JP4548918B2 - Coating apparatus and coating method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a coating apparatus and a coating method for applying a coating liquid to a paper or metal web, and in particular, a coating apparatus capable of suppressing a pool of coating liquid on both sides of the web and It relates to a coating method.
[0002]
[Prior art]
As what applies a coating liquid with respect to the web which consists of paper or a metal etc., what has the dip tank which accommodated the coating liquid apply | coated to a web is known.
[0003]
When the web enters the dip tank, the coating liquid 20 is applied to both surfaces of the web 1 in the dip tank as shown in FIGS.
[0004]
[Problems to be solved by the invention]
As shown in FIG. 3A, the coating liquid 20 applied to the web 1 causes inclined portions 25 on the side edges 2 of the web 1 on both sides of the web 1. The inclined portion 25 is thinner than other portions of the coating liquid 20 and dries quickly.
[0005]
When the inclined portion 25 of the coating liquid 20 is dried in this manner, the surface tension σ _{SOLID of the} solid content dissolved in the coating liquid is generally larger than the surface tension σ _{SOLV of the} solution, so that the surface tension of the inclined portion 25 is other than that. The surface tension of this portion becomes larger, and the solution flows to the inclined portion 25, and the liquid pool 20 a is generated at the side edge portion of the web 1.
[0006]
Thus, when the liquid pool 20a arises in the side edge 2 of the web 1, the film quality of the coating liquid 20 will become non-uniform | heterogenous, or product quality will fall by insufficient drying of the liquid pool 20a.
[0007]
The present invention has been made in consideration of the above points, and an object of the present invention is to provide a coating apparatus and a coating method capable of reliably suppressing a liquid pool generated on both side edges of a web.
[0008]
[Means for Solving the Problems]
The present invention is a dip tank in which a first coating liquid that is applied to the web and forms an inclined portion on both side edges of the web is accommodated as the web enters, and a downstream side in the web running direction of the dip tank. Provided at least on one side of the web, apply a second coating liquid having a higher concentration than the first coating liquid to both side edges of the web, and eliminate the inclined portion formed by the first coating liquid, A coating apparatus comprising a pair of coating means for forming flat portions by a second coating liquid at both edges of a web .
[0009]
The present invention includes a step of applying a first coating liquid on both sides of a web and forming inclined portions on both side edges of the web, and at least one side of the web from the first coating liquid with respect to both side edges. Applying a high-concentration second coating liquid to eliminate the inclined portion formed by the first coating liquid, and forming flat portions by the second coating liquid on both edges of the web . It is the coating method characterized by this.
[0010]
According to the present invention, the first coating liquid is applied to both sides of the web, and the second coating liquid having a higher concentration than the first coating liquid is further applied onto the first coating liquid at both side edges of the web. . Thereby, the first coating liquid can be pulled toward the second coating liquid side, and the inclined portion of the first coating liquid can be eliminated at both side edges of the web.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 are diagrams showing an embodiment of a coating apparatus and a coating method according to the present invention.
[0012]
1 and 2, the coating apparatus 10 includes a dip tank 11 in which a first coating liquid 21 to be applied to the web 1 is stored while the web 1 enters, and one side of the web 1 that comes out of the dip tank 11. A pair of nozzles (coating means) 13 that are provided and apply a second coating liquid 22 to both side edges 2 of the web 1 are provided. The pair of nozzles 13 may be provided on both sides of the web 1 to install a total of four nozzles.
[0013]
Of these, the web 1 is made of paper, plastic, or metal, and enters the dip tank 11 and is sent upward. The web 1 that has passed through the pair of nozzles 13 is then sent to a dryer (not shown) to dry the first coating liquid 21 and the second coating liquid 22 on the web 1.
[0014]
PVA or the like is used as the first coating liquid 21, and PVA or the like having a higher concentration than the first coating liquid 21 is used as the second coating liquid 22.
[0015]
Next, a coating method using the coating apparatus 10 having such a configuration will be described.
[0016]
