JP2002045761A - Method for feeding coating fluid into coater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for feeding a coating fluid into a coater of a closed recirculation system, whereby the coating fluid can be prevented from pulsation and bubble formation, and therefore thin coating nonproblematic in coating defects such as coating unevenness can be performed. SOLUTION: In a coater 10 provided with a feed system of a suction type, the relationships: P3>P0+P1-P2>-0.8 kgf/cm2 are satisfied, wherein P0 (kgf/ cm2) is the coating pressure loss across the coating head; P1 (kgf/cm2) is the pressure loss across the slit 46; P2 (kgf/cm2) is the pressure loss across the pipe from the head 18 to a suction pump 34, and P3 is the feed pressure loss across the pump 34. Thereby, the fluid 14 is prevented from suffering pulsation and bubble formation due to cavitation to permit the stable thin coating nonproblematic in coating defects such as coating unevenness.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for feeding a coating liquid from a coating apparatus, and more particularly, to a coating apparatus for coating a continuously running flexible support (hereinafter referred to as "web") with a coating liquid.
The present invention relates to a liquid feeding method of a coating apparatus for feeding a coating liquid to a coating head by a drawing method or a closed reflux method.

[0002]

2. Description of the Related Art Conventionally, as a coating device for coating a coating film having a desired thickness on a web surface, there are devices such as a bar coater system, a reverse roll coater system, a gravure roll coater system, and an extrusion coater system.
Among these, an extrusion coater type coating apparatus is frequently used because it can perform high-speed and thin-layer coating as compared with other types of coating apparatuses. In a coating apparatus of an extrusion coater system, a drawing method (Japanese Patent Laid-Open No. Hei 1-2) is one of methods for feeding a coating liquid to a coating head.
No. 36968). In this drawing method, a difference between a liquid supply amount to the coating head and a drawing amount from the coating head is applied to the web as a coating amount, and a drawing pump is provided in a coating liquid drawing system provided in the coating head, This is a method in which a part of the coating liquid supplied to the coating head by a supply pump is drawn out by a drawing pump. This liquid feeding method is characterized in that high shear can be applied until immediately before coating, and that the coating liquid is less likely to aggregate because there are few staying portions.

However, the application amount has become 1/10 or less of the supply amount due to the recent increase in density, and the pulsation of the application solution due to the pump performance has become a problem. When pulsation occurs in the coating liquid, coating defects such as coating unevenness occur in the coating film applied to the web. As a solution sending method to solve this problem, a closed reflux method has been developed (Japanese Patent Laid-Open No. 5-2934).
No. 27). In this closed reflux system, a single reflux drawing pump is provided in the closed reflux system to supply and withdraw the application liquid to the coating head. The application liquid is quantitatively supplied to the closed reflux system, and the amount of the supplied liquid is supplied. This is a method of applying as an application amount. This liquid feeding method can reduce the pulsation of the coating liquid caused by the pump performance as compared with the drawing method.

[0004]

However, in the extrusion type coating apparatus, in order to make the coating film thinner by controlling the coating amount with high precision while applying high shearing, a drawing method or a closed reflux method is required. Although a liquid feeding method of a system is indispensable, any of the liquid feeding methods has a problem that pulsation or bubbles are generated depending on application conditions. That is, in the drawing method, pulsation occurs, and in the closed reflux method, there is a problem that bubbles are generated in the pipe in addition to the pulsation, and stable application cannot be performed. In particular, in the closed reflux system, when bubbles are generated in the closed reflux system piping, since the structure cannot be made an open system, production must be stopped when foam is generated, and it has not been put to practical use. .

As described above, neither the pulling-out method nor the closed recirculation method has reached a fundamental solution. However, since the cause of the generation of pulsation and bubbles is not well understood, no countermeasure can be taken. .

