Drying apparatus

Abstract

To provide a technique capable of drying a coating liquid in a shorter time while suppressing the coating liquid from being blown away.SOLUTION: A drying device that dries a coating liquid applied to an upper surface of a base material includes a transport mechanism that transports the base material in a transport direction along a transport path, a plurality of first wind supply portions that are disposed below the base material along the transport path and send dry wind toward a lower surface of the base material, and a plurality of second wind supply portions that are disposed above the base material along the transport path and send dry wind toward the upper surface of the base material in a direction including a component of a direction opposite to the transport direction. The wind speed of the dry wind blown from the second wind supply unit disposed on the upstream side is lower than the wind speed of the dry wind blown from the second wind supply unit disposed on the downstream side.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a drying device. [Background technology]

[0002] Patent Document 1 discloses a method for manufacturing a catalyst layer for a fuel cell, in which an ultrasonic airflow is blown onto the catalyst ink on a transported substrate to dry the catalyst ink. The ultrasonic airflow is emitted from multiple positions along the transport direction of the substrate, and the output of the ultrasonic airflow at each position decreases from the upstream side to the downstream side in the transport direction. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-96944 Summary of the Invention [Problem to be solved by the invention]

[0004] When drying a coating liquid applied to a substrate, there is a demand for a technique that can dry the coating liquid in a shorter time while preventing the coating liquid from being blown away. [Means for solving the problem]

[0005] The present disclosure can be realized in the following forms.

[0006] According to one aspect of the present disclosure, there is provided a drying apparatus for drying a coating liquid applied to an upper surface of a substrate, the drying apparatus including: a conveying mechanism that conveys the substrate in a conveying direction along a conveying path; a plurality of first air supply units arranged below the substrate along the conveying path and that deliver dry air toward the lower surface of the substrate; and a plurality of second air supply units arranged above the substrate along the conveying path and that deliver dry air toward the upper surface of the substrate in a direction that includes a component opposite to the conveying direction, wherein the conveying mechanism conveys the substrate from an upstream side to a downstream side in the conveying direction, and the wind speed of the dry air delivered from the second air supply unit arranged on the upstream side is lower than the wind speed of the dry air delivered from the second air supply unit arranged on the downstream side. According to the drying device of this aspect, the coating liquid can be dried in a shorter time while preventing the coating liquid from being blown away. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 2 is a diagram schematically illustrating the configuration of a drying device. [Figure 2] FIG. 10 is a diagram showing the results of a simulation of the temperature distribution in a drying furnace. DETAILED DESCRIPTION OF THE INVENTION

[0008] A. First embodiment: FIG. 1 is a diagram schematically illustrating the configuration of a drying apparatus 100. FIG. 1 shows arrows representing mutually orthogonal X, Y, and Z directions. The X and Y directions are parallel to a horizontal plane. The Z direction is parallel to the vertical direction. The X, Y, and Z directions in FIG. 1 and the X, Y, and Z directions in other figures indicate the same direction. To specify a direction, positive and negative signs are used in combination to indicate the direction, with "+" indicating the positive direction indicated by the arrow and "-" indicating the negative direction opposite to the direction indicated by the arrow. The +Z direction is also referred to as up, and the -Z direction is also referred to as down.

[0009] The drying apparatus 100 is an apparatus for drying a coating liquid 92 applied to a sheet-like substrate 91. The coating liquid 92 is intermittently applied to the surface of the substrate 91 by a coating apparatus 200 before drying. In this embodiment, the drying apparatus 100 dries the coating liquid 92 to produce an electrode catalyst layer used in a membrane electrode assembly (MEA) of a fuel cell. The coating liquid 92 includes a solvent, a catalyst support, and an ionomer. For example, diacetone alcohol having a high boiling point is used as the solvent. The ionomer is an electrolyte resin having ionic properties, and for example, perfluorocarbon sulfonic acid resin is used as the ionomer. The catalyst support is a catalyst supported on a support. For example, platinum or a platinum alloy is used as the catalyst, and for example, carbon powder is used as the support. In this specification, the coating liquid 92 is also referred to as a catalyst ink. Note that the coating liquid 92 may be continuously applied to the surface of the substrate 91.

[0010] The drying apparatus 100 includes a conveying mechanism 10, a drying furnace 20, an airflow generating section 30, a heater 40, a first air supply section 50, a second air supply section 60, and a control section 70. In this embodiment, the drying apparatus 100 includes four first air supply sections 50 and six second air supply sections 60. Hereinafter, when the first air supply sections 50 and the second air supply sections 60 are referred to without distinction, they will simply be referred to as air supply sections.

