JPS581980B2 - Painting method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is applied to reverse roll coating equipment. By pressing a bar roll with a wire of a predetermined diameter wrapped around a core material against an applicator roll or pick-up roll and controlling the amount of paint that passes between the bar roll and these rolls, uniform and smooth coating can be achieved. The present invention relates to a coating method characterized by obtaining a film surface.

The coating method of the present invention is of course suitable for general roll coating paints, but it is particularly suitable for high viscosity paints and paints containing aggregates with large particle sizes, which cannot be coated with conventional roll coating methods. Even with special paints that are possible, it has the advantage of providing a smooth, beautiful-looking paint surface.

Furthermore, the coating method of the present invention has the advantage that the coating thickness can be easily controlled with high precision, which is extremely difficult with conventional roll coating methods, and eliminates the need for operator skill.

The present invention having these advantages will be explained in detail with reference to the drawings.

FIG. 1A is a schematic diagram of a conventional roll coating equipment consisting of an applicator roll and a pick-up roll.

1 in the figure is the material to be coated, which is iron, aluminum, or stainless steel. It is a band made of cloth, synthetic resin film, etc.

2 is an applicator roll, and pick-up roll 3
The paint 6 transferred from the paint 6 is applied to the material 1 to be painted.

The material is generally urethane or butyl rubber.

A pickup roll 3 picks up the paint 6 in the paint pan 5 and transfers it to the applicator roll 2.

The material is generally urethane, butyl rubber, or steel.

Reference numeral 4 is a back up roll that supports the material 1 to be coated.

5 is a paint pan, and 6 is paint. In the conventional coating method, the paint 6 filled in the paint pan 5 is picked up by the rotation of the pick-up roll 3 and squeezed between the pick-up roll 3 and the applicator roll 2 by normal rotation between the rolls.

At this time, pick up roll 3 and ablicator roll 2
The amount of paint deposited on the surface of the applicator roll 2 is controlled by the pressing pressure and circumferential speed of the applicator roll 2.

The applicator roll 2 rotates in the opposite direction to the traveling direction of the material 1 to be coated, and the paint on the applicator roll 2 is placed on the surface of the material 1 to be coated, resulting in uniform coating. .

Typical roll coating paints have the property that even if the coating film has some degree of unevenness in the undried state, the undried coating film itself tends to become smooth before drying, as shown in Figure 1A. A smooth coating film can be obtained using this coating method.

However, the coating thickness control of this coating method is difficult. Since the pressing pressure and circumferential speed ratio between the pick-up roll 3 and the applicator roll 2 are adjusted, operator skill is required to improve the accuracy of the coating film thickness. Moreover, there is a drawback that the thickness of the coating film changes due to changes in the viscosity of the coating over time during the coating process or due to swelling of the rubber roll due to the solvent during coating.

Furthermore, when painting with high viscosity paints or paints with large particle size aggregates mixed into the paint, the undried paint film itself has a weak tendency to become smooth, and the unevenness of the paint film that has formed once is dried. It remains until after the coating has been applied, making it impossible to obtain a good, smooth coating surface.

In the coating method shown in FIG. 1A, unevenness occurs in the coating film immediately after the paint is squeezed by the pick-up roll 3 and the applicator roll 2.

That is, the amount of paint supplied is controlled by the big up roll 3 and the applicator roll 2, and some paint that has passed between the rolls adheres to the surface of the pickup roll 3 immediately after passing, while others adhere to the surface of the applicator roll 2. When the paint passes between the rolls, the single layer of paint is torn into two.

Due to the viscosity of the paint during this pulling, the paint film placed on the surface of the ablator roll 2 becomes a paint film with large irregularities.

FIG. 1B is a schematic diagram of the roll coating equipment according to claim 1 of the present invention.

In the figure, 1 to 6 are the same as those in FIG. 1A, and 9 is a bar roll, and the structure of the bar roll 9 is shown in FIG. 3.

That is, a wire rod 11 made of a material with high wear resistance similar to the core material is tightly wound around a strong cylindrical core material 10 such as steel, stainless steel, or hard rubber.

There is no particular specification for the diameter of the bar roll.

However, if the diameter is too small, there is a risk that the paint will go over the top of the bar roll when the bar roll is pressed, and if it is too large, the negative sum of the equipment will increase, so it should be the same as each roll of the roll coating equipment. A diameter of about 100 mL or slightly smaller is appropriate.

