JP2012241922A - Batch type coating film drying furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a batch type coating film drying furnace, which is capable of promptly discharging vapor of an organic solvent to the outside of a furnace and efficiently drying the coating film.SOLUTION: The furnace includes a stage 2 on which a flat workpiece 3 coated with the coating film is put, an infrared heating device 5 to heat the workpiece 3, which is arranged on a ceiling above the stage 2, and a blower 11 and a discharging unit 12 each arranged at both sides of the stage 2. This structure generates a side wind at a height distant from the topside of the workpiece 3 in a space between the infrared heating device 5 and the workpiece 3 and promptly discharges the vapor of the organic solvent emitted from the coating film, to the outside of the furnace.

Description

  The present invention relates to a batch-type coating film drying furnace used for film drying in which a paste is applied by a coating apparatus, such as an electrode coating film for a lithium ion battery and an electrode coating film for photovoltaic power generation.

  As a coating film drying furnace as described above, there is known a furnace having a structure in which a large number of infrared heaters are arranged on a ceiling as disclosed in Patent Document 1. The coating film as described above contains an organic solvent, and a large amount of organic solvent vapor is generated from the work on which the coating film is formed in the drying process. Since this organic solvent vapor may explode when heated to a predetermined concentration or higher and 300 ° C. or higher, it is necessary to quickly discharge it to the outside of the furnace.

  For this reason, conventionally, a large amount of hot air is blown into the furnace chamber to accelerate drying, and at the same time, the organic solvent vapor is diluted and discharged out of the furnace together with the hot air. However, in the conventional coating film drying furnace, hot air is brought into direct contact with the workpiece, so that the coating film is dried from the surface. For this reason, the solvent inside the coating film moves toward the surface, and the binder dissolved in the solvent also moves toward the surface side. As a result, the binder concentration inside the coating film is high on the surface side, and the base sheet such as a metal foil or glass plate side tends to be low, and the adhesive strength with the sheet tends to be insufficient. In particular, the electrode for a lithium ion battery has a coating film formed on a metal sheet, and because of the multiple winding or folding structure at the time of assembly, the decrease in the adhesion between the sheet and the coating film is caused by the sheet and coating film. Cause a peeling of the battery and directly leads to a decrease in the yield of the battery.

  Moreover, when drying progresses from the coating film surface, a binder will precipitate on the surface and a film | membrane will be formed, and there also exists a problem that the movement of the solvent from the inside of a coating film is prevented. In such a state, the coating film drying speed is reduced, and it takes a long time to complete the drying, leading to a reduction in productivity.

Japanese Patent No. 3953911

  Therefore, the object of the present invention is to solve the above-mentioned conventional problems, to quickly discharge organic solvent vapor to the outside of the furnace, and to efficiently dry the coating film without reducing the adhesive strength with the sheet. It is to provide a batch type coating film drying furnace capable of performing the following.

  The present invention made to solve the above problems includes a stage on which a planar workpiece on which a coating film is formed is placed, an infrared heating device that is disposed on the ceiling portion above the workpiece and heats the workpiece, and this infrared heating In the space between the apparatus and the workpiece, there is provided a blower unit and an exhaust unit that are installed across the stage in order to form a cross wind with a height separated from the upper surface of the workpiece. is there.

  In addition, it is preferable that a ventilation means is provided with the slit for ventilation, and an exhaust means is provided with the slit for suction. Further, the stage on which the workpiece is placed is adjustable in height, and a structure in which the separation distance of the cross wind from the upper surface of the workpiece is variable is preferable, and the separation distance of the cross wind from the upper surface of the workpiece is in the range of 10 to 500 mm. It is preferable that Further, the infrared heating device is preferably a double tube heater in which a quartz tube in which a filament is enclosed is enclosed in an outer tube to which a cooling fluid is supplied.

  According to the present invention, the cross wind is formed at a height separated from the upper surface of the workpiece by the blowing unit and the exhaust unit installed across the stage on which the workpiece is placed. For this reason, the organic solvent vapor | steam generated from the coating film of the workpiece | work heated by the infrared heating apparatus is rapidly discharged | emitted out of a furnace with this cross wind. Moreover, since the cross wind does not directly contact the workpiece, the coating film on the workpiece surface is exclusively dried by infrared rays. Infrared rays can penetrate the inside of the coating film by controlling the wavelength, so that it is possible to dry the entire coating film more evenly than when the hot air is directly applied to the surface of the workpiece to dry it. The coating film can be efficiently dried without reducing the adhesive strength.

