JP2022107147A - Coating head, and manufacturing device and manufacturing method of web with coating - Google Patents

Abstract

To provide a double-side coating head capable of simultaneously forming high-quality coatings on both surfaces of a web by suppressing coating stripe generated when forming a coating on a web.SOLUTION: A coating head has a liquid storage portion for storing a coating liquid, which is formed by a pair of liquid storage members opposite to a web traveling surface, and a metering portion for adjusting a coating to a desired thickness, which is formed by a pair of metering members oppositely provided at an interval across the web traveling surface on the downstream side in a web traveling direction of the liquid storage portion. The metering member is configured by a first metering surface extending in a web width direction, a groove, and a second metering surface, sequentially from the upstream side to the downstream side in the web traveling direction. Concerning the groove, a surface ranging to a boundary between the groove and the second metering surface from a bottom of the groove approaches the web traveling surface toward the upstream side in the web traveling direction.SELECTED DRAWING: Figure 1

Description

The present invention relates to a coating device for simultaneously forming a coating film on both surfaces of a film, a non-woven fabric, paper, etc., and a manufacturing method.

Conventionally, in the double-sided simultaneous coating method in which coating films are simultaneously formed on both sides of the web, coating heads such as bars, rolls, knives, and slit dies are arranged facing each other on the front and back surfaces of the web, and high-quality coating films are formed on both front and back surfaces. There are widely known ways to do this.

As an example of such a coating head, Patent Document 1 discloses a coating head having a measuring unit provided at a predetermined interval and a liquid storage unit for storing a coating liquid above the measuring unit. Also disclosed is a method of manufacturing a coated web in which a web is passed through a liquid storage portion and a measuring portion of the coating head to apply a coating liquid to both sides of the web at the same time.

In such a double-sided simultaneous coating method, coating defects due to running wrinkles on the web, coating unevenness in which the film thickness distribution becomes uneven, or coating streaks are major problems.

In response to these problems, Patent Document 2 discloses a coating head having a measuring unit provided at a predetermined interval and a liquid storage unit for storing the coating liquid above the measuring unit, as in Patent Document 1. Therefore, a method of reducing running wrinkles of the web by providing a groove in the middle of the measuring surface in the width direction of the web is disclosed.

JP-A-2017-164682 JP-A-2018-75531

However, even with the coating head disclosed in Patent Document 2, if the traveling speed of the web is increased or a coating liquid having a small surface tension is used, coating streaks may occur. It is known that many of these drawbacks occur near the outlet of the coating head, and the pressure of the coating liquid from the outlet of the measuring part to the inside is increased by the surface tension of the coating liquid near the outlet of the coating head and the tensile force due to the running of the web during coating. Since the pressure is lowered and a negative pressure region is formed at the outlet of the measuring unit, the coating liquid is drawn into the measuring unit to generate coating streaks in the traveling direction of the web. This phenomenon occurs more prominently when the running speed of the web is increased or when a coating liquid having a low surface tension is used.

As a countermeasure, it is possible to reduce the degree of negative pressure formed at the outlet of the measuring part and eliminate the coating streaks by reducing the running speed of the web or using a coating liquid with a large surface tension. can. However, the low speed running of the web reduces the production capacity of the coated web. In addition, the use of a coating liquid having a large surface tension narrows the selection range of the coating liquid formulation, which imposes restrictions on the coating liquid properties.

In this way, in the coating head having the measuring unit provided at a predetermined interval and the liquid storage unit for storing the coating liquid above the measuring unit, the traveling speed of the web is increased in order to improve the productivity. , When the negative pressure area at the outlet of the measuring part expands due to the change of the coating liquid due to the switching of the production type, for a wide range of coating liquids while maintaining the production capacity without generating coating streaks. No coating head has been found for stable coating.

Therefore, the present invention provides a double-sided coating head capable of simultaneously forming a high-quality coating film on both sides of the web without generating coating streaks on the web.

The coating head of the present invention that solves the above problems is a coating head that simultaneously applies a coating liquid to both sides of a traveling web.
A liquid storage unit for storing the coating liquid, which is formed by a pair of liquid storage members facing the web running surface,
For adjusting the coating film to a desired thickness, which is formed by a pair of measuring members provided so as to sandwich the traveling surface of the web on the downstream side in the traveling direction of the web from the liquid storage portion. It has a measuring part and
The measuring member is composed of a first measuring surface, a groove, and a second measuring surface extending in the web width direction in order from the upstream side in the web traveling direction to the downstream side.
In the groove, the surface extending from the bottom of the groove to the boundary between the groove and the second measuring surface approaches the web traveling surface toward the downstream side in the web traveling direction.

