JP5848161B2 - Manufacturing method of honeycomb molded body - Google Patents

Description

  The present invention relates to a method for manufacturing a honeycomb formed body in which drying and firing are continuously performed by irradiating a honeycomb structure with microwaves.

Honeycomb compacts are widely used for industrial applications such as electrical appliances and automobile exhaust gas. When manufacturing such a honeycomb formed body, first, ceramics is used as a main raw material, water and additives are kneaded to form a uniform clay, and then a honeycomb-shaped structure (hereinafter, referred to as extrusion structure) is formed. In some cases, the honeycomb structure is dried and fired.
The extruded honeycomb structure has a moisture content of about 40% by mass, and if the firing process is carried out as it is, cracks, cracks and the like are generated in the honeycomb structure. In order to prevent this, a drying step is required to reduce the moisture content of the honeycomb structure to about 10% by mass in advance.

As a method for drying the honeycomb structure, a natural drying method in which the honeycomb structure is allowed to stand at room temperature, a humidity control drying method in which the humidity of the drying environment is adjusted and drying is performed, or the honeycomb structure is irradiated with microwaves for drying. The microwave drying method to perform etc. are mentioned.
The microwave drying method can significantly reduce the drying time as compared with the natural drying method and the humidity control drying method, and can improve the production efficiency. As a drying method, a batch-type drying method in which a honeycomb structure is installed in a drying furnace having a uniform electric field distribution, or a honeycomb structure is continuously passed through a microwave irradiation tank equipped with a microwave generator. A continuous drying method is known (eg, cited documents 1 and 2).

  The firing step after drying the honeycomb structure has generally been performed using a firing furnace using a firing burner or the like as a heat source. By adjusting the heating power of the burner, the firing conditions can be easily changed, and it is easy to stabilize the firing conditions, so it can be said that this is a highly versatile firing step.

However, burning burners often use heavy oil, light oil, gasoline or the like as fuel. For this reason, the fuel may become soot at the time of firing and may be scattered in the firing furnace and adhere to the surface or inside of the honeycomb structure, which may lead to a decrease in performance of the honeycomb formed body.
If soot or the like adheres, the soot attached to the honeycomb structure must be removed by thermal decomposition. Even if the firing of the honeycomb structure has been completed, a firing time is required for removing the soot. I had to extend it.

  Conventionally, the drying process and the firing process of the honeycomb structure have been performed separately. As an example, the drying process is performed using a microwave dryer, and the firing process is performed using a firing burner. The respective processes are not continuous, but are independent processes that are batch processes. . Therefore, for example, the honeycomb structure after drying by the continuous drying method is taken out from the dryer one after another, and the honeycomb structure corresponding to one batch of the firing treatment is moved from the taken out to the firing furnace. In addition, it takes time and effort, which not only complicates the manufacturing procedure of the honeycomb formed body, but also reduces the production efficiency.

JP 2006-88685 A JP 2003-100441 A

  An object of the present invention is to provide a method for manufacturing a honeycomb formed body capable of improving production efficiency.

In order to solve the above problem, the present inventor has reviewed the drying process and the firing process of the honeycomb structure in order to simplify the manufacturing procedure of the honeycomb formed body.
In such a case, if not only the drying process but also the firing process is performed by irradiating with microwaves, no soot is generated, so there is no need to extend the firing time for removing soot, and the honeycomb structure. It has been found that the firing time of can be shortened.
Furthermore, if the drying step and the firing step are performed by irradiating with microwaves, it is found that the manufacturing procedure of the honeycomb formed body can be simplified by continuously performing these steps, and the present invention is completed. It was.

  That is, the first embodiment according to the present invention is a method for manufacturing a honeycomb formed body, wherein the honeycomb structure is irradiated with microwaves and dried, and the moisture content of the honeycomb structure is 5% by mass to 20% by mass. And at least a firing step of irradiating the honeycomb structure with microwaves and firing the honeycomb structure at a temperature of 300 ° C. to 1000 ° C., wherein the drying step and the firing step include A method for manufacturing a honeycomb formed body, which is performed continuously.

  According to the method for manufacturing a honeycomb formed body of the present invention, the manufacturing procedure can be simplified by continuously performing the drying step and the firing step, and the production efficiency can be improved.

It is a cross-sectional view of a continuous irradiation apparatus used in the method for manufacturing a honeycomb formed body of the present invention. It is a cross-sectional view of the continuous irradiation apparatus of the aspect different from FIG. It is the figure which looked at the conveyor which mounted the honeycomb structure. It is the figure which looked at the conveyor which mounted the honeycomb structure in the aspect different from FIG. It is the figure which looked at the conveyor which mounted the honeycomb structure in the aspect different from FIG. 3, FIG. 4 from right above. It is the figure which looked at the conveyor which mounted the honeycomb structure in the aspect different from FIGS. It is the figure which looked at the conveyor which mounted the honeycomb structure in the aspect different from FIG. 6 from right above. It is a perspective view showing one mode of a polygonal columnar honeycomb structure coated with a covering material. FIG. 4 is a perspective view showing an example of a polygonal columnar honeycomb structure coated with a coating material in a mode different from that in FIG. 3. Fig. 4 is a perspective view in which a polygonal columnar honeycomb structure different from that in Fig. 3 is coated with a coating material. It is a perspective view which shows one aspect | mode of the cylindrical honeycomb structure which coat | covered the coating material. FIG. 7 is a perspective view in which a cylindrical honeycomb structure having a mode different from that in FIG. 6 is coated with a coating material. It is a mimetic diagram showing one mode of a continuous drying device which dries a honeycomb structure continuously. It is the result of having measured the moisture content of the honeycomb structure after irradiating a microwave with the method of Example 6. FIG. It is the result of having measured the moisture content of the honeycomb structure after irradiating a microwave with the method of the comparative example 2. FIG.

Hereinafter, the general form of the method for manufacturing a honeycomb formed body according to the present invention will be described in detail.
First, the manufacturing method of the present invention includes at least a step of irradiating the honeycomb structure with microwaves to dry and fire. And a drying process and a baking process are not performed separately, but are performed continuously. By continuously performing these steps, the manufacturing procedure of the honeycomb formed body can be simplified.
Here, the honeycomb structure is not a fixed shape, and the honeycomb surface may be a polygonal column shape having a polygonal shape such as a quadrangle, pentagon, or hexagon, or a cylindrical shape having a honeycomb surface having a circular shape. Can be mentioned.
And a drying process is a process of reducing the moisture content of a honeycomb structure from about 40 mass% to 5 mass%-20 mass% by drying. When fired in a state where the moisture content is about 40% by mass, cracks and cracks occur in the honeycomb structure due to rapid evaporation of moisture, etc., so it is necessary to prevent this by reducing the moisture content in advance. is there. When the moisture content of the honeycomb structure is about 10% by mass, cracks and cracks in the firing process can be prevented regardless of the shape and size of the honeycomb structure.
Next, the firing process is a process in which the temperature of the honeycomb structure after the drying process is fired at 300 to 1000 degrees. By this step, the adjacent ceramic raw material particles gradually adhere to each other, and the gap between the particles becomes small, whereby a strong honeycomb formed body is obtained. The entire firing process takes about 10 hours, and within this time, a temperature between 300 ° C. and 900 ° C., preferably a temperature of 500 ± 50 ° C., is 1 hour to 5 hours, preferably 2 hours to 3 hours. By holding, sufficient strength of the honeycomb formed body can be ensured.
Microwave is a general term for radio waves having a frequency of 300 MHz to 30 GHz (wavelength 1 cm to 1 m), and a microwave with a frequency in this range can be used as the microwave irradiated to the honeycomb structure. In general, a microwave having a frequency of around 2450 MHz is used, and the wavelength (λ) of the microwave in this case is about 120 mm.

