JP2008134036A - Drying device, drying method of ceramic compact and method of manufacturing honeycomb structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drying device capable of uniformly drying ceramic compact. <P>SOLUTION: This drying device comprises a plurality of microwave radiating portions alternately disposed at upper and lower parts of a dried object conveying member, and a plurality of hot air supply portions, the microwave is alternately applied to the dried object from the upper and lower parts, and the hot air is applied in parallel with the dried object. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a drying apparatus, a method for drying a ceramic molded body, and a method for manufacturing a honeycomb structure.

Recently, it has become a problem that particulates such as soot contained in exhaust gas discharged from internal combustion engines such as vehicles such as buses and trucks and construction machinery cause harm to the environment and the human body.
Accordingly, various proposals have been made using a honeycomb structure made of porous ceramics as a filter for collecting particulates in exhaust gas and purifying the exhaust gas.

Conventionally, when manufacturing a honeycomb structure, first, for example, two types of ceramic powders having different average particle diameters, a binder, a dispersion medium liquid, and the like are mixed to prepare a wet mixture. Further, by using a screw mixer or the like, the wet mixture is further mixed, and continuous extrusion molding is performed with a die, and the extruded molded body is cut into a predetermined length to obtain a prismatic shape. A honeycomb formed body is produced.

Next, the obtained raw honeycomb molded body is dried using microwave drying or hot air drying to produce a dried honeycomb molded body that has a certain strength and can be easily handled.

After this drying step, a predetermined cell is plugged and either end of the cell is sealed with a sealing material layer, and then the honeycomb formed body is 400 to 650 ° C. in an oxygen-containing atmosphere. The degreasing treatment is performed in order to volatilize the solvent in the organic binder component and to decompose and eliminate the resin component. Further, the honeycomb formed body is fired at 2000 to 2200 ° C. in an inert gas atmosphere to produce a honeycomb fired body.

After that, the honeycomb fired body assembly in which a large number of honeycomb fired bodies are bundled through the sealing material layer (adhesive layer) by applying a sealing material paste to the side surfaces of the honeycomb fired bodies and bonding the honeycomb fired bodies to each other. Create a body. Next, the honeycomb fired body aggregate obtained is cut into a predetermined shape such as a cylinder or an elliptical cylinder using a cutting machine or the like to form a ceramic block, and finally, a sealing material is provided on the outer periphery of the ceramic block The manufacturing of the honeycomb structure is completed by applying the paste to form a sealing material layer (coat layer).

And in such a manufacturing method of a honeycomb structure, when drying a honeycomb formed body, a method of drying a honeycomb formed body by emitting microwaves from one direction is known (for example, Patent Document 1, 2).

JP 2001-130970 A JP 2005-131800 A

However, when the honeycomb formed body is dried as described above, when the honeycomb formed body is dried by radiating microwaves from one direction to the honeycomb formed body, the moisture content of the dried honeycomb formed body is reduced. There is a problem that unevenness is likely to occur depending on the location, and warpage or the like is likely to occur due to such non-uniformity of drying.
Further, when a honeycomb fired body is manufactured by performing a degreasing process and a firing process on a honeycomb formed body whose drying has progressed non-uniformly, there is also a problem that the strength of the honeycomb fired body tends to decrease.

The present inventors have intensively studied to solve the above-mentioned problems, radiate microwaves alternately on the ceramic molded body from the top and bottom, and further perform drying treatment with hot air in parallel to further uniformly form the ceramic. It was found that the body can be dried, and the drying apparatus of the present invention, the method for drying a ceramic molded body, and the method for manufacturing a honeycomb structure have been completed.

The drying apparatus of the present invention includes a plurality of microwave radiating units arranged alternately above and below the object to be dried and a plurality of hot air blowing units,
The object is characterized in that microwaves are alternately emitted from above and below the object to be dried and hot air is irradiated in parallel with the object to be dried.

The method for drying a ceramic molded body according to the present invention is a method for drying a ceramic molded body, wherein the ceramic molded body is dried by passing through a drying apparatus for a predetermined time by a conveying member,
The drying apparatus includes a plurality of microwave radiating units arranged alternately above and below the conveying member, and a plurality of hot air blowing units,
Microwaves are alternately emitted from the upper and lower sides of the ceramic molded body, and drying with hot air is performed in parallel.

