JP2000246159A - Roll coater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniformly apply a coating liquid and to excellently control the coating quantity of the coating liquid even in thin film coating by making the roll diameter of a doctor roll smaller than that of a pickup roller. SOLUTION: The lover part of the pickup roll 2 is dipped into the coating liquid 6 in a coating material pan 5, the doctor roll 4 is arranged to be pressed to the pickup roll 2 and the roll diameter of the doctor roll 4 is smaller than that of the pickup roll 2. In the case of applying the coating liquid 6 thin using the roll coater, the coating liquid 6 picked up by the pickup roll 2 is adjusted in the coating quantity by the doctor roll 4. The coating liquid after the adjustment is transferred to an applicator roll 3 and further transferred on a travelling steel plate S. The occurrence of roving pattern in the coating liquid 6 on the pickup roll 2 after the adjustment of the coating quantity is prevented since the roll diameter of the doctor roll 4 is smaller than that of the pickup roll 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a roll coating apparatus,
More particularly, the present invention relates to a roll coating apparatus capable of uniformly applying a coating liquid and having excellent controllability of the coating liquid amount.

[0002]

2. Description of the Related Art Roll coating apparatuses are widely used for continuously applying a coating liquid to a strip such as a steel sheet. As such a roll coating device, for example, Japanese Patent Publication No. Sho 6
There is a roll coating device described in JP-A-55552. As shown in FIG. 3, this roll coating device includes a backup roll 1 around which a band S is wound, a pickup roll 2 whose lower part is immersed in a coating solution 6 in a paint pan 5, and pressing against the pickup roll 2. And an applicator roll 3 that is disposed. Then, the coating liquid 6 of the paint pan 5 adheres to the rotating pickup roll 2, and the applied coating liquid 6 is wound around the backup roll 1 via the applicator roll 3 and is applied to the traveling belt-shaped material S.

[0003]

In the roll coating apparatus shown in FIG. 3, the rotation of the pick-up roll 2 and the applicator roll 3 is a so-called natural rotation, that is, the rolls are rotating in opposite directions, and both rolls are rotated. Both peripheral surfaces are moving in the same direction at the position where the peripheral surfaces meet. Therefore, a roping phenomenon occurs on the exit side of the roll gap where the peripheral surfaces of both rolls are separated. Due to this roping phenomenon, the coating liquid 6 adhering to the surface of the applicator roll 3 becomes uneven in the roll width direction, streak-like unevenness (roping pattern) occurs, and the roping pattern is transferred to the coating surface of the strip S, The amount of coating liquid 6 on the coating surface becomes uneven.

The rotation of the pick-up roll 2 and the applicator roll 3 is a so-called reverse rotation, that is, when the two rolls rotate in the same direction and move in opposite directions at the position where the circumferential surfaces of both rolls meet, roping is performed. It is known that the phenomenon can be prevented. In this case, as shown in FIG. 4, a doctor roll 4 is further provided to adjust the amount of the coating liquid of the pickup roll 2 to be transferred to the applicator roll 3. When the doctor roll 4 and the pickup roll 2 rotate in a natural manner, a roping phenomenon occurs at a position where the peripheral surfaces of both rolls are separated from each other, and the amount of the coating liquid on the coating surface of the strip S applied via the applicator roll 3 becomes uneven. Become.
When the doctor roll 4 and the pickup roll 2 are rotated in reverse, a roping pattern does not occur. However, when the film thickness is small, the roll abrasion increases, and there is a problem in that the coating liquid amount cannot be appropriately adjusted. That is, when the film thickness is small, there is a problem that uniform application of the coating liquid and appropriate adjustment of the coating liquid amount cannot be achieved at the same time.

An object of the present invention is to solve the above problems and to provide a roll coating apparatus which is excellent in uniform coating of a coating liquid and controllability of a coating liquid amount even in a thin film.

[0006]

Means of the present invention for solving the above problems are as follows.

(1) A roll coating apparatus including a pickup roll, an applicator roll, and a doctor roll, wherein the roll diameter of the doctor roll is smaller than the roll diameter of the pickup roll.

(2) The roll coating apparatus according to (1), wherein the rotation directions of the doctor roll and the pickup roll are arranged so as to be able to rotate naturally.

(3) The roll coating apparatus according to (2), wherein the doctor roll is a non-drive roll.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below together with the background to the invention.

According to the conventional knowledge, in the case of natural rotation, a roping pattern occurs on the exit side of the roll gap where the peripheral surface of the roll separates, but in the case of reverse rotation, the exit side of the roll gap where the peripheral surface of the roll separates. No roping pattern occurs. However, in the case of the reverse rotation, when the film thickness of the coating liquid is small, the roll wear is large, so that it is not possible to appropriately adjust the amount of the coating liquid. Therefore, when the thickness of the coating liquid is small, it is impossible to achieve both prevention of the roping pattern and excellent controllability of the coating liquid amount.

The present inventors have found that when the doctor roll and the pick-up roll rotate naturally, if the roll diameters of the two rolls are different, the tendency of the occurrence of the roping pattern changes, and further studied this point. As a result, as shown in FIG. 1, it was found that when the ratio of the roll diameter of the doctor roll to the pickup roll was reduced, the occurrence of the roping pattern was reduced.

