JP2005262115A - Apparatus for circulating coating liquid and coating apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for circulating a coating liquid for resolving retention of an air bubble in a coating head causing occurrence of a coating failure such as nonuniformity, dislocation, a string or the like simply and without wasting the coating liquid, and a coating apparatus attached with the same. <P>SOLUTION: A discharge coating liquid passage for passing the coating liquid discharged from the slit opening end of the coating head includes a horizontal orientation U-shaped recess covering the horizontal orientation lip tip end of the coating head from a vertical direction at one end and also is provided with at least a horizontal orientation slit-like opening at the center of the U-shaped recess, wherein the coating liquid discharged from the slit opening end of the coating head is flowed in from the slit-like opening of the discharge coating liquid passage, then discharged from the discharge port of the other end, and further reintroduced into a supply tank of the coating apparatus through the coating liquid path located at the lower stream side and a switchable valve. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a coating liquid circulation device that can be attached to a lip tip of an extrusion type coating head and can remove bubbles remaining in the coating head, and an extrusion type coating device to which the coating liquid circulation device is attached. It is.

  In the production of functional optical films, photographic light-sensitive materials, magnetic recording media, surface-treated steel sheets, etc., there is a step of applying a coating solution onto a support, in which case essential components such as a photosensitive agent or magnetic particles are added. A coating solution obtained by mixing with a resin binder, adding various additives as necessary, and diluting with an organic solvent or the like is used.

  As a method of applying such a coating solution to a support, various coating methods such as a roll coater, a gravure coater, a knife coater, an extrusion type coater (coating apparatus), or various reverse coaters are used. Yes. Among these, the extrusion type coating apparatus is not exposed to air until immediately before coating, so the change of the coating liquid is small, the film thickness in the width direction of the coating film is excellent, In recent years, its use has increased due to its excellent smoothness.

  However, in the extrusion type coating apparatus, the film is discharged in a mixed manner with non-uniformity of film thickness due to the air that is carried along with the conveyance of the support, leakage, streaks due to foreign matter, bubbles remaining in the coating head, or coating liquid. Application failures such as leakage and streaks are likely to occur due to air bubbles coming in, and various countermeasures are taken for each failure.

  In particular, a coating failure caused by bubbles in the coating head is caused by the formation of a bubble retention portion in the process of filling the manifold with the coating liquid, and the bubbles in the retention portion. In order to cope with such a situation, a defoaming device is provided in the middle of the coating liquid transport pipe upstream from the coating head to perform the defoaming process. However, even if such a process is performed, bubbles remain. In some cases, the coating liquid is filled in the coating head, and since many coating heads are made of metal blocks, it is difficult to confirm the presence or absence of the coating head.

  In addition, as a countermeasure against coating failures other than the above, a method of extruding bubbles by excessively feeding the coating liquid into the coating head before starting the coating operation and increasing the pressure inside the coating head, and the slit opening end of the coating head upward At the production site, a method of extracting the air bubbles directed toward the surface or a method of combining the two is performed.

  However, when the coating liquid is excessively fed into the coating head, a large amount of the coating liquid is discharged before the start of the coating operation, which is wasteful. In order to reduce the waste, the discharged coating liquid is again sent to the supply tank. In this case, there is a possibility that the composition may change when the coating solution is exposed to air.

  In addition, when installing the coating head so that its slit portion is in the horizontal direction, the structure is such that the coating head can take an upward angle from the horizontal in order to remove bubbles with the slit opening end of the coating head facing upward. It must be installed on a pedestal with However, in that case, the structure of the pedestal becomes complicated, and it is very difficult to maintain the accuracy of the position and the robust structure that are important for application.

  The present invention has been made in view of the situation as described above, and in the coating using the extrusion type coating apparatus, the retention of bubbles in the coating head, which causes the occurrence of coating failures such as unevenness, leakage, streaks, It is an object of the present invention to provide a coating liquid circulation device for eliminating the coating liquid simply and without wasting it before starting the coating operation, and a coating apparatus to which the coating liquid is attached.