In the method for drying a ceramic molded body of the present invention, it is desirable that the moisture content after drying the ceramic molded body is 30% by weight or more and less than 70% by weight of the moisture content before drying.
Moreover, in the drying method of the said ceramic molded body, it is desirable that the temperature of the said hot air shall be 40-80 degreeC.

The method for manufacturing a honeycomb structured body of the present invention includes forming a columnar honeycomb formed body in which a large number of cells are arranged in parallel in the longitudinal direction with cell walls separated by forming a ceramic raw material. A honeycomb structure comprising a honeycomb fired body after firing a dried honeycomb molded body after performing a molded body drying step in which the molded body is placed on a conveying member and passed through a drying apparatus for a predetermined time and dried. A method for manufacturing a honeycomb structure for manufacturing
The drying apparatus includes a plurality of microwave radiating units arranged alternately above and below the conveying member, and a plurality of hot air blowing units,
The honeycomb molded body is dried by alternately radiating microwaves from the upper and lower sides of the honeycomb molded body and drying with hot air in parallel.

In the method for manufacturing a honeycomb structured body of the present invention, it is desirable that the moisture content after drying of the honeycomb formed body is 30% by weight or more and less than 70% by weight of the moisture content before drying.
Moreover, in the manufacturing method of the said honeycomb structure, it is desirable that the temperature of the said hot air shall be 40-80 degreeC.

According to the drying apparatus of the present invention, microwaves can be alternately emitted from the top and bottom to the object to be dried, and hot air can be irradiated in parallel with the object to be dried. Can be dried. Therefore, warpage or the like does not occur in an object to be dried using the drying apparatus of the present invention.

According to the method for drying a ceramic molded body of the present invention, microwaves are alternately emitted from the top and bottom of the ceramic molded body, and hot air is irradiated in parallel to the ceramic molded body, so that the ceramic molded body is uniformly dried. Therefore, warpage or the like does not occur in the ceramic molded body after drying.

The method for manufacturing a honeycomb structured body of the present invention includes a step of subjecting the manufactured honeycomb formed body to a drying process. In this step, microwaves are radiated from above and below the honeycomb formed body, Since the formed body is irradiated with hot air, the honeycomb formed body can be uniformly dried, and warpage or the like does not occur in the dried honeycomb formed body.
Therefore, the honeycomb structure manufacturing method of the present invention can manufacture a honeycomb structure having a predetermined shape.
Further, in the method for manufacturing a honeycomb structured body of the present invention, the honeycomb formed body can be uniformly dried, so that a honeycomb structured body made of a honeycomb fired body having high strength can be manufactured.

First, a drying apparatus and a method for drying a ceramic molded body of the present invention will be described.
The drying apparatus of the present invention includes a plurality of microwave generation sources alternately disposed above and below the object to be dried, and a plurality of hot air blowing units.
The object is characterized in that microwaves are alternately emitted from above and below the object to be dried and hot air is irradiated in parallel with the object to be dried.

The method for drying a ceramic molded body according to the present invention is a method for drying a ceramic molded body, wherein the ceramic molded body is dried by passing through a drying apparatus for a predetermined time by a conveying member,
The drying apparatus includes a plurality of microwave radiating units arranged alternately above and below the conveying member, and a plurality of hot air blowing units,
Microwaves are alternately emitted from the upper and lower sides of the ceramic molded body, and drying with hot air is performed in parallel.
Therefore, the method for drying a ceramic molded body of the present invention can be suitably performed using the drying apparatus of the present invention.

FIG. 1 is a plan view showing an outline of the drying apparatus of the present invention. 2A is a partial cross-sectional view of the drying apparatus according to the present invention shown in FIG. 1, and FIG. 2B is a sectional view taken along line BB of the drying apparatus of the present invention shown in FIG. It is a fragmentary sectional view.
As shown in FIG. 1, the drying device 10 includes an object to be dried conveying member (belt conveyor 11), microwave radiating portions 14 a to 14 i arranged alternately above and below the belt conveyor 11, and a belt conveyor so as to crawl the floor. 11, a drying furnace main body 19 provided with a plurality of hot air blowing portions 15a to 15d and hot air suction portions 15a 'to 15d' provided at a low position close to 11, a microwave radiating portion 14a to 14i, and a waveguide Microwave transmitters 13a to 13i connected via 16a to 16i, and microwave leakage prevention regions for preventing microwave leakage provided on the inlet side and the outlet side of the drying furnace body 19, respectively. 12a and 12b are provided.
Therefore, the drying apparatus 10 can alternately radiate microwaves from the top and bottom of an object to be dried such as the ceramic molded body 1.