The present invention has been made in view of such circumstances, and in a method of feeding a coating apparatus of a drawing type or a closed reflux type, pulsation of a coating liquid and generation of bubbles are suppressed.
It is an object of the present invention to provide a liquid feeding method of a coating apparatus which can perform coating with a thin layer and without coating defects such as coating unevenness.

[0007]

The present invention achieves the above object.
Pocket to supply the coating liquid in the coating head
Section and a slit for discharging the coating liquid out of the coating head.
Coating device, which is supplied to an entrance of the pocket portion.
A part of the applied coating solution is pumped from the outlet of the pocket.
In the liquid sending method of the withdrawing liquid sending system, the discharge side pressure of the pump is
Force (Kgf / cm^Two) To P_Three, The coating pressure loss of the coating head is P₀
(Kgf / cm^Two), The pressure loss at the slit is P ₁(Kgf / cm^Two),
Pulling out from the pocket outlet in the pulling-out system
Pipe pressure loss to the pump_Two(Kgf / cm^Two)
And P_Three> P₀+ P₁−P_Two> -0.8 (Kgf / cm^Two)
Characterized by

According to the present invention, a pocket in a coating head is provided.
Suction side pressure of the pump that pulls out part of the coating liquid supplied to the section
Force (Kgf / cm^Two), Ie P₀+ P₁−P_TwoIs -0.8 (Kgf
/cm ^Two) Slit width and pocket
Controls pipe diameter and length from outlet to pump
Cavitation was suppressed by applying
Application of thin layer and uneven coating without generation of liquid pulsation or bubbles
Coating without defects can be stably performed.

[0009]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a coating apparatus according to the present invention.

FIG. 1 is an overall configuration diagram of a first embodiment of a coating apparatus 10 provided with a drawing type liquid feeding system to which the liquid feeding method of the present invention is applied.

As shown in FIG. 1, the drawing-type liquid feed system includes a supply system and a drawing system. The coating liquid 14 stored in the stock tank 12 is supplied to the coating head 18 by the supply system 16. At the same time, a part of the application liquid 14 supplied to the application head 18 is extracted by the extraction system 20.

The supply system 16 has a supply pipe 24 connecting the stock tank 12 and the inlet 22A of the pocket portion 22 of the coating head 18. The supply pipe 24 has a supply pump 26, a coating liquid, A filter 25 for filtering 14 and a flow meter 28 for measuring the supply flow rate are provided. Then, the supply controller 30 is configured to control the liquid supply pump 26 based on the flow rate detection signal from the flow meter 28. As a result, the supply head 16
Can be supplied with the desired amount of the coating liquid 14 very accurately.

The drawing system 20 has a drawing pipe 32 connecting the outlet 22B of the pocket portion 22 of the coating head 18. The drawing pipe 32 has a drawing pump 34 and a flow meter for measuring the drawing flow rate in order from the coating head 18 side. 36 are provided. Further, the drawing controller 38 is configured to control the drawing pump 34 based on the flow rate detection signal from the flow meter 36. This makes it possible to control the amount of application liquid drawn out from the application head 18 very accurately.

FIG. 2 is a partial cutaway view for explaining the extrusion type coating head 18, which will be described by way of an example of a coating head for performing two-layer coating of a lower layer and an upper layer. The coating head 18 is not limited to the extrusion type, and may be of a type that discharges the coating liquid 14 supplied to the pocket portion 22 in the coating head 18 from the slit tip through the slit 46. For example, a slide coating type coating head that slides the coating liquid 14 discharged from the tip of the slit onto a slide surface to apply the coating liquid may be used.

As shown in FIG. 2, the coating head 18 includes
Two cylindrical pockets 22, 22 parallel to the width direction of the web 40 are formed therein, a supply pipe 24 is connected to an inlet 22 </ b> A of the pocket 22, and a drawing pipe 32 is connected to an outlet 22 </ b> B of the pocket 22. Is connected. Each pocket portion 22 has a slit 4 formed substantially equal to the application width.
6 and 46 are connected to the respective slit tips 46A and 46A formed on the edge surface 29 of the coating head 18.