In addition, the coating film-coated web manufacturing apparatus of the present invention includes the coating head of the present invention and a transport device for transporting the web.

Further, in the method for producing a web with a coating film of the present invention, the web is introduced into the gap between the pair of measuring members by using the coating head of the present invention, and the web is stored in the liquid storage part in the liquid storage part. The coating liquid is adhered to both sides of the web, and the gap between the pair of measuring members is adjusted to form a coating film having a desired thickness on both sides of the web.

By using the coating head of the present invention, even when the traveling speed of the web is increased, a high-quality coating film without coating streaks can be formed on both sides of the web at the same time.

It is the schematic sectional drawing of the coating head by one Embodiment of this invention. It is an enlarged view of the measuring part of the coating head of FIG. It is a figure which shows the measuring part of the conventional coating head, and the pressure distribution of the coating liquid at the time of coating. It is a figure which shows the measuring part of the coating head of FIG. 1 and the pressure distribution of the coating liquid at the time of coating. It is the schematic which shows an example of the web manufacturing apparatus with a coating film of this 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 form shown in the drawings, and various changes may be made as long as the object of the invention can be achieved and the gist of the invention is not deviated.

See FIG. FIG. 1 is a schematic cross-sectional view of an embodiment of the coating head 100 of the present invention. When the web 1 passes through the coating head 100, the coating liquid 2 is applied to both surfaces of the web 1, and the web 3 with a coating film is formed. The inside of the coating head 100 includes a liquid storage unit X1 for storing the coating liquid and a measuring unit Y1 for adjusting the coating film to a desired thickness.

The coating head 100 is composed of liquid storage members 101 and 101'and a pair of measuring members 102 and 102', and the liquid storage members 101 and 101'are in the liquid storage unit X1 for storing the coating liquid 2. It becomes a wall surface. The measuring members 102 and 102'are arranged to face each other with a narrow gap t so as to sandwich the traveling surface of the web 1 on the downstream side in the traveling direction of the web 1 from the liquid storage members 101 and 101'. A liquid storage portion X1 is formed together with the liquid storage members 101 and 101'as the bottom surface of the X1.

Although not shown, in the coating head 100, the liquid storage members 101, 101'and the liquid storage members 101, 101'and are placed on the front side and the back side of the paper surface of FIG. Side plates are provided so as to sandwich the measuring members 102 and 102'.

See FIG. FIG. 2 is an enlarged view of the wetted portion of the measuring portion Y1 of the coating head of FIG. The surfaces of the measuring unit Y1 in contact with the coating liquid 2 are the first measuring surfaces 103 and 103', the grooves 104 and 104', and the second measuring surfaces 105 and 105' in order from the upstream side to the downstream side in the traveling direction of the web 1. It is configured and all extend in the width direction of Web 1. The surfaces of the grooves 104 and 104'that are continuous from the bottom of the grooves 104 and 104'to the boundary between the second measuring surfaces 105 and 105'approach the traveling surface of the web 1 toward the downstream side in the traveling direction of the web 1, respectively. It is formed like this.

As described above, when the web is passed through the measuring portion having a narrow gap t to form a coating film on both sides of the web at the same time, coating streaks may occur in the traveling direction of the web. The mechanism by which the coating streaks are generated will be described with reference to FIG. FIG. 3 shows the details of the measuring portion Y2 in the coating head 200 having the conventional shape and the graph of the pressure distribution of the coating liquid 2 existing in the measuring portion Y2 at the time of coating. The conventional coating head 200 does not have a groove and a second measuring surface in the measuring portion, and has only the first measuring surfaces 203 and 203'. When the web is coated at a low speed using the coating head 200, the surface tension of the coating liquid and the tensile force due to the running of the web cause the upstream side from the outlet of the measuring unit Y2 located on the most downstream side of the coating head 200. The pressure is decreasing toward the inside of the measuring unit, and a negative pressure region is formed at the outlet of the measuring unit as shown by the dotted line in the graph on the right of FIG. As the traveling speed of the web 1 increases, the tensile force due to the traveling of the web increases. Therefore, as shown by the solid line in the graph on the right of FIG. 3, the negative pressure region expands to the inside of the measuring portion, and the coating liquid 2 is weighed accordingly. It is drawn into the department. Then, when the pull-in exceeds a certain amount, coating streaks are generated in the traveling direction of the web. The amount of drawing in which the coating streaks are generated differs depending on the coating liquid.