[0011] The control unit 70 is configured by a computer including one or more processors and a storage unit including a ROM and a RAM. The control unit 70 controls each part of the drying apparatus 100 by the processor executing a program stored in the storage unit. Note that the control unit 70 may be realized by a configuration combining a plurality of circuits instead of being configured by a computer.

[0012] The conveying mechanism 10 conveys the substrate 91 in the conveying direction along the conveying path. The conveying mechanism 10 includes a feed roller 11, a plurality of conveying rollers 12, and a take-up roller 13. Each roller is rotated about a horizontal axis by a motor (not shown). The substrate 91 is fed from the feed roller 11, conveyed along the conveying path defined by the plurality of conveying rollers 12, and taken up by the take-up roller 13. Each conveying roller 12 conveys the substrate 91 in the conveying direction by rotating about a horizontal axis. The substrate 91 is conveyed in the conveying direction while being tensioned by the conveying mechanism 10. For example, if the substrate 91 is made of polytetrafluoroethylene (PTFE) with a width of 300 mm, the tension applied to the substrate 91 is preferably in the range of 50 N to 70 N.

[0013] The drying furnace 20 is a housing having an internal space for drying the coating liquid 92. An inlet 21 is provided at an end face of the drying furnace 20 on the −X direction side, and an outlet 22 is provided at an end face of the drying furnace 20 on the +X direction side. The substrate 91 coated with the coating liquid 92 is carried into the drying furnace 20 through the inlet 21, dried inside the drying furnace 20, and then carried out from the drying furnace 20 through the outlet 22. That is, a portion of the transport path is disposed inside the drying furnace 20. In this embodiment, the drying furnace 20 is composed of a first drying furnace 23 and a second drying furnace 24 that are connected to each other. The second drying furnace 24 is provided on the +X direction side of the first drying furnace 23. The substrate 91 is transported by the transport mechanism 10, with the surface coated with the coating liquid 92 facing up, to pass through the interior of the drying furnace 20 through the first drying furnace 23 and then the second drying furnace 24 in that order. The conveyance direction of the substrate 91 inside the drying furnace 20 is the +X direction. In this specification, with respect to any position on the conveyance path, the side of the delivery roller 11 is referred to as the "upstream side," and the side of the take-up roller 13 is referred to as the "downstream side." In other words, the conveyance mechanism 10 conveys the substrate 91 from the upstream side to the downstream side in the conveyance direction.

[0014] The airflow generating unit 30 generates an airflow and supplies it to the heater 40. A compressor such as a blower or an air blower such as a fan can be used as the airflow generating unit 30. The heater 40 heats the airflow supplied from the airflow generating unit 30 to generate dry air and supplies it to each air supply unit. The heater 40 is provided so as to be able to adjust the temperature of the dry air sent out from each air supply unit. The control unit 70 controls the temperature of the heater 40 to adjust the temperature of the dry air sent out from each air supply unit. The airflow generating unit 30 and the heater 40 may be provided for each air supply unit.

[0015] The first air supply unit 50 is a nozzle that blows dry air toward the substrate 91. A plurality of first air supply units 50 are arranged inside the drying oven 20 below the conveying path along the conveying direction. That is, the first air supply units 50 are arranged below the substrate 91 and blow dry air toward the underside of the substrate 91. In this embodiment, two first air supply units 50 are arranged inside each of the first drying oven 23 and the second drying oven 24. Hereinafter, the first air supply units 50 will be referred to as the first nozzle 51, the second nozzle 52, the third nozzle 53, and the fourth nozzle 54, in the order from the first air supply unit 50 arranged upstream in the conveying direction to the first air supply unit 50 arranged downstream. The first nozzle 51 and the second nozzle 52 are arranged inside the first drying oven 23, and the third nozzle 53 and the fourth nozzle 54 are arranged inside the second drying oven 24.

[0016] The first air supply unit 50 blows dry air from two slits formed on its upper surface. The two slits are formed so that the dry air blown from each slit collides with each other, causing the dry air to be blown upward from the first air supply unit 50. In this specification, the first air supply unit 50 is also referred to as a floating nozzle. The speed of the dry air blown from each first air supply unit 50 is determined by the width of the slit. The slits of each first air supply unit 50 are formed so that the speed of the dry air blown from the first air supply unit 50 located upstream is lower than the speed of the dry air blown from the first air supply unit 50 located downstream. The slits of each first air supply unit 50 are formed so that the speed of the dry air blown from the first nozzle 51 is 1 m / s, the speed of the dry air blown from the second nozzle 52 is 20 m / s, and the speed of the dry air blown from the third nozzle 53 and the fourth nozzle 54 is 30 m / s, for example.