In the method for manufacturing a honeycomb formed body of the present invention, the drying step and the firing step can include a step of irradiating the honeycomb structure with microwaves using a continuous microwave irradiation apparatus.
Here, the continuous microwave irradiation apparatus includes a microwave irradiation tank for drying provided with a microwave generation apparatus that generates microwaves, irradiates the honeycomb structure, and dries, and generates a microwave in the honeycomb structure. A firing microwave irradiation tank provided with a microwave generator for irradiation and firing, a drying microwave irradiation tank inlet provided with an electromagnetic shutter, a firing microwave irradiation tank outlet provided with an electromagnetic shutter, and a honeycomb structure And a conveying device that sequentially conveys the drying microwave irradiation tank inlet, the drying microwave irradiation tank, the baking microwave irradiation tank, and the baking microwave irradiation tank outlet.
With such a continuous microwave irradiation apparatus, the honeycomb structure is transferred from the drying microwave irradiation tank inlet to the drying microwave irradiation tank by sequentially placing the honeycomb structure on the transfer apparatus. Is dried, and subsequently transferred into the firing microwave irradiation tank and fired, and then, after the fired honeycomb structure transported to the firing microwave irradiation tank outlet is taken out, continuous drying, A baking process becomes possible.

In the method for manufacturing a honeycomb formed body according to the present invention, the transport device includes at least a honeycomb structure and transports the drying microwave irradiation tank inlet and the drying microwave irradiation tank, and the honeycomb transport body. It can consist of a carrier device for firing which places the structure and carries the inside of the microwave irradiation tank for firing and the outlet of the microwave irradiation tank for firing.
In this way, by separating the transport device in the drying process and the firing process, the honeycomb structure transport speed in the drying process and the transport speed in the firing process are made constant according to the microwave irradiation conditions and the like. It can be changed, increasing versatility.
In addition, when only the drying process is performed, the baking conveyance device can be stopped, and when only the baking process is performed, the drying conveyance device can be stopped, which reduces the power cost. Can be reduced.

In the method for manufacturing a honeycomb formed body of the present invention, the conveyance speed of the honeycomb structure by the conveyance device is constant, and the microwave power density in the drying step is 0.01 kW / kg to 1 kW / kg per honeycomb structure. The microwave power density in the firing step can be 0.1 kW / kg to 1 kW / kg per honeycomb structure.
By keeping the conveyance speed of the honeycomb structure constant, it takes a certain time from the start of the drying process to the end of the firing process, so the extrusion process as the previous process and the cross-section cutting process of the honeycomb structure as the subsequent process It becomes easy to make a production plan by all processes including the above. The conveyance speed is preferably 0.1 m / min to 3.0 m / min. If it is slower than 0.1 m / min, the production efficiency is poor, and if it is faster than 3.0 m / min, it is difficult to place the honeycomb structure on the conveying device and to take out the honeycomb structure from the conveying device. It becomes.
If the microwave power density in the drying process is in the range of 0.01 kW / kg to 1 kW / kg per honeycomb structure, the moisture content of the honeycomb structure can be set to 5 mass% to 20 mass%. . A power density in the range of 0.1 kW / kg to 1 kW / kg is more preferable because the moisture content of the honeycomb structure can be about 10% by mass.
Further, if the microwave power density in the firing step is 0.1 kW / kg to 1 kW / kg per honeycomb structure, the honeycomb structure can be fired at a temperature of 200 to 1000 degrees. If the output density is 0.3 kW / kg or more, the temperature of the honeycomb structure can be set to 500 ° C. or more, which is more preferable.
In the drying step and the firing step, the output density can be adjusted to the above range by controlling the microwave irradiation output of the microwave generator.

In the method for manufacturing a honeycomb formed body of the present invention, the honeycomb structure transport speed S1 by the drying transport device is 0.1 m / min to 3.0 m / min, and the honeycomb structure transport by the firing transport device is The speed S2 is 0.01 m / min to 1.0 m / min, and the conveyance speed S1 satisfies the relationship of 3 to 10 times the conveyance speed S2, and the microwave output density in the drying step is honeycomb structure. The power density of the microwaves in the firing step can be 0.1 kW / kg to 1 kW / kg per honeycomb structure, and 0.01 kW / kg to 1 kW / kg per body.
If the honeycomb structure transport speed in the firing process is slower than the drying process and firing takes longer than the drying process, the microwave irradiation output in the firing process can be reduced, reducing the manufacturing cost. can do.
If the conveyance speed of the honeycomb structure in the drying process is slower than 0.1 m / min, the production efficiency is low and not appropriate. On the other hand, if it is faster than 3.0 m / min, the step of placing the honeycomb structure on the conveying device becomes difficult. In the drying process, when the honeycomb structure is conveyed at a speed of 0.1 m / min to 3.0 m / min, the drying can be satisfactorily performed in consideration of the manufacturing efficiency and the previous process.
Moreover, when the conveyance speed of the honeycomb structure in the firing process is lower than 0.01 m / min, the manufacturing efficiency is low and not appropriate. On the other hand, if it is faster than 1.0 m / min, it is necessary to increase the irradiation output amount of the microwave, so that the effect of reducing the manufacturing cost is diminished. In the firing step, the honeycomb structure can be fired satisfactorily in consideration of production efficiency and production cost by setting the conveyance speed of the honeycomb structure to 0.01 m / min to 1.0 m / min.
If the microwave power density in the drying process is in the range of 0.01 kW / kg to 1 kW / kg per honeycomb structure, the moisture content of the honeycomb structure can be set to 5 mass% to 20 mass%. . A power density in the range of 0.1 kW / kg to 1 kW / kg is more preferable because the moisture content of the honeycomb structure can be about 10% by mass.
Further, if the microwave power density in the firing step is 0.1 kW / kg to 1 kW / kg per honeycomb structure, the honeycomb structure can be fired at a temperature of 300 to 1000 degrees. If the output density is 0.3 kW / kg or more, the temperature of the honeycomb structure can be set to 500 ° C. or more, which is more preferable.
In the drying step and the firing step, the output density can be adjusted to the above range by controlling the microwave irradiation output of the microwave generator.

  The method for manufacturing a honeycomb formed body of the present invention further includes a placing step of placing a plurality of honeycomb structures on a conveying device, and the placing step has an interval in a direction parallel to the conveying direction of the plurality of honeycomb structures. It may be a series mounting step of mounting in series on the transfer device so as to be at least twice the wavelength (λ) of the microwave. If a plurality of honeycomb structures are placed on the transfer device, they are transferred to the drying microwave irradiation tank and the firing microwave irradiation tank through the irradiation tank inlet. When the passing honeycomb structure is irradiated with microwaves, it can be dried and fired.

Here, in the placing step, the plurality of honeycomb structures are placed in series on the carrying device so that the interval in the direction parallel to the carrying direction is at least twice the wavelength (λ) of the microwave. It is a placing process. Even when the moisture content of adjacent honeycomb structures is different, the microwaves are evenly irradiated evenly by setting the interval between the honeycomb structures at least twice the wavelength of the microwaves. Further, since the honeycomb structure is not irradiated with radiation, any honeycomb structure can be uniformly dried and fired as a result.
When the interval is shorter than twice the wavelength of the microwave, unevenness occurs in the irradiation of the microwave, or a honeycomb structure in which the irradiation is skipped appears. In addition, even if the interval is too long, it does not affect the drying and baking itself, but the drying efficiency and the baking efficiency are reduced, so the interval of about 4 times the wavelength of the microwave is set as the upper limit, The honeycomb structure can be dried and fired.
The honeycomb structure is placed in series on the transfer device. The method of mounting in a row in the direction parallel to the transfer device on the transfer device, and a method of mounting in parallel in two or more rows will be described below.
In addition, it is preferable that the distance of the microwave generator used as the microwave irradiation source and the honeycomb structure is 2 to 10 times the wavelength of the microwave. When the distance is shorter than twice, a near electric field is generated, and there is a possibility that the microwaves are concentrated only in one place of the honeycomb structure, and drying unevenness or firing unevenness occurs. On the other hand, when the distance is longer than 10 times, the influence of multiple reflection becomes large, which may cause uneven drying and uneven firing. If the distance is within the range of 2 to 10 times, there is no fear of such drying unevenness or firing unevenness, and the honeycomb structure can be dried and fired satisfactorily.