  If the blowing means is provided with a blowing slit and the exhaust means is provided with a suction slit as in claim 2, the cross wind can be formed into a strip shape with a thin width in the height direction, The generated organic solvent vapor can be reliably exhausted, and contact with the crosswind work can be reliably prevented.

  The optimum separation distance between the cross wind and the upper surface of the workpiece changes depending on the type of the coating film or the workpiece. Therefore, if the height of the stage on which the workpiece is placed can be adjusted, the optimum distance can be easily set. The optimum distance is in the range of 10 to 500 mm.

  In addition, if the infrared heating device uses a double tube heater in which the filament tube is enclosed in an outer tube to which a cooling fluid is supplied, the filament temperature is increased to about 700 ° C. to dry the coating film. The outer surface temperature of the heater can be maintained at a low temperature of 150 ° C. or lower while irradiating a suitable near infrared ray, and the rise in the furnace temperature can be suppressed. It becomes possible to prevent.

It is sectional drawing which shows embodiment of this invention. It is explanatory drawing of a double tube | pipe type heater.

Preferred embodiments of the present invention are shown below.
FIG. 1 is a sectional view of a batch type coating film drying furnace of the present invention, and 1 is a box-shaped furnace body. A stage 2 on which the work 3 is placed is provided at the lower center of the furnace body 1. In this embodiment, the workpiece 3 is an electrode sheet for a lithium ion battery, and a coating film having a thickness of 100 to 300 μm is formed on a sheet of aluminum or the like. This coating film is a paste in which lithium cobaltate as a positive electrode active material, carbon powder as a conductive material, PVDF (polyvinylidene fluoride) as a binder and the like are kneaded with NMP (N-methyl-pyrrolidone) as an organic solvent. belongs to. The stage 2 is supported by a lifting rod 4 penetrating the furnace bottom so that the stage 2 can be moved up and down, and the height can be adjusted.

  An infrared heating device 5 for heating the workpiece 3 is provided on the ceiling of the furnace body 1 above the stage 2. In the present invention, the type of the infrared heating device 5 is not particularly limited, but a double tube heater is used in the present embodiment.

  As shown in FIG. 2, this double tube heater has a structure in which a quartz tube 7 in which a filament 6 is enclosed is enclosed in an outer tube 8 to which a cooling fluid is supplied. Both the quartz tube 7 and the outer tube 8 are made of quartz glass. A cooling fluid supply port 9 and a cooling fluid discharge port 10 are provided in the vicinity of the end portion of the outer rod 8, and the outer rod 8 is cooled by flowing cooling air that is a cooling fluid.

  Quartz glass has a function as a low-pass filter, and almost completely absorbs infrared rays having a wavelength of 3.5 μm or more among infrared rays emitted from the filament 6. For this reason, if the temperature of the filament 6 is set to a high temperature of 700 ° C. or higher, only near infrared rays having a wavelength of not more than 3.5 μm, which is excellent in the ability to cut hydrogen bonds in the organic solvent and water molecules, are transmitted to the workpiece 3. Can be irradiated.

  Since the temperature of the quartz tube 7 and the outer tube 8 that absorbs long-wavelength infrared light rises, when no cooling fluid is flowed, the quartz tube 7 itself becomes an infrared radiator, and the furnace wall is heated to raise the temperature inside the furnace. Invite. However, in this embodiment, since the surface temperature of the outer tube 8 can be maintained at less than 150 ° C. by flowing cooling air, the near-infrared light having a wavelength of 3.5 μm or less is suppressed while suppressing an increase in the furnace temperature. Efficient coating drying is possible.

  In the embodiment shown in FIG. 2, the quartz tube 7 in which the filament 6 is enclosed is U-shaped and has a structure in which power can be supplied from only one side. You may supply. In the present invention, the infrared heating device 5 is not necessarily limited to a double tube heater, and a general ceramic infrared heater or warm air heater can be used in combination with the double tube heater.

  In the present invention, a cross wind having a height separated from the upper surface of the work 3 is formed in the space between the infrared heating device 5 and the work 3. For this purpose, box-shaped air blowing means 11 and exhaust means 12 are formed at the left and right positions across the stage 2.