Further, as shown in FIGS. 2 (a) and 2 (b), the drying furnace main body 19 has a micro for uniformly radiating the microwaves from the microwave radiation portions 14a to 14i to the object to be dried. A wave stirring blade 17 (not shown in FIG. 1) is provided.
Therefore, by rotating the microwave stirring blade 17, the microwave can be uniformly radiated to the material to be dried. In the drying apparatus of the present invention, the microwave stirring blade may be provided as necessary.
The number and attachment position of the microwave stirring blades 17 are not particularly limited, but are attached in the vicinity of each of the microwave radiation portions (14b, 14c, 14f, 14h) for emitting microwaves from above the material to be dried. It is desirable that

In the drying apparatus 10, the ceramic molded body 1 is loaded into the interior from the inlet of the drying apparatus 10 by placing the ceramic molded body 1 on the belt conveyor 11, and is unloaded from the outlet of the drying apparatus 10 after a predetermined time has elapsed. Is done.
Here, the belt conveyor 11 is set to move intermittently.

That is, the belt conveyor 11 is set to repeat the operation of moving for a predetermined time at a predetermined speed, then temporarily stopping for a predetermined time, and moving again for a predetermined time at a predetermined speed. The hot air blowing portions 15a to 15d are set so as to strike the ceramic molded body 1 in a stationary state directly and parallel to the longitudinal direction of the ceramic molded body 1.
Note that in the drying apparatus of the present invention, the belt conveyor 11 (object to be dried) is not necessarily moved intermittently, and may be moved continuously at a constant speed or a variable speed.

Moreover, in the drying apparatus 10, the hot air blowing parts 15a to 15d and the hot air suction parts 15a 'to 15d' are arranged to face each other, so that the hot air can be more reliably applied to the longitudinal direction of the ceramic molded body.
In addition, the said hot air suction part does not necessarily need to be provided.

The method for drying a ceramic molded body of the present invention can be performed using such a drying apparatus of the present invention.
Here, preferable drying conditions and the like will be described by taking as an example a case where a columnar honeycomb formed body in which a large number of cells are arranged in parallel in the longitudinal direction with a cell wall interposed therebetween is used as the ceramic formed body to be dried.
Of course, the object to be dried in the drying method of the present invention is not limited to the honeycomb formed body, and various ceramic formed bodies are to be dried.

In the drying method of the present invention, microwaves are alternately emitted from the upper and lower sides of the honeycomb formed body, and drying with hot air is also performed in parallel.
In this way, by alternately radiating microwaves from the upper and lower sides of the honeycomb formed body, moisture is uniformly removed from each part of the honeycomb formed body, and thus the dried honeycomb formed body may be warped. Absent. In addition, since drying with hot air is performed together with the radiation of microwaves, the drying near the center of the honeycomb molded body tends to be difficult to dry with only the microwave, and as a result, the honeycomb molded body is slightly warped. However, such inconvenience can be avoided. From this, it can be said that the ceramic molded body dried by the drying method of the present invention is desirably the honeycomb molded body.

Further, the drying apparatus 10 shown in FIG. 1 includes four microwave radiating portions (14b, 14c, 14f, 14h) for radiating microwaves from above the honeycomb formed body, and microwaves from below the honeycomb formed body. Are provided with five microwave radiating portions (14a, 14d, 14e, 14g, 14i), and the number of microwave radiating portions for radiating microwaves to the honeycomb formed body from below is higher. It is increasing. This is because when microwaves are radiated to the honeycomb molded body from below, microwaves are radiated through the belt conveyor, and therefore the lower side of the honeycomb molded body tends to be difficult to dry.
Note that the number of microwave radiating portions may be the same between the upper side and the lower side of the honeycomb formed body, or the upper side may be larger.
Further, the microwave radiating portion may be the same above and below the honeycomb formed body, and the microwave power radiated from below the honeycomb formed body may be increased.
The specific number of the microwave radiating parts is not particularly limited, but it is desirable to provide two or more above the object to be dried and three or more below.

In addition, conditions such as microwave power in the drying method of the present invention depend on the shape and size of the object to be dried, such as a target ceramic molded body. A honeycomb formed body (ceramic formed body) having a size of 33 mm × 33 mm × 300 mm, a cell number of 31 / cm ² , and a cell wall thickness of 0.35 mm is dried. In this case, the power of the microwaves ejected from each microwave radiation portion is preferably 3 to 7 kW, and more preferably 5 kW.

