JP2015066519A - Drying device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drying device which can dry a coating film in a short time with high quality by utilizing effect of infrared rays even when the coating film is a solvent coating film while suppressing cost.SOLUTION: A drying device 13 dries a solvent coating film coated on a web 10, and includes an injection nozzle 20 which is arranged on a lower surface side of the web and directly injects hot air on a rear surface of the web; and an infrared radiation device 21 which is arranged on an upper surface side of the web and radiates the infrared rays on the coating film on the web. A surface temperature of the infrared radiation surface of the infrared radiation device is equal to or higher than a temperature of the hot air injected from the injection nozzle.

Description

  The present invention relates to an apparatus for drying a coating film applied on a web.

  As a method of drying the coating film applied on the web, a drying method using hot air is common, but in particular, in a jet flow type hot air drying apparatus in which high-speed hot air is directly sprayed from the nozzle to the coating film, Very high drying efficiency is obtained, and the coating film can be dried in a short time.

  However, in the case of a thick film with a hot air drying device, only the surface of the coating film is heated first, and there is a problem of skinning that forms a dry film on the coating film surface, or hot air is applied to the coating film when the viscosity of the coating liquid is low. Due to the problem of drying unevenness that occurs when sprayed directly, many drying apparatuses using an infrared heater characterized by high efficiency, no wind, and internal heating in the initial stage of drying have been proposed.

  On the other hand, as an infrared heater for drying equipment for coating films containing organic solvents from the viewpoint of explosion protection, heat heater oil or steam is generally used as the heat source. Since there is a problem in terms of maintainability, a drying apparatus using an electrically heated infrared heater that is superior in these respects has also been proposed for drying a coating film containing an organic solvent.

  Patent Document 1 states that an electrically heated infrared heater has an explosion-proof structure, so that even if an organic solvent is contained, there is no risk of explosion and it can be safely operated. Further, in Patent Document 2, an electric heating infrared heater can be safely used by replacing the inside of the drying apparatus with an inert gas such as nitrogen gas.

  However, even when an electrically heated infrared heater is used, the upper limit temperature of the heater surface is limited to a low level in accordance with the explosion-proof regulations when a solvent having a low ignition point temperature is included. In addition, when used with an inert gas, there is a problem that the running cost is high, and an infrared heater that uses heat transfer oil or steam as a heat source even in a drying device using an electrically heated infrared heater. It was insufficient as an alternative to the drying device using

Japanese Patent Laid-Open No. 2001-221469 Japanese Patent Laid-Open No. 11-254642

  Accordingly, an object of the present invention is to provide a drying apparatus capable of drying a coating film in a short time with high quality by utilizing the effect of infrared rays even if it is a solvent-based coating film, while suppressing the cost. To do.

  The inventor has found that the effect of infrared rays is manifested when the temperature of the infrared heater is equal to or higher than the temperature of the hot air in the drying apparatus, and has completed the present invention.

As means for solving the above problems, the invention according to claim 1 is a drying apparatus for drying a solvent-based coating film applied on a web,
An ejection nozzle that is arranged on the lower surface side of the web and blows hot air directly on the back surface of the web;
An infrared radiation device that is disposed on the upper surface side of the web and radiates infrared rays to the coating film on the web;
The drying apparatus is characterized in that a surface temperature of an infrared radiation surface of the infrared radiation device is equal to or higher than a temperature of hot air ejected from the ejection nozzle.

  The invention described in claim 2 is characterized in that the hot air blown from the discharge nozzle of the drying device is a hot air obtained by heating the infrared radiation surface of the infrared radiation device. It is a drying device.

  Moreover, invention of Claim 3 is a drying apparatus of Claim 1 or 2 characterized by the distance of the infrared radiation surface of the said infrared radiation apparatus and a web being 10 mm-100 mm.

  By carrying out the above, it is possible to dry the solvent-based coating film applied on the film in a high quality and in a short time, particularly with a low cost apparatus.

It is a conceptual diagram which shows an example of the coating line containing a drying apparatus. It is a cross-sectional schematic diagram which shows an example of a general drying apparatus. It is a cross-sectional schematic diagram which shows an example of the drying apparatus of this invention. (A) And (b) is a conceptual diagram which shows an example of the supply / exhaust system of the drying apparatus of this invention. It is a table | surface figure which shows the result of a present Example.

  Hereinafter, the present invention will be described in more detail. FIG. 1 shows a conceptual diagram of a coating line including a drying device. The coating line mainly includes a feeding device 11 for feeding out the web 10, a coating device 12 for applying a coating liquid onto the web 10, a drying device 13 for drying a coating film formed on the web 10, and coating and drying. The web 10 includes a winding device 14 that winds up the web 10 and a number of guide rollers 15 that transport the web 10 while supporting it.