The mounting step according to the present invention includes a parallel mounting step of mounting a plurality of honeycomb structures in parallel on the transfer device such that the interval in the direction orthogonal to the transfer direction is twice or more the wavelength of the microwave. Further can be included. This is because a large number of honeycomb structures can be efficiently dried and fired when the honeycomb structures are placed in two or more rows in parallel.
In the case of mounting in parallel, the honeycomb structures that are adjacent in parallel are mounted so that the interval between them is at least twice the wavelength (λ) of the microwave. Even when the moisture content of the honeycomb structures adjacent in parallel is different, the microwaves are evenly irradiated evenly by setting the interval at least twice the wavelength of the microwaves. Further, since the honeycomb structure is not irradiated with radiation, any honeycomb structure can be uniformly dried and fired as a result.
When the interval is shorter than twice the wavelength of the microwave, unevenness occurs in the irradiation of the microwave, or a honeycomb structure in which the irradiation is skipped appears. In addition, even if the interval is too long, it does not affect the drying and baking itself, but the drying efficiency and the baking efficiency are reduced, so the interval of about 4 times the wavelength of the microwave is set as the upper limit, The honeycomb structure can be dried and fired.

The microwave generator is installed on the ceiling of the microwave irradiation tank for drying and firing, and the placing step sets the axial direction of the cells of the plurality of honeycomb structures to the horizontal direction and the cell with respect to the conveying direction. The distance between the end of the honeycomb structure in the front row and the end of the side of the honeycomb structure placed next to the front row is a microwave. The step of mounting can be included so as to be twice or more of the wavelength.
A microwave generator is installed on the ceiling of the microwave irradiation tank for drying and firing, and the cell is placed on the transfer device with the axial direction of the cells of the honeycomb structure as the horizontal direction. The incident density of waves can be higher than the incident density on the honeycomb surface. Since the honeycomb side surface has a larger area to be irradiated than the honeycomb surface, drying and firing can be promoted by increasing the incident density on the honeycomb side surface.
The angle of inclination in the axial direction of the cells of the honeycomb structure with respect to the conveying direction is that the honeycomb structure is placed obliquely with respect to the traveling direction so that the entire honeycomb structure is not irradiated with microwaves at once. This is because microwaves are irradiated from the end of the structure.
If the honeycomb structure has a slight deviation in the distribution of moisture content, if the entire honeycomb structure is irradiated with microwaves at once, the microwaves are concentrated and irradiated on the portion with a large amount of moisture. This is because there is a risk of causing uneven drying, uneven firing, whitening, cracks, cracks, and the like. If microwaves are gradually irradiated from the end to the whole of the honeycomb structure, the drying proceeds from the end, so that drying can be performed satisfactorily without causing unevenness of drying or unevenness of firing.
The reason why the inclination angle is 35 to 75 degrees is that drying unevenness and firing unevenness can be more effectively prevented when the inclination angle is within this range. Even if the tilt angle exceeds this range, the prevention effect is weakened, but it is possible to uniformly dry and fire.
Moreover, the honeycomb structure is placed so that the distance between the end of the honeycomb structure in the front row and the end of the honeycomb structure placed next to the front row is at least twice the wavelength of the microwave. In this way, the interval between the honeycomb structures is thus more than twice the wavelength of the microwaves, so that even when the moisture content of adjacent honeycomb structures is different, the microwaves are evenly irradiated evenly. . Further, since the honeycomb structure is not irradiated with radiation, any honeycomb structure can be uniformly dried and fired as a result.
Further, since any one of the honeycomb structures is always irradiated with the microwave, there is no waste in irradiation, and as a result, the irradiation output can be reduced.

In the method for manufacturing a honeycomb formed body of the present invention, the drying step and the firing step include a step of irradiating the honeycomb structure with microwaves using the same batch type microwave irradiation apparatus, and the batch type microwave irradiation. The apparatus includes at least a microwave irradiation tank, and the microwave irradiation tank generates at least one microwave for irradiating the honeycomb structure, and rotation for driving and rotating the honeycomb structure. The microwave power density in the drying process is 0.01 kW / kg to 1 kW / kg per honeycomb structure, and the microwave power density in the firing process is 0 per honeycomb structure. .1 kW / kg to 1 kW / kg.
When a general-purpose honeycomb molded body is manufactured in large quantities, the use of a continuous microwave irradiation apparatus is superior in terms of manufacturing efficiency and manufacturing cost. However, when manufacturing a small number of honeycomb structures for reasons such as made-to-order production or custom-made products, it is better to use a batch-type microwave irradiation device in terms of manufacturing efficiency and manufacturing costs. This may be more advantageous than using a microwave irradiation apparatus of the type.
The drying process and the baking process can be performed continuously using the same batch-type microwave irradiation device, thereby saving time and labor when moving from the drying process to the baking process. In addition, since the above-described batch type irradiation apparatus can rotate the honeycomb structure, it is possible to uniformly irradiate microwaves, and locally drying the honeycomb structure due to uneven irradiation. It can prevent overburning.
If the microwave power density in the drying process is in the range of 0.01 kW / kg to 1 kW / kg per honeycomb structure, the moisture content of the honeycomb structure can be set to 5 mass% to 20 mass%. . A power density in the range of 0.1 kW / kg to 1 kW / kg is more preferable because the moisture content of the honeycomb structure can be about 10% by mass.
Further, if the microwave power density in the firing step is 0.1 kW / kg to 1 kW / kg per honeycomb structure, the honeycomb structure can be fired at a temperature of 300 to 1000 degrees. If the output density is 0.3 kW / kg or more, the temperature of the honeycomb structure can be set to 500 ° C. or more, which is more preferable.
In the drying step and the firing step, the output density can be adjusted to the above range by controlling the microwave irradiation output of the microwave generator.

In the method for manufacturing a honeycomb formed body of the present invention, the honeycomb structure is a polygonal columnar honeycomb structure having a polygonal honeycomb surface, and at least the corners of the surface of the honeycomb structure before the drying step and Each side can include a coating step of coating a coating material that protects the honeycomb structure from microwaves. When the moisture content of the honeycomb structure after the drying process is around 20% by mass, the honeycomb structure may be whitened, cracked, cracked, or the like in the firing process. Occurrence of whitening or the like can be prevented.
In the polygonal honeycomb structure, at least one of the diagonal lines of the honeycomb surface, the length of the side of the polygon, or the height of the honeycomb structure has a microwave wavelength. When the ratio is 0.5 times or more, whitening or the like may occur in the honeycomb structure in the drying step. Therefore, the covering material can be coated in order to prevent such whitening from occurring in advance. The diagonal line is a line segment excluding the side among the line segments connecting two different vertices on the polygon, and all polygons other than the triangle have two or more diagonal lines.
In the coating step, a coating material is coated on at least the corners and each side of the surface of the honeycomb structure. Since microwaves tend to concentrate on corners and sides, if these parts are covered, they can be prevented from being whitened, cracked, cracked, etc. even when dried or fired by microwave irradiation. I can do it.
When coating with a coating material, the coating interval is preferably 0.5 to 2 times the wavelength of the microwave. In the honeycomb structure, at least one of the diagonal lines of the honeycomb surface, the length of the side of the polygon, or the height of the honeycomb structure is 0.5 times or more of the wavelength of the microwave. In some cases, cracks, cracks, etc. are likely to occur on the honeycomb surface or side surface having a width of 0.5 times or more due to the drying process or firing process, and these can be prevented. For example, when the height of the honeycomb structure is 0.5 to 2 times the wavelength of the microwave, whitening is achieved by coating the corners and each side of the honeycomb side surface with a coating material. Cracks and cracks can be prevented. Further, when the height of the honeycomb structure is at least twice as long as the wavelength of the microwave, the honeycomb side surface is cracked only by covering the corner and each side of the honeycomb side surface with a coating material. Since cracks or the like may occur, it is preferable to cover the honeycomb side surface at a distance of 0.5 to 2 times the wavelength of the microwave from each side in addition to the corners and each side. .