Further, as already described, the movement of the honeycomb formed body by the belt conveyor may be continuous or intermittent, but is desirably intermittent.
In this case, the moving speed of the belt conveyor is desirably 2 to 8 m / min. Further, the time during which the belt conveyor is stationary is preferably about 2 seconds. The moving speed of the belt conveyor is calculated as a moving distance per unit time without distinguishing between moving and stopping.

Moreover, it is desirable that the time (drying time) for which the honeycomb formed body exists in the drying apparatus is 2 to 3 minutes. If the drying time is less than 2 minutes, drying may not be sufficient. On the other hand, if it exceeds 3 minutes, drying may proceed excessively and warpage may occur.

In the drying method of the present invention, the moisture content after drying of the ceramic molded body (honeycomb molded body) is desirably 30% by weight or more and less than 70% by weight of the moisture content before drying.
If the moisture content after drying is less than 30% by weight of the moisture content before drying, the moisture content in the honeycomb molded body becomes too small, and the honeycomb molded body may be warped or cracked. When the amount of water is reduced to less than%, microwaves are absorbed by the ceramic powder, and the temperature of the ceramic powder in the honeycomb formed body rapidly increases and degreasing may start. On the other hand, if the water content after drying is 70% by weight or more, the drying is insufficient and the handleability is still poor.
The amount of water after drying can be adjusted by adjusting the drying time, adjusting the output of the microwave, the temperature of the hot air, and the like.

Moreover, in the said drying method, as for the temperature of the said hot air, 40-80 degreeC is desirable.
If the temperature is lower than 40 ° C., the effect of using the above-described hot air may not be enjoyed. On the other hand, if the temperature exceeds 80 ° C., the drying proceeds too rapidly and warps the ceramic molded body (honeycomb molded body). This is because cracks and the like may occur.

Furthermore, the wind speed of the hot air is preferably 20 to 40 m / sec.
When the wind speed is less than 20 m / sec, the drying speed becomes slow and drying unevenness may occur in the ceramic molded body. When the wind speed exceeds 40 m / sec, only the surface portion of the ceramic molded body is excessively dried. Because there are things.
By using such a drying method, the ceramic molded body can be dried so as to have a desired water content without warping or cracking.

Next, the manufacturing method of the honeycomb structure of the present invention will be described.
The method for manufacturing a honeycomb structured body of the present invention is to form a columnar honeycomb formed body in which a large number of cells are arranged in parallel in the longitudinal direction with cell walls separated by forming a ceramic raw material, and the honeycomb formed body is conveyed. A molded body drying step is performed in which the molded body is dried by being placed on a member and passed through a drying apparatus for a predetermined time to be dried, and further, the dried honeycomb molded body is fired to produce a honeycomb structure including a honeycomb fired body A method for manufacturing a honeycomb structure, comprising:
The drying apparatus includes a plurality of microwave radiating units arranged alternately above and below the conveying member, and a plurality of hot air blowing units,
The honeycomb molded body is dried by alternately radiating microwaves from the upper and lower sides of the honeycomb molded body and drying with hot air in parallel.

FIG. 4 is a perspective view schematically showing one type of honeycomb structure manufactured by the method for manufacturing the honeycomb structure, and FIG. 5A schematically shows a honeycomb fired body constituting the honeycomb structure. (B) is the AA sectional view taken on the line.

In such a honeycomb structure 130, normally, a plurality of honeycomb fired bodies 140 as shown in FIGS. 5A and 5B are bundled through a sealing material layer (adhesive layer) 131 to form a ceramic block 133. Further, a sealing material layer (coat layer) 132 is formed on the outer periphery of the ceramic block 133. Further, as shown in FIG. 4, the honeycomb fired body 140 has a large number of cells 141 arranged in parallel in the longitudinal direction, and the cell walls 143 separating the cells 141 function as a filter.

That is, in the cell 141 formed in the honeycomb fired body 140, as shown in FIG. 5B, either the inlet side or the outlet side end of the exhaust gas is plugged by the sealing material layer 142. The exhaust gas that has flowed into 141 always passes through the cell wall 143 separating the cells 141 and then flows out from the other cells 141. When the exhaust gas passes through the cell wall 143, the particulates in the exhaust gas It is captured by the cell wall 143 and the exhaust gas is purified.
Such a honeycomb structure 130, in which the honeycomb fired body 140 is made of silicon carbide, is extremely excellent in heat resistance and easy to regenerate, etc., so it is used in various large vehicles, vehicles equipped with diesel engines, etc. Has been.

