JP6724270B2 - Drying device for high-concentration coater and drying method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a drying device and a drying method for efficiently drying a coating layer applied at a high concentration.

When drying a work coated at a high concentration, it is necessary to slowly dry the work in a conventional batch type hot air oven so as to eliminate unevenness in drying. For example, in the case of drying by blowing hot air, heat is transmitted only from the surface, so that only the surface is overdried to form a film, and the low boiling point solvent is often confined inside.
Therefore, among the good and bad points of contact with hot air and the effect of temperature difference due to thermosiphon, if you focus on the worst point and do not dry slowly over time, uneven drying will increase. ..

FIG. 11 shows a cross section of a ceramic substrate with the surface coated, but when the concentration of the coating liquid (solid content) is, for example, 70%, the solvent does not appear on the surface and the solid content is scattered inside. Is exposed.
FIG. 12 shows the case where hot air is blown onto a work coated with such a high concentration to dry it. The solvent on the surface is blown off by the hot air blown, and at the same time, the surface of the exposed solid content becomes a film. Turn into (harden). The solvent easily dries outside the furnace (in the air), and a part of the work that has been left for a long time is formed into a film, which causes variations in the dryness of the product.

In addition, the drying by blowing hot air is too good in drying efficiency, the evaporation material inside the solid content does not move to the surface in time, and the film formation on the surface proceeds, so even if there is no problem on the surface Since the solvent remains inside the components, there is a possibility that the quality may be affected in the subsequent process. Therefore, in the conventional hot air drying, the drying efficiency is lowered by circulating hot air at a low air velocity, and the time required for the solvent to reach the surface is taken in batches for about 60 minutes.

FIG. 13 shows a case of irradiating with far infrared rays and drying. By using far infrared rays having a long wavelength, it is possible to give a heat quantity to the inside of the work. It is possible to obtain the effect of accelerating the time for the solvent in the solid content to move to the surface by warming and drying from the inside of the coating liquid. When the solvent inside the solid content moves to the surface, the solvent is covered with the evaporation material, and the drying is most promoted.
However, since the far-infrared effect alone is not effective in drying from the surface, it is necessary to use it together with hot air forced convection drying.

As described above, the drying by blowing hot air and the drying by far-infrared irradiation have the above problems. The problem to be solved by the present invention is this problem. provide.

The drying device according to the present invention is configured to have both advantages by using far-infrared ray drying and hot air drying together. That is, the state shown in FIG. 13 is created by far infrared rays, and the solvent that has moved to the surface is blown off with hot air that has the highest drying efficiency to reduce the drying time.

Therefore, the drying device for a high-concentration coating machine of the present invention has a flat far-infrared heater arranged in a single row or a plurality of rows on the inlet side, and a predetermined distance is set between the surface of the heat generating portion and the work to be dried. There is. For example, in the case of a three-row structure, the distance between the surface of the heat generating portion and the work to be dried may not be constant but may be changed stepwise.
In order to form a stable air flow boundary layer on the dry surface irradiated with far infrared rays, air blowing nozzles are provided on both sides of the far infrared heater, and the blowing angle of the nozzles is set to, for example, 30° to 60°. The structure is such that the interference of the secondary flow after the collision is minimized, and at the same time, the exhaust gas can be quickly sucked to the lower portion near the inlet of the outlet nozzle.
Without this, far-infrared rays of short-distance irradiation cannot be uniformly dried due to large temperature unevenness due to the thermosyphon.

The speed of the air blown from the above-mentioned spray nozzle is controlled so as to control the coating surface temperature, and it is possible to suppress the work surface temperature from being overheated by far-infrared irradiation. Then, a bar-shaped heater with a radiation type reflection plate is used at an intermediate portion of the drying device, and a predetermined distance is provided from the bar-shaped heater to the work drying surface.
Furthermore, a nozzle for hot air only is installed at the end of the dryer (outlet side), and the surface is over-dried by taking advantage of the convection that heat is transferred only from the surface at a temperature that does not dry the high-boiling solvent after drying the low-boiling solvent. -It is made into a film so that the change of mass after drying can be suppressed. However, a conventional tube-type far infrared ray may be used for a coating material having no temperature restriction.

The dryer for a high-concentration coating machine according to the present invention has the goodness of far-infrared rays that can continuously heat the inside of the coating layer, and at the same time promotes the movement of the vaporized substance to the surface, it can be used at a long distance in the preheat zone. While keeping the infrared surface temperature the same, the capacity is increased (generally flat far infrared), and room temperature to low boiling solvent wet-bulb temperature plus α, for example, 20 to 30°C from 50°C with hot air, instantaneously. Starting up is an absolute prerequisite for reducing the drying time.