In the method for manufacturing a honeycomb formed body of the present invention, the honeycomb structure is a cylindrical honeycomb structure having a circular honeycomb surface, and before the drying step, at least at the column end of the surface of the honeycomb structure, A coating step of coating a coating material that protects the honeycomb structure from microwaves can be included. When the moisture content of the honeycomb structure after the drying process is around 20% by mass, the honeycomb structure may be whitened, cracked, cracked, or the like in the firing process. Occurrence of whitening or the like can be prevented.
Further, in the above cylindrical honeycomb structure, when either the diameter of the circular honeycomb surface or the height of the honeycomb structure is 0.5 times or more the microwave wavelength, the drying step In this case, since whitening or the like may occur in the honeycomb structure, the covering material can be coated to prevent the occurrence of whitening, cracking, cracking, or the like.
In the coating step, a coating material is coated on at least the cylindrical end portion of the surface of the honeycomb structure. The cylindrical end portion is a portion where the honeycomb surface and the honeycomb side surface are in contact with each other, and is a portion where the microwave tends to concentrate. If this cylindrical end is covered, it is possible to prevent whitening, cracks, cracks, and the like from occurring even if drying or baking is performed by microwave irradiation.
When coating with a coating material, the coating interval is preferably 0.5 to 2 times the wavelength of the microwave. In the honeycomb structure, when either the diameter of the honeycomb surface or the height of the honeycomb structure is 0.5 times or more of the wavelength of the microwave, the width or the like is 0.5 times or more. This is because cracks, cracks, and the like are likely to occur on a certain honeycomb surface or side surface by a drying process or a firing process, and these can be prevented. For example, when the diameter of the honeycomb surface is 0.5 to 2 times the wavelength of the microwave, the cylindrical end of the honeycomb structure is covered with a coating material, thereby whitening, cracks, cracks, etc. Can be prevented. In addition, when the honeycomb surface has a diameter that is twice or more the wavelength of the microwave, cracking, cracking, or the like generated on the honeycomb surface can be achieved only by covering the cylindrical end of the honeycomb structure with a coating material. In view of the possibility of occurrence, it is preferable to cover the honeycomb surface and the honeycomb side surface at a distance of 0.5 to 2 times the wavelength of the microwave from the column end in addition to the column end. In other words, in this case, the honeycomb material is coated on the honeycomb side surface so that the honeycomb surface is coated with a solar cruciform and the honeycomb surface at the top of the honeycomb structure is connected to the cruciform coating material coated on the bottom honeycomb surface. The material will be coated.

  In this invention, it is preferable that the coating width | variety at the time of coat | covering with a coating material is 0.5 times or less of the wavelength of a microwave. This is because if the coating width exceeds 0.5 times, the microwave may excessively hinder the penetration of the honeycomb structure, resulting in a drying delay. If the coating width is 0.1 times or more of the wavelength of the microwave, the honeycomb structure can be sufficiently protected from the microwave. By setting the reference of the coating width to 0.2 times the wavelength of the microwave and appropriately adjusting the coating width according to the shape and size of the honeycomb structure, the honeycomb structure can be efficiently dried.

  When the covering material includes a microwave reflecting material, the microwave reflecting material is preferably a metal material having electrical conductivity. If it is a metallic material having electrical conductivity, it is possible to effectively reflect the microwave and sufficiently protect the honeycomb structure from the microwave. Examples of the conductive metal material include materials made of any of aluminum, copper, iron, stainless steel, brass, or a combination thereof.

Note that even if the firing process is performed with the honeycomb structure covered with the coating material, the honeycomb structure itself is not affected, but depending on the metal material used as the coating material, the honeycomb structure may melt depending on the firing conditions. There is. In the case of using such a metal material having a low melting point, there may be a step of removing the covering material from the honeycomb structure after the drying step and before the firing step.
In addition, the use of a metal material having a high melting point that can withstand the firing process as the covering material can eliminate the step of removing the covering material.

  Next, embodiments of the method for manufacturing a honeycomb formed body of the present invention will be described more specifically with reference to the drawings. In this case, the present invention is not limited to the embodiment with reference to the drawings.

FIG. 1 is a cross-sectional view of a continuous irradiation apparatus that can be used in the method for manufacturing a honeycomb formed body of the present invention. The continuous irradiation apparatus 1 is basically based on microwave irradiation tanks 2a and 2b made of a metal casing that multi-reflects microwaves, and the microwave irradiation tanks 2a and 2b respectively include microwave generators 3a and 3b therein. Prepare. The microwave irradiation tank 2a is provided with an irradiation tank inlet 4, and the microwave irradiation tank 2b is provided with an irradiation tank outlet 5. Between the microwave irradiation tanks 2a and 2b, an irradiation tank entrance 6 for connecting these irradiation tanks is installed. The irradiation tank inlet 4, the irradiation tank outlet 5, and the irradiation tank inlet / outlet 6 are provided with an electromagnetic wave shutter 7 for preventing the microwave from being emitted to the outside of the irradiation tank.
Next, the case where a drying process and a baking process are performed using such a continuous irradiation apparatus will be described. The honeycomb structure 8 is placed on a conveyor 9 as a transfer device, and is sent from the irradiation tank inlet 4 to the inside of the microwave irradiation tank 2a. Then, the microwave generator 3a irradiates the honeycomb structure 8 with microwaves, and when the honeycomb structure 8 is dried, the microwaves are sent into the microwave irradiation tank 2b through the irradiation tank entrance 6. Inside the microwave irradiation tank 2b, the microwave generator 3b irradiates the honeycomb structure 8 with microwaves and fires, and after firing, the honeycomb structure 8 is sent out from the microwave irradiation tank 2b through the irradiation tank outlet 5.

FIG. 2 is a cross-sectional view of a continuous irradiation apparatus having a mode different from that in FIG. Basic configurations such as the microwave irradiation tanks 2a and 2b, the irradiation tank inlet 4, the irradiation tank outlet 5, and the irradiation tank inlet / outlet 6 are the same as those of the continuous drying apparatus shown in FIG. Each of the microwave irradiation tanks 2a and 2b is provided with conveyors 9a and 9b.
A process using such a continuous irradiation apparatus will be described. The honeycomb structure 8 placed on the conveyor 9a is dried in the microwave irradiation tank 2a, further placed on the conveyor 9b at the irradiation tank inlet / outlet 6 and fired in the microwave irradiation tank 2b, and the irradiation tank outlet 5 is discharged. It is sent to the outside via.

  FIG. 3 is a view of a conveyor on which a honeycomb structure is placed in a continuous drying apparatus. In FIG. 3A, the honeycomb structure 8 is placed so that the cell axis direction 11 of the honeycomb structure is perpendicular to the traveling direction (conveying direction) 10 of the conveyor 9. In this case, the honeycomb surface 8a is oriented in a direction perpendicular to the traveling direction 10 of the conveyor 9, and the cell axis direction 11 is a horizontal direction as shown in the cross-sectional views of FIGS. ing. In the honeycomb structure, the interval 12 in the direction parallel to the conveyance direction 10 is at least twice the wavelength of the microwave.