FIG. 4 shows a partially enlarged cross section of the bar roll.

A wire rod 11 having a predetermined diameter is pressed against the surface a of a pickup roll or an applicator roll, thereby creating gaps 12 at equal intervals.

If you want to make this gap larger, you can increase the wire diameter, and if you want to make it smaller, you can make the wire diameter smaller.

When coating is applied by pressing the bar roll 9 having such a shape onto the surface of the ablator roll 2, the paint 6 filled in the paint pan 5 is picked up by the pick-up roll 3,
It is squeezed between the pick-up roll 3 and the applicator roll 2.

In the conventional method shown in Fig. 1A, controlling the supply amount by squeezing was the most important factor in determining the thickness and smoothness of the final coating film, but in the method of the present invention shown in Fig. 1B, between the rolls. The squeezed coating film, which has become more uneven due to the coating pulling phenomenon, passes through the gap between the applicator roll 2 and the bar roll 9.

As described above, this gap is determined by the wire diameter of the wire rod 11 wound around the bar roll 9, and by selecting a predetermined wire diameter, the amount of paint supplied can be arbitrarily selected.

The coating film that has passed through the gap between the bar roll 9 and the applicator roll 2 has irregularities at equal intervals and the heights of the protrusions are made small, and is transferred to the material 1 from the applicator roll 2. Even if the paint has a weak tendency to smooth itself before it is applied and dried, it can easily become a smooth paint film.

FIG. 1C is a schematic diagram of the roll coating equipment according to claim 2 of the present invention.

1 to 6 in the figure are the same as those in FIG. 1A, and show the case where the bar roll 9 is pressed against the pickup roll 3.

In this case, the amount of paint supplied is determined by the gap between the bar roll 9 and the pick-up roll 3, so that the unevenness of the paint film can be reduced and made uniform. It is placed on the material to be coated 1 via the ablator roll 2.

This method differs from the method of the present invention shown in FIG. Furthermore, there is a process of transferring the coating material twice from the applicator roll 2 to the material to be coated 1, and by using means such as changing the circumferential speed of each roll, the smoothing of the coating film is promoted. This makes it possible to obtain a coating film that is smoother than the method shown in FIG. 1B.

FIG. 2A shows a conventional reverse roll coating method using three rolls.

In the figure, 1 to 6 are the same as those in FIG. 1A, and 7 is a doctor roll and 8 is a doctor blade.

The feature of this coating method is that the paint 6 picked up by the pickup roll 3 is constantly scraped off with a doctor blade 8 to keep the surface clean.The doctor roll 7, which is rotated in reverse, is pressed against the pickup roll 3 to pick it up. This method scrapes off a certain amount of paint on the surface of the roll 3 to make the amount of paint supplied to the ablator roll 2 uniform.

This method can provide a coating surface with better smoothness than the two-roll coating method shown in FIG. 1A.

However, the drawback of this method is that the accuracy of controlling the coating film thickness is poor, and it is currently only used for applications where the coating film is relatively thick and does not require strict film thickness accuracy. be.

The method of the invention eliminates this drawback. That is, the method of the present invention in a three-roll coating facility is shown in FIG. 2B.

Items 1 to 7 in the figure are the same as in Figure 2 A, and by pressing the bar roll 9 onto the surface of the pickup roll 3, the accuracy of coating thickness control, which was the biggest drawback of this method, is very good. becomes.

Furthermore, if a paint containing large aggregates is applied using the method shown in Figure 2 A, when the doctor roll γ scrapes off the paint, only the large aggregates in the paint will be selectively scraped off, causing the paint to fail. However, there are problems such as poor distribution of aggregate in the paint film. According to the method of FIG. 2B of the present invention. The maximum height of the gap between the bar roll 9 and the pickup roll 3 is
Even aggregates with large particle sizes, which are larger than the average coating thickness after passing through the voids, can easily pass through the voids, making it possible to paint with good aggregate distribution.

The bar roll has a cross-sectional shape as shown in Figure 4.
If the purpose is to smooth the paint film, it is theoretically better to apply a smooth-sided doctor roll or doctor blade to the uneven paint film surface at a certain distance from the roll surface.

Similar to this technique is the method using a doctor roll shown in FIG. 2A, which is superior in terms of surface smoothness.

