JP7540342B2 - Coating head, apparatus and method for producing coated web - Google Patents

Description

The present invention relates to a coating device and manufacturing method for simultaneously forming a coating film on both sides of a film, nonwoven fabric, paper, etc.

Conventionally, the double-sided simultaneous coating method, which simultaneously forms a coating film on both sides of a web, is widely known as a method in which coating heads such as bars, rolls, knives, and slit dies are arranged facing each other on the front and back of the web to form high-quality coating films on both sides.

As an example of such a coating head, Patent Document 1 discloses a coating head having a measuring section provided at a predetermined distance and a liquid storage section above the measuring section for storing coating liquid. It also discloses a method for producing a coated web in which the web is passed through the liquid storage section and measuring section of the coating head to simultaneously apply coating liquid to both sides of the web.

This type of simultaneous double-sided coating method can cause problems such as poor coating due to wrinkles on the web as it travels, uneven coating due to uneven film thickness distribution, and coating streaks caused by foreign objects getting caught between the measuring part of the coating head and the web.

To address the problem of poor coating caused by wrinkles on the web as it travels, Patent Document 2 discloses a method for reducing wrinkles on the web as it travels, using a coating head that has a measuring section spaced apart at a predetermined distance from one another, as in Patent Document 1, and a liquid storage section that stores coating liquid above the measuring section, by providing a groove along the width of the web midway along the measuring surface.

For foreign matter that gets caught between the metering section of the coating head and the web, different measures are taken depending on the origin of the foreign matter. Foreign matter brought into the coating head can be broadly divided into foreign matter from the surrounding environment, foreign matter from the coating liquid, and foreign matter that has adhered to the web. As a measure against foreign matter from the surrounding environment, coating is generally performed in a clean room or clean booth in the coating web manufacturing process. Foreign matter from the coating liquid can be suppressed by installing a filter that collects foreign matter in the coating liquid delivery path from the delivery tank to the coating head.

Regarding the remaining foreign matter adhering to the web, in a coating head having a measuring section with a specified gap therebetween and a liquid storage section that stores the coating liquid above the measuring section, as in Patent Document 1, the web passes through the coating head, so foreign matter adhering to the web is carried directly into the liquid storage section and measuring section of the coating head, and the foreign matter is likely to become caught between the measuring section and the web. Foreign matter getting caught in the measuring section is a major problem as it causes coating streaks.

Although the main purpose is not to prevent foreign matter adhering to the web from becoming caught between the measuring part of the coating head and the web, Patent Document 3 discloses a method of pre-coating both sides of the web with a liquid that has a lower viscosity and surface tension than the coating liquid. In the examples of Patent Document 3, it is disclosed that by pre-coating, foreign matter adhering to the web is washed off, preventing the foreign matter from becoming caught between the web and the coating head.

JP 2017-77544 A JP 2018-75531 A JP 2008-36607 A

However, the coating head disclosed in Patent Document 3 requires a pre-coating process and a squeezing roll in addition to the coating process, which not only increases the size of the equipment and complicates the process of manufacturing a coated web, but also leads to increased costs for the coating liquid used in the pre-coating process.

As described above, in a coating head having a measuring section spaced a predetermined distance apart and a liquid storage section that stores coating liquid above the measuring section, no coating head has been found that can perform stable coating without the occurrence of coating streaks caused by foreign matter without adding additional processes.

Therefore, the present invention provides a double-sided coating head that can simultaneously form a high-quality coating film on both sides of a web without causing coating streaks caused by foreign matter.

The coating head of the present invention, which solves the above problems, is a coating head that simultaneously applies a coating liquid to both sides of a traveling web,
a liquid storage section for storing a coating liquid, the liquid storage section being formed by a pair of liquid storage members facing the web running surface;
a metering section for adjusting the coating film to a desired thickness, the metering section being formed by a pair of metering members disposed opposite each other with a gap therebetween, downstream of the liquid storage section in the web running direction, and sandwiching the web running surface;
The liquid storage section has one or more locations where the gap between the pair of liquid storage members narrows between the entrance where the web enters and the exit where the web exits, and is divided into a plurality of liquid storage sections aligned in the running direction of the web by the locations where the gap narrows,
Among the divided liquid storage sections, the liquid storage section located at the most downstream side in the web running direction has a smaller volume than the other liquid storage sections, and in the part connected to the metering section, the distance between the pair of liquid storage members gradually narrows toward the downstream side in the web running direction.