Hereinafter, the manufacturing method of the honeycomb structure of the present invention will be described in the order of steps.
Here, the method for manufacturing a honeycomb structure of the present invention will be described by taking as an example the case of manufacturing a honeycomb structure whose main component is silicon carbide.
Of course, the main component of the constituent material of the honeycomb structure is not limited to silicon carbide. Other examples include nitride ceramics such as aluminum nitride, silicon nitride, boron nitride, and titanium nitride, zirconium carbide, and titanium carbide. And carbide ceramics such as tantalum carbide and tungsten carbide, and oxide ceramics such as alumina, zirconia, cordierite, mullite, and aluminum titanate.
Of these, non-oxide ceramics are preferred, and silicon carbide is particularly preferred. It is because it is excellent in heat resistance, mechanical strength, thermal conductivity and the like. In addition, silicon-containing ceramics in which metallic silicon is blended with the above-mentioned ceramics, ceramics bonded with silicon or a silicate compound, and the like can also be cited as constituent materials. Among these, silicon carbide is blended with metallic silicon ( Silicon-containing silicon carbide) is desirable.

First, an inorganic powder such as silicon carbide powder having a different average particle size and an organic binder are dry mixed to prepare a mixed powder, and a liquid plasticizer, a lubricant and water are mixed to prepare a mixed liquid, Subsequently, a wet mixture for producing a molded body is prepared by mixing the mixed powder and the mixed liquid using a wet mixer.

The particle size of the silicon carbide powder is not particularly limited, but it is preferable to have less shrinkage in the subsequent firing step, for example, 100 parts by weight of powder having an average particle size of 0.3 to 50 μm and 0.1 to 1.0 μm. A combination of 5 to 65 parts by weight of a powder having an average particle diameter of 5 to 65 parts by weight is preferred.
In order to adjust the pore diameter and the like of the honeycomb formed body, it is necessary to adjust the firing temperature, but the pore diameter can be adjusted by adjusting the particle size of the inorganic powder.

The organic binder is not particularly limited, and examples thereof include methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, and polyethylene glycol. Of these, methylcellulose is desirable.
The amount of the binder is usually preferably 1 to 10 parts by weight with respect to 100 parts by weight of the inorganic powder.

It does not specifically limit as said plasticizer, For example, glycerol etc. are mentioned.
The lubricant is not particularly limited, and examples thereof include polyoxyalkylene compounds such as polyoxyethylene alkyl ether and polyoxypropylene alkyl ether.
Specific examples of the lubricant include polyoxyethylene monobutyl ether and polyoxypropylene monobutyl ether.
In some cases, the plasticizer and the lubricant may not be contained in the mixed raw material powder.

Moreover, when preparing the said wet mixture, you may use a dispersion medium liquid, As said dispersion medium liquid, alcohol, such as water, organic solvents, such as benzene, methanol, etc. are mentioned, for example.
Furthermore, a molding aid may be added to the wet mixture.
The molding aid is not particularly limited, and examples thereof include ethylene glycol, dextrin, fatty acid, fatty acid soap, polyalcohol and the like.

Furthermore, a pore-forming agent such as balloons that are fine hollow spheres containing oxide-based ceramics, spherical acrylic particles, and graphite may be added to the wet mixture as necessary.
The balloon is not particularly limited, and examples thereof include an alumina balloon, a glass micro balloon, a shirasu balloon, a fly ash balloon (FA balloon), and a mullite balloon. Of these, alumina balloons are desirable.

Moreover, it is desirable that the temperature of the wet mixture using the silicon carbide powder prepared here is 28 ° C. or less. It is because an organic binder may gelatinize when temperature is too high.
The organic content in the wet mixture is desirably 10% by weight or less, and the water content is desirably 8.0 to 20.0% by weight.

Next, the wet mixture is put into an extrusion molding machine, and a columnar honeycomb molded body in which a large number of cells are arranged in parallel in the longitudinal direction with a cell wall therebetween is produced by extrusion molding.
Thereafter, a formed body drying step is performed in which the honeycomb formed body is placed on the conveying member and passed through the drying apparatus for a predetermined time to be dried.
Here, the honeycomb formed body is dried by the drying method of the present invention using the drying apparatus of the present invention. In addition, since the specific drying method has already been demonstrated, the specific description is abbreviate | omitted here.
Further, in the method for manufacturing a honeycomb structure of the present invention, since the drying method described above is employed in this step, the composition of the wet mixture (the type of ceramic, the type of binder, etc.) constituting the honeycomb formed body is questioned. Therefore, the honeycomb formed body can be dried uniformly without occurrence of warp or the like.