On the other hand, a web 40 to which the coating liquid 14 is applied
The upstream side and the downstream side of the coating head 18 are mounted on a pair of pass rollers (not shown), and the web 40 continuously travels while the web 40 is pressed against the edge surface 29 of the coating head 18 by the pass rollers.

At the time of coating, the coating liquid 14 is supplied to the pocket portion 22 of the coating head 18 by the supply pump 26, and at the same time, a part of the coating liquid 14 in the pocket portion 22 is drawn by the drawing pump 34. A desired amount of the coating liquid is discharged from the slit end 46A by the discharge side pressure. As a result, the difference between the amount of liquid supplied to the application head 18 and the amount withdrawn from the application head 18 is applied to the web 40 as the application amount.

However, when using the coating apparatus 10 provided with the above-mentioned drawing-type liquid feeding system, in the conventional liquid feeding method, pulsation occurs in the coating liquid 14 and the coating liquid applied to the web 40 is coated. There is a problem that coating defects such as unevenness occur.

The inventor of the present invention has analyzed the cause of pulsation and bubbles in the liquid feeding method in the drawing type liquid feeding system. In the conventional liquid feeding method, the suction side pressure of the drawing pump 34 of the drawing system 20 is reduced. Extreme negative pressure has caused cavitation, which has been identified as a cause of pulsation, and pulsation and bubbles have been effectively suppressed by setting the suction side pressure of the extraction pump 34 to near atmospheric pressure. I learned that I can do it.

In this case, the pressure on the suction side of the drawing pump 34 is reduced by the coating pressure loss of the coating head 18 (the pressure loss between the web 40 and the edge surface 29 of the coating head 18) and the slit 46.
It has been found that it is preferable to set the pressure loss based on the following three factors: the pressure loss in the pipe and the piping pressure loss from the pocket outlet 22B of the coating head 18 to the drawing pump 34.

Further, in order to effectively set the suction side pressure of the drawing pump 34 to around the atmospheric pressure, the slit width (W) of the slit 46 and the diameter (D) and length (L) of the drawing pipe 32 are set. ) Was found to be preferable to change at least one of them.

The first embodiment of the present invention is based on the above knowledge, and the coating liquid 14 supplied to the pocket portion 22 in the coating head 18 is supplied from the slit tip 46A through the slit 46. A coating apparatus 10 for discharging and applying the coating liquid 14 to a continuously running web 40,
In a drawing-type liquid feeding method in which a part of the coating liquid 14 supplied to the inlet 22A of the pocket portion 22 is drawn from the outlet 22B of the pocket portion 44 by the drawing pump 34 via the drawing pipe 32, the following formula (1) is used. ) Is configured so as to satisfy the above condition.

[0023]

P ₃ > P ₀ + P ₁ −P ₂ > −0.8 (Kgf / cm ² ) (1) where P ₀ : coating pressure loss of coating head (Kgf / cm ² ) P ₁ : slit Pressure loss (Kgf / cm ² ) P ₂ : Pipe pressure loss (K
gf / cm ² ) P ₃ : Discharge side pressure of the drawing pump (Kgf / cm ² ) In this case, among the above P ₀ , P ₁ , P ₂ , and P ₃ , in particular, the pressure loss at the slit 46 and the pipe pressure loss Is effective, and specifically, the slit width (W) and the diameter (D) and the length (L) of the drawing pipe 32 are preferably set so as to satisfy the above equation (1). .

As a result, the suction side pressure (P ₀ + P ₁ −P ₂ ) of the drawing pump 34 can be set near the atmospheric pressure without an extreme negative pressure, so that cavitation does not occur. Here, -0.8 (Kgf / cm ² ) is the lower limit of the suction side pressure of the drawing pump 34 that can suppress the generation of pulsation. The reason why P ₀ + P ₁ −P _{2 is set} to be less than P ₃ is that if the suction side pressure of the drawing pump 34 becomes larger than the discharge side pressure of the drawing pump 34, the coating head 1
This is because it becomes impossible to quantitatively withdraw a part of the coating liquid 14 from 8.

