JP2013057438A - Drying device for coating film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drying device capable of shortening a drying time by using effects of infrared rays while suppressing costs.SOLUTION: The device for drying a coating film applied to a web includes: a plurality of hot air injection nozzles disposed to face upper and lower sides of the web and supporting the web in a floating manner; and infrared ray radiation plates disposed to face the upper and lower sides of the web, installed between pitches of the plurality of hot air injection nozzles and emitting infrared rays by hot air injected from the hot air injection nozzles. Infrared ray radiation covering layers covered with infrared ray radiating substances which emit infrared rays by hot air injected from the hot air injection nozzles are installed on hot air injection faces of the hot air injection nozzles opposing the web.

Description

  The present invention relates to a drying apparatus, and more particularly to a drying apparatus for drying a coating film applied on a web.

  A drying method using hot air is generally used as a method for drying a coating film applied on a web. In particular, in a jet flow type hot air drying apparatus in which high-speed hot air is directly sprayed from a nozzle onto a coating film, it is very high. Drying efficiency is obtained, and the coating film can be dried in a short time.

  Furthermore, as a technique for shortening the drying time, a drying apparatus utilizing infrared rays has been proposed. In the infrared drying, the amount of heat transfer of hot air drying is proportional to the difference between the hot air temperature and the temperature of the object to be heated, whereas it is proportional to the difference between the fourth power of the heater temperature and the fourth power of the object to be heated. It can be heated faster than drying.

  Also, especially when the coating film is thick, only the surface of the coating film is heated first by hot-air drying, and the coating film surface becomes a skinned state where drying is difficult to proceed. On the other hand, since infrared drying is uniformly heated from the inside of the coating film, it can be dried faster than hot air drying.

  Furthermore, infrared drying is a heating method that involves molecular vibrations and promotes the chemical reaction of the polymer material, so that it is expected to improve the adhesion of the coating film. However, infrared drying alone forms a boundary layer with high-concentration steam in the vicinity of the coating film and hinders mass transfer, so it is often used in combination with hot air drying.

For example, there has been proposed a drying apparatus that combines hot air drying of an ejection flow type (hereinafter referred to as floating type) and infrared drying. By installing an infrared heating device between the nozzle pitches and alternately repeating heating with infrared rays and removal of the boundary layer with hot air, the drying time can be greatly shortened (Patent Documents 1 and 2).
Known documents are shown below.

Japanese Patent No. 2694325 JP-A-5-203355

  However, a drying device that combines an infrared drying device and a hot air drying device increases the initial cost and the running cost. Further, when the web is a film substrate, it is necessary to provide a shutter mechanism or the like in the infrared heating device or to set the temperature of the infrared heating device to be equal to or lower than the melting point of the film in order to prevent the film from fusing at the time of abnormal stop. . Furthermore, in the case of a solvent system, the surface temperature of the infrared heating device that can be used at the ignition point temperature of the solvent included from the explosion-proof regulations is limited. When a shutter mechanism or the like is provided, it becomes a further cost factor, and when the temperature of the infrared heating device is kept low, the cost effectiveness is reduced.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a drying apparatus capable of shortening the drying time by utilizing the effect of infrared rays while suppressing cost.

  The inventor has found that the above problem can be solved by specifying an infrared radiation method, and has completed the present invention.

  That is, the invention according to claim 1 is an apparatus for drying a coating film applied on a web, and is arranged so as to face the top and bottom of the web, and a plurality of floatingly supporting the web. A hot air jet nozzle, and an infrared radiation plate that is arranged so as to face the upper and lower sides of the web, is installed between the pitches of the plurality of hot air jet nozzles, and emits infrared rays with hot air ejected from the hot air jet nozzle. It is the drying apparatus characterized.

  According to a second aspect of the present invention, an infrared radiation coating layer is provided on the hot air ejection surface facing the web of the hot air ejection nozzle, which is coated with an infrared radiation material that emits infrared rays by hot air ejected from the hot air ejection nozzle. The drying apparatus according to claim 1.