  In order to solve such a problem, the invention according to claim 1 is configured to send the coating liquid from the transportation path side of the coating head having a coating liquid inflow portion in which the transportation path, the manifold, and the slit are continuously provided. Pumped from the supply tank by a pump, discharges the coating liquid from the slit opening end of the coating liquid inflow section, and seals the tip of the lip of the extrusion type coating head that applies the discharged coating liquid onto the support transported there It can be attached so as to be wrapped in a state, and is connected to the discharge coating liquid delivery section that delivers the coating liquid discharged from the slit opening end of the coating head, and is connected to the discharge coating liquid delivery section. Coating liquid circulation apparatus comprising at least a coating liquid transport pipe and an openable / closable valve for re-feeding the coating liquid discharged after flowing into the supply tank of the coating apparatus The discharge coating liquid delivery section has a horizontally long U-shaped recess that wraps the horizontally long lip tip of the coating head from above and below at one end, and a horizontally long slit-shaped opening at the center of the U-shaped recess. Is provided, and the coating liquid discharged from the slit opening end of the coating head flows from the slit-shaped opening of the discharge coating liquid delivery section, and then is discharged from the discharge port at the other end, and is located further downstream. The coating liquid circulating apparatus is characterized in that it is re-entered into the supply tank of the coating apparatus via the coating liquid flow path and the openable / closable valve.

  A second aspect of the present invention is an extrusion type coating apparatus to which the coating liquid circulating apparatus according to the first aspect is attached.

  Furthermore, the invention according to claim 3 is the coating apparatus according to claim 2, wherein at least a filter and a defoaming device are provided between the transport path of the coating head and the coating liquid discharge portion of the supply tank. In addition, a pressure sensor is installed on the way to the coating head manifold. From the measured value measured by the pressure sensor, the output of the liquid feed pump in the coating device and the opening and closing of the coating fluid circulation device It is characterized in that the opening / closing amount of the free valve can be controlled.

  According to the present invention, bubbles staying in the coating head of the extrusion-type coating apparatus can be efficiently and accurately removed, and application failures such as streaks or leakage caused by the bubbles staying in the coating head can be prevented. Generation | occurrence | production can be suppressed significantly and the application | coating liquid can be apply | coated on a support body.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 2 is an explanatory view showing a schematic configuration of a general extrusion-type coating apparatus and a usage pattern thereof.

The coating liquid charged in the supply tank 21 is sent to the coating head 23 by the liquid feed pump 22. The coating head 23 has a coating liquid inflow portion formed by connecting a transport path 27, a manifold 26, and a slit 28 inside, and the coating liquid charged in the supply tank 21 is transported by the transport pump 22 by the transport pump 29. After being fed from the side, it is discharged from the slit opening end 30 of the application liquid inflow portion, and the applied application liquid can be applied onto the support 8 conveyed there. In the drawing, members indicated by 24 and 25 are an upstream lip and a downstream lip constituting the coating head 23, and these constitute a lip.

  The manifold 26 has a substantially semicircular cross-sectional shape in the transport direction of the support 8 to which the coating liquid is applied, and the same direction as the width direction of the support 8 is the same as or substantially the same as this cross-sectional shape. It is a space that expands horizontally in shape. The semicircular inner diameter of the cross section of the manifold 26 in the transport direction of the support 8 is about 5 to 50 mm, and is set to the best size according to the properties, viscosity, etc. of the coating liquid, and both ends thereof are sealed. The coating liquid is blocked by a plate or the like so as not to leak out of the coating head 23.

  The slit 28 is a slit-shaped coating liquid passage having a width of 0.05 to 0.5 mm that opens from the manifold 26 toward the support 8, and the distance from the manifold 26 to the lip tip 30. Is about 5 to 100 mm. The width and distance of the slit 28 are also appropriately determined depending on the properties of the coating solution and various conditions such as coating speed and coating film thickness.

  As shown in FIG. 2, using the extrusion type coating apparatus having such a configuration, the slit opening end of the slit 28 of the coating head 23 with respect to the support 8 conveyed while being held by the backup roll 9. The desired application is performed while discharging the application liquid from 30.

  On the other hand, FIG. 1 is explanatory drawing which shows the schematic structure of the coating-liquid circulation apparatus of this invention, and the extrusion-type coating device which attached it.

