JPH1034048A - Curtain coater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a curtain coater capable of reducing the production loss by preventing a longitudinal streak from generating on a coating liquid film coated on a web. SOLUTION: In a slide hopper type curtain coater in which a coating liquid 12 is allowed to flow on a slide surface 22 of a coating head inclined downwards and the coating liquid film 12A dropped from a lip tip of the lower end of the slide surface 22 in a curtain film shape is applied on a running web surface, the coating liquid drooping from the lip tip is prevented from infiltrating on the rear surface 28 of the lip tip by providing a water repelling material 30 in the rear surface 28 of the lip tip of forming step difference.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a curtain coating apparatus, and particularly to continuous running in the production of photographic films, photographic printing papers, magnetic recording tapes, adhesive tapes, pressure-sensitive recording papers, offset printing plates, batteries and the like. The present invention relates to a slide hopper type curtain coating apparatus for applying a liquid coating composition (hereinafter, referred to as “coating liquid”) to a strip-shaped member to be coated (hereinafter, referred to as “web”).

[0002]

2. Description of the Related Art Conventionally, various methods have been proposed as a method of continuously applying a coating liquid to a running web surface.
Typical coating methods include bead coating and curtain coating in addition to well-known roll coating and spray coating. In the bead coating, a bead is formed in a gap between an outflow port of a coating apparatus from which a coating liquid flows out and a running web, and coating is performed through the bead.

[0003] On the other hand, in curtain coating, a coating liquid is dropped from a coating apparatus into a curtain film and applied to a running web surface. In this curtain coating, a slide hopper type curtain coating apparatus causes the coating liquid supplied into the manifold of the coating head to flow down the slide surface of the coating head through a slit, and from the sharp lip tip at the lower end of the slide surface. The coating is performed by dropping the film on the running web surface in the form of a curtain film so as to cover the web surface with a coating film (for example, Japanese Patent Publication No. 49-35447).

[0004]

When an emulsion is applied as a coating liquid to, for example, a web of a photographic film using a slide hopper type curtain coating apparatus, it is necessary to reduce the loss of the emulsion during the preparation operation. The flow rate of the coating solution supplied to the slide surface is low. As a result, as shown in FIG. 9, a curtain film is not formed on the coating liquid 4 flowing on the slide surface 2 of the coating head 1 and falling from the lip tip 3, so that the coating liquid becomes interdigital. Then, when shifting from the preparation operation to the full-scale operation, the application flow rate is increased to the specified flow rate and the application is started. FIG. 6 shows a case in which a preparation operation is performed in which two kinds of coating liquids are flown in layers on the slide surface 2.

At the time of the transition from the preparation operation to the full-scale operation,
That is, when a coating liquid having a prescribed flow rate sufficient to form a curtain film is dropped from a state in which the coating liquid is falling in a blind shape in which a curtain film is not formed, in the case of a conventional curtain coating apparatus, FIG. As shown in the drawing, the coating liquid film applied on the surface of the web 5 has a so-called “vertical” in which convex portions having a large application amount and concave portions having a small application amount are alternately repeated along the width direction of the web 5. There is a disadvantage that "streaks" occur. This “vertical stripe” occurs because the contact line unevenness formed on the back surface of the lip tip 3 in the web width direction is not corrected in a straight line for a while after the transition to the full-scale operation due to the interdigital curtain during the preparation operation. The longer the "vertical streak" occurs, the more product loss occurs.

The present invention has been made in view of such circumstances, and a curtain coating apparatus capable of reducing product loss by preventing vertical streaks from being formed on a coating liquid film applied to a web. The purpose is to provide.

[0007]

According to the present invention, in order to achieve the above object, a coating liquid is caused to flow on a slide surface of a coating head inclined downward and dropped in a curtain film form from a lip tip at a lower end of the slide surface. In a curtain coating apparatus for applying the applied coating liquid film on a running web surface, the back surface of the lip tip is made of a water-repellent material.