Next, FIG. 4 is used for the appearance of the coating liquid 2 in the liquid storage members 101, 101'and the measuring members 102, 102' when the coating film is formed on both sides of the web using the coating head 100 of the present invention. Will be explained in detail. FIG. 4 shows the details of the measuring unit Y1 in the coating head 100 and the graph of the pressure distribution of the coating liquid 2 existing in the measuring unit Y1 at the time of coating.

See FIG. 2 again. The coating head 100 of the present invention is provided with grooves 104, 104'extending in the web width direction in the middle of the measuring portion Y1. Further, in the grooves 104 and 104', the surfaces 106 and 106'that are continuous from the bottom of the grooves 104 and 104'to the boundary between the grooves 104 and 104'and the second measuring surfaces 105 and 105'are the traveling directions of the web 1. It approaches the running surface of Web 1 toward the downstream side. As a result, between the surfaces 106 and 106'and the web 1, the flow path of the coating liquid 2 that follows the running of the web 1 becomes narrower toward the downstream side in the traveling direction of the web 1, and the second measuring surface 105 , 105'A compressive force is applied to the coating liquid 2 that is about to enter the gap, and a high-pressure portion P is formed as shown by a dotted line in the right graph of FIG. Therefore, when the coating head of the present invention is used, even if the traveling speed of the web is increased, the negative pressure region formed at the outlet of the measuring portion Y1 is the high pressure portion as shown by the solid line in the right graph of FIG. P does not hinder the expansion to the inside of the measuring unit. That is, it is possible to suppress the drawing of the coating liquid into the measuring section. In order to further suppress the expansion of the negative pressure region, the high pressure portion P may be formed near the outlet of the measuring portion Y1, so that the lengths of the second measuring surfaces 105 and 105'in the web traveling direction are coated with a coating film. It is preferable that the thickness of the coating film of the web 3 is short as long as the thickness does not change.

In the embodiments of FIGS. 1 and 2, the surfaces 106 and 106'are flat, but in the coating head of the present invention, the surfaces 106 and 106'approach the web traveling surface toward the downstream side in the web traveling direction. As long as it is, it is not limited to a flat surface, but may be a curved surface. Further, the depth and shape of the grooves 104 and 104'can be variously changed within a range that does not deviate from the gist of the invention, but it is preferably determined by the physical characteristics of the coating liquid 2 to be used. Further, the groove depth t1 is preferably shallow in consideration of the ease of cleaning the coating head 100.

When the surfaces 106 and 106'are flat, the angle θ formed by the surfaces 106 and 106'and the second measuring surfaces 105 and 105'is preferably 10 ° or more and 70 ° or less, and the pressure of the high pressure portion P is increased. In order to suppress the expansion of the negative pressure region, it is more preferably 10 ° or more and 45 ° or less.

It is known that the thickness of the coating film when the coating film-coated web 3 is formed by using the coating head 100 of the present invention is approximately half of the minimum gap between the measuring members 102, 102'and the surface of the web 1. The gap t of the measuring portion Y1 is determined by the desired thickness of the coating film and the thickness of the web 1. That is, the installation positions of the measuring members 102 and 102'are determined. Further, at this time, since the first measuring surfaces 103 and 103'and the second measuring surfaces 105 and 105'are parallel to the traveling surface of the web 1, the hydraulic pressures on both sides of the web 1 become equal. , It 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 102 and 102', the coating head 100 may be provided with means (not shown) capable of moving the measuring members 102 and 102'in the thickness direction. preferable. As such a means, a moving table or the like on which the measuring members 102 and 102'are mounted and the measuring members 102 and 102' can be moved together with the measuring members 102 and 102'in the thickness direction of the web 1 can be exemplified. By providing such a means of transportation, 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 with the same gap t regardless of the operator. Further, in order to continuously manufacture the web 3 with a coating film, when the seam in which the old and new webs 1 are bonded with tape or the like passes through the measuring members 102, 102', there is a gap between the measuring members 102, 102'. Move in the direction of widening. At that time, it is preferable that the gap between the web 1 and the measuring members 102, 102'moves in the same gap with the web 1 in between.