Therefore, the generation of pulsation in the coating liquid 14 can be suppressed, so that the coating can be stably performed with a thin layer and without generation of coating defects such as coating unevenness. in this case,
When the coating head 18 is of an extrusion type, the coating liquid is applied between the slit tip 46A and the web 40 via a bead of the coating liquid, so that the coating liquid 14 discharged from the slit tip 46A is not opened to the atmosphere. Tip 46
Since the pressure is applied at A, the suction side of the drawing pump 34 is less likely to be negative pressure than the slide coating type.

FIG. 3 is an overall configuration diagram of a second embodiment of a coating apparatus 50 provided with a closed reflux type liquid feeding system to which the liquid feeding method of the present invention is applied. The application head 18 is the same as that of the first embodiment shown in FIG.

As shown in FIG. 3, the liquid feeding system is configured as a closed reflux system in which the inlet 22A and the outlet 22B of the pocket portion 22 are connected in a ring through a pump 62, and the coating solution stored in the stock tank 12 is provided. The liquid 14 is supplied to the closed reflux system 54 via the supply system 52 at a constant rate. The same devices as those in the first embodiment will be described with the same reference numerals.

The supply system 52 is provided with a supply pipe 56 extending from the stock tank 12 to the closed reflux system 54. The supply pipe 56 is arranged to feed the coating liquid 14 quantitatively from the stock tank 12 side. A liquid sending pump 58 and a flow meter 60 for measuring the flow rate of the coating liquid 14 are provided. Then, the supply controller 61 is configured to control the fixed-rate liquid supply pump 58 based on the flow rate detection signal from the flow meter 60. As a result, a constant amount of the coating liquid 14 can be supplied from the supply system 52 to the closed reflux system 54 very accurately.

The closed reflux system 54 includes a reflux pipe 64 in a high-pressure area where the coating head 18 inlet side 22A and the discharge side 62A of the reflux drawing pump 62 feed the coating liquid to the coating head 18.
The outlet side 22B of the coating head 18 and the suction side 62B of the reflux drawing pump 62 are connected by a reflux pipe 66 in a low pressure region for drawing the coating liquid from the coating head 18.
Then, the supply pipe 56 of the supply system 52 is connected to an appropriate position of the reflux pipe 66 in the low pressure region. Thereby, the coating liquid 14 flowing through the supply system 52 and the coating liquid 14 flowing through the closed reflux system 54
Since the joining resistance at the joining portion 68 can be reduced, the coating solution 14 can be smoothly supplied from the supply system 52 to the closed reflux system 54 at a constant rate.

A filter 72 and a flow meter 7 are sequentially connected to the reflux pipe 64 in the high-pressure region from the reflux drawing pump 62 side.
0 is provided, and the controller 74 for reflux is
Is configured to control the reflux drawing pump 62 based on the flow rate detection signal from the controller. Thereby, the closed reflux system 5
The amount of reflux of the coating solution 14 that refluxes 4 can be controlled very accurately.

At the time of coating, the coating solution 14 supplied quantitatively from the supply system 52 to the closed reflux system 54 is circulated through the pocket portion 22 by the reflux suction pump 62, and is controlled by the discharge side pressure of the reflux suction pump 62. A desired amount of the coating liquid 14 is discharged from the slit tip 46A. As a result, a fixed amount supplied from the supply system 52 to the closed reflux system 54 is applied to the web 40 as an application amount.

However, even if the above-described closed reflux type coating apparatus 50 is used, the coating liquid 14 generates pulsation or foams in the conventional liquid feeding method, so that the coating liquid applied to the web 40 is formed. There is a problem that coating defects such as coating unevenness occur in the film.