The coating web manufacturing apparatus of the present invention also includes the coating head of the present invention and a conveying device for conveying the web.

The method for producing a coated web of the present invention uses the coating head of the present invention to introduce and pass a web through the liquid storage section and the metering section of the coating head, and in the liquid storage section, the coating liquid stored in the liquid storage section is applied to both sides of the web, and a coating film of the desired thickness is formed on both sides of the web by adjusting the gap between the metering section and the web running surface.

By using the coating head of the present invention, it is possible to suppress streaks caused by foreign matter and form a high-quality coating film on both sides of the web simultaneously.

1 is a schematic cross-sectional view of a dispensing head according to one embodiment of the present invention; 2 is an enlarged view of a second liquid storage portion of the coating head in FIG. 1 and a diagram showing the flow direction of the coating liquid during coating. FIG. 13A and 13B are enlarged views of a second liquid storage section of a coating head different from that of the present invention and a view showing the flow direction of the coating liquid during coating. 4 is a schematic cross-sectional view of a coating head according to another embodiment of the present invention. 1 is a schematic diagram showing an example of an apparatus for producing a coated web of the present invention.

A preferred embodiment of the present invention will be described with reference to the drawings. However, the present invention is not limited to the embodiment shown in the drawings, and various modifications are possible as long as the object of the invention can be achieved and the gist of the invention is not deviated from.

Refer to Figure 1. Figure 1 is a schematic cross-sectional view of one embodiment of a coating head 100 of the present invention. When a web 1 passes through the coating head 100, both sides of the web 1 are coated with coating liquid 2, resulting in a coated web 3. The interior of the coating head 100 comprises a liquid storage section X for storing the coating liquid and a metering section Y for adjusting the coating film to a desired thickness. Furthermore, the liquid storage section X is divided into a first liquid storage section X1 and a second liquid storage section X2 by a pair of dividing members 103 and 103', in that order from the upstream side in the web running direction.

This coating head 100 is composed of first liquid storage members 101 and 101', second liquid storage members 102 and 102', partition members 103 and 103', and a pair of metering members 104 and 104'. The first liquid storage members 101 and 101' form the inner wall surface of the first liquid storage section X1 for storing the coating liquid 2. The partition members 103 and 103' are arranged opposite each other with a narrow gap t1 between them, so as to sandwich the running surface of the web 1 downstream of the first liquid storage members 101 and 101' in the running direction of the web 1, and form the first liquid storage section X1 together with the first liquid storage members 101 and 101' as the bottom surface of the first liquid storage section X1. The second liquid storage members 102 and 102' form the inner wall surface and bottom surface of the second liquid storage section X2 for storing the coating liquid 2. The measuring members 104, 104' are arranged facing each other with a narrow gap t between them, downstream of the second liquid storage members 102, 102' in the running direction of the web 1, so as to sandwich the running surface of the web 1. The coating film can be made to the desired thickness by adjusting this gap t.

When the liquid storage section X is considered to be composed of a liquid storage member consisting of a first liquid storage member 101, a second liquid storage member 102, and a partition member 103, and a liquid storage member consisting of a first liquid storage member 101', a second liquid storage member 102', and a partition member 103', the gap between the pair of liquid storage members of the liquid storage section X is narrowed at the point sandwiched between the partition members 103, 103'.

The second liquid storage section X2 has a smaller volume than the first liquid storage section X1, and the second liquid storage members 102, 102' are formed so that the surface communicating with the measuring members 104, 104' approaches the running surface of the web 1 as it moves downstream in the running direction of the web 1.

Although not shown, in this coating head 100, in order to prevent the coating liquid 2 from leaking from the liquid storage section X and the measuring section Y, side plates are provided at the front and back of the paper surface of FIG. 1 to sandwich the first liquid storage members 101, 101', the second liquid storage members 102, 102', the dividing members 103, 103', and the measuring members 104, 104'.

Here, we will explain in detail the appearance of the first liquid storage members 101, 101', the second liquid storage members 102, 102', the dividing members 103, 103' and the measuring members 104, 104' when a coating film is formed on both sides of a web using the coating head 100 of the present invention.

