passes through.

Incidentally, FIG. 1 shows that the running direction of the article 6 to be coated (the rotating direction of the backup roll 5) and the rotating direction of the applicator roll 2 are opposite to each other, which is "natural". This is an example of the "roll coating method". On the contrary,
FIG. 2 shows an example of the "reverse roll coating method" in which the rotation direction of the applicator roll 2 is the same as the rotation direction of the backup roll 5 (the running direction of the object 6 to be coated). Is.

As described above, in the roll coating method, first, the coating liquid contained in the coating liquid pan 4 is scraped up onto the surface of the coating liquid by the pickup roll 1 to pick up the pickup roll 1.
And squeeze between App Roller 2 and App Roll
The image is transferred to the surface of the roll 2, and then transferred from the applicator roll 2 to the object 6 to be coated. At present, the applicator roll has a surface covered with an elastic body 3 (generally urethane rubber) as shown in FIGS. Elevated multi-layer rolls are used.

Incidentally, in carrying out the roll coating method, a coating device (roll coater) is used.
One of the important performances required for the "a function of uniformly applying a predetermined amount of coating liquid to the surface of the object to be coated" is to meet the required function, and the applicator roll mill The thickness of the coating film is controlled by adjusting the distance between the rolls and the rotation speed of the rolls in the turret portion. And
In recent years, due to the remarkable progress in control technology, it has become possible to finely adjust the distance between rolls and the like, and the quality of coating materials has improved significantly.

However, recently, the required level for the quality of coating materials tends to be more and more advanced. Therefore, considering the coating materials obtained by roll coating from such a viewpoint, when the coating work is started, From a certain time (4 ~
The phenomenon in which the thickness and surface condition of the coating film gradually change at the point where 5 hours) has passed is considered to be an obstacle to the production of high-quality coating materials with even higher levels of yield. It was

However, it is possible to empirically cope with the above phenomenon to some extent by changing the distance between the rolls or changing the rotation speed of the roll. However, even from the viewpoint of productivity, coating thickness control relying on experience and intuition in this way is not preferable, and there is a rolling technology that can obtain a constant coating thickness and surface condition from beginning to end only by setting control factors. Wanted

Therefore, the object of the present invention was to establish a roll coating method capable of stably forming a uniform coating film having a constant thickness throughout the coating operation. .

[0009]

[Means for Solving the Problems] The inventors of the present invention have obtained the following knowledge as a result of earnest research to achieve the above object. That is, in roll coating, one of the important factors that determines the thickness of the coating film and the state of the surface is the roll spacing of the milling portion.
The “applicator roll whose surface is covered with an elastic material such as urethane rubber” applied to the above causes the elastic layer to start to swell with the coating solution or its solvent when the coating solution such as paint is touched, and its characteristics change. The roll interval of the metering portion gradually changes, causing variations in the thickness and surface condition of the coating film. However, in advance, a resin for preventing swelling of the coating liquid or its solvent is applied to the elastic body surface of the applicator roll,
Alternatively, if a thin film layer is formed by vapor deposition of metal or electroless plating, the characteristics of the applicator roll are prevented from changing during the coating work and the roll interval of the metering part is kept constant. In addition to being drunk, there is no particular adverse effect on the painting work,
A coating material with a constant coating thickness and a smooth surface can be obtained from beginning to end.

The present invention has been completed on the basis of the above-mentioned findings and the like, and it is possible to obtain a strip-shaped body by roll coating using "a coating roll having at least a surface layer made of an elastic body". When performing continuous coating, a thin film of resin or metal is formed on the surface of the coating roll to prevent swelling of the elastic body due to the coating liquid or its solvent, and coating is performed, whereby the variation in coating thickness It has the advantage of being able to stably mass-produce coating materials with excellent surface conditions. ”

Here, the "resin for preventing the swelling of the coating liquid or its solvent" may be any known resin which does not dissolve in the coating liquid or its solvent or allow it to infiltrate, for example, "paint resistance" or "resistivity". Fluorine resin, PTFEP resin, CE resin, PF resin, FF resin, XF resin and the like which are known to have "paint solvent resistance" are mentioned. It suffices to apply these resins to the surface of the elastic body (wet rubber, etc.) of the coating roll in a thickness of about 10 to 300 μm by means of air spray or the like.

The thin metal film can be easily formed by vacuum deposition or electroless plating, and the film thickness is from 1 to 1.
About 0 μm is sufficient. The type of metal to be applied is not particularly limited as long as it is not affected by the coating liquid or its solvent, but aluminum, zinc, etc. are preferable from the viewpoint of forming a thin film and cost.