The inventor of the present invention has analyzed the cause of pulsation and bubbles in the closed reflux system liquid feeding method.
8) The suction side pressure of the reflux drawing pump 62 downstream becomes an extremely negative pressure and causes cavitation. It is found that this is a cause of pulsation and bubbles, and the suction side pressure of the reflux drawing pump 62 is reduced to atmospheric pressure. It was found that pulsation and bubbles could be effectively suppressed by setting it near.

In this case, the suction side pressure of the reflux drawing pump 62 is determined by three factors: the coating pressure loss of the coating head 18, the pressure loss at the slit 46, and the piping pressure loss from the pocket outlet 22B of the coating head 18 to the reflux drawing pump 62. It was found that it is preferable to set on the basis of.

Further, in order to effectively set the suction side pressure of the reflux drawing pump 62 near the atmospheric pressure, the slit 4
6 and at least one of the diameter (D) and the length (L) of the recirculation pipe 66 of the low-pressure area pipe of the closed recirculation system.
It has been found that it is preferable to change one.

The present invention has been made on the basis of the above knowledge, and the coating liquid 14 supplied to the pocket portion 22 in the coating head 18 is supplied to the slit tip 46A through the slit 46.
From the coating solution 14 on the continuously running web 40.
A coating device for coating the pocket 2 with an inlet 2
A pipe 64 of a closed reflux system 54 connecting the 2A and the outlet 22B,
In a closed reflux type liquid feeding method in which the coating liquid 14 is quantitatively supplied to the closed reflux system 54 while the coating liquid 14 is refluxed through the pocket portion 22 by the reflux drawing pump 62 provided at 66, the following equation (2) is obtained. The liquid feeding method is configured to satisfy.

[0037]

P ₃ > P ₀ + P ₁ −P ₂ > −0.8 (Kgf / cm ² ) (2) where P ₀ : coating pressure loss of coating head (Kgf / cm ² ) P ₁ : slit Pressure loss (Kgf / cm ² ) P ₂ : piping pressure loss (Kgf / cm ² ) from the outlet of the pocket to the reflux drawing pump P ₃ : discharge side pressure of the reflux drawing pump (Kgf / cm ² ) Of P ₀ , P ₁ , P ₂ , and P ₃ , it is particularly effective to adjust the pressure loss in the slit 46 and the pressure loss in the recirculation pipe 66 in the low-pressure region. Specifically, the slit width (W) It is preferable that the diameter (D) and the length (L) of the recirculation pipe 66 are set so as to satisfy the above equation (2).

As a result, the suction side pressure (P ₀ + P ₁ −P ₂ ) of the reflux drawing pump 62 can be set to around the atmospheric pressure without an extreme negative pressure, so that cavitation does not occur. Therefore, it is possible to suppress the generation of pulsation and the generation of bubbles in the coating liquid 14 flowing through the closed reflux system 54, and to stably perform the coating with a thin layer and without generation of coating defects such as coating unevenness. Can be. here,
−0.8 (Kgf / cm ² ) is the lower limit of the suction-side pressure of the reflux drawing pump 62 that can suppress pulsation and generation of bubbles. In addition, the reason that P ₀ + P ₁ −P ₂ is less than P ₃ is that
When the suction side pressure of the reflux drawing pump 62 becomes larger than the discharge side pressure of the reflux drawing pump 62, the coating head 18
This is because it becomes impossible to supply the coating liquid 14 in a fixed amount.
In this case, when the application head 18 is of the extrusion type, the suction side of the reflux drawing pump 62 is less likely to be negative pressure than in the slide application type, as in the above-described drawing method.