In order to achieve the above object, the present invention provides a coating liquid film formed by flowing a coating liquid on a slide surface of a coating head inclined downward and dropping it in a curtain film form from a lip tip at a lower end of the slide surface. Is applied to a running web surface, wherein a step is formed on the back surface of the tip of the lip. Further, the present invention provides
In order to achieve the above object, the coating liquid is applied to the slide surface of the coating head inclined downward, and the coating liquid film dropped in the form of a curtain film from the lip tip at the lower end of the slide surface is coated on the running web surface. Curtain coating equipment
There is a step on the back surface of the tip of the lip, and the step has water repellency by a water repellent material.

According to the present invention, the back surface of the tip of the lip of the coating head is made of a water-repellent material, or a step is formed on the back surface of the tip of the lip. Thus, the occurrence of the "vertical stripe" can be quickly eliminated.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a curtain coating apparatus according to the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is an overall configuration diagram of a slide hopper type curtain coating device, and FIG. 2 is a perspective view showing a main part of the configuration. In the present embodiment, an example in which two types of coating liquids are applied so as to form two layers on the web surface will be described below.

The coating solution 12 applied to the surface of the web 10 is
The liquid is supplied from a coating liquid tank (not shown) to the manifold 18 in the coating head 16 at a uniform flow rate by the metering pump 14. The coating liquid 12 supplied to the manifold 18 is expanded to a predetermined coating width, and then extruded from a discharge port on the upper surface of the coating head 16 through a slit 20 and discharged to a slide surface 22 inclined downward. Two types of coating liquid 12
Is applied to the surface of the web 10, the coating head 1
6 are connected in series as shown in FIG.

The two coating liquids 12 discharged to the slide surface 22 come into contact with each other and form a layer without flowing and flow down the slide surface 22, and flow down the slide surface 12 from the lip tip 24 at the lower end of the slide surface 12 to form a curtain film. Liquid film 12A
And fall naturally. The lip tip 24 is coated with the coating liquid 1
As shown in FIG. 1, a vertical section is formed in a triangular sharp shape so that 2 can easily fall by gravity.

The coating liquid film 12 dropped from the lip tip 24
A is a web 10 running around a roller 26.
The coating liquid film 12A is applied so as to land on the surface and cover the surface of the web 10. Therefore, in order to apply the coating liquid 12 evenly on the surface of the web 10, the web width direction W (FIG.
An important point is to form a curtain film having a uniform thickness (see FIG. 1).

However, during the preparatory operation before starting the full-scale application operation, the amount of the application liquid supplied to the slide surface 22 of the application head 16 is low from the viewpoint of reducing the loss of the application liquid 12. The coating liquid film 12A dropped and formed from the lip tip 24 has the interdigital shape shown in FIG. 9, and a uniform curtain film is not formed in the web width direction W. In the conventional slide hopper type coating apparatus, when the operation shifts from the preparation operation in which the curtain film is not formed to the full-scale operation of supplying a coating liquid at a specified flow rate capable of forming the curtain film, the interdigital state is uniformly changed from the interdigital shape. As shown in FIG. 7, the smooth transition to the curtain film was not performed, and as shown in FIG. 7, the “longitudinal streaks” occurred due to the uneven application amount in the web width direction W over the application surface of the web 10 in the vertical direction (web running direction). Is generated.

Therefore, the inventor has diligently studied measures for preventing the occurrence of "vertical stripes". As a result, as shown in FIG. 3, when the coating liquid 12 falls from the lip tip 24,
The coating liquid 12 is moved from the lip tip 24 to the back surface 28 of the lip tip.
Wrap around. Then, the coating liquid 1 is shaped like a blind in the preparation operation.
2 is falling, the back surface 28
The contact line of the coating liquid 12 formed in the above is not a straight line in the width direction W of the lip tip 24 but is a wave-like unevenness. As a result, even if the operation shifts to the full-scale operation at the specified flow rate, the uneven contact line that has been formed once is not easily eliminated, so that "vertical stripes" of light and shade due to the distribution of the application amount in the width direction occur on the web 10. I understood that.