However, it is extremely difficult to control the coating thickness at regular intervals on such a smooth surface.

In other words, the factors that determine the accuracy of the coating thickness include the mechanical accuracy of interval adjustment, the roundness of the rolls, and the swelling of the rubber roll due to the solvent during painting, and coating thickness accuracy is not required when painting a relatively thick film. Although it can be used for coatings, it is unsuitable when precision in coating film thickness is required.

In contrast to this. In the case of bar rolls, the amount of paint supplied is determined by contacting the roll surface. Even if there are problems such as poor roundness or swelling of the roll, the supply amount does not change, and the mechanical precision of pressing is not required, so the coating thickness can be controlled with high precision.

Furthermore, the structure in which the wire is wound around the core material has the advantage that when the wire becomes worn or the surface of the bar roll is damaged due to trouble, only the wire that has been wound around the surface of the bar needs to be re-wound, making repairs possible in a short period of time and at low cost. .

Also, the bar roll does not need to be rotated in normal cases. If the paint contains aggregate or if the paint contains dust, etc., it is desirable to rotate the bar roll in the positive direction at low speed relative to the pressed roll.

However, if the speed is too high, there will be a problem that the paint will pull and the paint surface will not be completely smooth. It is desirable that the rotation be performed as slowly as possible.

The structure of the bar roll used in the present invention is conventionally made of synthetic resin film or paper. The principle is the same as the steel bar coater used when coating strips such as cloth.

Normally, when coating these strips, a bar coater is applied directly to the moving target material.

However, this coating method using a bar coater in direct contact has various problems.

First, normal bar coater painting can only be used on flexible materials such as the aforementioned synthetic resin films and cloth, and is not suitable for hard materials such as metal plates and wood plywood. That's true.

This 1 is a method in which the coating is performed by direct contact between the bar coater and the object to be coated. The contact between the bar coater and the material to be coated is F
It is necessary that the coating be uniform, but hard materials such as metal plates and plywood with rough surfaces or poor flatness will result in uneven contact and unstable coating film thickness.

Flexible materials such as synthetic resin films and cloth do not have this problem because they blend well with the bar coater and the contact is uniform. It is for this reason that the materials to be coated with bar coater coating are limited to these materials.

Secondly, in the case of bar coater coating, the coating thickness is determined by the wire diameter of the wire used in the bar coater, making it impossible to control the coating thickness over a wide range.

Therefore, when it is desired to change the thickness of the coating film, it is necessary to replace the bar coater with a bar coater suitable for that thickness, which has the drawback of greatly reducing work efficiency.

That is, the present invention solves these drawbacks of the barcoder coating method by using a special combination of the roll coating method and the barcoater coating method. Furthermore, it is an epoch-making coating method that overcomes the drawbacks of roll coating methods.

The problems with the roll coating method and their solutions have already been discussed above. The disadvantages of the barcoder coating method are completely solved in the present invention for the following reasons.

Regarding the first drawback, which is the instability of coating film thickness on hard materials to be coated, in the method of the present invention, the bar roll does not directly contact the material to be coated, but instead uses a flexible rubber ablicator roll. Because it is coated, even if the surface is rough or uneven, it will hit evenly and there will be no instability in the coating thickness.

Regarding the second drawback, which is that it is impossible to control the coating thickness over a wide range, the amount of paint supplied to the material to be coated can be adjusted by changing the peripheral speed of the applicator roll, pickup roll, etc. It is clear that a very wide range of coating thickness control is possible with a bar roll of one wire diameter.

Furthermore, another advantage of the present invention is that in the conventional bar coater painting method, the coating is applied by pressing the bar coater directly onto the material to be coated, so the unevenness of the coating film that has passed through the bar coater is smoothed by the tendency of the paint itself to become smooth. However, according to the present invention, unevenness on the coating surface that passes through the gap between the bar roll and the applicator roll or the pickup roll is transferred from these rolls to the roll or from the roll to the material to be coated. At this point, the smoothing of the coating film is physically promoted and a smoother coating film can be obtained.

In order to promote smoothing of unevenness on the coating surface when the paint is transferred from the applicator roll to the material to be coated or from the pick-up roll to the applicator roll, the advancing speed or circumferential speed of each should be adjusted to the following ratio. It is preferable to set

That is, when the bar roll is pressed against the surface of the applicator roll, the circumferential speed of the applicator roll is 1.0 to 3 times the advancing speed of the coating system. When the bar roll is pressed against the pick-up roll, the circumferential speed of the pick-up roll is 10 to 3 times the circumferential speed of the applicator roll, and the circumferential speed of the applicator roll is 1.0 times the advancing speed of the material to be coated. A 3x range is recommended.

