JP2015155091A - Dryer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dryer capable of utilizing the effect of infrared rays without using an electric heating type infrared heater for the irradiation of infrared rays in the dryer including the irradiation of infrared rays and without replacement by an inert gas such as nitrogen gas and the like to a solvent-based coating film.

SOLUTION: In a dryer for drying a solvent-based coating film coated on a web 10, a hot air drying device in which a solvent is vaporized from the coating film by hot air and drying and hardening are performed and an infrared drying device 13b where the solvent is vaporized from the coating film and drying and hardening are performed by an infrared irradiation device 30 in which an infrared irradiation substance irradiating infrared rays with hot air is coated at the downstream side of the hot air drying device 13a in the carrying direction of the web 10 are disposed. The infrared irradiation device 30 of the infrared drying device is heated by using hot air having a higher temperature than the hot air in the hot air drying device.

COPYRIGHT: (C)2015,JPO&INPIT

Description

  The present invention relates to a drying apparatus for a coating film applied on a web, and more particularly to a drying apparatus in which the coating film is used in drying thick film coating.

  A drying apparatus using hot air is generally used as a method for drying the coating film applied on the web.

  FIG. 4 shows a schematic sectional view of a general drying apparatus. The drying device includes an air supply duct (not shown) for supplying hot air to the nozzle and an exhaust duct (not shown) for exhausting the hot air from which the coating film has been dried. Further, the drying apparatus is divided into several chambers, and the temperature, the exhaust air volume, etc. can be set independently for each chamber in accordance with the drying characteristics of the coating film.

  The nozzles 20 are arranged on the web 10 at regular intervals. The nozzle 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 a web is advanced by the hot air which spouted.

  The conventional drying apparatus as shown in FIG. 4 is often divided into a plurality of drying zones, and the drying conditions are often determined by defining the temperature and air volume in each drying zone. As a method for increasing the drying efficiency, there were many parts that were limited to raising the heating temperature or increasing the air volume.

  Regarding the temperature, the temperature range of the heated and heated gas that can be introduced into the drying zone is the temperature range of the drying zone as it is, and the amount of gas that can be introduced into the drying zone is the air volume of the drying zone as it is. For this reason, the drying efficiency of the drying zone is limited to some extent. In particular, in the case of thick film coating having a film thickness of about 100 μm (wet thickness), only the surface of the coating film is often dried and the inside of the coating film is often undried. was there.

  However, when trying to increase the web conveyance speed for the purpose of improving production efficiency, it is necessary to lengthen the drying device in order to secure the drying time, so higher drying efficiency can be obtained than the drying device using hot air. Many drying apparatuses using an infrared heater capable of drying a coating film in a short time have been proposed.

  On the other hand, in the drying apparatus using the infrared heater, when an organic solvent is included in the coating film, an infrared heater using a heat medium oil or steam as a heat source is generally used from the viewpoint of explosion prevention. In some cases, since a boiler or the like is required, there is a problem in terms of initial cost and maintainability, and a drying apparatus using an electrically heated infrared heater has been proposed as a solution.

  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 if an electrically heated infrared heater is used, if it contains a solvent with a low ignition point temperature, the upper limit temperature of the heater surface is limited to a low level in accordance with the explosion protection regulations, so its cost effectiveness is reduced. End up. In addition, when replacing with an inert gas, there is a problem that the running cost becomes high, and the electric heating type infrared heater is not sufficient as an alternative to the infrared heater using heat transfer oil or steam as a heat source. there were.

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

  The present invention is a drying apparatus including infrared radiation, without using infrared heating of an electric heating type infrared heater, without replacing the solvent-based coating film with an inert gas such as nitrogen gas, An object of the present invention is to provide a drying apparatus that can utilize the effect of infrared rays.

  The present inventor has found that if the temperature of the infrared radiation is set higher than the temperature of the hot air in the drying apparatus, the effect of infrared rays is exhibited, and the present invention has been completed.

As means for solving the above problems, the invention according to claim 1 is an apparatus for drying a solvent-based coating film applied on a web,
A hot air drying device for evaporating the solvent from the coating film with hot air and drying and curing;
An infrared drying device that coats an infrared radiation that radiates infrared rays with heated air, evaporates the solvent from the coating film, and dries and cures the infrared drying device is disposed downstream of the hot air drying device in the web conveyance direction. The drying apparatus is characterized in that the infrared radiation of the infrared drying apparatus is heated using hot air having a temperature higher than that of the hot air of the hot air drying apparatus.

  The invention according to claim 2 uses hot air having a temperature higher than that of hot air of the hot air drying device for heating the infrared radiation, heating air exhausted from the hot air drying device. The drying apparatus according to claim 1, characterized in that it is a drying apparatus.

  The invention according to claim 3 is the drying apparatus according to claim 1 or 2, wherein a distance between the infrared radiation device and the web is 10 mm to 100 mm.