In addition, the distribution of long wavelengths (for example, 3.5 μm or more) that heats the inside increases as the far-infrared surface temperature decreases. However, the heat transfer effect diminishes when the far-red surface temperature decreases. Therefore, in order not to reduce the effect, it is necessary to shorten the irradiation distance to increase the radiation heat absorption efficiency.

Schematic which shows the drying apparatus which concerns on this invention. Ceramic substrate before the coating liquid is applied. A specific example showing a work in which a coating liquid is applied to the surface of a ceramic substrate to form a coating layer. A process of irradiating far infrared rays to the coating layer coated on the surface of the ceramic substrate and blowing air to suppress overheating. A process in which the dry solvent moves to the surface side by irradiating the coating layer applied to the surface of the ceramic substrate with far infrared rays, and air is blown to suppress overheating. By irradiating far infrared rays through the reflector to the coating layer coated on the surface of the ceramic substrate, the dry solvent moves to the surface side and solidifies the inside, and blows air to suppress overheating. Process. By irradiating far infrared rays to the coating layer coated on the surface of the ceramic substrate through the reflection plate, the dry solvent moves to the surface side and the inside is further solidified, and air is blown to suppress overheating. Process. This is a process of coating the surface of a ceramic substrate, irradiating far infrared rays, and blowing hot air to the dried coating layer. Good. The specific example which shows a flat far infrared heater. The specific example which shows the rod-shaped heater which combined the reflective plate. The state where the coating liquid is applied to the ceramic substrate and the solvent is scattered. A state where the surface is coated by blowing hot air onto the coating layer formed by coating the ceramic substrate with the coating liquid. A state in which the coating layer formed by coating the ceramic substrate with the coating liquid is irradiated with far infrared rays and the inside is partially solidified.

FIG. 1 is an embodiment showing a schematic view of a drying device for a high-concentration coating machine, and 1a, 1b, 1c... In the figure show objects to be coated and dried (hereinafter referred to as works). , 2c, 2d, 2e... Nozzles, 3c and 3d are flat far infrared heaters, 4e and 4f are rod heaters, and 5e and 5f are reflectors, respectively.
The works 1a, 1b... Are placed on the conveyor 6 and can move at a constant speed as the conveyor 6 moves.

By the way, the drying device of the present invention is configured to be able to dry the works 1a, 1b,...
FIG. 2 is a cross-sectional view showing the work 1a before being coated (portion A in FIG. 1) before entering the drying device, and the work 1a before coating is a ceramic having predetermined vertical and horizontal dimensions and thickness. The substrate. However, the material of the work 1a as the base is not limited to ceramic.

The work 1b shown in FIG. 3 is in the state of the portion B in which the coating liquid 8 is applied to the surface of the ceramic substrate 7 of the work 1a to form the coating layer 9, and the applied coating liquid is In No. 8, the dry solvent is dispersed on the surface and inside of the coating layer 9.
Therefore, the work 1b whose surface is coated can be dried in a short time by placing the work 1b on the conveyor inside the drying apparatus of the present invention and moving it.

FIG. 4 shows the work 1c in the section C of the drying device. A flat far infrared heater 3c and a cooling nozzle 2c are arranged in the portion C, and the work 1c coated on the ceramic substrate 7 is irradiated with far infrared rays from the flat far infrared heater 3c for the purpose of residual heat. The rapid heating is performed. However, air is blown from the nozzle 2c in order to prevent partial overheating of the coating liquid 8.

FIG. 5 shows the work 1d in the D section of the drying device. Far infrared rays are radiated from the flat far infrared heater 3d and heated from the inside of the coating liquid 8 so that the dry solvents 10, 10... As in the case of the portion C shown in FIG. 4, air is ejected from the nozzle 2d to prevent partial overheating.
Unlike the conventional case where hot air is blown, the surface is not filmed (cured).

FIG. 6 shows the work 1e in the E section of the drying device. A rod-shaped heater 4e is arranged in the E portion, and a reflector 5e is combined with the rod-shaped heater 4e. Far-infrared rays emitted from the rod-shaped heater 4e are reflected by the reflection plate 5e and applied to the work 1e, and the dry solvent 10 inside the coating liquid 8 moves to the surface. Then, the air ejected from the nozzle 2e hits the surface, and the drying solvent 10 moved to the surface is dried so as to suppress overheating and prevent the surface from becoming a film. Therefore, the coating layer 9 can be gradually solidified from the inside.