Based on the above results, the inventor of the present invention, in order to prevent "vertical streaks" when shifting from preparation operation to full-scale operation,
It has been found that the coating liquid 12 is hard to wrap around the back surface 28 at the tip of the lip, or that even if the coating liquid 12 slightly wraps around, the contact line should be formed linearly. FIGS. 4 and 5 are cross-sectional views of a principal part for explaining an improved part of the curtain coating apparatus of the present invention, which is capable of preventing "vertical stripes" based on the above findings.

FIG. 4 shows a structure in which a water-repellent resin film 30 is formed on the back surface 28 at the tip of the lip using a water-repellent material. As the water-repellent material, any resin having a water-repellent property to the coating solution such as a fluororesin, a polyacetal resin, a polyethylene resin, and a polystyrene resin may be used. Among them, Teflon (Dupont, USA) Polytetrafluoroethylene, which is a fluororesin known under the trade name (trade name), and Delrin (Dupont, USA)
Polyacetal resins known under the trade name of the company) are preferred.

As described above, by imparting water repellency to the rear surface 28 at the tip of the lip, the occurrence of "vertical stripes" can be quickly eliminated when shifting from the preparation operation to the full-scale operation. The reason for this is that the surface energy of the back surface 28 is reduced by applying water repellency to the back surface 28 of the lip tip, so that the coating liquid 12 falling from the lip tip 24 is less likely to flow from the lip tip 24 to the back surface 28. During operation, the back surface 28 of the lip tip 24
It is considered that the uneven contact line formed in the slab was easily eliminated in full-scale operation.

FIG. 5 shows a step 32 on the back surface 28 at the tip of the lip.
Is formed. The step 32 is provided so as to be parallel to the lip tip line. The distance (L) from the lip tip 24 to the step 32 is 0.2 to 2 mm.
And preferably 0.5 to 1 mm. Further, the step (t) is preferably 0.1 to 0.5 mm.

As described above, by forming the step 32 on the back surface 28 at the tip of the lip, the occurrence of "vertical stripes" can be quickly eliminated when shifting from the preparation operation to the full-scale operation. The reason for this is that by forming a step 32 on the back surface 28 of the lip tip, the coating liquid 12
It can be considered that the contact line can be formed in a straight line at the corner of the step 32 by being able to block the wraparound from the back surface 4 to the back surface 28. In this case, if the lip tip 24 and the step 32 are flush with each other without being separated (L is zero), it is not preferable because the lip tip 24 cannot be stopped around the back surface 28 of the lip tip. On the other hand, if the distance (L) is larger than 2 mm, the application liquid 12 wrapping around the back surface 28 does not reach the step 32, so that there is no effect. On the other hand, if the dimension of the step (t) is smaller than 0.1 mm, the effect of blocking the wraparound coating solution is lost,
If it is larger than 0.5 mm, the contact line cannot be formed linearly at the corner of the step 32.

When the material of the step 32 shown in FIG. 5 is made water-repellent, "vertical stripes" are less likely to occur. As the water-repellent material used for the step 32, the above-described water-repellent resin such as Teflon can be used. Further, in the present embodiment, an example has been described in which two types of coating liquids 12 are applied in layers on the surface of the web 10, but one type of coating liquid 12 or two or more types may be used.

Further, as shown in FIGS. 4 and 5, the angle .theta.
2 is preferably 45 ° or more.
The reason for this is that if the angle θ of the slide surface 22 is too small, the speed of flowing on the slide surface 22 becomes too low, so that the coating liquid 12 falling from the lip tip 24 tends to wrap around to the back surface 28 when falling from the lip tip 24. It is considered as a reason.