  From the above, it is possible to dry / cure while using low-cost equipment without using explosion-proof equipment, especially for drying solvent-based coatings applied on films with inert gases such as nitrogen gas. Can be performed in a short time.

It is the plane conceptual diagram explaining the drying apparatus provided with the infrared radiation apparatus 30 using the infrared radiation thing of this invention. It is the cross-sectional conceptual diagram explaining the drying apparatus provided with the infrared radiation apparatus 30 using the infrared radiation material of this invention. It is the conceptual diagram explaining the coating line including the drying apparatus provided with the infrared radiation apparatus 30 using the infrared radiation thing of this invention. It is the conceptual diagram explaining the general drying apparatus.

Hereinafter, the present invention will be described in more detail. FIG. 3 shows a conceptual diagram of a coating line including the drying apparatus of the present invention. The coating line mainly includes a feeding device 11 for feeding out the web 10, a coating device 12 for applying a coating liquid on the web, a drying device 13 for drying a coating film formed on the web, and a coated / dried product. And a large number of guide rollers 15 that convey the web 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 before coating.

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

  FIG. 1 is a schematic plan view illustrating a drying device using the infrared radiation material of the present invention. In addition to a general hot air drying device 13a, an infrared radiation device 30 is provided on the upper and lower surfaces of the web on the downstream side in the conveying direction. An infrared drying device 13b is installed.

  As the drying of the coating film, generally, a constant rate drying mainly used for evaporation of the solvent is performed, and then a reduction rate drying mainly consisting of a curing reaction leads to a step of curing the coating film. In general, in the rate of drying area at the end of the drying process and in the curing process after drying, the surface temperature of the coating film rises to the same level as the oven temperature, so the inflow of heat (convection heat transfer) by hot air is It is very small.

  However, by installing an infrared radiation device in the reduced rate drying area behind the hot air drying device like the drying device of the present invention, it is possible to heat from the inside of the coating film by radiant heat transfer. From the viewpoint of construction, a state in which only the surface is dried and the inside is not dried does not occur, and even in the case of a thick film, it can be efficiently dried and cured in a short time.

  As the infrared radiation device 30 installed on the upper surface side of the web, a metal duct surface such as stainless steel coated with an infrared radiation material is used. A fired ceramic or the like can also be used, but it is preferable to use a metal duct surface coated with infrared radiation to uniformly heat a large area, particularly when the web width 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 the infrared radiation is 0.9 or more, preferably 0.95 or more. For example, a ceramic coat etc. are mentioned, As a ceramic coat, far-red type III (Nissan Industrial Co., Ltd.) can be fried.

  The infrared radiation device 30 is heated by supplying the air exhausted from the hot air drying device 13a with the infrared radiation device heater 43 and supplied to the inside of the metal duct whose surface is coated with the infrared radiation material.

  At this time, the temperature of the air heated by the infrared radiation device heater 43 is set higher than the temperature of the air fed into the infrared radiation device 30, thereby radiating infrared rays.

  The infrared radiation device 30 is preferably installed in a range of 10 to 100 mm from the web. If it is less than 10 mm, there is a risk of contact with the web 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 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 infrared radiation device in the flow direction is preferably as large as possible so that the solvent vapor removed at the time of drying does not stay so that the time facing the infrared radiation device becomes longer.

  The surface temperature of the infrared radiation device 30 is preferably maintained at the same temperature or higher as that of the drying device. Generally, the greater the difference between the surface temperature of the infrared radiation device and the temperature of the web, the greater the effect of infrared radiation, but the equipment cost increases. On the other hand, when the surface temperature of the infrared radiation device is lower than the temperature 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 device at a temperature equal to or higher than that of the drying device so as to obtain the effect of infrared rays without much cost.

  The infrared radiation device 30 is heated by reheating the hot air exhausted from the hot air drying device as shown in FIG. That is, air for heating the infrared radiation device is supplied from the exhaust blower 41 of the hot air drying device 13a to the infrared radiation device 30 in the infrared drying device 13b through the heater 40.

  The hot air used for heating the infrared radiation device is then released into the infrared drying device and finally exhausted from the infrared drying device 13b.

  In this way, the temperature of the infrared radiation device can be about the same as the temperature of the drying device, or it can be maintained higher than the temperature of the drying device by the amount of heat used for drying the coating film or the heat loss in the duct in the middle. it can.

In addition, it is possible to save energy by reusing the amount of heat discarded as exhaust air from the hot air dryer, and to reduce the size of the heater for reheating the infrared radiation device. Because it is used for drying and curing in the factory, the exhaust to be reused as the heating heat source of the infrared radiation device can be selected from the drying chamber exhaust with a small amount of solvent contained in the hot air exhausted from the hot air drying device Is preferred.

  The present invention is configured as described above, and by utilizing the effect of infrared rays, the solvent-based coating applied on the film can be dried and cured in a short time. The equipment can be made smaller than the drying device.