[0017] The second air supply unit 60 is a nozzle that blows dry air toward the substrate 91. A plurality of second air supply units 60 are arranged inside the drying oven 20, above the conveying path and along the conveying direction. That is, the second air supply units 60 are arranged above the substrate 91 and blow dry air toward the upper surface of the substrate 91. The distance between the second air supply units 60 and the substrate 91 is preferably approximately 5 mm. In this embodiment, three second air supply units 60 are arranged inside each of the first drying oven 23 and the second drying oven 24. Hereinafter, the second air supply units 60 will be referred to as the fifth nozzle 61, the sixth nozzle 62, the seventh nozzle 63, the eighth nozzle 64, the ninth nozzle 65, and the tenth nozzle 66, in the order from the second air supply unit 60 arranged upstream in the conveying direction to the second air supply unit 60 arranged downstream. The fifth nozzle 61, the sixth nozzle 62, and the seventh nozzle 63 are arranged inside the first drying oven 23, and the eighth nozzle 64, the ninth nozzle 65, and the tenth nozzle 66 are arranged inside the second drying oven 24.

[0018] The shape of the second air supply section 60 arranged on the most upstream side is different from the shapes of the other second air supply sections 60. Specifically, the shape of the fifth nozzle 61 is different from the shapes of the sixth nozzle 62 to the tenth nozzle 66. The sixth nozzle 62, seventh nozzle 63, eighth nozzle 64, ninth nozzle 65, and tenth nozzle 66 have the same shape.

[0019] The fifth nozzle 61 is a nozzle whose lower portion is hemispherical. A plurality of holes are formed in the surface of the lower portion of the fifth nozzle 61. The fifth nozzle 61 radially blows dry air downward and to the sides from the plurality of holes. In this specification, the fifth nozzle 61 is also referred to as a punching nozzle.

[0020] A slit is formed in each of the sixth to tenth nozzles 62 to 66 on their undersides. The sixth to tenth nozzles 62 to 66 blow dry air from the slits formed in their undersides. The slits of the sixth to tenth nozzles 62 to 66 are formed so that the dry air is blown downward in a direction that includes a component in the opposite direction to the conveying direction. Specifically, the slits are formed so that the dry air is blown in a direction that includes components in the -X and -Z directions. In this specification, the sixth to tenth nozzles 62 to 66 are also referred to as counterflow nozzles.

[0021] The speed of the dry air blown out from each second air supply unit 60 is determined by the size and spacing of the holes provided on the surface and the width of the slits. The holes on the surface of the fifth nozzle 61 and the slits of the sixth to tenth nozzles 62 to 66 are formed so that the speed of the dry air blown out from the second air supply unit 60 located upstream is slower than the speed of the dry air blown out from the second air supply unit 60 located downstream. The holes on the surface of the fifth nozzle 61 and the slits of the sixth to tenth nozzles 62 to 66 are formed so that the speed of the dry air blown out from the fifth nozzle 61 is 1 m / s, the speed of the dry air blown out from the sixth and seventh nozzles 62 and 63 is 20 m / s, and the speed of the dry air blown out from the eighth, ninth, and tenth nozzles 64, 65, and 66 is 30 m / s. The width of the slits of the sixth to tenth nozzles 62 to 66 is preferably approximately 4 mm to 8 mm.

[0022] The control unit 70 controls the heater 40 so that the temperature of the drying air blown out from each air supply unit arranged in the first drying oven 23 is the same. The control unit 70 controls the heater 40, for example, so that the temperature of the drying air blown out from the first nozzle 51, the second nozzle 52, the fifth nozzle 61, the sixth nozzle 62, and the seventh nozzle 63 is 130°C. The control unit 70 also controls the heater 40 so that the temperature of the drying air blown out from each air supply unit arranged in the second drying oven 24 is the same. The control unit 70 controls the heater 40, for example, so that the temperature of the drying air blown out from the third nozzle 53, the fourth nozzle 54, the eighth nozzle 64, the ninth nozzle 65, and the tenth nozzle 66 is 150°C. The temperature of the drying air blown out from the air supply units is controlled to a temperature at which the coating liquid 92 on the substrate 91 will not ignite.

