JPH05138104A - Coating applicator - Google Patents

Abstract

PURPOSE:To establish the coating applying means which can assure a uniform coating film thickness even if there are thickness fluctuations in a band-shaped material as a material to be coated and rotational run-out of a backing roll at the time of continuously applying a coating liquid to the traveling band- shaped material. CONSTITUTION:This coating applicator continuously applies the coating liquid 11 on the band-shaped material 5 transported in contact with the outer peripheral surface of the rotating back roll 4 while the coating liquid is supplied from an opened slit 6 to the front end of a die 7 installed apart a slight spacing from the band-shaped material. At least the front end of the due 7 of the applicator is constituted of an elastic material 10. The front end of the die is formed to a shape with which the spacing between the band-shaped material 5 and the die 5 decreases gradually down to the progressing direction of the band- shaped material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for uniformly and continuously applying a coating solution on the surface of a running belt-shaped material.

[0002]

2. Description of the Related Art Conventionally, coating liquids such as paints, inks, magnetic materials, adhesives, and functional chemicals have been applied to the surface of continuously running strip-shaped materials (steel strips, various films, paper tapes, etc.). In this case, the "roll coating method" is generally adopted.

FIG. 5 is a conceptual diagram for explaining a typical example of the roll coating method. A pickup roll 1 and an applicator roll 2 are used, and a coating solution in a paint pan 3 is backed up. The state of transferring and applying to a coating object (strip material) 5 traveling along the rule 4 is shown.

However, in the case of the roll coating method, the transfer of the coating solution between the rolls or between the rolls and the article to be coated tends to be non-uniform, resulting in a streak pattern on the coating film. It has been pointed out that the problem is that it is likely to occur. When applied to a steel plate or the like, an applicator roll covered with an elastic body such as rubber is used. Therefore, the applicator roll is used.
The surface of the steel plate that contacts the edge of the
There are also problems that it is necessary to change the roll frequently, and that the change of the plate width of the object to be coated is limited to the case of "from wide width to narrow width". Further, in the case of the roll coating method, since only a coating solution having a relatively low viscosity can be applied, a large amount of diluting solution such as an organic solvent must be used,
This has been one of the causes of lowering the efficiency and cost of the baking and drying furnace.

Therefore, in order to make up for the drawbacks of the roll coating method, a die coating method has been devised in which the coating solution is caused to flow through a narrow slit formed in the die and is applied. As shown in FIG. 6, this die-coating method has a slit 6 for supplying a coating liquid by providing a minute gap with respect to a belt-shaped material 5 which is conveyed in contact with the outer peripheral surface of the backing roll 4. A means for coating a strip-shaped material 5 by supplying a coating liquid while controlling the flow rate from the slit part of the die 7 by disposing a die coating device equipped with the die 7 ″ is used in this case. It is a very important point to obtain a uniform coating film by accurately controlling the interval of the minute gap between the first and second electrodes. However, it is very difficult to keep the interval properly when there is a fluctuation in the thickness of the strip-shaped material or when the backing roll has a fluctuation in rotation, which is a great obstacle in obtaining a uniform coating film. There is.

Therefore, as shown in FIG. 7, the die 7 is movably held in the direction of the strip-shaped material, and the die 7 is
Is constantly pressed by the force P ₂ so as to balance with the pressure generated by the shear flow of the coating liquid discharged between this and the strip-shaped material 5, thereby making it possible to follow the position change of the strip-shaped material surface and move the die and the strip-shaped material. There has been proposed a method of controlling so that the minute gap between the two is always constant, that is, the coating liquid film thickness is uniform (Japanese Patent Laid-Open No. 3-38271).

Separately from this, as shown in FIG. 8, between the die 7 and the band-shaped material 5, the above-mentioned "application covered with an elastic body" which is often used in conventional roll coater equipment. There is also a proposal to realize accurate coating by interposing a tarpaulin 9 "and pressing it against the surface of the band-shaped material to absorb the variation in the thickness of the band-shaped material (Actual Kaihei 2- 17259). In this case, since the coating liquid is supplied from the die 7 to the high-rigidity transfer roll 8, the supply unevenness does not occur.

However, although the means shown in FIG. 7 (means relating to Japanese Patent Laid-Open No. 3-38271) is effective against the thickness variation of the strip-shaped material 5 in the traveling direction as shown in FIG. It was ineffective against the thickness variation in the width direction as shown in Fig. 10.