The coating liquid 14 used in the present embodiment is
Has a softening temperature of 150 ° C. or less as a thermoplastic resin,
Average molecular weight of 10,000 to 300,000, polymerization amount of about 5
About 0-2000, for example, vinyl chloride vinyl acetate copolymer, vinyl chloride vinylidene chloride copolymer, vinyl chloride acrylonitrile copolymer, acrylate acrylonitrile copolymer, acrylate vinylidene chloride copolymer, acrylic Acid ester styrene copolymer, methacrylic acid ester acrylonitrile copolymer,
Methacrylate vinylidene chloride copolymer, methacrylate ester styrene copolymer, urethane elastomer, nylon-silicone resin, nitrocellulose-polyamide resin, polyvinyl fluoride, vinylidene chloride acrylonitrile copolymer, butadiene acrylonitrile copolymer, polyamide Resin, poyvinyl butyral, cellulose derivatives (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose, etc.), styrene butadiene copolymer, polyester resin, chlorovinyl ether acrylate copolymer, Amino resins, various synthetic rubber-based thermoplastic resins and mixtures thereof can be used.

The thermoplastic resin or reactive resin has a molecular weight of 200,000 or less in the state of a coating solution,
After the composition for forming a magnetic layer is applied and dried, these resins may undergo a reaction such as condensation or addition to have an infinite molecular weight. Further, among these resins, it is desirable that the resin does not soften or melt until the resin is thermally decomposed. Specifically, for example, phenol resin, epoxy resin, curable polyurethane resin, urea resin, melamine resin, alkyd resin, silicone resin, reactive acrylic resin, epoxy polyamide resin, nitrocellulose melamine resin, high molecular weight polyester resin and Mixture of isocyanate prepolymer, mixture of methacrylic acid copolymer and diisocyanate prepolymer, urea formaldehyde resin, low molecular weight glycol / high molecular weight diol /
There are a mixture of triphenyl methane triisocyanate, a polyamide resin and a mixture thereof.

The ferromagnetic fine powder dispersed in the binder, a dispersant as a solvent or an additive, a lubricant, an abrasive, an antistatic agent, a nonmagnetic support, and the like may be the same as those conventionally used. used.

Examples of the organic solvent used for the coating solvent include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; esters such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, and glycol monoethyl ether; ,toluene,
There are aromatic carbons such as xylene and chlorinated hydrocarbons such as methylene chloride, ethylene chlorohydrin and cyclobenzene.

Examples of the material of the web include polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, vinyl resins such as polyvinyl chloride, polycarbonates and polyamide resins. Films of plastic shutters such as polysulfone, metal materials such as aluminum and copper, glass, ceramic and the like can be used. These webs may be previously subjected to a pretreatment such as a corona discharge treatment, a plasma treatment, an undercoat treatment, a heat treatment, a metal deposition treatment, and an alkali treatment.

[0044]

EXAMPLES The coating liquid used in the examples was prepared by adding each component having the composition shown in Table 1 to an epoxy resin (epoxy equivalent 500) 30
It is prepared by mixing and dispersing uniformly by adding parts by weight.

[0045]

[Table 1]

Example 1 Two-layer coating was carried out on a web under the coating conditions shown in Table 2 using a coating apparatus having a drawing-type liquid feed system shown in FIG. 1 and a coating head shown in FIG. Was.
Although the drawing method was adopted for both the upper layer and the lower layer, the liquid feeding method of the present invention will be described with an example of the upper layer.

[0047]

[Table 2]

The pressure loss of the slit and the pipe can be theoretically expressed by the following equation.

[0049]

## EQU3 ## Slit pressure loss per unit length of slit (per slit unit width) dP ₁ / dx = −12 μq / W ³ (3)

[0050]

