JPH04227884A - Coating method and equipment for sheet materials - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is a method for sealing fluid coating materials.
The present invention relates to a technique for coating a sheet material, and more specifically to a roll coating method and apparatus used in the above coating technique.

0002

[Prior art] The roll coating equipment currently in use is
It generally includes an applicator roll onto the surface of which a flowable coating composition is metered to form a film. The sheet material coated with the coating composition contacts the roll under tension, thereby transferring the coating composition from the roll to the sheet. A device of this type is described in British Patent No. 1,151,690.

0003

[Problems to be Solved by the Invention] However, the above-mentioned roll coating device cannot coat low-viscosity coating compositions with
m/min or higher, and typically about 16-2 m/min.
0g/m2 coating amount (wet basis), dry basis 4~
When coating at a coating weight of 5 g/m2, it is sufficient to ensure complete transfer of the coated film onto the sheet (i.e. to avoid skip coating, which results in uncoated areas). Because of the need to apply a large amount of tension to the sheet, the sheet often broke. When this situation occurs, the coating equipment must be stopped or the operating speed must be reduced so that the sheet can be re-inserted into the dryer, resulting in a decrease in productivity. .

It is an object of the present invention to provide a method and apparatus for effectively transferring a coating composition to a sheet even under substantially reduced tension, thereby substantially alleviating the above-mentioned problems. It's about trying.

[0005]

[Means for Solving the Problems] The present invention provides a method for coating a sheet material with a low viscosity coating composition in a low coating amount and at a high speed. The endless transfer surface is moved along the convex track of the coating station while the flowable film of the coating mixture applied to the sheet material is moved in the same direction as the direction of movement of the endless transfer surface. The thickness of the film formed on the transfer surface and the distance between the endless guide surface disposed at the coating station and the transfer surface are determined in accordance with the thickness of the film formed on the transfer surface and the transfer surface. - keeping the thickness of the material itself substantially equal to the combined thickness;
and passing the sheet material around said endless guide surface.

The present invention also provides an apparatus for applying a low viscosity coating composition to a sheet material at a low coating weight and at a high speed, the apparatus comprising a rotatable Application
a tar roll, means for forming a film of the coating mixture on the applicator roll, and guiding the sheet material in the same direction as the direction of rotation of the applicator roll. The distance between the applicator roll and the guide surface is determined based on the thickness of the film of the coating mixture formed on the applicator roll and the thickness of the film of the coating mixture formed on the applicator roll. - means for maintaining the combined thickness of the sheet material substantially equal;

[0007] In a typical design, the applicator roller
The distance between the cable and the surface of the sheet material is between 3,000 and 4,000 mm.
When coating a sheet with a thickness of 1/000th inch (75 to 100 microns), a thickness of 75 to 150 microns, and a basis weight of 50 g, the distance between the applicator roll and the guide surface is 150 ~200 microns.

[0008] The applicator roll of the present invention can be comprised of one of the rolls in a three-roll coating system, in which case the other two rolls are The two are a pick-up roll that transfers the coating mixture from the storage tank to the applicator roll, and a metering roll. Such a coating system is described in British Patent No. 1,151,690.
listed in the number.

The guide surface may be provided by a holddown or presenter roll driven at substantially the same surface speed as the sheet material. When applying a backcoat to a sheet that has already been coated with microcapsules, when using a presser roll or a presenter roll, the backcoat can be suitably applied without damaging the microcapsules. For this purpose, the surface of the roll may be provided with a surface coating having a certain hardness, typically a shore hardness of about 35 DEG.

[0010] In order to efficiently meter the coating amount so that the coating amount on the sheet is maintained at a low level, the applicator
The rolls are driven to rotate at a surface velocity that is less than the linear velocity of the sheet material.

The invention will now be described in more detail with reference to the accompanying drawings. FIG. 1 shows a known coating device, which comprises an applicator roll (1), a pick-up roll (2) with attached coating mixture pan (3), and a roll. (1) a metering drawer fitted with a pan (5) for receiving excess coating mixture stripped from the
(4). For example, the sheet material (6), which is paper, is rolled (
1) It is sent while being in contact with this so as to more or less envelop it.