When the coated web 3 is manufactured, the web 1 first enters the first liquid storage section X1 of the coating head 100, then passes through the gap t1 between the partitioning members 103, 103' and enters the second liquid storage section X2. Foreign matter that has previously adhered to the web 1 also enters the first liquid storage section X1, and then enters the partitioning members 103, 103'. At this time, foreign matter larger than the gap t1 between the partitioning members 103, 103' cannot pass through the gap between the partitioning members 103, 103' and does not enter the second liquid storage section X2, so the web from which the foreign matter has been removed enters the second liquid storage section X2 and then passes through the measuring section Y. As a result, the occurrence of streaks due to foreign matter adhering to the web can be suppressed.

Next, the state of the coating liquid 2 in the second liquid storage section X2 and the metering section Y when a coating film is formed on both sides of a web using the coating head 100 of the present invention will be described in detail with reference to FIG. 2. FIG. 2 shows the details of the second liquid storage section X2 in the coating head 100 and the flow direction of the coating liquid 2 present in the second liquid storage section X2 during coating.

In the present invention, the volume of the second liquid storage section X2 is made smaller than the volume of the first liquid storage section X1. This makes it possible to shorten the residence time of the coating liquid 2 in the second liquid storage section X2, thereby suppressing deterioration of the coating liquid 2 and re-aggregation of solids, and preventing foreign matter from being generated in the second liquid storage section X2 and adhering to the web 1. In other words, it is possible to suppress the occurrence of coating streaks caused by foreign matter. Furthermore, the second liquid storage members 102, 102' are formed so that the surface communicating with the metering members 104, 104' approaches the running surface of the web 1 as it moves downstream in the running direction of the web 1. As a result, the coating liquid flows in the second liquid storage section X2 as shown by the arrow in FIG. 2, and the flow of the coating liquid 2 reaches the bottom corner of the second liquid storage section X2. As a result, the coating liquid does not accumulate on the bottom surface of the second liquid storage section X2, which suppresses deterioration of the coating liquid 2 in the second liquid storage section X2 and re-aggregation of solids, and prevents foreign matter from being generated in the second liquid storage section X2 and adhering to the web 1. In other words, the occurrence of coating streaks caused by foreign matter can be suppressed.

Here, for comparison, the state of the coating liquid 2 in the second liquid storage section X2' and the metering section Y' when a coating film is formed using a coating head 200 that is different from the coating head 100 of the present invention only in the second liquid storage section X2 will be described in detail with reference to FIG. 3. FIG. 3 is an enlarged view of the second liquid storage section X2' of a coating head 200 different from the present invention, and a diagram showing the flow direction of the coating liquid 2 during coating. Unlike the coating head 100 of the present invention, the coating head 200 has a surface that communicates with the metering members 204, 204' of the second liquid storage members 202, 202' that does not approach the running surface of the web 1 as it moves downstream in the running direction of the web 1. The other configurations are the same as those of the coating head 100 of the present invention. In this case, as shown by the arrow in FIG. 3, in the coating head 200, the flow in the second liquid storage section X2' does not reach the bottom corners of the second liquid storage section X2', and coating liquid retention sections Z, Z' are formed. As a result, foreign matter may be generated due to deterioration or re-aggregation of the coating liquid 2, and may adhere to the web 1. In other words, coating streaks may occur due to foreign matter.

In the present embodiment shown in FIG. 2, the surface of the second liquid storage member 102, 102' that communicates with the measuring member 104, 104' is flat, but in the present invention, as long as the surface of the second liquid storage member 102, 102' that communicates with the measuring member 104, 104' approaches the running surface of the web 1 as it moves downstream in the running direction of the web 1, it is not limited to being flat and may be curved.

The gap t1 between the dividing members 103, 103' can be changed in various ways without departing from the scope of the invention, but it is preferable to determine it based on the physical properties of the coating liquid 2 used, the size of the foreign matter to be captured, and the gap t of the metering section Y. If the thickness of the web 1 is Wt (mm), it is preferable to determine the gap t1 (mm) between the dividing members 103, 103' within a range that satisfies Wt + 0.005 mm ≦ t1 ≦ Wt + 0.3 mm. If the gap t1 is (Wt + 0.005 mm) or more, the dividing members 103, 103' are less likely to come into contact with the web 1, or the conveyance resistance of the web 1 is increased, which causes the web 1 to break. If the gap t1 is (Wt + 0.3 mm) or less, the dividing members 103, 103' can capture foreign matter of a size normally expected.