Moreover, in the said molded object drying process, it is desirable that the moisture content after drying of a honeycomb molded object shall be 30 weight% or more and less than 70 weight% of the moisture content before drying.
In this step, the honeycomb formed body immediately after forming has a high moisture content and is easily deformed by drying to the honeycomb formed body. By reducing the amount of water in the molded body, the handleability is improved. Therefore, in this step, it is desirable that the moisture content after drying the honeycomb formed body is less than 70% by weight of the moisture content before drying.
Further, the reason why it is desirable that the moisture content after drying of the honeycomb molded body is 30% by weight or more of the moisture content before drying is that the honeycomb molded body is warped or cracked when the moisture content is further reduced. This is because the microwave may be absorbed by the ceramic powder, and the temperature of the ceramic powder in the honeycomb molded body may rapidly rise to start degreasing.

Moreover, in the said molded object drying process, it is desirable that the temperature of a hot air is 40-80 degreeC. The reason is as described above.

Next, in order to remove the moisture in the honeycomb molded body almost completely, it is desirable to further perform a drying process. Here, a hot air dryer is used with the honeycomb molded body held by a drying jig. It is desirable to perform the drying process.
Hereinafter, the drying jig used in this step will be briefly described.

FIG. 3 is a cross-sectional view schematically showing an example of the drying jig.
As shown in FIG. 3, the drying jig 20 is composed of an upper jig 21 produced by bonding the long sides of two elongated plate-like bodies so that the main surface is perpendicular, and a lower jig having the same shape. 22 and two jigs. As shown in FIG. 3, the upper jig 21 is provided with a fixing member 23 for fixing the upper jig 21 and the lower jig 22 after being combined. The fixing member may be provided on the upper jig or may be provided on the lower jig.

The fixing member 23 includes a fixing tool 23a fixed to the plate-like body using screws and a pressing tool 23b attached to the fixing tool 23a via a spring 23c so as to be rotatable. As shown in FIG. 3, the fixing member 23 is in a fixed state in which the presser 23b presses and fixes the lower jig 22, and conversely, in an open state in which the presser 23b falls down in substantially the same direction as the fixture 23a. Divided. In the fixing member 23, when the upper end of the pressing member 23b in the open state is moved outward (in a direction away from the fixing member 23a) by a certain distance, the fixing member 23 is switched to the fixing state and the lower jig 22 is firmly pressed and fixed. On the other hand, when the holding tool 23b in the fixed state is moved inward (in a direction approaching the fixing tool 23a) by a predetermined distance, the holding tool 23b is switched to the open state.

As described above, in the drying process for removing the moisture of the honeycomb formed body substantially completely, it is desirable to perform the drying process by holding the honeycomb formed body 1 with the drying jig 20 as shown in FIG. .
Using such a drying jig, the honeycomb molded body is pressed from the surroundings, and the drying process is performed in a state where the shape is fixed so as not to change, without causing warpage or the like in the honeycomb molded body, It can be dried to almost no moisture.

Moreover, although the drying jig 20 shown in FIG. 3 is composed of two separable jig members, the drying jig used in the present invention is, for example, one jig member that can be opened and closed. It may consist of.
Further, as shown in FIG. 3, the drying jig may be used by being stacked in multiple stages such as two stages, or may be used only in one stage. May be.

Next, if necessary, the end portion on the outlet side of the inlet side cell group and the end portion on the inlet side of the outlet side cell group are filled with a predetermined amount of a sealing material paste as a sealing material, Seal it.
Although it does not specifically limit as said sealing material paste, The thing from which the porosity of the sealing material manufactured through a post process becomes 30 to 75% is desirable, For example, the thing similar to the said wet mixture can be used. .

The sealing material paste may be filled as necessary. When the sealing material paste is filled, for example, a honeycomb structure obtained through a subsequent process is preferably used as a honeycomb filter. In the case where the sealing material paste is not filled, for example, a honeycomb structure obtained through a subsequent process can be suitably used as a catalyst carrier.