  Further, the initial cost can be suppressed because the drying apparatus main body has a very simple structure. Also, the running cost can be reduced by reusing the hot air exhausted from the hot air drying device as the heat source of the infrared radiation device.

  The length of the drying device 13 and the conveyance speed of the substrate 10 should be determined depending on whether or not the coating film is dried, and optimal conditions may be set depending on the type of coating liquid and the film thickness. Generally, the length of the drying apparatus is about 5 m to 100 m.

  The drying device 13 may be divided and installed to some extent as shown in FIG. 1, and the method for dividing the drying zone is not particularly limited.

  Examples of the present invention will be described below.

A coating solution containing a polyol as a main agent, an isocyanate as a curing agent, and a main solvent as MEK (methyl ethyl ketone) was applied to a PET substrate with a die coater and dried at 150 ° C. to prepare a protective sheet. 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)
The specifications of the drying device and infrared radiation device are as follows:
Furnace length: 2m x 4 chambers = 8m
Air volume: 10m3 / min
Infrared radiation device:
Width: 400mm (base material width: 300mm)
Length: 1.8m
Installation location: 3, 4 rooms (second half 2 rooms)
It is.

  The temperature of the air introduced into the infrared radiation device is 170 ° C., the temperature of the air introduced into the infrared drying device is higher than 150 ° C., the distance between the infrared radiation device and the substrate is set to 50 mm, 30 A dried coating film was obtained in which the drying time was changed from 5 seconds to 60 seconds at intervals of 5 seconds. The nozzle and the infrared radiation device were ceramic coated with an infrared emissivity of 0.95, and the air volume was constant.

  A dry coating film was obtained under the same conditions as in Example 1 except that the temperature of the air introduced into the infrared radiation device was 170 ° C. and the distance between the infrared radiation device and the substrate was set to 10 mm.

  A dry coating film was obtained under the same conditions as in Example 1 except that the temperature of the air introduced into the infrared radiation device was 170 ° C. and the distance between the infrared radiation device and the substrate was set to 100 mm.

<Comparative Example 1>
The temperature of the air introduced into the infrared radiation device was 130 ° C., and the same conditions as in Example 1 except that 150 ° C. air was introduced into the infrared drying device separately from the air used for heating the infrared radiation device, A dry coating was obtained.

<Comparative Example 2>
The temperature of the air introduced into the infrared radiation device was 150 ° C., and the same conditions as in Example 1 except that 150 ° C. air was introduced into the infrared drying device separately from the air used for heating the infrared radiation device, A dry coating was obtained.

<Comparative Example 3>
A dry coating film was obtained under the same conditions as in Example 1 except that the temperature of the air introduced into the infrared radiation device was 170 ° C. and the distance between the infrared radiation device and the substrate was set to 200 mm.

<Comparative Example 4>
In a general drying apparatus as shown in FIG. 2, the other conditions were the same as in Example 1, and the temperature of the air blown to the fourth zone was set to 170 ° C. to obtain a dried coating film.

  The results are shown in Table 1.

From Examples 1 to 3 and Comparative Examples 1 and 2, the temperature of the air introduced into the infrared radiation device is made higher than the temperature of the air introduced into the hot-air drying device and the infrared drying device, thereby the effect of the infrared radiation device. Can be seen. Further, when the drying apparatus of the present invention is used, the coating film can be dried and cured in a short time. Moreover, it turns out that an effect is so high that the distance of an infrared radiation board and a base material is short.

  By utilizing infrared radiation as in the present invention, the production efficiency can be improved at a low cost compared to conventional drying apparatuses.

DESCRIPTION OF SYMBOLS 10 ... Web 11 ... Delivery apparatus 12 ... Coating apparatus 13 ... Drying apparatus 13a ... Hot air drying apparatus 13b ... Infrared drying apparatus 14 ... Winding apparatus 15 ... Guide Roller 20 ... Spray nozzle 30 ... Infrared radiation device 40 ... Heater 41 ... Exhaust blower 42 ... Supply air blower 43 ... Infrared radiation device heater

Claims (3)

An apparatus for drying a solvent-based coating film applied on a web,
A hot air drying device for evaporating the solvent from the coating film with hot air and drying and curing;
An infrared drying device that coats an infrared radiation that radiates infrared rays with heated air, evaporates the solvent from the coating film, and dries and cures the infrared drying device is disposed downstream of the hot air drying device in the web conveyance direction. A drying apparatus that heats the infrared radiation of the infrared drying apparatus using hot air having a temperature higher than that of the hot air of the hot air drying apparatus.   2. The drying apparatus according to claim 1, wherein hot air having a temperature higher than that of hot air of the hot air drying apparatus is used for heating the infrared radiation material by heating the air exhausted from the hot air drying apparatus. .   The drying apparatus according to claim 1 or 2, wherein a distance between the infrared radiation device and the web is 10 mm to 100 mm.