FIG. 3B is a view of the conveyor placed from above so that the axial direction of the cells of the honeycomb structure is in the vertical direction so that the honeycomb surface is up.
Small size in which the honeycomb surface has a polygonal column shape having a polygonal shape or the honeycomb surface has a circular column shape, and the cell length in the axial direction of the honeycomb structure is shorter than 0.5 times the wavelength of the microwave In the case of this honeycomb structure, there is no possibility that the honeycomb structure is deformed by its own weight, so that this method can be used. By placing the cells in the honeycomb structure so that the axial direction of the cells is in the vertical direction, the volatilized water can easily escape from the inside of the honeycomb structure to the outside, so that the drying time can be shortened.

  FIG. 4 is a view of the conveyor on which the honeycomb structure is placed in a mode different from that in FIG. 3. In FIG. 4, the honeycomb structure 8 is placed so that the cell axis direction 11 of the honeycomb structure is parallel to the traveling direction 10 of the conveyor 9. In this case, the honeycomb surface 8 a faces the direction parallel to the traveling direction 10 of the conveyor 9. That is, the honeycomb surface is suitable for the traveling method. Further, the cell axis direction 11 is a horizontal direction as in the case of FIG. In the honeycomb structure, the interval 12 in the direction parallel to the conveyance direction 10 is at least twice the wavelength of the microwave.

  FIG. 5 is a view of a conveyor on which a honeycomb structure is placed in a manner different from that of FIGS. Similar to FIG. 4, the cell axis direction 11 of the honeycomb structure is parallel to the advancing direction 10 of the conveyor 9, and is set to be horizontal, and the interval 12 is parallel to the transport direction 10. The honeycomb structure 8 is placed so that becomes more than twice the wavelength of the microwave. Furthermore, the honeycomb structures are placed in parallel on the conveyor 9 so as to form two rows, and the interval 13 in the direction orthogonal to the conveying direction 10 is twice or more the wavelength of the microwave.

Fig. 6 is a view of the conveyor on which the honeycomb structure is placed in a mode different from Figs. In the honeycomb structure 8, the axial direction of the cells is horizontal, the axial direction of the cells is inclined with respect to the transport direction 10a, and the inclination angle 14 is 35 to 75 degrees (FIG. 6 ( a)).
The plurality of honeycomb structures are such that the distance between the end of the honeycomb structure in the front row and the end of the side of the honeycomb structure placed subsequent to the front row is at least twice the wavelength of the microwave. As there is. That is, in the plurality of honeycomb structures, the interval 12 in the direction parallel to the conveyance direction 10 is at least twice the wavelength of the microwave (FIG. 6B).

  FIG. 7 is a view of the conveyor on which the honeycomb structure is placed in a mode different from that in FIG. 6 as seen from directly above. The honeycomb structure 8 has a point in which the axial direction of the cell is a horizontal direction, a point in which the axial direction of the cell is inclined with respect to the transport direction 10, and an inclination angle 14 is 35 to 75 degrees. The interval 12 in the direction parallel to the conveyance direction 10 is the same as that in FIG. 6 in that it is at least twice the wavelength of the microwave. In FIG. 7, the honeycomb structures are further placed in parallel on the conveyor 9 in two rows, and the interval 15 in the direction orthogonal to the transport direction 10 is twice or more the wavelength of the microwave.

FIG. 8 is a perspective view showing an example of a polygonal columnar honeycomb structure coated with a coating material applicable to the manufacturing method of the present invention. The honeycomb structure 8 is a quadrangular columnar structure having a honeycomb surface 8a having a quadrangular shape, and an aluminum plate 16 is coated as a covering material so as to protect the corners 8b and the sides 8c on the surface of the honeycomb structure. ing.
The honeycomb structure 8 has a length of each side of the honeycomb surface and a height of the honeycomb structure that is 0.5 to 2 times the wavelength of the microwave. If the part 8b and each side 8c are protected by a covering material, whitening, cracks, cracks, and the like due to drying by irradiation with microwaves can be prevented.

  FIG. 9 is a perspective view in which an aluminum susceptor is used as a covering material on the honeycomb structure 8 similar to that in FIG. The susceptor 17 covers the corner portion 8b and the side 8c of the surface of the honeycomb structure, similarly to the aluminum plate of FIG. The upper and lower susceptors and the susceptors covering the sides are connected by aluminum bolts 18.

FIG. 10 is a perspective view in which a rectangular pillar-shaped honeycomb structure different from the honeycomb structure of FIG. 8 is coated with an aluminum plate as a coating material. In the honeycomb structure 8, the length of each side of the honeycomb surface is 0.5 to 2 times the wavelength of the microwave, while the height of the honeycomb structure is 2.5 times the wavelength of the microwave. Is double. Therefore, in order to prevent whitening, cracks, cracks, and the like due to microwave irradiation, not only the corners and sides of the honeycomb structure 8 are protected with a covering material, but also the honeycomb side surface is 0.5 times the wavelength. It is necessary to protect with a covering material at intervals of up to twice as long. In FIG. 10, the honeycomb side surface is protected by an aluminum plate 16 so as to be divided into two equal parts, and the honeycomb side surface is coated with a coating material at intervals of a length of 1.25 times the wavelength of the microwave. .
Here, when the width of the aluminum plate is uniformly 0.25 times the wavelength of the microwave, the honeycomb structure can be dried satisfactorily. Furthermore, only the aluminum plate in the longitudinal direction of the honeycomb structure has a width A ′ of 0.4 times the wavelength of the microwave, whereby the honeycomb structure is uniformly dried. In this way, the honeycomb structure can be dried more efficiently by setting the reference of the coating width to 0.2 times the wavelength of the microwave and appropriately adjusting the coating width according to the shape and size of the honeycomb structure. Can do.

FIG. 11 is a perspective view showing an example of a columnar honeycomb structure coated with a covering material. The honeycomb structure 8 has a circular honeycomb surface 8a, and is coated with an aluminum plate 16 as a covering material so as to protect the cylindrical end portion 19 on the surface of the honeycomb structure.
The honeycomb structure 8 has a honeycomb surface diameter and a honeycomb structure height of 0.5 to 2 times the wavelength of the microwave, and therefore covers the cylindrical end 19 of the honeycomb structure 8. If it protects with a material, whitening, a crack, a crack, etc. by irradiating with a microwave and drying can be prevented.

  FIG. 12 is a perspective view in which a cylindrical honeycomb structure different from the honeycomb structure of FIG. 11 is coated with an aluminum plate as a coating material. In the honeycomb structure 8, the height of the honeycomb structure is 0.5 to 2 times the wavelength of the microwave, while the diameter of the honeycomb surface is 2.5 times the wavelength of the microwave. Therefore, in order to prevent whitening, cracks, cracks, and the like due to microwave irradiation, not only the cylindrical end portion of the honeycomb structure 8 is protected by the covering material, but also the honeycomb surface and the honeycomb side surface are 0.5 times the wavelength. It is necessary to protect with a covering material at intervals of up to twice as long. In FIG. 12, the honeycomb surface and the honeycomb side surface are protected by an aluminum plate 16 so as to be divided into four equal parts, and the honeycomb surface and the honeycomb side surface are covered with a coating material at intervals of 1.25 times the wavelength of the microwave. Will be.

  The honeycomb structure coated with the covering material shown in FIGS. 8 to 12 is dried and fired according to the present invention to form a honeycomb formed body.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example at all.

Creation of honeycomb structure [honeycomb structure m]
A mixture of talc, kaolin, alumina, titanium oxide and silica, etc., a binder, water, additives and the like are kneaded into a uniform clay-like shape, and extruded to obtain a honeycomb surface having a length of 50 mm and a honeycomb surface. A square prism-shaped small honeycomb structure m (water content: 40% by mass) having a width of 50 mm, a height of 50 mm, a wall thickness of 1 mm, and 484 cells (vertical direction: 22 pieces, horizontal direction: 22 pieces) was prepared. .

