JPH0615213A - Coating device - Google Patents

Abstract

PURPOSE:To prevent skipping or coat unevenness due to an imperfect migration of coating liquid from occurring by providing an air shutoff device which reduces or shuts off the air entrained by a web on an extrusion die as an after- measuring type liquid feeder. CONSTITUTION:First, a coating liquid is applied to a web 4 which continuously runs in close contact with a backup roll 3 from an extrusion die 5, and the amount of the applied liquid is measured using a measurement head 2 to form a coated layer. The coating device of this design is equipped with an air shutoff device 1 which shuts off the air entrained by the web 4, in the upstream side of the extrusion die 5. The air shutoff device 1 is equipped with exhaust pipes provided in a width direction for reducing suction irregularities in the width direction. In addition, the air shutoff device 1 is fixed so that gap between the device 1 and the web 4 is narrow enough to shut off the air stream entrained by the web 4. Thus, it is possible to eliminate the formation of an uncoated part due to skipping and thereby ensure a rapid coating operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating apparatus used for manufacturing pigment coated paper, thermal recording paper, pressure sensitive recording paper, etc.
In particular, after supplying the excess coating liquid to the continuous support,
The present invention relates to a post-weighing type coating device that weighs with a weighing device such as a blade, an air knife, and a rod bar.

[0002]

2. Description of the Related Art There are various types of coating devices for coating a continuous support, but they are divided into a pre-weighing type and a post-weighing type coating device depending on the difference in the weighing system. As pre-weighing type coating devices, there are slide coaters, curtain coaters, die coaters, lip coaters, transfer roll coaters, etc., and those with a structure in which a specified amount of coating liquid is measured by the coating head and applied to the support It is widely used in fields requiring precise coating such as multi-layer coating at a relatively low speed, such as pointers, photographic emulsions and magnetic materials.

On the other hand, post-weighing type coating devices include a blade coater, an air knife coater, a rod bar coater and the like. After supplying an excessive amount of coating liquid to a support,
This refers to a structure in which excess liquid is scraped off by a measuring unit, and is widely used in fields where high speed and high productivity are important, such as pigment-coated paper, heat-sensitive recording paper, and pressure-sensitive recording paper.

The post-metering type coating apparatus is characterized in that the coating liquid supply section and the metering section are separated, and the name of the coater often refers to the shape of the metering section. Here, there are various methods of supplying the coating liquid, but as a typical method, a method of supplying by a roll and an extrusion of supplying a liquid flow having a velocity component in one direction passing through a narrow slit to the web are representative. There is a die supply system. These supply methods can be arbitrarily used as a supply device in various post-metering type coating devices.

There are various types of coating liquid supply devices, one using a roll and the other using an extrusion die, and each of them has its own characteristics. When the rouge die is used in a coating device having a wide coating width, it is easier to uniformly adjust the supply amount in the width direction. In the field of the paper industry with a large production amount, there is a tendency to select a coating device with a wide coating width as a means for improving productivity, and when it is necessary to adjust the supply amount of the coating liquid in the width direction. In many cases, an extrusion die is selected as the supply device.

In the extrusion die, the amount of adhesion in the width direction can be easily made uniform by adjusting the opening of the slit through which the liquid passes in the width direction, and the coating width can be widened. However, it is not always a device that can sufficiently cope with the increase in coating speed taken as another means for improving productivity. In other words, as the coating speed increases, the amount of air that accompanies the web increases, and air penetrates between the web layer and the liquid supply layer in the liquid supply unit, preventing the web from getting wet (hereinafter referred to as skipping). Is more likely to occur. As means for suppressing this, a means for increasing the flow rate to increase the liquid flow rate and a means for narrowing the distance between the web and the lip tip of the die are taken, but the liquid flow rate is increased and supplied to the web. When the film thickness of the liquid increases, the amount of liquid scraped off at the time of measurement increases, so that a prescribed coating amount cannot be obtained, or problems such as uneven coating occur. If the distance between the web and the lip of the die is too small, another obstacle such as contact between the web and the lip may occur at the seam of the web.

Therefore, it is the current situation that the extrusion die which has been used as a post-measurement type liquid supply device up to now cannot sufficiently cope with the increase in coating speed.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is that when high speed coating is carried out, air entrained in the web remains between the coating liquid and the web, and the transfer of the coating liquid is incomplete. This is to suppress the occurrence of skipping and uneven coating caused by the phenomenon.

[0009]

According to the present invention, a coating liquid is supplied from an extrusion die 5 to a web 4 that continuously travels in contact with a backup roll 3, and a measuring head 2 measures the coating liquid. When the coating liquid is supplied to the web 4 by the extrusion die 5 in the coating device for forming the coating layer, the air that blocks the air entrained in the web 4 upstream of the extrusion die 5 is cut off. By using the coating device equipped with the blocking device 1, the air that enters between the web 4 and the coating liquid at the time of supplying the coating liquid is suppressed, and a high-speed coating operation is achieved without forming an uncoated portion by skipping. can do.