On the other hand, the means shown in FIG.
(Means related to No. 7259), as shown in FIG.
Since an elastic roll is used as the applicator roll 9, a phenomenon occurs in which the coating liquid leaks to the side opposite to the coating direction, which may adversely affect the coating film thickness. In order to reduce this "leakage", it is necessary to strongly press the applicator roll 9 (elastic roll) against the strip material 5,
In this case, the coating liquid film thickness between the strip-shaped material 5 and the applicator roll 9 (elastic roll) becomes thin, resulting in poor lubrication, and the elastic roll wears in a short time. −
The same problem as in the rucoating method occurred. Therefore, in order to suppress the abrasion of the elastic roll, it is necessary to allow the above-mentioned "leakage of the coating liquid" to some extent, and thus it becomes difficult to control the coating film thickness with high accuracy. It was difficult.

From the above, the object of the present invention is to continuously coat a running strip-shaped material with a coating liquid,
The object was to establish a coating means capable of ensuring a uniform coating film thickness even when the thickness of the strip-shaped material to be coated varies or the backing roll rotates.

[0011]

Means for Solving the Problems As a result of intensive studies to achieve the above-mentioned object, the present inventor has found that "when a coating solution is continuously applied to a strip-shaped material by a die coating method, Even when there is a thickness variation as shown in FIG. 9 or FIG. 10 in the work-like strip material, or when there is rotational runout in the backing roll (which results in the same variation as in FIG. 9), If the die material is made elastic and the shape of this die is devised to effectively utilize the “pressure generated by the shear flow of the coating liquid discharged between the die and the strip material”, the fluctuation of the strip material surface becomes elastic. It is absorbed by the die made by the body and the gap between the die and the strip-shaped material surface can be kept constant, which makes it possible to maintain a uniform coating film thickness. "

The present invention has been made on the basis of the above findings and the like. "As shown in FIG. 1, the strip-shaped material 5 which is conveyed in contact with the outer peripheral surface of the rotating backing roll 4,
In a coating apparatus for continuously coating while supplying a coating liquid 11 from a slit 6 opened at the tip of a die 7 installed with a minute gap therebetween, at least the tip of the die 7 is composed of an elastic body 10, and The shape of the tip of the die is a shape in which the distance between the band-shaped material 5 and the die 7 becomes gradually smaller as it goes down in the traveling direction of the band-shaped material. "

[0013]

As described above, at least the tip of the die is made of an elastic body, and the shape of the die is such that the gap between the die and the article to be coated (strip-shaped material) becomes gradually narrower in the direction of travel. The effective fluid pressure is generated in the gap due to the shear flow of the coating liquid discharged from the die, and the elastic body portion of the die is deformed so as to balance with this pressure.

When the coating operation is advanced in this state, when the gap between the band-shaped material and the die becomes narrow, the generated pressure increases to try to push the gap wide, and conversely, when the gap becomes wide. The generated pressure becomes low and the gap tends to become small due to the restoring force of the elastic body. Therefore, for example, even if the thickness of the strip-shaped material fluctuates not only in the traveling direction but also in the width direction, the gap between the strip-shaped material and the die can be kept constant in the traveling direction and the width direction.

That is, according to the lubrication theory of fluid mechanics, FIG.
The wedge-shaped gap shown in Fig.
When moved by, the fluid attached to the lower surface is dragged and drawn into the wedge. As a result, the pressure inside the wedge increases and the upper surface is pushed up. The force P generated at this time is Becomes Where μ is the viscosity of the fluid.

When h ₁ / h ₂ that maximizes the load P is obtained, "h ₁ / h ₂ = 2.2" is obtained, and the load P at that time is given by the following equation.

The present invention skillfully utilizes this "pressure generation principle". At least the tip of the die is made of an elastic material, and a "wedge-shaped gap" is formed between the die tip and the strip material surface. When the die is arranged so that the die is formed and die coating is performed, a fluid pressure by the coating liquid (fluid) discharged from the die acts on the slope (die tip surface) of the "wedge-shaped gap", The coating is performed with the die deformed as shown by. Then, as described above, for example, when the thickness of the strip-shaped material 5 changes in the traveling direction or the width direction and the gap between the strip-shaped material 5 and the die 7 changes, the fluid pressure changes in accordance with the change ( When the gap becomes narrower, the pressure becomes higher, and when the gap becomes wider, the pressure becomes lower. Accordingly, the elastic die changes the degree of deformation, and as a result, the distance between the strip-shaped material 5 and the die 7 is kept constant. Become.