First, the web 1 enters the dip tank 11, and the first coating liquid 21 is applied to both surfaces of the web 1 in the dip tank 11. The application method of the first coating liquid 21 in the dip tank 11 is a so-called “simmering” method, and can be easily applied on the web 1. In this case, inclined portions 25 (see FIG. 3A) of the first coating liquid 21 are formed on both side edges 2 of the web 1.
[0017]
Then, the 2nd coating liquid 22 is apply | coated on the 1st coating liquid 21 from a pair of nozzle 13 with respect to the both-sides edge 2 of the web 1. Thus, the 1st coating liquid 21 is pulled to the 2nd coating liquid 22 side by apply | coating the 2nd coating liquid 22 of higher concentration than the 1st coating liquid 21 with respect to the both-sides edge 2 of the web 2. FIG. be able to. Therefore, the inclined portions 25 of the first coating liquid 21 are eliminated at both side edges 2 of the web 1, and the second coating liquid 22 can be maintained flat at both side edges 2 of the web 1 (FIG. 2). ).
[0018]
As described above, since the inclined portions 25 can be eliminated at the both side edges 2 of the web 1, it is possible to prevent the coating liquid from drying and solidifying at the both side edges 2 of the web 1, thereby preventing liquid pooling. .
[0019]
As described above, according to the present embodiment, the first coating liquid can be applied to the web 1 by the dip tank 11, and a pair of nozzles are formed on both side edges 2 of the web 1 so as to overlap the first coating liquid 21. The second coating liquid 22 can be applied from 13, and the inclined portions of the coating liquid at both side edges 2 of the web 1 can be eliminated to prevent liquid pooling. For this reason, it is possible to prevent the coating liquid from being made uniform in film thickness and product quality.
[0020]
【Example】
Next, examples of the present invention will be described. The following was used as the first coating liquid 21.
1. Coating solution concentration 10.0 vol%
2. Coating liquid temperature 40.0 ℃
3. Coating liquid viscosity 15.0 cps
4). Coating liquid density 1.0 g / CM ³
5). Application speed 1.0 m / min
The coating film thickness t by the first coating liquid 21 is obtained using the equation (1).
t = K (ηv / ρg) ^1/2 (1)
Here, K: constant (0.8 for Newtonian fluid), η: viscosity of liquid, v: coating speed, ρ: density of liquid, g: acceleration of gravity using equation (1), t = 0.8 × ( 15.0 × 10 ⁻³ × 1.0 / 60 /
(1.0 × 9.8 × 10 ³ ) ^1/2 ≈130 μm.
In this case, the film thickness td at the time of drying is approximately 13 μm.
The application conditions of the second coating liquid 22 at this time are as follows.
Concentration 50.0 vol%
Coating thickness 26.0 μm (Dry film thickness ≒ 13 μm)
Using the first coating liquid 21 and the second coating liquid 22 as described above, the first coating liquid 21 and the second coating liquid can be accurately obtained without causing a liquid pool on the both side edges 2 of the web 1. It was able to be applied well.
[0021]
【The invention's effect】
As described above, according to the present invention, since the inclined portion of the first coating liquid can be eliminated at both side edges of the web, it is possible to prevent the occurrence of a liquid pool of the coating liquid. For this reason, the film thickness of the coating liquid can be kept uniform at both side edges of the web.
[Brief description of the drawings]
FIG. 1 shows a coating apparatus according to the present invention.
FIG. 2 is a view showing a first coating liquid and a second coating liquid applied to a web.
FIG. 3 is a view showing a coating liquid applied by a conventional coating method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Web 2 Side edge 10 Coating apparatus 11 Dip tank 13 A pair of nozzle 21 1st coating liquid 22 2nd coating liquid

Claims (3)

A dip tank in which a first coating liquid that is applied to the web and forms inclined portions on both side edges of the web is accommodated as the web enters, and
The first coating liquid is provided on the downstream side of the dip tank in the web traveling direction and at least on one side of the web, and a second coating liquid having a higher concentration than the first coating liquid is applied to both side edges of the web. A coating apparatus comprising: a pair of coating means that eliminates the inclined portion formed by the above and forms flat portions by the second coating liquid on both edges of the web .   2. The coating apparatus according to claim 1, wherein the pair of application means are provided on both sides of the web. Applying the first coating liquid on both sides of the web and forming inclined portions on both side edges of the web ;
At least one side of the web is coated with a second coating liquid having a concentration higher than that of the first coating liquid on both side edges to eliminate the inclined portions formed by the first coating liquid, thereby And a step of forming a flat portion with a second coating liquid on the edge .

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