The device operates in forward mode. In Figure 1, the applicator roll (1) rotates in the same direction as the sheet material. The pickup roll (2) can rotate in any direction, but the metering roll
The roll (4) rotates in the same direction as the applicator roll (1).

When coating is performed using an apparatus configured as shown in FIG. 1, it is necessary to use a sheet (
6) Sufficient tension must be applied to. This tension is applied by creating a difference in the rotational speed of the two guide rolls (7), which causes the sheet (6) to
is pressed downward against the roll (1) as shown by the arrow (8). This tension often breaks the paper, resulting in the need to reinsert the paper into the dryer, which necessitates stopping or slowing down the coating equipment and reducing productivity. There is also a disadvantage in terms of the occurrence of

FIG. 2 shows a coating device similar to the three-roll coating device explained in FIG. 1, and the same parts are designated by the same numbers. According to what is proposed in the invention, the sheet material is provided with a presser roll or a presenter roll (
10). In this case, no nip is formed between the roll (10) and the applicator roll (1), and as detailed in FIG. - Maintains an adjustable distance from the roll (1). The configuration shown in Figure 2 is suitable for coating operations carried out at high speeds of approximately 750 m/min or higher, in which downward pressure as shown in Figure 1 is applied to the sheet (6). has been done.

FIG. 3 is an enlarged view of a portion of FIG. 2 with the applicator roll operating in advanced mode. As shown in the figure, roll (1) and roll (10) indicated by arrow A
) is determined by the thickness B of the paper sheet (6) and the roll (1
) is approximately equal to the sum of the thickness C of the coating mixture applied. Typically, paper (6) and applicator
When coating paper with a thickness of 75 to 100 microns and a basis weight of 50 g, the distance C with the roll (1) is approximately 300 microns.
0 to 4000th of an inch (75 to 100 microns)
The distance between roll (1) and roll (10) is about 150 to 200 microns. It is important that the roll (10) presents the sheet material at the location of the applicator roll (1) without applying pressure.

The applicator roll rotates at a surface speed of about 1/6 of the linear speed of the sheet (6), thereby
Effective stripping of the coating mixture is achieved, which is necessary to maintain a low level of coverage. That is, the thickness of the coating layer on the sheet is less than the distance C. The coating mixture is of low viscosity, with typical coating weights of about 16-3 on a wet basis.
0 g/m2, which is equal to 4-5 g/m2 on a dry basis of the coated sheet. To form a layer of coating mixture on the applicator roll by stripping as described above, approximately 6 times the desired coating weight of the coating mixture is applied to the applicator roll. - It is necessary to apply it to the surface. In other words,
When the coating amount is 16g/m2, approximately 96g/m2
(which corresponds to a thickness of about 100 microns) of the coating mixture must be applied to the applicator roll.

4 to 6 show the construction of a roll coating apparatus according to the present invention. In the drawing, the device (20) is shown on a stand (
23) and is composed of a frame (21) assembled with two side members (22) separated by a column (24). As shown in FIG. 5, each side member (22) has an upper strut (
26) and two vertical members (25) separated by an intermediate strut (27). The shaft (28) of the applicator roll (29) has both ends mounted in bearings (30) in the strut (27).
It is pivoted inside.

A pick-up roll (31) is placed below the applicator roll (29) to pick up the coating mixture from the pan (32).
), whereby rotation of the two rolls transfers a film of the coating mixture onto the applicator roll (29). Metering roll (
33) is also rotatably installed within the drain pan (34),
As the roll (29) and roll (33) rotate, the roll
At step (31), the previously applied coating mixture film is stripped off. A roll coating system as shown in FIG. 5 is known as described above, and is described in British Patent No.
No. 690.

[0019] The holding roll, ie, the presenter roll (37), is located directly above the applicator roll (29), and its shaft (38) is rotatable by a bearing part (39). It is pivoted on. As shown in detail in FIG. 5, the bearing portion (39) includes a slider (40) that can move up and down on a slideway (41) formed on the inner surface of the vertical member (25).

[0020] The spindle (
42) extends upwardly through the strut (26) and constitutes an extension of the piston rod of the aerodynamic piston-cylinder arrangement (43). Piston-cylinder device (
43) is used to position the presser roll (37) approximately vertically with respect to the applicator roll (29).