Next, the honeycomb formed body filled with the above-mentioned sealing material paste is degreased (for example, 200 to 500 ° C.) and fired (for example, 1400 to 2300 ° C.) under predetermined conditions, so that a plurality of cells become cell walls. A columnar honeycomb fired body that is arranged in parallel in the longitudinal direction with a gap therebetween and sealed at either end of the cell can be produced.
As the conditions for degreasing and firing the honeycomb formed body, the conditions conventionally used when manufacturing a filter made of a porous ceramic can be applied.

Next, a sealing material paste to be a sealing material layer (adhesive layer) is applied to the side surface of the honeycomb fired body with a uniform thickness, and another honeycomb fired body is sequentially laminated on the sealing material paste layer. The process is repeated to produce a honeycomb fired body aggregate having a predetermined size.

As said sealing material paste, what consists of an inorganic binder, an organic binder, an inorganic fiber, and / or an inorganic particle etc. are mentioned, for example.
Examples of the inorganic binder include silica sol and alumina sol. These may be used alone or in combination of two or more. Among the inorganic binders, silica sol is desirable.

Examples of the organic binder include polyvinyl alcohol, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, and the like. These may be used alone or in combination of two or more. Among the organic binders, carboxymethyl cellulose is desirable.

Examples of the inorganic fiber include ceramic fibers such as silica-alumina, mullite, alumina, and silica. These may be used alone or in combination of two or more. Among the inorganic fibers, alumina fibers are desirable.

Examples of the inorganic particles include carbides and nitrides, and specific examples include inorganic powders made of silicon carbide, silicon nitride, and boron nitride. These may be used alone or in combination of two or more. Among the inorganic particles, silicon carbide having excellent thermal conductivity is desirable.

Furthermore, a pore-forming agent such as a balloon, which is a fine hollow sphere containing an oxide-based ceramic, spherical acrylic particles, or graphite, may be added to the sealing material paste as necessary.
The balloon is not particularly limited, and examples thereof include an alumina balloon, a glass micro balloon, a shirasu balloon, a fly ash balloon (FA balloon), and a mullite balloon. Of these, alumina balloons are desirable.

Next, the aggregate of the honeycomb fired bodies is heated to dry and solidify the sealing material paste to form a sealing material layer (adhesive layer).
Next, using a diamond cutter or the like, an aggregate of the honeycomb fired bodies in which a plurality of honeycomb fired bodies are bonded via a sealing material layer (adhesive layer) is cut to produce a cylindrical ceramic block. The shape of the ceramic block manufactured by the method for manufacturing a honeycomb structure of the present invention is not limited to a cylindrical shape, and may be other columnar shapes such as an elliptical columnar shape.

And by forming the sealing material layer (coat layer) on the outer periphery of the ceramic block using the sealing material paste, a plurality of honeycomb fired bodies are bonded to each other via the sealing material layer (adhesive layer). A honeycomb structure in which a sealing material layer (coat layer) is provided on the outer periphery of the ceramic block can be manufactured.

Thereafter, if necessary, a catalyst is supported on the honeycomb structure. The catalyst may be supported on the honeycomb fired body before producing the aggregate.
When the catalyst is supported, it is desirable to form an alumina film having a high specific surface area on the surface of the honeycomb structure, and to apply a promoter such as platinum and a catalyst such as platinum to the surface of the alumina film.

As a method for forming an alumina film on the surface of the honeycomb structure, for example, a method in which a honeycomb structure is impregnated with a solution of a metal compound containing aluminum such as Al (NO ₃ ) ₃ and heated, an alumina powder is contained. For example, the honeycomb structure may be impregnated with a solution to be heated and heated.
Examples of a method for applying a promoter to the alumina film include a method in which a honeycomb structure is impregnated with a solution of a metal compound containing a rare earth element such as Ce (NO ₃ ) ₃ and heated. .
As a method for imparting a catalyst to the alumina membrane, for example, a dinitrodiammine platinum nitric acid solution ([Pt (NH ₃ ) ₂ (NO ₂ ) ₂ ] HNO ₃ , platinum concentration 4.53% by weight) or the like is applied to the honeycomb structure. Examples of the method include impregnation and heating.
Alternatively, the catalyst may be applied by a method in which a catalyst is applied to the alumina particles in advance, and the honeycomb structure is impregnated with a solution containing the alumina powder to which the catalyst is applied and heated.

In addition, the method for manufacturing a honeycomb structure described so far has a structure in which a plurality of honeycomb fired bodies are bundled through a sealing material layer (adhesive layer) (hereinafter also referred to as a collective honeycomb structure). However, the honeycomb structure manufactured by the manufacturing method of the present invention is a honeycomb structure in which a cylindrical ceramic block is composed of one honeycomb fired body (hereinafter also referred to as an integral honeycomb structure). May be.