The web 10 used in the present invention includes paper, plastic film, metal, resin-coated paper, synthetic paper, and the like. The material of the plastic film is, for example, a polyolefin such as polyethylene or polypropylene, a vinyl polymer such as polyvinyl acetate, polyvinyl chloride, or polystyrene;
Polyamide such as nylon, polyethylene terephthalate, polyester such as polyethylene {2,6} naphthalate, polycarbonate, cellulose triacetate,
Cellulose acetate such as cellulose diacetate is used. The resin used for the resin coated paper is typically a polyolefin such as polyethylene, but is not necessarily limited to this. As the metal web, for example, there is an aluminum web.

[0024]

Next, an embodiment of a curtain coating apparatus according to the present invention will be described with reference to an example in which a step is formed on the back surface of the tip of the lip described with reference to FIG. Nos. 1 to 7 in Table 1 are examples of the present invention, and No. 8 is a comparative example. In the example, the case where Teflon, vinyl chloride, and stainless steel (SUS) were used as the material of the back surface of the lip tip was performed. As a comparative example, a conventional slide hopper type curtain coating apparatus which does not use a water-repellent material or a step on the back surface of the lip tip was used.

In No. 1, the material of the back surface of the lip tip is Teflon, and the distance (L) from the lip tip to the step is 1 m.
m and the step (t) is 0.1 mm. No.2
Is a case where the material of the back surface of the lip tip is Teflon, the distance (L) from the lip tip to the step is 1 mm, and the step (t) is 0.2 mm. No. 3 is the case where the material of the back surface of the lip tip is Teflon, the distance (L) from the lip tip to the step is 0 mm, and the step (t) is 0.2 mm.

In No. 4, the material of the back surface of the lip tip is Teflon, and the distance (L) from the lip tip to the step is 1 m.
m and the step (t) is 0.5 mm. No.5
Is made of polyvinyl chloride as the material on the back surface of the lip tip, the distance (L) from the lip tip to the step is 1 mm, and the step (t) is 0.1 mm.
This is the case of 5 mm. No. 6 is a case where the material of the back surface of the lip tip is stainless steel, the distance (L) from the lip tip to the step is 0 mm, and the step (t) is 0.2 mm.

In No. 7, the material of the back surface of the lip tip is stainless steel, and the distance (L) from the lip tip to the step is 1
mm and the step (t) is 0.2 mm. No.8
Is a case of a conventional curtain coating apparatus in which neither a water-repellent material nor a step is applied to the back surface of the lip tip. The application conditions are as follows.

Coating solution: 7% aqueous solution of alkali-treated gelatin containing 0.17% by weight of sodium dodecylbenzenesulfonate as an anionic surfactant Viscosity of coating solution: 40 cp (centipoise) Preparation operation: coating flow rate 0.27 cc / Flow for 10 minutes at cm · s. Full-scale operation: After the preparatory operation, the application flow rate is increased to 2 cc / cm.

The evaluation of the "vertical stripes" was performed by measuring the time (minutes) from the start of full-scale operation until the occurrence of the "vertical stripes". The angle θ of the lip tip was unified to 67 ° in both the example and the comparative example.
Table 1 shows the test results of Examples and Comparative Examples.

[0030]

[Table 1] As can be seen from Table 1, the conventional slide hopper-type curtain coating device that does not use a water-repellent material or a step on the back surface of the lip tip has a “longitudinal” coating surface applied to the web surface after shifting to full-scale operation. Time to eliminate streaks is 15
Minutes were long.

On the other hand, in Nos. 1 to 4 of the embodiment in which a water-repellent Teflon step is provided on the back surface of the lip tip, the time until the "vertical streak" disappears is 4 minutes or less, and the web surface A good coating without "vertical stripes" could be applied to the coating film of No. In particular, when the distance (L) from the tip of the lip to the step is 1 mm and the step (t) is 0.2 mm,
In No. 2, the time until the "vertical streak" disappeared was 1 minute, and an extremely good result was obtained.