When the liquid storage section X is divided into three or more sections by multiple dividing members, it is preferable to determine the gap between each dividing member according to the size of the foreign matter to be captured by each dividing member. More preferably, the gap between the dividing members is gradually narrowed from the upstream side to the downstream side in the running direction of the web 1. This makes it possible to efficiently capture foreign matter of different sizes.

In addition, in order to suppress deterioration of the coating liquid 2 in the second liquid storage section X2, it is preferable to fill the second liquid storage section X2 with the coating liquid 2 to avoid contact between the coating liquid 2 and air. When the coating liquid 2 has a low viscosity, the air remaining in the second liquid storage section X2 can be eliminated by filling the liquid storage section X with the coating liquid 2. However, when air remains in the second liquid storage section X2 even after filling the liquid storage section X with the coating liquid 2 due to reasons such as high viscosity of the coating liquid 2, it is preferable to eliminate the air remaining in the second liquid storage section X2 when initially filling the coating liquid. Specifically, examples include a method of reducing the pressure on the downstream side of the coating head 100, and a method of moving the dividing members 103, 103' of the coating head 100 in the thickness direction of the web 1 immediately before starting coating to widen the gap t1 between the dividing members 103, 103' and then returning to a predetermined gap, but are not limited thereto.

It is known that the thickness of the coating film when the coated web 3 is formed using the coating head 100 of the present invention is approximately half the gap between the metering members 104, 104' and the surface of the web 1, and the gap t of the metering section Y is determined by the desired coating thickness and the thickness Wt of the web 1. In other words, the installation positions of the metering members 104, 104' are determined. In addition, at this time, the surfaces of the metering members 104, 104' that come into contact with the coating liquid 2 are parallel to the running surface of the web 1, so that the liquid pressure on both sides of the web 1 is equal, which has the effect of making the thickness of the coating film uniform on both sides of the web 1.

As described above, since the thickness of the coating film depends on the installation position of the measuring members 104, 104', it is preferable that the coating head 100 is provided with a means (not shown) for moving the measuring members 104, 104' in the thickness direction. An example of such a means is a moving table on which the measuring members 104, 104' are mounted and which can move the measuring members 104, 104' in the thickness direction of the web 1. By providing such a moving means, the thickness of the coating film can be adjusted uniformly and easily with good reproducibility. As a result, the coating head 100 can be installed at the same gap t regardless of the operator. In addition, in order to continuously manufacture the coated web 3, when the seam where the new and old webs 1 are pasted with tape or the like passes through the measuring members 104, 104', the measuring members 104, 104' are moved in the direction in which the gap becomes wider. At that time, it is preferable that the gap between the web 1 and the measuring members 104, 104' moves at the same gap across the web 1.

As described above, by using the coating head of the present invention, a coating film can be formed simultaneously on both sides of a web without causing streaks caused by foreign matter, so a coating web manufacturing device using the coating head of the present invention can manufacture a high-quality coated web without streaks caused by foreign matter.

It is preferable that the application head 100 is composed of the first liquid storage member 101, 101', the second liquid storage member 102, 102', the partition member 103, 103', and the measuring member 104, 104', but each member may be an integral part. Also, each member may be composed of multiple parts.

Figure 4 is a schematic cross-sectional view of a coating head 300 according to another embodiment of the present invention. In the coating head 300, the corners of the surfaces of the dividing members 303, 303' that face the running surface of the web 1 are rounded at the upstream corners of the running surface of the web 1. As a result, even if a foreign object captured between the dividing member 303 (303') and the web 1 presses the web 1 toward the dividing member 303' (303) and comes into contact with the dividing member 303' (303), the web 1 is less likely to be torn or scratched.

Next, a coated web manufacturing apparatus 4 using the coating head 100 of the present invention will be described with reference to FIG. 5. FIG. 5 is a schematic diagram showing a coated web manufacturing apparatus of the present invention. However, the present invention is not limited to the form shown in the drawing.