  The coating liquid circulation device can be attached so as to wrap the tip end portion of the extrusion type coating head 3 in a hermetically sealed state, and is a discharge coating liquid delivery section that delivers the coating liquid ejected from the slit opening end 40 of the coating head 3. 10 and the coating liquid transport unit 10 connected to the discharge coating liquid delivery unit 10 for re-injecting the coating liquid discharged after flowing into the coating liquid delivery unit 10 into the supply tank 1 of the coating apparatus. It is a device comprising at least a tube 15 and an openable / closable valve 14. The discharge coating liquid delivery section 10 has a horizontally long U-shaped recess at one end that wraps the horizontally long lip tip of the coating head 3 from above and below, and a horizontally long slit-shaped opening at the center of the U-shaped recess. The coating liquid discharged from the slit opening end 40 of the coating head 3 flows from the slit-shaped opening 11 of the discharged coating liquid delivery section 10 and is discharged from the discharge port 13 at the other end. Further, it is re-entered into the supply tank 1 of the coating liquid coating apparatus via the coating liquid flow path 15 and the openable / closable valve 14 located further downstream. In addition, the part shown by 12 is a groove part provided in the middle of the flow path of the coating liquid in the discharge coating liquid delivery part 10.

  The discharge coating liquid delivery section 10 shown in the figure is teflon (R) between a horizontally long U-shaped recess so that the lip tip of the coating head 3 is attached in a sealed state without damaging it. It is firmly fixed by a bolt or the like through a sealing member 16 made of a flexible resin such as (fixed state not shown). Further, the width of the slit-shaped opening 11 is set to be equal to or wider than the width of the slit 38 of the coating head 3.

  In the coating apparatus to which the coating liquid circulation apparatus having such a configuration is attached, the coating liquid charged into the supply tank 1 is supplied to the coating head 3 by the liquid feed pump 2 via the filter 17 and the defoaming apparatus 18. It is sent to the manifold 36.

  A pressure sensor 19 is arranged on the way to the manifold 36, and the manifold is controlled by controlling the output of the liquid feed pump 2 and the opening / closing amount of the openable / closable valve 14 based on the measurement value obtained by the measurement by the pressure sensor 19. The pressure of the coating liquid in 36 can be freely changed.

  In short, when the inside of the manifold 36 is filled with the coating liquid and discharge of the coating liquid is started from the slit opening end 40 of the slit 38, the output of the liquid feeding pump 2 is changed based on the measured value of the pressure sensor 19, and the inside of the manifold 36 is changed. The pressure is adjusted, and the coating solution is gradually poured from the slit 38 of the coating head 3 into the groove 12 in the coating solution delivery section 10 with a predetermined pressure.

  At this time, if the internal pressure of the manifold does not reach a desired pressure only by delivering the coating liquid by the liquid feed pump 2, the pressure is increased by closing the openable / closable valve 14 to an appropriate state, and the necessary pressure is obtained. You can make it.

  The pressure in the manifold for removing bubbles staying in the manifold 36 is appropriately selected according to the width of the slit 38 of the coating head 3, the slit length, the coating solution viscosity, the coating solution surface tension, and the installation angle of the coating head. Adjust to.

  For example, when a polyurethane acrylate coating solution having a viscosity of 3.5 mPa · s and a surface tension of 26.5 mN / m is used, when the coating head is set horizontally, the slit exit portion is 10 °. In the upward direction, 30 kPa or more is a guideline for the inner thickness of the manifold necessary for air bubble removal.

  The coating liquid that has passed through the openable / closable valve 14 based on the above operation passes through the coating liquid flow path 15 and is charged again into the supply tank 1. Then, by circulating the coating liquid as described above for 5 minutes or more, preferably 15 minutes or more, the bubbles remaining in the manifold 36 of the coating head 3 are removed.

  Therefore, in the defoaming process inside the coating head before the start of the coating operation, a series of defoaming operations can be performed efficiently without causing a loss of the coating liquid during the filling process of the coating liquid as in the past. In addition, it is difficult for the coating liquid to be exposed to the air to change its composition. Embodiments of the present invention will be described below with reference to the drawings.

  First, 24 parts by weight of silica beads having an average particle diameter of 0.5 μm and a refractive index of 1.5 μm are mixed with 100 parts by weight of a polyester resin, and diluted with toluene so that the solid content ratio becomes 50%. A coating solution adjusted to 5 mPa · s was prepared. Further, a triacetyl cellulose film having a thickness of 80 μm was used as a support on which the coating solution was applied.

Next, the coating liquid circulating apparatus shown in FIG. 1 is temporarily retracted, and after the coating liquid having the above composition is charged into the supply tank 1, the internal coating liquid inflow portion is empty at a flow rate of 0.000050 m ³ / min. The coating liquid is made to flow sequentially into the coating head 3 and the coating liquid is discharged from the slit opening end 40 to apply (wet film thickness 10 μm) to the support sent at a speed of 10 m / min. It was. Table 1 shows the situation of application 1 minute, 5 minutes and 15 minutes after the start of application.