Also, as shown in Table 1, Nos. 5 to 7 of the examples in which a step of vinyl chloride or stainless steel was provided on the back surface of the lip tip, compared to No. 8 in which no water repellency and no step were provided. Although good results were obtained, Teflon was even better. Although not shown in Table 1,
In Example No. 1 of the present invention, when the angle θ was less than 45 °, the time until the “vertical streak” disappeared increased.
For this reason, in order to prevent the coating liquid from flowing around the back surface of the lip tip when falling from the lip tip, in addition to the water-repellent material and the step, the coating liquid flowing on the slide surface forms a normal layer. 4 slide surfaces below the limit that can be formed
It is considered more preferable to set the angle to 5 ° or more.

Further, when the present invention is used, the coating liquid is less likely to flow to the back surface at the tip of the lip, so that a uniform curtain film can be easily formed even if the coating liquid film is made thin.
It is also possible to reduce the amount of the coating liquid in full-scale operation as compared with the conventional case. This makes it possible to apply a thinner and more uniform coating liquid film on the web, as compared with a conventional slide hopper type curtain coating apparatus.

[0034]

As described above, according to the curtain coating apparatus of the present invention, the coating liquid is applied to the lip by applying water repellency to the back surface of the lip tip or forming a step on the back surface of the lip tip. It is possible to make it hard to go from the tip to the back. As a result, it is possible to prevent vertical stripes from being generated in the coating liquid film applied to the web, thereby reducing product loss.

Further, since the coating liquid does not easily flow to the back surface of the tip of the lip, the coating liquid film falling from the tip of the lip can be made thin, so that the thickness of the coating liquid film can be made thinner and more uniform as compared with the conventional curtain coating apparatus. it can.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of a curtain coating device.

FIG. 2 is a perspective view illustrating a configuration of a curtain coating device.

FIG. 3 is a cross-sectional view illustrating a state of a coating liquid film falling from a lip tip.

FIG. 4 is a sectional view of an essential part for explaining an improved part of the curtain coating apparatus according to the present invention, in which a water-repellent material is provided on the back surface of the tip of the lip.

FIG. 5 is a cross-sectional view of an essential part for explaining an improved portion of the curtain coating apparatus of the present invention, in which a step is formed on the back surface of the lip tip.

FIG. 6 is a perspective view showing a state of a coating liquid film falling from a lip tip during a preparation operation.

FIG. 7 is a state diagram showing a state in which “vertical stripes” have occurred in a coating film on a web surface.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Web 12 ... Coating liquid 12A ... Coating liquid film 16 ... Coating head 18 ... Manifold 20 ... Slit 22 ... Slide surface 24 ... Lip tip 26 ... Roll 28 ... Backside of lip tip 30 ... Water repellent resin film 32 ... Step

Claims (4)

[Claims] 1. A curtain coating method in which a coating liquid is caused to flow on a slide surface of a coating head inclined downward, and a coating liquid film dropped in the form of a curtain film from a lip tip at a lower end of the slide surface is coated on a running web surface. In the apparatus, the back surface of the tip of the lip is made of a water-repellent material. 2. A curtain coating method in which a coating liquid is caused to flow on a slide surface of a coating head inclined downward, and a coating liquid film dropped in a curtain film form from a lip tip at a lower end of the slide surface is coated on a running web surface. In the apparatus, a step is formed on a back surface of a tip of the lip. 3. A curtain coating for applying a coating liquid on a slide surface of a coating head inclined downward and applying a coating liquid film dropped in a curtain film form from a lip tip at a lower end of the slide surface onto a running web surface. In the apparatus, there is provided a step on a back surface of a tip of the lip, and the step has water repellency by a water repellent material. 4. The step is 0.1 to 0.5 mm, and the distance from the lip tip to the step is 0.2 to 2 m.
4. The curtain coating device according to claim 2, wherein m is m.