There are various types of measuring heads, but a blade, an air knife, a rod bar, etc. are typical. The air blocking device attached to the coating device according to the present invention exhibits good effects regardless of the type of the measuring head. In other words, skipping, which is suppressed by the air blocking device, is a coating defect that occurs regardless of the type of the measuring head, because it is an uncoated portion that occurs when the coating liquid is supplied. In addition, since it is not necessary to increase the liquid supply amount more than necessary by installing an air shutoff device, the hydrodynamic force applied to the measuring head by the supply liquid during measurement is reduced, and various coating defects are avoided. can do. Specifically showing such defects, streaks occurring in the blade coating method and rod coating method, coating unevenness called scratches and burring,
In the air knife coating method, the occurrence of coating unevenness called an air knife pattern can be mentioned.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, but it goes without saying that the present invention is not limited to these embodiments and various modifications can be made.

FIG. 1 is a schematic side view of a coating apparatus showing an embodiment of the present invention. The air entrained in the web 4 that is in continuous contact with the backup roll 3 is shut off by the air shutoff device 1, then the coating liquid is supplied from the extrusion die 5 to the web 4, and further, by the measuring head 2.
The coating liquid is measured to form a coating layer. Here, the gap between the web 4 and the air blocking device 1 needs to be fixed with a gap small enough to block the flow of air entrained in the web 4, and the range of the gap is preferably 10 m.
m or less. Further, if there is no problem in terms of quality or operation of the coated object, it is possible to bring the air blocking device 1 into contact with the web 4. Further, if necessary, the inside of the air cutoff device is steadily decompressed and exhausted, and the direction of the flow of air entrained in the web 4 is changed to a direction different from the traveling direction of the web 4, and as a result, It is also possible to take a method of reducing the amount of entrained air. In such a case, in the air cutoff device 1, a surface facing the backup roll 3,
That is, it is preferable that the surface for sucking air is a perforated plate or a wire mesh. This is to reduce suction unevenness particularly in the width direction by increasing the flow resistance of the suction surface.

FIG. 2 is a schematic front view of the coating apparatus showing the embodiment of the present invention. The air blocking device 1 is
A plurality of exhaust pipes are provided in order to reduce suction unevenness in the width direction.

FIG. 3 is a schematic side view of a coating apparatus showing another embodiment of the present invention. The air entrained in the web 4 that continuously travels in contact with the backup roll 3 is blocked by ejecting air from the air doctor 6 toward the upstream side, and then the coating liquid is applied to the web 4 from the extrusion die 5. After being supplied, the coating liquid is further measured by the measuring head 2 to form a coating layer.

FIGS. 4 and 5 show a coating portion where the coating liquid 6 flowing out from the extrusion die 5 is transferred to the web 4. FIG. 4 shows an example of the coating unit when coating is performed without using the air cutoff device. Coating liquid 6
Immediately after flowing out of the extrusion die 5, the particles do not transfer to the web 4, but transfer occurs slightly downstream. in this case,
Unsteadily, air remains between the coating liquid 6 and the web 4,
Causes a skipping phenomenon.

In FIG. 5, except that the air shutoff device 1 is used,
An example in which coating is performed under the same conditions as the example in FIG. 4 is shown. As compared with FIG. 4, the liquid returns to the upstream side, the coating liquid 6 completely adheres to the web 4, and the air does not remain between the coating liquid 6 and the web 3.

From this fact, it is possible to perform the coating operation by adding an air shutoff device to the extrusion die without increasing the supply amount of the coating liquid and skipping or other obstacles even during high-speed coating operation. I understand.

[0018]

The extruding die used as a post-weighing type liquid supplying device is provided with an air blocking device for reducing or blocking air entrained in the web, so that a coating defect does not occur at a high speed and a stable state is obtained. The coating operation can be carried out.

[0019]

EXAMPLES Examples will be given below in order to further clarify the effects of the present invention. In the examples, all parts are parts by weight, the concentration is% by weight of the solid content, and the coating amount is the coating amount after drying, unless otherwise specified.

Example 1 As a liquid supply device, a blade coating device using an extrusion die equipped with an air blocking device shown in FIG. 1 was used, and a dry coating amount of 60 g / m ² was applied to a high-quality paper. 12 g
/ M ² so that the solid content concentration of the following formulation is 61%
The coating liquid of was coated at a coating speed of 1200 m / min. Here, the amount of coating liquid supplied from the extrusion die is 190 Liters per 1 m of coating width.
It was / min.