[0013]

As described above, in roll coating, the thickness and surface condition of the coating film are roll coaters.
In the conventional roll coater, the distance between the rolls is greatly affected by the condition of the distance between the rolls in the rolling portion, but the distance between the rolls gradually changes with the start of the coating work. This ro
A major cause of the fluctuation of the roll distance is swelling of the applicator roll at least the surface layer of which is made of an elastic material such as urethane rubber.

That is, an elastic body such as urethane rubber gradually swells by being impregnated with the coating liquid or its solvent when it is in contact with the coating liquid such as paint, and the hardness decreases due to the swelling depending on the material. As a result, the pressing pressure between the rolls changes, and this change in pressing pressure leads to variations in the thickness and surface condition of the coating film.

The swelling of this elastic body saturates with time, but normally it takes about 4 to 5 hours to saturate, so that the swelling gradually progresses until then. Therefore, the thickness of the coating film gradually changes for 4 to 5 hours after the coating work is started, so that it is not possible to produce a product of stable quality. FIG. 3 shows the change in hardness of the roll surface layer portion depending on the contact time (measurement time) when the applicator roll having the urethane rubber layer on the surface layer portion is contacted with the high molecular polyester resin coating material. Although it is a graph showing the situation, from FIG. 3 as well,
It can be confirmed that it takes 4 to 5 hours for the swelling of the rubber to be saturated.

However, when the coating roll surface is coated with a thin film of the above-mentioned "resin which prevents the swelling of the coating liquid or its solvent", the coating liquid (paint, functional material, etc.) or The solvent (toluene, xylene, etc.) is prevented from seeping into the surface layer of the elastic body of the roll, the swelling of the roll is sufficiently suppressed during the coating work, and there is no particular hindrance to the coating work. Therefore, the thickness of the coating film becomes constant, and the surface condition of the coating film becomes stable. Therefore, it is possible to reduce the number of “trial coating” performed for setting the coating film thickness before coating.

The same effect can be obtained when the coating roll surface is coated with a thin metal film such as aluminum or zinc (evaporation film or electroless plating film), which improves the quality of the coated product and the coating work. Can improve productivity. As described above, if the metal thin film to be coated has a thickness of 1 to 10 μm, the expected performance can be obtained, and that the metal coating is so thin that the coating material is not damaged. .

The present invention will be described below with reference to examples.

EXAMPLE A continuous coating test of a strip steel sheet was carried out by a method of the present invention and a conventional method using a reversing coating type two roll coater. The diameter of the applicator roll covered with a urethane rubber layer (thickness: 25 mm) is 3 mm.
The roll was 00φ and the core diameter was 250φ, and this roll was used as it was as the “conventional method”, and aluminum was vacuum-deposited to a thickness of 5 μm on this roll as the “method of the present invention”. .

In each test, a high-molecular polyester paint was used as the paint and the line speed was set to 3
0 m / min, and the peripheral speed ratio of each roll is "line / applicator roll / pickup roll = 1 / 1.4 / 0.
4 ", and a coating thickness of 50 μm as a wet film thickness was set as a target value.

The change in "deviation from the target film thickness" with time was investigated by the above coating test. The results are shown in FIG. 4 comparing the method of the present invention with the conventional method. From the results shown in FIG. 4, the film thickness changes rapidly with the change in time in the conventional method, whereas the deviation from the target film thickness is 2% according to the method of the present invention over time. You can see that it is below. Further, in the case of the method of the present invention, it was confirmed that the surface condition of the coating film was stable because there was no need to change the amount of roll pushing. As described above, according to the method of the present invention, stable coating can be performed from the beginning, so that the number of trial coatings can be reduced and the productivity is also improved.

[0021]

[Summary of Effects] As described above, according to the present invention, a roll coating method has been established which enables stable coating with a constant film thickness throughout the coating operation. This makes it possible to produce excellent coating materials with high efficiency, resulting in a very useful effect in industry.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a natural roll coating method.

FIG. 2 is an explanatory diagram of a reverse roll coating method.

FIG. 3 is a graph showing "a change state of hardness of roll surface layer portion depending on contact time (measurement time)" when the applicator roll is brought into contact with the coating material.

FIG. 4 is a graph showing a result of a roll coating test in which “a change with time from a target film thickness” is compared between the conventional method and the method of the present invention.

[Explanation of symbols]

 1 Pickup roll 2 Applicator roll (Paint roll) 3 Elastic body 4 Coating liquid pan 5 Backup roll 6 Object to be coated

Claims (1)

[Claims] 1. A continuous coating of a belt-shaped body by roll coating using "a coating roll having at least a surface layer made of an elastic material", and a coating solution or a coating solution on the surface of the coating roll. A continuous coating method for a belt-shaped body, characterized in that a thin coating film of resin or metal is formed to prevent swelling of the elastic body due to a solvent, and coating is performed.