[Honeycomb structure n]
As in the method for producing the honeycomb structure 1, a clay-like one was extruded and formed to have a honeycomb surface length of 150 mm, a honeycomb surface width of 150 mm, a height of 200 mm, a wall thickness of 1 mm, and a cell number of 484 (longitudinal direction). : 22 pieces, lateral direction: 22 pieces) square pillar-shaped honeycomb structure n was prepared.
The following drying treatment was performed using the prepared honeycomb structures m and n.

Drying and firing of honeycomb structure using continuous irradiation device [Example 1]
The honeycomb structure m was continuously irradiated with microwaves using the continuous irradiation apparatus shown in FIG. 1 to perform a drying step and a firing step.
The specifications of the microwave irradiation apparatus are: irradiation output of the microwave generation apparatus 3a: 1.5 kW (continuous variable), frequency: 2450 ± 30 MHz, power input: three-phase AC, 200 V, irradiation output of the microwave generation apparatus 3b : 1.5 kW (continuously variable), frequency: 2450 ± 30 MHz, power input: three-phase AC, 200V. Further, the distance between the microwave generators 3a and 3b and the honeycomb structure 8 was set to four times the wavelength of the microwave as the shortest distance.
The specifications of the microwave irradiation tanks 2a and 2b are both internal dimensions: 600W × 700H × 1200L (mm) and inner furnace material: SUS304.
The conveyor 9 enters the microwave irradiation tank 2a at the start of the drying process, enters the microwave irradiation tank 2b at the start of the firing process via the irradiation tank inlet / outlet 6 after the drying process, and enters the microwave irradiation tank 2b at the end of the firing process. The conveyance speed was adjusted to be constant at 0.5 m / min so as to exit from the wave irradiation tank 2b. The microwave irradiation time was 1 hour in the drying process and 5 hours in the firing process per honeycomb structure.
The microwave power density in the drying process was 0.05 kW / kg per honeycomb structure, and the microwave power density in the firing process was 0.3 kW / kg per honeycomb structure. By adjusting the output density in this manner, the moisture content of the honeycomb structure m after the drying treatment was set to 10% by mass, and the temperature of the honeycomb structure in the firing step was set to 500 degrees.
The moisture content of the honeycomb structure m after the drying step is determined by using a moisture measuring microwave oscillator while the honeycomb structure m passes through the irradiation tank inlet / outlet 6 and using a microwave having the same frequency band as that of the drying microwave. Waves were applied to the honeycomb structure m at an output of 20 mW, and the microwave reflected from the honeycomb structure m was measured. A total of 20 drying processes and firing processes were performed for each honeycomb structure.

[Example 2]
The honeycomb structure m was continuously irradiated with microwaves using the continuous irradiation apparatus shown in FIG.
The specifications of the microwave irradiation apparatus are: irradiation output of the microwave generation apparatus 3a: 1.5 kW (continuous variable), frequency: 2450 ± 30 MHz, power input: three-phase AC, 200 V, irradiation output of the microwave generation apparatus 3b : 1.5 kW (continuously variable), frequency: 2450 ± 30 MHz, power input: three-phase AC, 200V. Further, the distance between the microwave generators 3a and 3b and the honeycomb structure 8 was set to four times the wavelength of the microwave as the shortest distance.
The specifications of the microwave irradiation tanks 2a and 2b are both internal dimensions: 600W × 700H × 1200L (mm) and inner furnace material: SUS304.
The conveyors 9a and 9b enter the microwave irradiation tank 2b at the start of the baking process via the irradiation tank inlet / outlet 6 after the drying process, and the honeycomb structure m enters the microwave irradiation tank 2b at the start of the drying process. It adjusted so that it might come out from the microwave irradiation tank 2b later. The conveyance speed of the honeycomb structure m by the conveyor 9a was 0.5 m / min, and the conveyance speed of the honeycomb structure m by the conveyor 9b was 1.0 m / min. The microwave irradiation time was 1 hour in the drying process and 5 hours in the firing process per honeycomb structure.
The microwave power density in the drying process was 0.05 kW / kg per honeycomb structure, and the microwave power density in the firing process was 0.3 kW / kg per honeycomb structure. By adjusting the output density in this manner, the moisture content of the honeycomb structure m after the drying treatment was set to 10% by mass, and the temperature of the honeycomb structure in the firing step was set to 500 degrees.
In addition, the moisture content of the honeycomb structure m after the drying step was measured using a microwave oscillator for measuring the moisture content, as in Example 1. A total of 20 drying processes and firing processes were performed for each honeycomb structure.

[Example 3]
In order to protect the corners and each side of the honeycomb structure n, a stainless steel plate (SUS304) having a thickness of 0.1 mm and a width A (FIG. 3) of 30 mm was coated as a covering material (FIG. 3). In addition, the microwave irradiation time was continuously irradiated with microwaves under the same conditions as in Example 1 except that the drying time per honeycomb structure was 1 hour in the drying process and 10 hours in the firing process. The process and the baking process were performed.

[Example 4]
The honeycomb structure m was coated with a coating material under the same conditions as in Example 3 except that the honeycomb structure m after the drying treatment reached a moisture content of 20% by mass, and the drying process was performed. In addition, a firing step was performed. A total of 20 drying processes and firing processes were performed for each honeycomb structure.

[Example 5]
Except for not covering the honeycomb structure m with the coating material, the drying process and the firing process were performed under the same conditions as in Example 4 in which the process proceeds to the firing process when the water content becomes 20% by mass.

[Example 6]
Ten honeycomb structures m were used, and the influence on the drying and firing given by the interval between the plurality of honeycomb structures was verified.
As shown in FIG. 3 (a), the plurality of honeycomb structures m are placed so that the cell axis direction 11 of the honeycomb structures m is perpendicular to the traveling direction (conveying direction) 10 of the conveyor 9. In addition, the honeycomb surface 8a is oriented in a direction perpendicular to the traveling direction 10 of the conveyor 9, and the cell axis direction 11 is a horizontal direction. In the honeycomb structure m, the interval 12 in the direction parallel to the conveyance direction 10 is set to twice the wavelength of the microwave.
Otherwise, the drying and firing steps were performed in the same manner as in Example 1.

[Example 7]
As shown in FIG. 4, 10 honeycomb structures m are used so that the cell axis direction 11 of the honeycomb structure m is parallel to the traveling direction 10 of the conveyor 9, and the honeycomb structure m The surface 8a faces a parallel direction with respect to the traveling direction 10 of the conveyor 9, and the cell axis direction 11 is a horizontal direction. In the honeycomb structure m, the interval 12 in the direction parallel to the conveyance direction 10 is set to twice the wavelength of the microwave.
Otherwise, the drying and firing steps were performed in the same manner as in Example 6.

[Example 8]
Ten honeycomb structures m are used, and the placement is such that the cell axial direction is horizontal, and the cell axial direction 11 of the honeycomb structure m is parallel to the traveling direction 10 of the conveyor 9 as in FIG. In addition, the interval 12 in the direction parallel to the conveyance direction 10 is set to be twice or more the wavelength of the microwave. Furthermore, as shown in FIG. 5, the honeycomb structures m were placed in parallel on the conveyor 9 so as to form two rows, and the interval 13 in the direction orthogonal to the transport direction 10 was set to twice the wavelength of the microwave.
Otherwise, the drying and firing steps were performed in the same manner as in Example 7.

[Example 9]
In order to protect the corners and each side of the honeycomb structure n, a stainless steel plate (SUS304) having a thickness of 0.1 mm and a width A (FIG. 8) of 30 mm was coated as a covering material (FIG. 8).
The honeycomb structure m (10 bodies) thus coated with the covering material is to be dried and fired, and these placements are performed with the cell axial direction horizontal, as shown in FIG. The axial direction was inclined and the inclination angle 14 was set to 60 degrees (FIG. 6A). The interval 12 in the direction parallel to the transport direction 10 was set to twice the wavelength of the microwave (FIG. 6B). The microwave irradiation time was 1 hour in the drying process and 10 hours in the firing process per honeycomb structure.
Otherwise, the drying and firing steps were performed in the same manner as in Example 1.