<Undercoating liquid> Commercially available heavy calcium carbonate (Carbital 90) 20 parts Commercially available secondary kaolin (Caobrite) 40 parts Commercially available primary kaolin (Ultra White 90) 40 parts Commercially available polyacrylic acid-based dispersant 0.2 Part Commercially available phosphate esterified starch 3 parts Commercially available styrene / butadiene latex 13 parts Sodium hydroxide 0.1 part

Example 2 The same method as in Example 1 was applied except that the coating speed was 1500 m / min, and the amount of the coating liquid supplied from the extrusion die was 220 Liters / min per 1 m of coating width. , Coating was performed.

Example 3 A blade coating device using an extrusion die equipped with an air blocking device shown in FIG. 3 as a liquid supply device was used, and a dry coating amount of 12 g was applied to a high-quality paper having a basis weight of 60 g / m ^2.
/ M ² so that the solid content concentration of the following formulation is 61%
The coating liquid of was applied at a coating speed of 1500 m / min. Here, the amount of the coating liquid supplied from the extrusion die is 220 Liters per 1 m of coating width.
It was / min.

Example 4 Using an air knife coating device using an extrusion die equipped with the air blocking device shown in FIG. 1 as a liquid supply device, a dry paper coating amount of 12 g was applied to a high-quality paper having a basis weight of 60 g / m ^2.
/ M ² , a coating solution having the same composition as the solution used in Example 1 and a solid content concentration of 47% was prepared at a coating speed of 400 m / m 2.
Application was performed at min. Here, the supply amount of the coating liquid supplied from the extrusion die was 58 Liters / min per 1 m of coating width.

Comparative Example 1 Coating was carried out in the same manner as in Example 1 except that the air shutoff device was not used.

Comparative Example 2 Coating was carried out in the same manner as in Comparative Example 1 except that the amount of coating liquid supplied from the extrusion die was 230 Liters / min per 1 m of coating width.

Comparative Example 3 Coating was carried out in the same manner as in Example 2 except that the air blocking device was not used.

Comparative Example 4 Coating was carried out in the same manner as in Comparative Example 3 except that the amount of coating liquid supplied from the extrusion die was 285 Liters / min per 1 m of coating width.

Comparative Example 5 Coating was carried out in the same manner as in Example 3 except that the air shutoff device was not used.

Comparative Example 6 Coating was carried out in the same manner as in Comparative Example 5 except that the amount of coating liquid supplied from the extrusion die was 90 Liters / min per 1 m of coating width.

Comparative Example 7 Coating was carried out in the same manner as in Example 3 except that the air doctor was not used.

[0032]

[Table 1]

<Evaluation Results> As shown in the examples, even when any of the air blocking devices shown in FIG. 1 or 3 is used, the coating can be carried out without causing uneven coating or skipping. When the blocking device is not used, skipping occurs even if coating is performed under the same conditions (Comparative Examples 1, 3, 5, 7). Further, if the coating liquid is applied under the same conditions (Comparative Examples 2, 4, and 6) when the amount of liquid supplied to the extrusion die is increased without using the air shutoff device, the occurrence of skipping can be avoided. Occurrence of coating unevenness called burring in the blade coating device and occurrence of coating unevenness called air knife pattern in the air knife coating device can be seen. In both cases, the occurrence of coating defects cannot be avoided.

[0034]

EFFECTS OF THE INVENTION The coating apparatus of the present invention uses an extrusion die equipped with an air shutoff device as a liquid supply apparatus, so that coating operation can be performed at high speed without causing coating defects such as skipping and coating unevenness. can do.

[Brief description of drawings]

FIG. 1 is a side view of a coating apparatus showing an embodiment of the present invention.

FIG. 2 is a front view of a coating apparatus showing an embodiment of the present invention.

FIG. 3 is a side view of a coating apparatus showing an embodiment of the present invention.

FIG. 4 is a partial view of a coating section of a conventional coating device.

FIG. 5 is a partial view of a coating section of a coating apparatus showing an embodiment of the present invention.

[Explanation of symbols]

 1 Air cutoff device 2 Weighing head 3 Backup roll 4 Web 5 Extrusion die 6 Air doctor 7 Coating liquid

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location B41M 5/26 D21H 23/50 7199-3B D21H 5/00 H

Claims (1)

[Claims] 1. A coating liquid is supplied from an extrusion die 5 to a web 4 that continuously travels in contact with a backup roll 3, and then the coating liquid is measured by a measuring head 2 to form a coating layer. In the apparatus, a coating apparatus, which is provided with an air blocking device 1 for blocking the air entrained in the web when the coating liquid is supplied to the web by the extrusion die, on the upstream side of the extrusion die.