Since the thickness of the coating film does not depend on the traveling speed of the web 1, it can be applied in a wide speed range from low speed to high speed.

As described above, if the coating head according to the present invention is used, the coating film can be formed on both sides of the web at the same time without generating coating streaks even when the traveling speed of the web is increased. Therefore, the coating head of the present invention can be formed. The apparatus for producing a web with a coating film using the above can produce a high-quality web with a coating film without coating streaks.

The coating head 100 is preferably composed of liquid storage members 101, 101'and measuring members 102, 102', but the liquid storage unit 101 and the measuring unit 102, and the liquid storage unit 101'and the measuring unit 102' 'Is each may be one piece. Further, the liquid storage members 101 and 101'and the measuring members 102 and 102' may each be composed of a plurality of parts.

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

As shown in FIG. 5, the web manufacturing apparatus 4 with a coating film using the coating head 100 of the present invention has an unwinding portion 5, a coating head 100, and an aftertreatment device 7 that unwind the web 1 in this order from the upstream side in the web traveling direction. , A winding unit 6 for winding the web 1 is provided, and a transport roller is arranged between the winding units 6. Examples of the post-treatment device 7 include a dryer for drying and solidifying the coating film.

Next, a method for manufacturing the coated web 3 using the coating head 100 of the present invention will be described. The coated web 3 is manufactured by passing the web 1 through the gaps between the measuring members 102 and 102'after passing through the liquid storage portion X of the coating head 100. At this time, since the coating liquid 2 stored in the liquid storage unit X decreases with the application, the storage amount of the coating liquid 2 is managed, and the coating liquid 2 is supplied to the liquid storage unit X to store a certain amount or more. By maintaining the above, the web 3 with a coating film can be stably produced. As a means for managing the stored amount of the coating liquid 2, a method of detecting the liquid level of the coating liquid 2 in the liquid storage unit X with a liquid level sensor or the like can be exemplified. As a means for supplying the coating liquid 2, a method of supplying the coating liquid 2 by a liquid feeding pump or the like in response to a signal from a liquid level sensor or the like can be exemplified. However, neither means is limited to this method. Further, the coating liquid 2 is supplied when the liquid level sensor or the like detects that the liquid level has dropped to a predetermined height, even if the coating liquid consumption amount due to coating is calculated and constantly supplied. However, it may be in the form of intermittently supplying a fixed amount of the coating liquid 2.

Further, it is preferable to provide a means for measuring the thickness of the coating film on the running web after the coating film is formed by the coating head 100. When the measurement result of the coating film thickness deviates from the standard, the web 3 with a coating film having a desired thickness can be manufactured by adjusting the gap t between the pair of measuring members 102 and 102'. Specifically, if the coating film is larger than the desired thickness, the gap t is narrowed, and if it is small, the measuring members 102 and 102'are moved in the direction of widening the gap t.

Hereinafter, the present invention will be described in more detail with reference to Examples. The coating liquid 2 was applied onto the web 1 having a thickness of 10 μm using the coating head 100 shown in FIGS. 1 and 2.

[Example 1]
The measuring member has a shape having a first measuring surface 103, 103', a groove 104, 104', and a second measuring surface 105, 105'. The gap t in the direction orthogonal to the web surface of the measuring unit Y1 is 40 μm, and the lengths (L1, L3) of the first measuring surfaces 103 and 103'and the second measuring surfaces 105 and 105'in the web traveling direction are set. Was also set to 0.3 mm. The grooves 104 and 104'have a depth t1 of 0.3 mm and a length L2 in the web traveling direction of 2 mm. Further, the angle θ formed by the surfaces 106 and 106'and the second measuring surfaces 105 and 105'was set to 30 °.

[Example 2]
The same coating head as in Example 1 was used except that the angle θ formed by the surfaces 106 and 106'and the second measuring surfaces 105 and 105'was set to 60 °.

[Comparative Example 1]
The same coating head as in Example 1 was used except that the angle θ formed by the surfaces 106 and 106'and the second measuring surfaces 105 and 105'was set to 90 °. That is, in the coating head of Comparative Example 1, the surfaces 106 and 106'do not have a shape that approaches the traveling surface of the web 1 toward the downstream side in the web traveling direction.