  Subsequently, the discharge coating liquid delivery section 10 of the coating liquid circulation apparatus according to the present invention which has been temporarily saved in the above coating example is set at the lip tip of the coating head 3 as shown in FIG. With the universal valve 14 half-closed, the pressure inside the manifold becomes 46 kPa, and the inside application liquid inflow portion is sent to the empty application head 3 to apply air for 1 minute to remove bubbles in the manifold 36. After the liquid was circulated, coating (wet film thickness 10 μm) was performed on the support conveyed at a speed of 10 m / min. Similarly, coating was performed after the coating liquid was circulated for 5 minutes and 15 minutes. Table 1 shows the state of these coatings.

以上の結果、塗布液循環装置による塗布液の循環を行わずに塗布を行なった場合は、マニホールド内に塗布液を充填した後の吐出時間によらず５００ｍｍの塗布幅に対して５本前後のマニホールド内の気泡が原因と推測される塗布スジが発生した。

As a result of the above, when coating is performed without circulating the coating liquid by the coating liquid circulation device, the number of coatings is about 5 for a coating width of 500 mm regardless of the discharge time after filling the manifold with the coating liquid. A coating streak presumably caused by air bubbles in the manifold occurred.

  On the other hand, when coating is performed after the coating liquid is circulated using the coating liquid circulation device, the coating liquid circulation time after filling the manifold in the manifold is 500 mm. One application stripe was confirmed with respect to the application width, but no application stripe was observed when the circulation time was 5 minutes or more.

It is explanatory drawing which shows the structure of the outline of the coating-liquid circulation auxiliary | assistance apparatus of this invention, and the extrusion-type coating device which attached this. It is explanatory drawing which shows the general | schematic structure of an extrusion type coating device, and its usage form.

Explanation of symbols

1, 2 ··· Supply tanks 2 and 22 ·· Liquid feed pumps 3 and 23 ·· Coating heads 4 and 24 ·· Upstream lips 5 and 25 ·· Downstream lip 8 ·· Support 9 ·· Backup roll 10 ·・ Discharged coating liquid delivery part 11 ・ ・ Slit-shaped opening 12 ・ ・ Groove part 13 ・ ・ Discharge port 14 ・ Openable / closable valve 15 ・ Coating liquid flow path 16 ・ ・ Seal member 17 ・ ・ Filter 18 19 .. Pressure sensor 26, 36 .. Manifold 27, 29, 37 .. Transport path 28, 38 .. Slit 45 .. Transport pipe.

Claims (3)

  The coating liquid is fed from the supply tank by the feed pump from the coating path inflow side of the coating head having the coating liquid inflow portion formed by connecting the transport path, the manifold, and the slit, and the coating liquid is fed from the slit opening end of the coating liquid inflow portion. Can be attached so as to wrap the tip of the lip of an extrusion type coating head that applies the coating liquid onto the support transported there, and is discharged from the slit opening end of the coating head. A discharge coating liquid delivery section that delivers the coating liquid to be delivered, and a discharge coating liquid delivery section that is connected to the discharge coating liquid delivery section, and that discharges the coating liquid after flowing into the coating liquid delivery section. A coating liquid circulation device comprising at least a coating liquid transport pipe for opening and a valve that can be opened and closed, wherein the discharge coating liquid delivery section is a horizontally long lip tip of the coating head In addition, a horizontally long U-shaped concave portion that wraps the film from above and below is provided at one end, and at the center of the U-shaped concave portion, at least a horizontally long slit-shaped opening is provided, and discharged from the slit opening end of the coating head. After the coating liquid flows in from the slit-like opening of the discharged coating liquid delivery section, the coating liquid is discharged from the discharge port at the other end, and further through the coating liquid flow path and the openable / closable valve located downstream, the supply tank of the coating apparatus A coating liquid circulating apparatus, wherein the coating liquid circulating apparatus is re-introduced into the inside.   An extrusion-type coating apparatus, to which the coating liquid circulating apparatus according to claim 1 is attached.   At least a filter and a defoaming device are installed between the transport path of the coating head and the coating liquid discharge part of the supply tank via a transport pipe, and a pressure sensor is provided on the way to the manifold of the coating head. And an opening / closing amount of the openable / closable valve of the coating liquid circulating apparatus can be controlled from the measured value measured by the pressure sensor. Item 3. The coating apparatus according to Item 2.

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