Each bearing portion (39) has an independent threaded pin (44) whose lower end engages a capped nut (45). The cap (46) of the nut (45) can be engaged with the anvil (47) of the height adjustment device (48) by rotation of the nut (45).

Details of the height adjustment device (48) are shown in FIG. 6, and are of the type described in British Patent Nos. 1,429,727 and 1,561,984. As shown in FIG. 6, the height adjustment device (48) is
A roller (51) pivotally supported by an anvil (47) and a trunnion (53) provided on the actuator body (54).
) is movable horizontally between the reaction roller (52) which is pivotally supported by a spindle (49) having a wedge (49) at its tip.
50). This spindle (50) has a hole (
a series of pneumatic pistons (55) pressurizable from
). This device has each piston (5
5) allows the spindle (50) to move in different increments when pressurized. Therefore, the anvil (
47) is caused by the vertical movement of rollers (51) and (52).
) is caused by the wedge (49) moving horizontally between the two. By extending the slope of the wedge (49), the anvil (4
7) can be moved extremely small, typically on the order of 50 microns.

When starting the device, the piston-cylinder device (43) and the nut (45) are placed in such a way that the surface of the presser roll (37) is just in contact with the applicator roll (29). Adjust. In other words, zero setting is performed. Then the pneumatic piston (
By selectively pressurizing the anvil (55), the anvil (55) resists the load received from the piston-cylinder arrangement (43).
47) and adjust the spacing so that the thickness is equal to the sum of the thickness of the coating layer transferred from the applicator roll to the paper sheet as a film and the thickness of the paper sheet itself. do. Therefore, it can be seen that the coating layer is transferred to the sheet without being subjected to nip pressure.

[Brief explanation of the drawing]

[Fig. 1] Side view of a known coating device

[Fig. 2] Side view of the coating device of the present invention

[Fig. 3] Partially enlarged side view of the device shown in Fig. 2.

[Fig. 4] Front view of the coating device of the present invention

[Figure 5] Side view seen from line V-V in Figure 4

[Fig. 6] Cross-sectional view taken along the VI-VI line in Fig. 4

[Explanation of numbers]

Claims (10)

[Claims] 1. A flowable film of coating mixture applied to a sheet material is controlled by moving the endless transfer surface along a convex track of a coating station. The film formed on the transfer surface is formed on the transfer surface in the same direction as the transfer surface, and the distance between the transfer surface and the endless guide surface disposed on the coating station is passing the sheet material around said endless guide surface while maintaining the thickness of the sheet material itself substantially equal to the combined thickness of the sheet material. A method of applying a mixture to sheet material at high speed and with low coverage. 2. The method of claim 1, wherein said guide surface is provided by a holddown roll rotating at a surface speed substantially the same as the speed of movement of the sheet material. 3. The endless transfer surface is provided by an applicator roll rotating at a surface speed slower than the speed of movement of the sheet material so as to strip the applied coating mixture. The method described in 1. 4. The method according to claim 1, wherein the coating is applied as a back coating to a sheet material whose surface has been previously coated with microcapsules. 5. A rotatable applicator roll, means for forming a film of the coating mixture on the applicator roll, and a means for applying the sheet material to the applicator roll. means constituting an endless guide surface for guiding the applicator roll in the same direction as the direction of rotation; Apparatus for applying a low viscosity coating mixture to a sheet material at a high rate and at a low coating weight, the apparatus comprising means for maintaining the total thickness of the sheet material substantially equal to the total thickness of the sheet material. Claim 6: A three-roll coating system comprising a pick-up roll for taking out the coating mixture from a storage tank and a metering roll, the remaining one being an applicator roll. 6. The apparatus according to claim 5. 7. The apparatus according to claim 5, wherein the guide surface is provided by a rotatable presser roll or a presenter roll. [Claim 8] The presser roll or the presenter roll is sealed.
8. The apparatus of claim 7, wherein the apparatus is driven at a surface speed that is substantially the same as the speed of movement of the sheet material. 9. Apparatus according to claim 5, wherein the applicator roll is driven at a surface speed lower than the speed of movement of the sheet material. 10. Apparatus according to claim 7, wherein the presser roll or presenter roll is provided with a surface coating having a shore hardness of approximately 35°.