  As the web 10, a resin film such as PET (polyethylene terephthalate) or polycarbonate, a metal foil, paper, or the like can be used. Pretreatment such as corona treatment may be performed on the web 10 before application.

  The coating apparatus 12 can use various types such as a gravure coater, a die coater, and a curtain coater.

  FIG. 2 shows a schematic sectional view of a general drying apparatus. The drying device 13 includes an air supply duct (not shown) for supplying hot air to the ejection nozzle 20 and an exhaust duct (not shown) for exhausting the hot air from which the coating film has been dried.

  The ejection nozzles 20 are arranged on the web 10 at regular intervals, for example. The ejection nozzle 20 is provided with a slit, and hot air heated to a predetermined set temperature by a heating device (not shown) is ejected from the slit through the air supply duct. And the drying of the coating film on the web 10 is advanced by the hot air which spewed.

FIG. 3 shows a schematic cross-sectional view of the drying apparatus 13 according to the present invention. The spray nozzle 20 is installed on the lower surface side of the web 10 with respect to a general drying device, and the infrared radiation device 21 is installed on the upper surface side of the web 10. In this way, drying proceeds from the inside of the coating film due to convective heat transfer from the lower surface side (the back surface of the coating film surface) and radiant heat transfer from the upper surface (the coating film surface). And can be dried in a short time without causing skinning.

  As the infrared radiation device 21 installed on the upper surface side of the web 10, it is possible to use a metal duct surface such as stainless steel coated with an infrared radiation material. Ceramics or the like fired can also be used, but it is preferable to use a metal duct surface coated with infrared radiation to uniformly heat a large area, especially when the width of the web 10 is wide. .

  Infrared rays are classified into near infrared rays of 0.78 to 3 μm and far infrared rays of 3 to 1000 μm. Since most of the polymer materials have strong absorption bands of 3 to 4 μm and 6 μm or more, it is preferable to use a far infrared region that is efficiently absorbed by the polymer material and generates heat.

  As the infrared radiation to be coated on the surface of the metal duct, a substance having a large amount of infrared radiation is preferable, and a ceramic coat having an infrared radiation emissivity of 0.9 or more, more preferably 0.95 or more can be exemplified.

  The infrared radiation device 21 is preferably installed in a range of 10 to 100 mm from the web 10. If it is less than 10 mm, there is a risk of contact with the web 10 being conveyed, and if it is separated from 100 mm, the infrared rays are attenuated, so that a sufficient effect cannot be obtained. Further, the size of the infrared radiation device 21 in the width direction is preferably equal to or greater than the width of the coating film in order to uniformly heat the entire coating film surface. It is preferable that the size of the infrared radiation device 21 in the flow direction is as large as possible within a range in which the removed steam does not stay so that the time of facing the infrared radiation device 21 becomes long.

  The surface temperature of the infrared radiation surface of the infrared radiation device 21 is preferably maintained at a temperature equal to or higher than the hot air of the drying device 13. Generally, the greater the difference between the surface temperature of the infrared radiation surface of the infrared radiation device and the web temperature, the greater the effect of infrared irradiation, but the equipment cost increases. On the other hand, when the surface temperature of the infrared radiation surface of the infrared radiation device is lower than the temperature of the hot air of the drying device, the convective heat transfer by the hot air becomes dominant and the effect of the infrared radiation device hardly appears. Therefore, the present invention uses the heat source of the hot air generator and maintains the surface temperature of the infrared radiation surface of the infrared radiation device 21 at a temperature equal to or higher than that of the hot air of the drying device 13, thereby obtaining the infrared effect without much cost. It is about to try.

  The infrared radiation surface of the infrared radiation device 21 is heated by hot air supplied to the ejection nozzle 20 as shown in FIG. That is, air is fed from the air supply blower 31 to the heater 30, and the air heated by the heater 30 is first used for heating the infrared radiation surface of the infrared radiation device 21, and then dried as hot air ejected from the ejection nozzle 20. 13 is supplied to the inside. In this way, the surface temperature of the infrared radiation surface of the infrared radiation device 21 is approximately the same as the temperature of the hot air of the drying device 13, or the amount of heat used for drying the coating film and on the way to the ejection nozzle 20. The amount of heat loss in the duct can be maintained higher than the temperature of the hot air in the drying device 13. Moreover, since an independent heating source is not required unlike an electric or heat medium type infrared heater, the cost can be greatly reduced.