## EQU4 ## Pipe pressure loss per unit length of pipe dP ₂ / dx = −128 μq / πD ⁴ (4) where q: coating flow rate (g / min) W: slit width (m) Q: by drawing pump Drawing-out flow rate (g / min) D: Pipe diameter μ: Coating solution viscosity (cP) x: Method of advancing coating solution FIG. 4 shows Examples 1 to 11 satisfying the solution sending method of the present invention.
When, for the case of Comparative Examples 1 to 3 do not satisfy the liquid transfer method of the present invention, P _0, P _1, withdrawal pump suction side pressure from _{P 2 (P 0 + P 1} -P 2: "drawing P suction 4 Pressure)), the presence or absence of pulsation of the coating solution, generation of bubbles, etc., and the state of the coating film surface applied to the web (FIG. 4).
Was examined. 4. In FIG. 4, .largecircle. Means that there is no pulsation of the coating solution and the surface quality of the coating film is good, and .DELTA. Means that it is normal. Further, the pressure loss P ₁ in the slits of FIG. 4 the pipe pressure loss P
₂ is calculated by substituting the numerical values such as the application flow rate in FIG. 4 into the above-mentioned equations (3) and (4).

As can be seen from the results in FIG. 4, the suction side pressure (P ₀ + P ₁ −P ₂ ) of the drawing pump is P ₃ > P ₀ + P
₁ -P _2> -0.8 embodiment satisfies the (Kgf / cm ²⁾ Example 1
In the cases of Nos. To 11, there was no pulsation of the coating liquid and the like, and the surface quality of the coating film was good. In the embodiment, the embodiment 6 is as follows.
The value was close to the lower limit of 0.8 (Kgf / cm ² ), and the surface quality of the coating film was slightly inferior to those of the other examples.

On the other hand, the suction pump suction side pressure (P
₀+ P₁−P_Two) Is P_Three> P₀+ P ₁−P_Two> -0.8
In the case of Comparative Examples 1 to 3, which deviate from
This caused uneven coating on the coating film surface. Also, a comparative example
In the case of 3, 5 (Kgf
/cm^Two), The pressure on the suction side of the drawing pump exceeds
In addition, it became impossible to pull out with the pulling pump. (Actual
Example 2) Coating provided with a closed reflux type liquid feeding system shown in FIG.
Using the apparatus and the coating head shown in FIG.
Two layers were applied to the web under the conditions. With upper and lower layers
Although the closed reflux method was adopted, the upper layer
The liquid feeding method of the present invention will be described.

[0053]

[Table 3]

Further, the pressure loss of the slit and the pipe is the same as that of the above-mentioned equations (3) and (4), so that the description will be omitted.

FIG. 5 shows Examples 1 to 11 satisfying the liquid feeding method of the present invention and Comparative Example 1 not satisfying the liquid feeding method of the present invention.
This is the result of examining the suction side pump suction side pressure (P ₀ + P ₁ −P ₂ : “Reflux P suction pressure” in FIG. 5) from the numerical values of P ₀ , P ₁ , and P ₂ for the cases of Nos. _{1 to 3} . The presence or absence of pulsation of the coating solution, generation of bubbles, and the like, and the state of the coating film surface applied to the web ("application surface state" in FIG. 5) were examined.
In FIG. 1, ○ means that there is no pulsation of the coating solution and the surface quality of the coating film is good, and △ means that it is normal. Further, the pressure loss P ₁ and the pipe pressure drop P ₂ in the slit of FIG. 5 are calculated by substituting the value of the coating flow rate, etc. of FIG. 1 in the formula (4) and equation (3) described above.

As can be seen from the results shown in FIG. 5, the suction side pressure (P ₀ + P ₁ −P ₂ ) of the reflux drawing pump is P ₃ > P _0.
In the case of Examples 1 to 11 satisfying + P ₁ −P ₂ > −0.8 (Kgf / cm ² ), since the suction side of the reflux drawing pump does not become an extremely negative pressure, the coating liquid No pulsation was observed, and the surface quality of the coating film was good. Among the examples, Example 6 was close to the lower limit of -0.8 (Kgf / cm ² ), and the surface quality of the coating film was slightly inferior to the other Examples, but there was no problem as a product.