[Comparative Example 2]
The measuring member has a shape that does not have the grooves 104, 104'and the second measuring surfaces 105, 105', but has only the first measuring surfaces 103, 103'. The gap t in the direction orthogonal to the web surface of the measuring unit Y1 was set to 40 μm, and the length of the first measuring surfaces 103 and 103'in the web traveling direction was set to 2.6 mm.

A coating test was carried out with a coating head having the above shape to verify the rate at which coating streaks were generated. Further, by fluid analysis, the pressure value of the high pressure portion P formed between the surface connected to the boundary between the bottoms of the grooves 104 and 104'and the second measuring surfaces 105 and 105' and the web 1 was derived. These results are shown in Table 1.

[Comparison between Example 1 and Comparative Example 2]
In the first embodiment, by forming the high-pressure portion between the surfaces 106 and 106'and the web 1, the rate at which the coating streaks are generated is 4 as compared with 35 m / min when there are no grooves 104 and 104'. It doubled to 140 m / min.

[Comparison between Example 1 and Comparative Example 1]
In the first embodiment, the surfaces 106 and 106'are formed so as to approach the traveling surface of the web 1 toward the downstream side in the web traveling direction. As a result, the high pressure portion between the surfaces 106 and 106'and the web 1 became about 1.4 times higher pressure. As a result, the expansion of the negative pressure region could be suppressed, and the speed at which the coating streaks were generated increased from 90 m / min to 140 m / min, which was about 1.6 times.

[Comparison between Example 1 and Example 2]
In the first embodiment, the angle θ formed by the surfaces 106, 106'and the second measuring surfaces 105, 105'is smaller than that of the second embodiment. Therefore, the high pressure portion between the surfaces 106 and 106'and the web 1 became about 1.3 times higher pressure. As a result, the expansion of the negative pressure region could be suppressed, and the speed at which the coating streaks were generated increased 1.4 times from 100 m / min to 140 m / min.

From the comparison between the examples and the comparative examples, grooves 104 and 104'are provided in the middle of the measuring unit Y1 in the web width direction, and further, as the surfaces 106 and 106' move toward the downstream side in the traveling direction of the web, the web 1 is provided. It was confirmed that by forming the coating film so as to be close to the running surface, it is possible to suppress coating streaks and form a high-quality coating film on both sides of the web at the same time. It was also confirmed that the smaller the angle formed by the surfaces 106 and 106'and the second measuring surfaces 105 and 106', the greater the effect of suppressing the coating streaks.

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, metal thin film, or cloth, and a coating film-coated web manufacturing apparatus and manufacturing method provided with the coating head. It is not limited to.

1 Web 2 Coating liquid 3 Coating web 4 Coating coating web manufacturing equipment 5 Unwinding part 6 Winding part 7 Post-treatment device 100 Coating head 200 Coating head 101, 101'Liquid storage member 102, 102'Measuring member 103, 103'First weighing surface 104, 104' Groove 105, 105'Second measuring surface 106, 106' Surfaces extending from the bottom of the groove to the boundary between the groove and the second measuring surface 203, 203'First weighing Surface X1 Liquid storage unit Y1 Measuring unit Y2 Measuring unit P High pressure unit t Gap in the direction perpendicular to the web surface of measuring unit Y t1 Groove depth L1 Web traveling direction length of the first measuring surface L2 Web traveling direction length of the groove L3 Length of the second weighing surface in the web running direction

Claims (3)

A coating head that applies the coating liquid to both sides of the running web at the same time.
A liquid storage unit for storing the coating liquid, which is formed by a pair of liquid storage members facing the web running surface,
For adjusting the coating film to a desired thickness, which is formed by a pair of measuring members provided so as to sandwich the traveling surface of the web on the downstream side in the traveling direction of the web from the liquid storage portion. It has a measuring part and
The measuring member is composed of a first measuring surface, a groove, and a second measuring surface extending in the web width direction in order from the upstream side in the web traveling direction to the downstream side.
The groove is a coating head in which a surface extending from the bottom of the groove to the boundary between the groove and the second measuring surface approaches the web traveling surface toward the downstream side in the web traveling direction. A coating film-coated web manufacturing apparatus including the coating head according to claim 1 and a transport device for transporting the web. Using the coating head of claim 1, the web is introduced into the gap between the pair of measuring members and passed through, and in the liquid storage section, the coating liquid stored in the liquid storage section is adhered to both sides of the web, and the pair is formed. A method for manufacturing a web with a coating film, which forms a coating film on both sides of the web by adjusting the gaps between the measuring members.

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