The present invention is based on this finding. By making the roll diameter of the doctor roll smaller than the roll diameter of the pickup roll, it is possible to prevent the occurrence of a roping pattern even when the doctor roll and the pickup roll are rotated naturally. Can be reduced. It is more preferable to set the roll diameter of the doctor roll to の or less of the roll diameter of the pickup roll because the roping pattern can be at a level at which there is no practical problem. Also, because it is a natural rotation,
Since there is no problem of abrasion of the doctor roll, the controllability of the coating liquid amount is excellent.

When the roll diameter of the doctor roll is smaller than the roll diameter of the pickup roll, the roping pattern is reduced because the pressure difference between the entrance side and the exit side of the portion where the peripheral surfaces of both rolls meet increases, It is considered that the difference in pressure distribution between the two rolls is reduced, so that the roping phenomenon is less likely to occur on the exit side of the part where the peripheral surfaces of both rolls are separated.

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 2 shows a roll coating apparatus according to the embodiment of the present invention. In FIG. 2, 1 is a backing roll, 2 is a pickup roll, 3 is an applicator roll, 4 is a doctor roll, 5 is a paint pan, and S is a steel plate. The lower part of the pickup roll 2 is immersed in the coating liquid 6 in the paint pan 5. The doctor roll 4 is disposed so as to be able to be pressed against the pickup roll 2, and the doctor roll 4 and the pickup roll 2 are disposed so as to freely rotate naturally and reversely with each other. The roll diameter of the doctor roll 4 is the roll diameter of the pickup roll 2. Smaller diameter.

When the thin film coating liquid 6 is applied using this roll coating apparatus, the rotation directions of the doctor roll 4 and the pickup roll 2 are set to be natural rotation with each other, and the rotation directions of the pickup roll 2 and the applicator roll 3 are set with each other. Reverse rotation, and the rotation directions of the applicator roll 3 and the backing roll 1 around which the steel sheet S is wound are reverse rotation with each other.

The coating liquid 6 pumped by the pickup roll 2
The amount of the coating liquid is adjusted by the doctor roll 4, and the adjusted coating liquid 6 is transferred to the applicator roll 3 and further transferred to the traveling steel sheet S. Since the roll diameter of the doctor roll 4 is smaller than the roll diameter of the pickup roll 2, the coating liquid 6 of the pickup roll after the coating liquid amount is adjusted.
Has no roping pattern. In addition, since the pickup roll 2 and the backup roll 4 rotate naturally with respect to each other, there is no wear on the doctor roll 4 and the controllability of the coating liquid amount is excellent. Since the pick-up roll 2 and the applicator roll 3 are rotated in reverse to each other, the coating liquid 6 transferred to the applicator roll 3 does not have a roping pattern, and the coating thickness of the steel sheet S coated with the coating liquid 6 is made uniform. it can. When the roll diameter of the doctor roll 4 is set to a half or less of the roll diameter of the pickup roll 2, the effect of preventing the occurrence of a roping pattern can be further improved.

To reduce the wear of the doctor roll 4, it is advantageous to make the peripheral speeds of the pickup roll 2 and the doctor roll 4 the same. In this case, when the doctor roll 4 is rotated using the frictional force between the pickup roll 2 and the doctor roll 4 while the doctor roll is not driven, the above-described effect can be obtained with a simple device.

The coating apparatus of the present invention has a wet film thickness of 10
It is suitable when applying a coating liquid of μm or less.

When it is necessary to apply the thick film coating liquid 6, a doctor roll is provided so as to be drivable, and both rolls are reversely rotated to perform the coating operation. Since there is no occurrence of a roping pattern and there is no problem of abrasion of the doctor roll 4, there is no problem in controllability of the coating liquid amount.

[0021]

According to the present invention, even when a coating liquid of a thin film is applied, it is possible to prevent the occurrence of a roping pattern which is likely to occur in a roll coating apparatus, so that the coating liquid can be uniformly applied. Excellent control of liquid volume.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between a doctor roll diameter and a roping pattern.

FIG. 2 is a diagram showing a main part of the roll coating apparatus according to the embodiment of the present invention.

FIG. 3 is a diagram showing a main part of a conventional roll coating apparatus.

FIG. 4 is a diagram showing a main part of another conventional roll coating apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Backup roll 2 Pickup roll 3 Applicator roll 4 Doctor roll 5 Paint pan 6 Coating liquid S Strip (steel plate)

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Munehiro Ishioka, 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Inside Nihon Kokan Co., Ltd. (72) Yasuto Morikawa 1-2-1, Marunouchi, Chiyoda-ku, Tokyo No. Nippon Kokan Co., Ltd. F-term (reference) 4F040 AA22 AC01 BA23 CB05 CB36 CB37

Claims (3)

[Claims] 1. A roll coating apparatus comprising a pickup roll, an applicator roll, and a doctor roll, wherein the roll diameter of the doctor roll is smaller than the roll diameter of the pickup roll. 2. The roll coating apparatus according to claim 1, wherein the rotation directions of the doctor roll and the pickup roll are arranged so as to be able to rotate naturally. 3. The roll coating apparatus according to claim 2, wherein the doctor roll is a non-drive roll.