By making a speed difference in this way, when the paint film with fine irregularities passes through the bar roll and is transferred to the next roll or the material to be coated, the supply speed is faster than the advancing speed of the transferred paint film. By speeding up the process, the unevenness of the paint film is reduced.
Physically smoothing of the coating film is promoted.

At this time, if the supply speed is less than 1.0 times, the coating film will be stretched when it is transferred. On the contrary, the unevenness of the paint film is exacerbated. Moreover, even if it is made three times or more larger, the promoting effect remains unchanged and the negative phase associated with the equipment only becomes larger.

A technology that attempts to control the amount of paint supplied by the shape of the roll is called group roll, and generally involves digging grooves at regular intervals on the surface of a rubber roll. The technique of using this roll as a pick-up roll, an applicator roll, or an intermediate roll located between the pick-up roll and the applicator roll to make the coating film thickness uniform is known.

However, this group roll technology uses grooved group rolls as pick-up rolls in roll coating equipment.
Or applicator roll. Alternatively, it can serve as a substitute for the intermediate roll, and the essence of the present invention is to control the amount of paint supplied by pressing a bar roll from outside the rolls that make up the roll coating equipment. It's different.

Furthermore, when introducing a group roll into the configuration of roll coating equipment, the group roll must be rotated in the correct direction relative to the rolls in contact with it or the material to be coated. This is a system that supplies paint that has passed through the grooves. The aforementioned paint pulling phenomenon occurs due to the forward rotation of the rolls. Since the unevenness of the coating film is much larger than the depth of the grooves, the method of the present invention is also much more effective in smoothing the coating film.

As described above, according to the coating method of the present invention, the accuracy of coating film thickness is far superior to that of the conventional roll coating method, and it is also possible to uniformly coat the paint, which was considered impossible to achieve with the conventional method. Furthermore, the coating can be applied smoothly, and there is less selectivity of the material to be coated than with the conventional bar coater coating method, allowing for a wider control range of coating thickness and less unevenness on the coating surface.

Examples according to the present invention are shown below.

[Brief explanation of drawings]

Figure 1A is a schematic diagram of a conventional roll coating equipment consisting of an ablator roll and a pickup roll. Same B
is a schematic diagram of the roll coating equipment of the first invention of the present invention;
is a schematic diagram of the roll equipment of the second invention of the present invention, FIG. 2A
is an explanatory diagram of the conventional reverse roll coating method using three rolls, B is an explanatory diagram of the method of the present invention in three-roll coating equipment, and Figure 3 is an explanatory diagram of the bar roll in the present invention. FIG. 4 is a partial sectional view of the bar roll. 1...-- Material to be coated. 2...--Abriquet roll, 3...-Pick-up roll, 4...
...Backup o-ru. 5...Paint handle. 6...L, 7...Doctor roll, 8...Doctor blade, 9...Bar roll. 10...Core material, 11...Wire rod, 12...Void. a...Applicator roll surface.

Claims (1)

[Scope of Claims] 1. In coating using reverse roll coating equipment consisting of an applicator roll and a pick-up roll, a bar roll in which a wire rod of a predetermined diameter is tightly wound around a core material is pressed against the applicator roll. A coating method characterized by obtaining a uniform and smooth coating film thickness by controlling the amount of paint that passes between the tar roll and the bar roll. 2. Reverse roll coating equipment consisting of an applicator roll and a pick-up roll (in Koyoro coating).
By tightly winding a wire rod of a predetermined diameter around the core material, the bar roll is pressed against the pick-up roll and the amount of paint passing between the pick-up roll and the bar roll is controlled to create a uniform and smooth surface. A coating method characterized by obtaining a thick coating film. 3. In painting using reverse roll coating equipment consisting of an ablator roll, a pick-up roll, and a doctor roll, a bar roll with a wire rod of a predetermined diameter tightly wound around a core material is pressed against the pick-up roll, and the pick-up roll and the doctor roll are aligned. A coating method characterized by obtaining a uniform and smooth coating film thickness by controlling the amount of paint that passes between the rolls.