In FIG. 4A, when the heater 30 is controlled so as to control the surface temperature of the infrared radiation surface of the drying device 13 to the set temperature, the surface temperature of the infrared radiation surface of the infrared radiation device 21 becomes a matter of course. When the temperatures of the drying device 13 and the infrared radiation device 21 are controlled independently, the temperature of the infrared radiation surface of the infrared radiation device and the temperature of the hot air ejected from the hot air ejection nozzle are controlled independently. It ’s fine. For example, as shown in FIG. 4B, a part of hot air used for heating the infrared radiation device 21 is supplied to the mixing chamber 34, and hot air mixed with outside air is ejected from the ejection nozzle 20 of the drying device 13. By adopting such a configuration, the surface temperature of the infrared radiation surface of the infrared radiation device 21 can be controlled by the heater 30, and the temperature of the hot air of the drying device 13 can be controlled by the amount of outside air applied to the mixing chamber 34. It becomes.

  Thus, by using hot air drying and infrared drying together, the coating film can be dried with high quality in a short time, and the production efficiency can be improved. Further, since the infrared radiation device used uses hot air as a heat source, it can be efficiently dried at a low cost.

  Examples of the present invention will be described below.

A coating liquid prepared by uniformly mixing the main agent X part / curing agent Y part / main solvent Z part with a polyol as the main agent, isocyanate as the curing agent, and main solvent as MEK (methyl ethyl ketone), respectively, is applied to the PET substrate with a die coater. The protective sheet was prepared by applying and drying at 150 ° C. The dry state of the coating film was evaluated by the following criteria by evaluating the adhesion between the PET substrate and the coating film by a cross hatch test. Moreover, the presence or absence of drying unevenness generation was confirmed visually.
○ ... 100/100 (sufficiently dry and intimate contact)
Δ ... 1-99 / 100 (Insufficient drying or insufficient adhesion performance)
× ... 0/100 (not dry)

[Example 1]
In the drying apparatus of the present invention, a 7-level protective sheet was prepared in which the distance between the infrared radiation apparatus and the PET substrate was set to 10 mm, and the drying time was changed at intervals of 5 seconds from 30 seconds to 60 seconds. The spray nozzle and the infrared radiation surface of the infrared radiation device were coated with a ceramic coat having an infrared emissivity of 0.95.

[Example 2]
A protective sheet was produced in the same manner as in Example 1 except that the distance between the infrared radiation surface of the infrared radiation device and the PET substrate was set to 40 mm.

[Example 3]
A protective sheet was produced in the same manner as in Example 1 except that the distance between the infrared radiation surface of the infrared radiation device and the PET substrate was set to 80 mm.

[Example 4]
A protective sheet was produced in the same manner as in Example 1 except that the distance between the infrared radiation surface of the infrared radiation device and the PET substrate was set to 100 mm.

[Example 5]
A protective sheet was produced in the same manner as in Example 1 except that the distance between the infrared radiation surface of the infrared radiation device and the PET substrate was set to 120 mm.

[Comparative Example 1]
With a general drying apparatus as shown in FIG. 2, a 7-level protective sheet was produced in which the drying time was changed at intervals of 5 seconds from 30 seconds to 60 seconds.

As shown in FIG. 5, when the drying apparatus of the present invention is used, the coating film can be dried in high quality and in a short time. Moreover, it turns out that an effect is so high that the distance of an infrared radiation surface and PET base material is short.

  A coating film drying device that uses both hot air and infrared radiation to dry a coating film that cannot be satisfactorily dried because the coating film is formed on the surface of the coating film only with hot air drying. can do.

DESCRIPTION OF SYMBOLS 10 ... Web 11 ... Feeding device 12 ... Coating device 13 ... Drying device 14 ... Winding device 15 ... Guide roller 20 ... Jet nozzle 21 ... Infrared radiation Apparatus 30 ... Heater 31 ... Air supply blower 32 ... Exhaust blower 33 ... Air supply blower 34 ... Mixing chamber

Claims (3)

A drying device for drying a solvent-based coating film applied on a web,
An ejection nozzle that is arranged on the lower surface side of the web and blows hot air directly on the back surface of the web;
An infrared radiation device that is disposed on the upper surface side of the web and radiates infrared rays to the coating film on the web;
The drying apparatus, wherein a surface temperature of an infrared radiation surface of the infrared radiation device is equal to or higher than a temperature of hot air ejected from the ejection nozzle.   The drying apparatus according to claim 1, wherein the hot air blown from the discharge nozzle of the drying apparatus is hot air that heats the infrared radiation surface of the infrared radiation device.   The drying apparatus according to claim 1 or 2, wherein a distance between the infrared radiation surface of the infrared radiation device and the web is 10 mm to 100 mm.