  A third aspect of the present invention is the drying apparatus according to the first or second aspect, wherein the distance between the infrared radiation plate and the web is 10 mm to 100 mm.

  The drying apparatus of the present invention can dry a coating film applied on a web, particularly a solvent-based thick film, in a short time, and can obtain a film with good adhesion.

It is a conceptual diagram of the coating line including a drying apparatus. It is explanatory drawing which showed typically the general floating type drying apparatus. It is explanatory drawing which showed typically an example of the drying apparatus of this invention.

Hereinafter, modes for carrying out the present invention will be described.
First, the coating line incorporating the drying apparatus of the present invention will be described. 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. And a large number of guide rollers 15 that convey the web 10 while supporting it.

  As the web 10, a resin film such as polyethylene terephthalate (PET) or polycarbonate, 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 is an explanatory view schematically showing a general floating type drying apparatus.
The drying device 13 includes an air supply duct (not shown) for supplying hot air to the hot air jet nozzle 20 and an exhaust duct (not shown) for exhausting the hot air from which the coating film has been dried.

The hot air jet nozzles 20 are arranged in a staggered manner with the web 10 interposed therebetween. Hot air jet nozzle 2
A slit is provided in the web facing surface (hot air blowing surface) of 0, so that hot air heated up to a predetermined set temperature by a heating device (not shown) is blown out from the slit through the air supply duct. It has become. Then, the hot air blown out holds the web 10 in a floating manner so as to draw a sine wave, and the coating film on the web 10 is further dried.

FIG. 3 is an explanatory view schematically showing an example of the drying apparatus of the present invention.
In contrast to a general floating type drying device, an infrared radiation coating layer 21 is provided on the web facing surface (hot air ejection surface) of the hot air ejection nozzle 20 and coated with an infrared radiation material that emits infrared rays with a high radiation amount by heating. In addition, an infrared radiation plate 22 is installed between the pitches of a plurality of hot air ejection nozzles 20 provided.

  The infrared radiation plate 22 installed between the pitches of the hot-air ejection nozzles 20 is provided with an infrared radiation coating layer 21 in which a metal surface such as stainless steel is coated with an infrared radiation material. A material obtained by firing ceramic or the like can also be used, but it is preferable to use a metal surface coated with an infrared emitting material in order to uniformly heat a large area, particularly when the web width is wide.

  Infrared rays can be divided into near infrared rays of 0.78 to 3 μm and far infrared rays of 3 to 1000 μm, but most of 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 efficiently absorbs heat and generates heat.

  The infrared radiation material used for the infrared radiation coating layer 21 is preferably a material having a large amount of infrared radiation, and has an infrared emissivity of 0.9 or more, preferably 0.95 or more. For example, a ceramic etc. are mentioned. Moreover, the same infrared radiation substance as the material which coat | covered the infrared radiation board 22 can be used suitably also for the coating | cover to the web opposing surface (hot air ejection surface) of the hot air ejection nozzle 20. FIG.

  The infrared radiation plate 22 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.

  In addition, the size of the infrared radiation plate 22 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. The size of the flow direction of the infrared radiation plate 22 (web conveyance direction) is preferably as large as possible within a range where the steam removed by the hot air does not stay so that the time taken by the infrared radiation plate 22 becomes longer.

  The infrared radiation plate 22 is heated indirectly by heat in the drying device 13 (heat from hot air blown from the hot air jet nozzle 20). Therefore, the temperature of the infrared radiation plate 22 is the same as the set temperature of the drying device 13. Similarly, the infrared radiation coating layer 21 provided on the hot air ejection surface of the hot air ejection nozzle 20 is also indirectly heated by the heat in the drying device 13 (heat from the hot air ejection nozzle 20).

  Thus, by using floating type hot air drying and infrared drying together, the drying time of the coating film can be shortened, and the production efficiency can be improved. Moreover, since the infrared radiation material 21 used uses hot air as a heat source, it can be efficiently dried at the same running cost as a floating type drying apparatus.