On the other hand, the suction side pressure of the reflux drawing pump is
Force (P₀+ P₁−P_Two) Is P_Three> P ₀+ P₁−P_Two>-
In the case of Comparative Examples 1 to 3 deviating from 0.8, bubbles are generated.
And uneven coating on the coating film surface due to the pulsation of the coating liquid.
Was observed. In the case of Comparative Example 3, reflux drawing was performed.
5 (Kgf / cm^Two), Reflux extraction
The suction side pressure of the pump exceeds the
Quantitative liquid transfer by the above became impossible.

[0058]

As described above, according to the liquid feeding method of the coating apparatus of the present invention, the suction side pressure of the pump for extracting a part of the coating liquid supplied to the pocket in the coating head is extremely high. Since there is no negative pressure, pulsation and bubbles of the coating liquid due to cavitation can be suppressed. This makes it possible to apply the coating liquid discharged from the coating head to the flexible support in a thin layer so that coating defects such as coating unevenness do not occur.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram illustrating a drawing-type coating apparatus to which a liquid feeding method of a coating apparatus of the present invention is applied.

FIG. 2 is an explanatory view illustrating an extrusion type coating apparatus.

FIG. 3 is an overall configuration diagram illustrating a closed reflux type coating apparatus to which the liquid feeding method of the coating apparatus of the present invention is applied.

FIG. 4 is a table showing the results of Example 1 of the present invention.

FIG. 5 is a table showing the results of Example 2 of the present invention.

[Explanation of symbols]

10: a drawing type coating device, 12: a stock tank,
14 ... Coating liquid, 16 ... Supply system, 18 ... Coating head, 20
... Pull-out system, 22 ... Pocket part, 24 ... Supply piping, 26
... Supply pump, 28 ... Flow meter, 30 ... Supply controller, 3
4 ... Pull-out pump, 36 ... Flow meter, 38 ... Pull-out controller, 40 ... Web, 46 ... Slit, 46A ... Slit tip, 64 ... High-pressure recirculation pipe, 66 ... Low-pressure recirculation pipe, 68 ... Confluence , 70: flow meter, 72: filter, 74: controller for reflux

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Toshihiro Bandai 1-2-1 Ogimachi, Odawara-shi, Kanagawa Prefecture F-Film Co., Ltd. F-term (reference) 4D075 AC04 AC84 AC95 CA47 DA04 EA05 4F041 AB01 BA05 BA10 BA34 BA56 CA02 CA15 CA22 4F042 BA06 CB02 CB10

Claims (4)

[Claims] An application apparatus having a pocket for supplying an application liquid into an application head and a slit for discharging the application liquid to the outside of the application head, wherein one of the application liquid supplied to an entrance of the pocket is provided. In a liquid feeding method of a liquid feeding system in which a portion is drawn out from an outlet of the pocket portion by a pump, a discharge side pressure (Kgf / cm ² ) of the pump is P ₃ , and a coating pressure loss of the coating head is P ₀ (Kgf / cm ² ). ^2), wherein the pressure loss at the slits ^{_{P 1 (Kgf / cm 2)}} , the pipe pressure loss of P ₂ (K from the pocket portion outlet in the pull-out system to the withdrawal pump
gf / cm ² ), wherein P ₃ > P ₀ + P ₁ −P ₂ > −0.8 (Kgf / cm ² ). 2. The liquid feeding system is configured as a closed reflux system in which an inlet and an outlet of the pocket portion are connected in a ring through the pump, and the closed reflux system is configured such that P ₃ > P ₀ + P. ₁ −
P _2> -0.8 feeding method of coating apparatus according to claim 1, characterized in that satisfy (Kgf / cm ^2). _{3. The} P ₃ > by changing at least one of a slit width (W) of the slit and a diameter (D) and a length (L) of the pipe from the outlet of the pocket to the pump. _{P 0 + P 1 -P 2>} -0.8 (Kgf / cm 2)
The method according to claim 1 or 2, wherein the method (1) is satisfied. 4. The method according to claim 1, wherein said coating head is of an extrusion type.