As shown in FIG. 5, the coated web manufacturing apparatus 4 using the coating head 100 of the present invention is composed of, in order from the upstream side in the web running direction, an unwinding section 5 that unwinds the web 1, the coating head 100, a post-processing device 7, and a winding section 6 that winds up the web 1, with a transport roller disposed between them. An example of the post-processing device 7 is a dryer for drying and solidifying the coating.

Next, we will explain the method for manufacturing the coated web 3 using the coating head 100 of the present invention.

The coated web 3 is produced by passing the web 1 through the gap between the metering members 104 and 104' after passing through the liquid storage section X of the coating head 100. At this time, the coating liquid 2 stored in the liquid storage section X decreases as the coating is performed, so the amount of the coating liquid 2 stored is managed, and the coating liquid 2 is supplied to the liquid storage section X to maintain a certain amount or more of storage, thereby stably producing the coated web 3. An example of a means for managing the amount of the coating liquid 2 stored is a method for detecting the liquid level of the coating liquid 2 in the liquid storage section X using a liquid level sensor or the like. An example of a means for supplying the coating liquid 2 is a method for supplying the coating liquid 2 using a liquid supply pump or the like upon receiving a signal from a liquid level sensor or the like. However, the means are not limited to this method. The coating liquid 2 may be supplied either in a form in which the amount of coating liquid consumed by coating is calculated and supplied constantly, or in a form in which a certain amount of the coating liquid 2 is intermittently supplied only when it is detected that the liquid level has dropped to a predetermined height using a liquid level sensor or the like.

It is also preferable to provide a means for measuring the thickness of the coating film on the traveling web after the coating film is formed by the coating head 100. If the measured coating film thickness does not meet the standard, the gap t between the pair of measuring members 104, 104' can be adjusted to produce a coated web 3 of the desired thickness. Specifically, if the coating film is thicker than the desired thickness, the gap t is narrowed, and if it is thinner, the measuring members 104, 104' are moved in a direction that widens the gap t.

The present invention can be applied to a coating head that simultaneously forms a coating film on both sides of a web such as paper, film, thin metal film, or cloth, and to a manufacturing device and manufacturing method for a coated web equipped with the coating head, but is not limited to this.

1 Web 2 Coating liquid 3 Coated web 4 Coated web manufacturing apparatus 5 Unwinding section 6 Winding section 7 Post-processing device 100 Coating head 200 Coating head 300 Coating head 101, 101' First liquid storage member 102, 102' Second liquid storage member 103, 103' Partitioning member 104, 104' Measuring member 202, 202' Second liquid storage member 203, 203' Partitioning member 204, 204' Measuring member 303, 303' Partitioning member X Liquid storage section X1 First liquid storage section X2 Second liquid storage section Y Measuring section X2' Second liquid storage section Y' Measuring section Z, Z' coating liquid retention section t Gap t1 in a direction perpendicular to the web surface of the measuring section Y Gap in a direction perpendicular to the web surface of the partitioning member

Claims (3)

A coating head that simultaneously applies a coating liquid to both sides of a traveling web,
a liquid storage section for storing a coating liquid, the liquid storage section being formed by a pair of liquid storage members facing the web running surface;
a metering section for adjusting the coating film to a desired thickness, the metering section being formed by a pair of metering members disposed opposite each other with a gap therebetween, downstream of the liquid storage section in the web running direction, and sandwiching the web running surface;
The liquid storage section is
a gap between the pair of liquid storage members is narrowed at one or more points between an entrance where the web enters and an exit where the web exits;
The space between the liquid storage portions is divided into a plurality of liquid storage portions arranged in the running direction of the web by the narrowing portions of the space between the liquid storage portions,
The liquid storage section located at the most downstream side in the web running direction among the divided liquid storage sections is
It has a smaller volume than other reservoirs,
In the portion communicating with the metering portion, the distance between the pair of liquid storage members gradually narrows toward the downstream side in the running direction of the web.
Coating head. A coating web manufacturing device comprising the coating head of claim 1 and a conveying device for conveying the web. A method for producing a coated web, comprising the steps of: using the coating head of claim 1, introducing a web through the liquid storage section and the measuring section of the coating head; depositing the coating liquid stored in the liquid storage section on both sides of the web in the liquid storage section; and forming a coating film on both sides of the web by adjusting the gap between the measuring section and the web running surface.

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