  Examples of the present invention will be described below.

<Example 1>
An infrared radiation coating layer 21 of an infrared radiation plate 22 and a hot air jet nozzle 20 is formed on a web 10 in which a coating liquid in which a polyol is a main agent, an isocyanate is a curing agent, and a main solvent is MEK (methyl ethyl ketone) is applied to a PET substrate by a die coater With the drying device 13 of the present invention in which the distance between the provided web facing surface and the web 10 was set to 10 mm, a 7-level protective sheet was prepared in which the drying time was changed at intervals of 5 seconds from 30 seconds to 60 seconds. The hot air jet nozzle 20 and the infrared radiation plate 22 were coated with a ceramic coat having an infrared emissivity of 0.95 as an infrared radiation material.

<Example 2>
A protective sheet was prepared in the same manner as in Example 1 except that the distance between the web 10 and the web facing surface provided with the infrared radiation coating layer 21 of the infrared radiation plate 22 and the hot air jet nozzle 20 was set to 100 mm.

  Below, the comparative example of this invention is demonstrated.

<Comparative Example 1>
A protective sheet was prepared in the same manner as in Example 1 except that the distance between the web 10 and the web facing surface provided with the infrared radiation coating layer 21 of the infrared radiation plate 22 and the hot air jet nozzle 20 was set to 200 mm.

<Comparative example 2>
With a general floating type drying apparatus as shown in FIG. 2, a 7-level protective sheet was prepared in which the drying time was changed at intervals of 5 seconds from 30 seconds to 60 seconds.

<Test method>
According to the adhesion (cross-cut method) of JIS-K5600-5-6, the web 10 shows the dry / cured state of the protective sheet of the example prepared by the drying apparatus 13 of the present invention and the protective sheet of the comparative example. It evaluated as the following references | standards and evaluated as adhesiveness of a PET base material and a coating film. The results are summarized in Table 1.
○ ... 100/100 (sufficiently dry and intimate contact)
Δ ... 1-99 / 100 (Insufficient drying or insufficient adhesion performance)
× ... 0/100 (not dry)

以下に、実施例と比較例との比較結果について説明する。

Below, the comparison result of an Example and a comparative example is demonstrated.

<Comparison result>
As shown in Table 1, Examples 1 and 2 using the drying device 13 of the present invention can shorten the drying time. Moreover, it turns out that an effect is so high that the distance of the web opposing surface and the web 10 which were coated with the infrared radiation material 21 of the infrared radiation plate 22 and the hot-air ejection nozzle 20 is shorter.

  As described above, this is a floating type drying device that supports a web in a floating manner with hot air jet nozzles arranged so as to face the top and bottom of the web, and the infrared radiation material is heated by the hot air that is jetted to generate infrared rays. As a result, the drying time can be shortened as compared with the conventional drying apparatus, and the production efficiency can be improved without increasing the running cost.

DESCRIPTION OF SYMBOLS 10 ... Web 11 ... Delivery apparatus 12 ... Coating apparatus 13 ... Drying apparatus 14 ... Winding apparatus 15 ... Guide roller 20 ... Hot-air ejection nozzle 21 ... Infrared radiation Coating layer 22 ... Infrared radiation plate

Claims (3)

  An apparatus for drying a coating film applied on a web, the plurality of hot air jet nozzles arranged so as to face the top and bottom of the web and floatingly supporting the web, and facing the top and bottom of the web And an infrared radiation plate that is disposed between the plurality of hot-air ejection nozzles and emits infrared rays with hot air ejected from the hot-air ejection nozzles.   The infrared radiation coating layer which coat | covered the infrared radiation substance which emits infrared rays with the hot air which blows off from the said hot-air ejection nozzle is provided in the hot-air ejection surface which faces the said web of the said hot-air ejection nozzle. The drying apparatus as described.   The drying apparatus according to claim 1 or 2, wherein a distance between the infrared radiation plate and the web is 10 mm to 100 mm.

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