[Comparative Example 1]
The honeycomb structure m was subjected to a drying process by continuously irradiating microwaves using a continuous drying apparatus 20 shown in FIG.
The specifications of the continuous drying treatment apparatus 20 are: the output of the microwave generator 21: 1 kW (continuous variable), frequency: 2450 ± 30 MHz, power input: three-phase AC, 200 V, and the specification of the microwave irradiation tank 22 is internal Dimensions: 600W × 700H × 1200L (mm), inner furnace material: SUS304. Further, an irradiation tank inlet 24 and an irradiation tank outlet 25 each provided with an electromagnetic wave shutter 23 are installed before and after the microwave irradiation tank 22.
The conveyor 26 was adjusted in speed so that the honeycomb structure m entered the microwave irradiation tank at the start of the drying process and exited from the microwave irradiation tank at the end of the drying process. The microwave irradiation time was 1 hour per body. A total of 20 drying steps were performed for each honeycomb structure.
After the drying treatment, the honeycomb structure m was cooled at room temperature until reaching a temperature at which the honeycomb structure m could be transported (about 40 degrees), and moved to a firing furnace to perform the firing treatment.
Firing was carried out for 100 hours under the condition that the honeycomb structures were heated one by one with a combustion burner and the temperature of the honeycomb structures was 200 to 500 degrees.

[Comparative Example 2]
The same method as in Example 5 except that the honeycomb structure m (20 bodies) is an object to be dried and fired and the interval 12 in the direction parallel to the transport direction 10 is set to be 1 time the wavelength of the microwave. Thus, a drying and firing process was performed.

In Examples 1 to 3 and Comparative Example 1, abnormalities such as whitening, cracks, cracks, and defective firing were not observed in the manufactured honeycomb molded body, and there was no problem in the manufactured product.
According to the manufacturing methods of Examples 1 to 3, the honeycomb structure is cooled and moved between the drying step and the firing step as in Comparative Example 1 by continuously performing the drying step and the firing step. Can be omitted, and the firing can be completed by maintaining the condition that the temperature of the honeycomb structure is around 500 degrees for at least 3 hours. As a result of the simplified manufacturing procedure, manufacturing efficiency has improved.
Furthermore, in Example 2, since the conveyor 9a could be stopped after the drying process of all the 20 honeycomb structures was completed, the power cost could be reduced.
In addition, the honeycomb structure could be satisfactorily manufactured by coating the coating material, drying and firing (Example 3).
On the other hand, in the manufacturing method of Comparative Example 1, the honeycomb structure had to be cooled and moved between the drying step and the firing step. Furthermore, in the firing step, burner heating fuel becomes soot and adheres to the inside and the surface of the honeycomb structure. Therefore, the firing step has to be extended to decompose these soot. Due to these factors, it took a long time to produce a honeycomb formed body.
In Examples 1 and 2, it took 1 hour for the drying step and 5 hours for the firing step, and a honeycomb formed body could be manufactured by a drying and firing step for 6 hours. Further, in Example 3, the honeycomb formed body could be manufactured by the drying process and the firing process for 1 hour, and the firing process required 10 hours and the drying and firing process for 11 hours. On the other hand, in Comparative Example 1, the drying process took 1 hour and the firing process took 100 hours. From these results, it was confirmed that the manufacturing time of the honeycomb formed body can be greatly shortened by the manufacturing method of the present invention.

In Example 4, abnormalities such as whitening, cracks, cracks, and defective firing were not observed in the manufactured honeycomb formed body, and there was no problem in the manufactured product.
On the other hand, in Example 5 in which the coating material was not coated, out of 20 manufactured honeycomb formed bodies, 4 bodies were abnormally observed such as cracks and cracks, but 16 bodies were manufactured satisfactorily. Was made. Since 16 out of 20 bodies were good, the yield was 80%, which is an embodiment that can be implemented without problems from the viewpoint of production efficiency.
From the results of Examples 4 and 5, when firing a honeycomb structure having a moisture content of 20% by mass, it was confirmed that whitening, cracking, cracking, and the like could be prevented by coating the coating material. .

In Examples 6 to 9, abnormalities such as whitening, cracks, cracks, and defective firing were not observed in the manufactured honeycomb formed bodies, and there were no problems in the manufactured products.
FIG. 14 shows the results of measuring the moisture content of ten honeycomb structures m after the drying step of Example 6. The moisture content was calculated by measuring the mass change of the honeycomb structure. The vertical axis in FIG. 14 represents the moisture content, and the horizontal axis represents the processing order of the honeycomb structure.
As a result, the honeycomb structure of Example 6 had a moisture content of about 10% by mass when the distance between the honeycomb structures was twice the wavelength of the microwave, and could be dried well.
As for Example 7 to Example 9, as in Example 6, the moisture content was around 10% by mass and could be dried well.

FIG. 15 shows the results of measuring the moisture content of 20 honeycomb structures m after the drying process of Comparative Example 2.
In Comparative Example 2, since the interval between the honeycomb structures was too narrow, the microwave structure was not sufficiently irradiated, and a honeycomb structure with insufficient drying was observed. In addition, it was found that a honeycomb structure that was insufficiently dried appeared alternately with a sufficiently dried honeycomb structure. This tendency is considered to be due to the fact that the microwave skips one honeycomb structure and then irradiates the placed honeycomb structure.
In FIG. 15, the honeycomb structure having a moisture content of about 10% by mass could be fired satisfactorily and no abnormality such as whitening was observed. However, the honeycomb structure having a moisture content of 25% by mass or more due to poor drying was found to be defective in firing due to cracks and cracks.

  In Example 8, the honeycomb structure was placed in two rows on the conveyor, whereby the drying time and firing time of the 10 honeycomb structures were shortened, and the honeycomb formed body was manufactured in about half the time of Example 6. I was able to.

  In Example 9, by placing the honeycomb structure obliquely on the conveyor, microwaves are gradually irradiated from the end of the honeycomb structure to the whole, so that drying also proceeds from the end, and drying unevenness and firing unevenness are achieved. Thus, the honeycomb formed body could be manufactured satisfactorily.

Drying of honeycomb structure by batch type [Example 10]
Twenty honeycomb structures m were installed in a batch-type microwave irradiation apparatus one by one so that they could be uniformly dried, and were continuously irradiated with microwaves until the water content was 10% by mass.
As a batch type drying apparatus, a microwave generator and a microwave irradiation tank including a rotating body on which a honeycomb structure is mounted and driven to rotate are used.
The moisture content of the honeycomb structure m was reflected from the honeycomb structure m by irradiating the honeycomb structure m with a microwave having the same frequency band as the drying microwave at an output of 20 mW using a microwave oscillator. This was done by measuring microwaves.
After the honeycomb structure m was dried, the honeycomb structure m was fired as it was using the same microwave irradiation apparatus by changing the microwave irradiation conditions.
The microwave power density in the drying process was 0.02 kW / kg per honeycomb structure, and the microwave power density in the firing process was 0.3 kW / kg per honeycomb structure. By adjusting the output density in this manner, the moisture content of the honeycomb structure m after the drying treatment was set to 10% by mass, and the temperature of the honeycomb structure in the firing step was set to 500 degrees.
The specifications of the microwave irradiation apparatus are frequency: 2450 ± 30 MHz, power input: three-phase alternating current, 200 V, and the specifications of the microwave irradiation tank are internal dimensions: 600 W × 700 H × 1200 L (mm), inner furnace material: SUS304 It is.