  The blowing means 11 has a blowing slit 13 at the tip, and blows out air supplied from the air supply duct 14 at the back from the blowing slit 13. Reference numeral 15 is a punching metal for pressure dispersion disposed inside the blowing means 11, and 16 is a damper for adjusting the air volume. The blowing slit 13 is a flat slit having a narrow width in the height direction and a wide width in the direction perpendicular to the paper surface.

  On the other hand, the exhaust means 12 is also provided with a suction slit 17 having a similar shape. With this structure, a flat cross wind 18 can be stably formed between the blowing slit 13 and the suction slit 17. Since the lateral wind 18 has a small spread in the height direction, the separation distance from the upper surface of the work 3 to the lateral wind 18 can be set accurately. Reference numeral 19 denotes an exhaust duct connected to the exhaust means 12.

  The cross wind 18 has a role of discharging the organic solvent vapor generated from the heated work 3 to the outside of the furnace without directing the work 3 with the wind. For this purpose, the separation distance of the cross wind 18 from the upper surface of the workpiece 3 is preferably in the range of 10 to 500 mm. If the separation distance is less than 10 mm, there is a possibility that the cross wind 18 directly hits the work 3, which is not preferable because surface drying of the coating film is promoted. On the contrary, if it exceeds 500 mm, the ability to remove the organic solvent vapor generated from the work 3 is lowered, which is not preferable.

  It is preferable that this separation distance can be changed according to the type of the workpiece 3 or the coating film. Therefore, as described above, it is preferable that the height of the stage 2 on which the workpiece 3 is placed can be adjusted by the lifting rod 4 and the separation distance can be made variable.

  The batch type coating film drying furnace of the present invention configured as described above places the workpiece 3 on which the coating film is formed on the stage 2 and heats the workpiece 3 with near infrared rays emitted from the infrared heating device 5. To dry the coating film. As described above, if a double tube heater is used as the infrared heating device 5, it is possible to efficiently dry the coating film with near infrared rays having a wavelength of 3.5 μm or less while suppressing an increase in the temperature in the furnace. is there.

  Although the organic solvent vapor is generated as the coating film is dried, the organic solvent vapor concentration in the furnace is suppressed to a low level because the organic solvent vapor is quickly discharged to the outside by the cross air 18 having a height separated from the upper surface of the work 3. The Therefore, there is no risk of explosion due to organic solvent vapor. Moreover, since the cross wind 18 does not directly contact the upper surface of the work 3, there is no possibility of promoting the surface drying of the coating film.

  In addition, since the batch type coating film drying furnace of the present invention can set drying conditions such as temperature and separation distance relatively freely, it is used as a test furnace for obtaining optimum drying conditions according to the type of coating film. It is also possible.

DESCRIPTION OF SYMBOLS 1 Furnace 2 Stage 3 Work 4 Lifting rod 5 Infrared heating device 6 Filament 7 Quartz tube 8 Outer tube 9 Cooling fluid supply 10 Cooling fluid discharge port 11 Blower unit 12 Exhaust unit 13 Blower slit 14 Air supply duct 15 Punching metal 16 Air volume Adjustment damper 17 Suction slit 18 Cross wind 19 Exhaust duct

Claims (5)

  A stage on which a planar workpiece with a coating film is placed, an infrared heating device that is placed on the ceiling above the workpiece and heats the workpiece, and a space between the infrared heating device and the workpiece from the upper surface of the workpiece A batch-type coating film drying furnace comprising a blowing unit and an exhaust unit installed across the stage in order to form a cross-air with a separated height.   The batch type coating film drying furnace according to claim 1, wherein the blowing means includes a blowing slit, and the exhaust means includes a suction slit.   2. The batch type coating film drying furnace according to claim 1, wherein the stage on which the workpiece is placed is adjustable in height, and the separation distance of the cross wind from the upper surface of the workpiece is variable.   The batch type coating film drying furnace according to claim 1, wherein the separation distance of the cross wind from the upper surface of the workpiece is 10 to 500 mm.   2. The batch type coating film drying furnace according to claim 1, wherein the infrared heating device is a double tube heater in which a quartz tube in which a filament is enclosed is enclosed in an outer tube to which a cooling fluid is supplied. .

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