[0023] 2 is a diagram showing the results of a simulation of the temperature distribution in the drying oven 20 when the temperature and wind speed of the drying air blown out from the air supply unit are set to the above-mentioned values. In this case, as shown in FIG. 2, the temperature of the space above the substrate 91 in the drying oven 20 is uniform regardless of the position in the conveying direction.

[0024] According to the drying apparatus 100 of the first embodiment described above, the first air supply units 50, which are arranged below the substrate 91 along the conveying path, blow dry air toward the underside of the substrate 91, and the second air supply units 60, which are arranged above the substrate 91 along the conveying path, blow dry air toward the upper surface of the substrate 91 in a direction that includes a component opposite to the conveying direction. The wind speed of the dry air blown out from the second air supply units 60 arranged upstream in the conveying direction is slower than the wind speed of the dry air blown out from the second air supply units 60 arranged downstream in the conveying direction. Therefore, on the upstream side where the coating liquid 92 is not yet dried, the dry air with a slow wind speed blows on the substrate 91, and on the downstream side where the coating liquid 92 is drying, the dry air with a fast wind speed blows on the substrate 91. This prevents the coating liquid 92 from being blown away. Furthermore, as shown in FIG. 2, in this embodiment, the temperature of the space above the substrate 91 in the drying furnace 20 is uniform regardless of the position in the conveying direction. This improves the efficiency of heat conduction to the substrate 91 and the coating liquid 92, thereby shortening the time required to dry the coating liquid 92. As a result, the efficiency of manufacturing the electrode catalyst layer can be improved.

[0025] B. Other Embodiments: (B-1) In the above embodiment, the drying apparatus 100 includes four first air supply sections 50 and six second air supply sections 60. However, the drying apparatus 100 may include two first air supply sections 50, three first air supply sections 50, or five or more first air supply sections 50. The drying apparatus 100 may also include two to five second air supply sections 60, or seven or more second air supply sections 60.

[0026] (B-2) In the above embodiment, the slits of each first air supply section 50 are formed so that the wind speed of the dry air sent out from the first air supply section 50 arranged upstream is smaller than the wind speed of the dry air sent out from the first air supply section 50 arranged downstream. In contrast, the slits of each first air supply section 50 may be formed so that the wind speed of the dry air sent out from the first air supply section 50 arranged upstream is not smaller than the wind speed of the dry air sent out from the first air supply section 50 arranged downstream.

[0027] (B-3) In the above embodiment, the speed of the dry air blown out from each air supply unit is determined by the size and spacing of the holes provided on the surface of each air supply unit and the width of the slits. However, the speed of the dry air blown out from each air supply unit may be controlled by the control unit 70 controlling the airflow generation unit 30.

[0028] The present disclosure is not limited to the above-described embodiments and can be realized in various configurations without departing from the spirit thereof. For example, the technical features in the embodiments corresponding to the technical features in each aspect described in the Summary of the Invention section can be appropriately replaced or combined to solve some or all of the above-described problems or achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be appropriately deleted. [Explanation of symbols]

[0029] 10...conveying mechanism, 11...feed roller, 12...conveying roller, 13...winding roller, 20...drying furnace, 21...inlet, 22...outlet, 23...first drying furnace, 24...second drying furnace, 30...airflow generating section, 40...heater, 50...first air supply section, 51...first nozzle, 52...second nozzle, 53...third nozzle, 54...fourth nozzle, 60...second air supply section, 61...fifth nozzle, 62...sixth nozzle, 63...seventh nozzle, 64...eighth nozzle, 65...ninth nozzle, 66...tenth nozzle, 70...control section, 91...substrate, 92...coating liquid, 100...drying device, 200...coating device

Claims

[Claim 1] A drying device that dries a coating liquid applied to an upper surface of a substrate, a conveying mechanism that conveys the base material in a conveying direction along a conveying path; a plurality of first air supply units arranged below the base material along the transport path, each of which blows dry air toward a lower surface of the base material; a plurality of second air supply units arranged above the substrate along the transport path, each of which blows dry air toward an upper surface of the substrate in a direction including a component in the opposite direction to the transport direction; the conveying mechanism conveys the base material from an upstream side to a downstream side in the conveying direction, a wind speed of the dry air blown out from the second air supply unit arranged on the upstream side is lower than a wind speed of the dry air blown out from the second air supply unit arranged on the downstream side; drying equipment.

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