[Comparative Example 3]
As for the drying step, as in Example 10, the honeycomb structure m was placed in a batch-type drying apparatus and dried until the water content became 10% by mass.
After the drying treatment, the honeycomb structure m was cooled at room temperature until reaching a temperature at which the honeycomb structure m could be transported (about 40 degrees), and moved to a firing furnace to perform the firing treatment.
In the firing, each honeycomb structure was batch-treated, and the condition that the temperature of the honeycomb structure was 200 ° C. to 500 ° C. was maintained for 100 hours with a combustion burner.

In Example 10 and Comparative Example 3, abnormalities such as whitening, cracks, cracks, and defective firing were not observed in the manufactured honeycomb molded body, and there was no problem in the manufactured product.
According to the manufacturing method of Example 10, since the drying process and the firing process were continuously performed, cooling and movement of the honeycomb structure performed between the drying process and the firing process as in Comparative Example 2 were omitted. As a result of the simplified manufacturing procedure, the manufacturing efficiency was improved.
On the other hand, in the manufacturing method of Comparative Example 3, the honeycomb structure had to be cooled and moved between the drying step and the firing step. Furthermore, in the firing step, burner heating fuel becomes soot and adheres to the inside and the surface of the honeycomb structure. Therefore, the firing step has to be extended to decompose these soot. Due to these factors, it took a long time to produce a honeycomb formed body.
In Example 10, it took 5 hours for the drying process and 5 hours for the firing process, and a honeycomb formed body could be manufactured by the drying and firing process for 10 hours. On the other hand, in Comparative Example 3, the drying process required 5 hours and the firing process required 100 hours. From these results, it was confirmed that the manufacturing time of the honeycomb formed body can be greatly shortened by the manufacturing method of the present invention.

  According to the method for manufacturing a honeycomb formed body of the present invention, the manufacturing procedure can be simplified by continuously performing the drying step and the firing step, and the production efficiency can be improved, which is industrially useful. It is.

DESCRIPTION OF SYMBOLS 1 Continuous irradiation apparatus 2a Microwave irradiation tank 2b Microwave irradiation tank 3a Microwave generator 3b Microwave generator 4 Irradiation tank inlet 5 Irradiation tank outlet 6 Irradiation tank inlet / outlet 7 Electromagnetic shutter 8 Honeycomb structure 8a Honeycomb surface 8b Corner part 8c Side 9 Conveyor 9a Conveyor 9b Conveyor 10 Traveling direction 11 Cell axis direction 12 Interval 13 Interval 14 Inclination angle 15 Interval 16 Aluminum plate (coating material)
17 Susceptor 18 Bolt 19 End of cylinder 20 Continuous drying processing device 21 Microwave generator 22 Microwave irradiation tank 23 Electromagnetic shutter 23 Irradiation tank inlet 25 Irradiation tank outlet 26 Conveyor A Width of aluminum tape A 'Width of aluminum tape

Claims (9)

A method for manufacturing a honeycomb formed body,
Drying the honeycomb structure by irradiating with microwaves, and setting the moisture content of the honeycomb structure to 5% by mass to 20% by mass;
Thereafter, the honeycomb structure is irradiated with microwaves, and the honeycomb structure is fired at a temperature of 300 ° C. to 1000 ° C .;
A conveying step of conveying the honeycomb structure at a constant conveying speed during the drying step and the firing step;
Including at least
The drying step and the firing step, have rows in succession,
The microwave power density in the drying step is 0.01 kW / kg to 1 kW / kg per honeycomb structure, and the microwave power density in the firing step is 0.1 kW per honeycomb structure. / Kg ~ 1kW / kg,
In the placing step, the plurality of honeycomb structures are placed in series on the transport device so that an interval in a direction parallel to the transport direction is twice or more a microwave wavelength (λ). A method for manufacturing a honeycomb formed body. The drying step and the firing step include a step of irradiating the honeycomb structure with microwaves using a continuous microwave irradiation device,
The continuous microwave irradiation apparatus includes a microwave irradiation tank for drying provided with a microwave generation apparatus that generates microwaves and irradiates the honeycomb structure with drying;
A microwave irradiation tank for firing provided with a microwave generator for generating microwaves and irradiating and firing the honeycomb structure;
A microwave irradiation tank inlet for drying equipped with an electromagnetic shutter;
A microwave irradiation tank outlet for firing equipped with an electromagnetic shutter;
Used in the transfer step, the honeycomb structure is placed on the drying microwave irradiation tank inlet, the drying microwave irradiation tank, the firing microwave irradiation tank, and the firing microwave irradiation. A transport device for sequentially transporting the tank outlet;
A method for manufacturing a honeycomb formed body according to claim 1, comprising at least The transport apparatus includes at least the honeycomb structure and transports the drying microwave irradiation tank inlet and the drying microwave irradiation tank within the drying transport apparatus,
A firing conveying device for placing the honeycomb structure and conveying the firing microwave irradiation tank and the firing microwave irradiation tank outlet;
The method for manufacturing a honeycomb formed body according to claim 2, comprising: The honeycomb structure transport speed S1 by the drying transport apparatus is 0.1 m / min to 3.0 m / min, and the honeycomb structure transport speed S2 by the firing transport apparatus is 0.01 m / min. 1.0 m / min and satisfy the relationship that the transport speed S1 is 3 to 10 times the transport speed S2,
The microwave power density in the drying step is 0.01 kW / kg to 1 kW / kg per honeycomb structure, and the microwave power density in the firing step is 0.1 kW per honeycomb structure. The method for manufacturing a honeycomb formed body according to claim 2 , wherein the ratio is set to 1 kg / kg to 1 kW / kg. The carrying step further includes a placing step of placing the plurality of honeycomb structures on the carrying device,
The placement step further includes a parallel placement step of placing the plurality of honeycomb structures in parallel on the transport device such that an interval in a direction orthogonal to the transport direction is twice or more the microwave wavelength. The method for drying a honeycomb structure according to claim 4 . The microwave generator is installed on the ceiling of the drying microwave irradiation tank and the firing microwave irradiation tank,
In the preceding step, the cells in the plurality of honeycomb structures are set in the horizontal direction, the angle of inclination of the cells in the axial direction with respect to the transport direction is set to 35 degrees to 75 degrees, and the honeycomb structures in the front row the end of the side surface or the like, so that the distance of the end of the side surface or the like of the honeycomb structure is placed following the front row is at least 2 times the wavelength of the microwaves, in claim 5 including the step of placing The drying method of the honeycomb structure described. The drying step and the firing step include a step of irradiating the honeycomb structure with microwaves using the same batch-type microwave irradiation device,
The batch-type microwave irradiation apparatus includes at least a microwave irradiation tank, and the microwave irradiation tank generates at least one microwave to irradiate the honeycomb structure, and the conveying step. used provided comprising at least a rotating member for rotating by placing the honeycomb structure,
The microwave power density in the drying step is 0.01 kW / kg to 1 kW / kg per honeycomb structure, and the microwave power density in the firing step is 0.1 kW per honeycomb structure. The method for manufacturing a honeycomb formed body according to claim 1, wherein the flow rate is 1 kg / kg to 1 kW / kg. The honeycomb structure is a polygonal columnar honeycomb structure having a polygonal honeycomb surface,
Before the drying step, the present invention includes a coating step of covering the honeycomb surface of the honeycomb structure and the corners and sides of the honeycomb side surface with a coating material that protects the honeycomb structure from microwaves. 8. A method for drying a honeycomb structure according to any one of claims 7 to 10. The honeycomb structure is a cylindrical honeycomb structure having a circular honeycomb surface,
Prior to the drying step, the cylindrical end portion of the honeycomb faces and honeycomb side face of the honeycomb structure, one of the claims 1 to 7 comprising a coating step of coating a coating material to protect the honeycomb structure from the microwave A method for drying a honeycomb structure according to claim 1.

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