FIG. 7 shows the work 1f in the F section of the drying device, which is the same as the E section shown in FIG. Therefore, the rod-shaped heater 4f is arranged in the F portion, and the reflector 5f is combined with the rod-shaped heater 4f. Far-infrared rays emitted from the rod-shaped heater 4f are reflected by the reflection plate 5f to irradiate the work 1f, and the dry solvent 10 inside the coating liquid 8 further moves to the surface.
Then, the air ejected from the nozzle 2f hits the surface, and the drying solvent 10 that has moved to the surface is dried so as to suppress overheating and prevent the surface from becoming a film. Therefore, the curing further proceeds from the inside of the coating layer 9.

FIG. 8 shows a work 1g in the G part of the drying device. There is no far-infrared heater in the G section, and the two nozzles 2g, 2g are attached in pairs so that they can be sprayed onto the work 1g from both sides. Hot air is blown from the two nozzles 2g, 2g, and the dry solvent 10, 10... Then, the coating liquid can be dried and solidified.
In this way, the coating liquid 8 can be efficiently dried and solidified while the work 1 is placed on the conveyor 6 and moved in the drying device.
If there is no temperature restriction, general far infrared rays may be used for this portion.

FIG. 9 shows an example of the flat far-infrared heater 3, which can radiate far-infrared rays from the lower surface. Then, terminals 11 and 11 to which the electric cord is connected are provided at both ends. As shown in FIG. 1, the flat plate far infrared heater 3 is mounted so as to be vertically movable so that the distance to the work 1 can be adjusted.

FIG. 10 shows the rod-shaped heater 4 combined with the reflector 5. The reflection plate 5 is curved in an arc shape, and the rod-shaped heater 4 is arranged in the center of the reflection plate 5. Far-infrared rays emitted upward from the rod-shaped heater 4 hit the reflection plate 5 and are reflected, and are emitted downward to hit the work 1. Made of
The nozzles 2c, 2d, 2e, 2f for blowing air to suppress overheating of the work 1 form an angle of 30° with the horizontal plane, and the nozzle 2g provided on the outlet side for blowing hot air is on the horizontal plane. The angle from is 60° and is inclined.

Ducts 12c, 12d... For sucking air blown from the nozzles 2c, 2d... Are provided on the lower side of the conveyor 6 in the portions C, D...
By the way, in the drying device shown in FIG. 1, two sets of flat far-infrared heaters combined with the nozzles 2 and two sets of rod-shaped heaters with a reflector combined with the nozzles 2 are arranged, and a pair of hot air is blown on the outlet side. One set of two nozzles arranged in a line is provided.
In the present invention, the number of these sets is not limited and differs depending on the type and size of the work 1 to be dried.

1 Work 2 Nozzle 3 Flat Far Infrared Heater 4 Rod Heater 5 Reflector 6 Conveyor 7 Ceramic Substrate 8 Coating Liquid 9 Coating Layer
10 Dry solvent
11 terminals
12 ducts

Claims (3)

In a drying device for drying a coating layer of a work formed by applying a coating liquid on the surface of a substrate, a conveyor that moves the work at a constant speed is placed for the purpose of shortening the heating time. with arranging a flat far-infrared heater on the inlet side of the drying device, an inclined nozzle for forming an air flow boundary layer provided in order to remove temperature irregularity by the irradiation of the far-infrared heater, the inclined nozzle of the spray angle workpiece 30° to 60° with respect to the surface , an exhaust duct is provided so that the secondary flow due to the collision of the jetting air does not disturb the far infrared rays, and the amount of heat lost to the latent heat of vaporization is provided in the middle part of the drying device. Arranged a rod-shaped far-infrared heater combined with a reflection plate to replenish the inside of the coating liquid, arranged a nozzle for injecting air, and arranged a nozzle for ejecting only hot air on the outlet side of the drying device. A dryer for a coating machine characterized by. In the drying method of drying the coating layer of the work formed by applying the coating liquid on the surface of the substrate, the work moves on the conveyor from the entrance to the exit and moves from the far infrared heater on the entrance side. Infrared rays are applied to the work to heat it, and air is blown from an inclined nozzle with a blowing angle of 30° to 60° in order to suppress overheating so that the secondary flow due to the collision of the jetted air does not become a disturbance of far infrared rays. Exhaust from the exhaust duct, in the middle part, irradiate far infrared rays from the rod-like far infrared heater combined with a reflecting plate in order to replenish the amount of heat lost to the latent heat of vaporization into the coating liquid through the reflecting plate, A method for drying a coating layer is characterized in that air is blown from a nozzle to hit the surface of the work, and hot air blown from the nozzle is applied to the work at the outlet side to dry the work. The coating layer drying method according to claim 2, wherein heating is performed by a far-infrared heater instead of hot air blowing by a nozzle provided on the outlet side.