In the apparatus according to the present invention, the gap between the band-shaped material and the die can be maintained at a constant distance by the extremely simple apparatus configuration as described above, and the coating with a uniform film thickness can be stably performed. Can last.

At this time, in order to efficiently generate the fluid pressure and to easily deform the die of the elastic body,
It is desirable to consider so that the shape of the "wedge-shaped gap" formed between the die tip surface and the strip-shaped material surface is "h ₁ / h ₂ = about 2.2" as shown in FIG.

The effects of the present invention will be described more specifically below with reference to examples.

[Example] As shown in FIG. 4, "a tip portion is composed of an elastic body 10 and the distance from the object to be coated (steel plate) gradually decreases as it goes down in the traveling direction of the object to be coated (steel plate) 5. Using a die coating apparatus equipped with a die having a smaller shape, a coating test of paint on a steel plate was conducted under the following conditions.

A) Equipment dimensions: L ₁ ... 10.0 mm, L ₂ ... 10.0 mm, L ₃ ... 0.15 mm, L ₄ ... 0.3 mm, L ₅ ... 35.0 mm. b) width of steel plate: 1100 mm, c) thickness of steel plate: 1.5 mm, d) flatness of steel plate (difference between the most protruding part and the lowest part): 0.01 and 0.1, e) steel plate conveying speed: 60 m / min, f) Painted steel plate length: 10 m, g) Paint viscosity: 3.5 P, h) Paint supply flow rate: 5.28 liters / min, i) JIS hardness of the elastic body constituting the die: 53.

The following results were obtained. [When the flatness of the steel plate is 0.01] Average coating film thickness: 80.1 μm, film thickness deviation (difference between the thickest film thickness and the thinnest film thickness):
0.2 μm. [When the flatness of the steel plate is 0.1] Average coating film thickness: 79.8 μm, film thickness deviation (difference between thickest film thickness and thinnest film thickness):
0.3 μm.

As is clear from the above-mentioned coating results, when the coating apparatus according to the present invention is used, even if the flatness of the strip-shaped material to be coated is poor, high-precision coating can be performed without impairing the uniformity of the coating film thickness. It can be seen that can be carried out stably.

[0024]

[Summary of Effects] As described above, according to the present invention, the thickness variation of the band-shaped material (material to be coated) and the backing roll can be reduced.
It is possible to provide a die coating device with a simple structure that can coat with a uniform film thickness while suppressing the gap variation between the band-shaped material and the die even when there is run-out of the roll, and high precision coating liquid coating at low cost. It has an industrially useful effect such that it can be performed.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a coating apparatus according to the present invention.

FIG. 2 is an explanatory diagram relating to a generated pressure of a fluid drawn into a wedge-shaped gap.

FIG. 3 is an explanatory diagram related to the operation of the coating apparatus of the present invention.

FIG. 4 is an explanatory diagram related to a main part of a die used in an example.

FIG. 5 is an explanatory view of a conventional roll coating method.

FIG. 6 is a schematic explanatory diagram of a dico-tig method.

FIG. 7 is a schematic explanatory diagram of a conventional improved die-coating method.

FIG. 8 is a schematic explanatory diagram relating to another example of a conventional improved die-coating method.

FIG. 9 is an explanatory diagram of a thickness variation state in a traveling direction of a strip-shaped material that is an object to be coated.

FIG. 10 is an explanatory diagram of a variation in thickness in the width direction of a strip-shaped material that is an object to be coated.

FIG. 11 is an explanatory diagram related to a problem of the conventional improved die-coating method shown in FIG.

[Explanation of symbols]

 1 Pick-up roll 2 Applicator roll 3 Paint pan 4 Backing roll 5 Work piece (strip material) 6 Slit 7 Die 8 Transfer roll 9 Applicator roll 10 Elastic body 11 Coating liquid

Claims (1)

[Claims] 1. A continuous coating of a belt-shaped material, which is conveyed in contact with the outer peripheral surface of a rotating backing roll, while supplying a coating liquid from a slit opened at the tip of a die installed with a minute gap therebetween. In the coating device, at least the tip portion of the die is made of an elastic body, and the shape of the die tip portion is such that the distance between the band-shaped material and the die becomes gradually smaller as it goes down in the traveling direction of the band-shaped material. A coating device characterized by the above.