When manufacturing such an integral honeycomb structure, first, the aggregated honeycomb structure is formed except that the size of the honeycomb molded body formed by extrusion molding is larger than that when manufacturing the aggregated honeycomb structure. A honeycomb formed body is manufactured by using the same method as that for manufacturing.
Here, since the method of conveying and storing the wet mixture before forming is the same as the method of manufacturing the aggregated honeycomb structure, the description thereof is omitted here.

Next, similarly to the production of the aggregated honeycomb structure, the honeycomb formed body is dried by the drying method of the present invention using the drying apparatus of the present invention. Further, if necessary, a drying process for removing moisture in the honeycomb formed body substantially completely may be performed. Next, a predetermined amount of a sealing material paste serving as a sealing material is filled in the outlet side end portion of the inlet side cell group and the inlet side end portion of the outlet side cell group, and the cells are sealed.
Thereafter, in the same manner as in the production of the aggregated honeycomb structure, a ceramic block is produced by performing degreasing and firing, and if necessary, a sealing material layer (coat layer) is formed, whereby an integral honeycomb structure is obtained. Can be manufactured. Further, the above-mentioned integral honeycomb structure may be loaded with a catalyst by the method described above.

In the case of manufacturing the honeycomb structure by the manufacturing method as described above, when manufacturing the aggregated honeycomb structure, silicon carbide or silicon-containing silicon carbide powder may be used as the main component of the constituent material. Desirably, when manufacturing an integral honeycomb structure, it is desirable to use cordierite or aluminum titanate as the main component of the constituent material.

Here, the description has been made mainly on the honeycomb filter used for the purpose of collecting the particulates in the exhaust gas as the honeycomb structure, but the honeycomb structure is also suitable as a catalyst carrier (honeycomb catalyst) for purifying the exhaust gas. Can be used for
As described above, in the method for manufacturing a honeycomb structure of the present invention described above, a honeycomb structure having a predetermined shape can be preferably manufactured.

The present invention will be described in more detail with reference to examples below, but the present invention is not limited to these examples.
(Example 1)
(1) 250 kg of α-type silicon carbide powder having an average particle size of 10 μm, 100 kg of α-type silicon carbide powder having an average particle size of 0.5 μm, and 20 kg of an organic binder (methylcellulose) were mixed to prepare a mixed powder.
Next, separately, 12 kg of lubricant (Unilube manufactured by NOF Corporation), 5 kg of plasticizer (glycerin), and 65 kg of water are mixed to prepare a liquid mixture, and this liquid mixture and the mixed powder are mixed in a wet mixer. And mixed to prepare a wet mixture.
Next, extrusion molding using this wet mixture and subsequent cutting were performed to prepare a honeycomb molded body.

(2) Next, the honeycomb formed body was dried using the drying apparatus 10 shown in FIGS. 1 and 2, and the water content (water residual ratio) was set to 50% by weight of the water content before drying.
Specifically, the honeycomb formed body is intermittently moved by an operation in which the belt conveyor 11 is moved for 2 seconds at a moving speed of 4.5 m / min in the drying furnace main body 19 having a moving distance of 15 m and repeatedly stopped for 2 seconds. The honeycomb molded body was produced by emitting 5.0 kW microwaves from the microwave radiating portions disposed above and below, and blowing hot air at 50 ° C. from the hot air blowing portion at a wind speed of 30 m / sec. Dried.
Further, the moisture residual ratio of the honeycomb formed body was calculated based on the mass change of the moisture content before and after drying.

(3) Next, the following drying treatment was performed.
The honeycomb formed body was held by a drying jig (made of epoxy resin) shown in FIG. 3, and this drying jig was stacked in two stages and placed in a hot air dryer and dried.
Here, the drying conditions were a temperature inside the dryer of 100 ° C. and a residence time in the dryer of 15 minutes.

(4) Next, the honeycomb formed body subjected to the drying treatment was taken out from the drying jig, and a predetermined cell was filled with a sealing material paste having the same composition as the wet mixture.
Next, after drying again using a dryer, the honeycomb formed body filled with the sealing material paste was degreased at 400 ° C. and fired at 2200 ° C. for 3 hours in an atmospheric argon atmosphere. The porosity is 40%, the average pore diameter is 12.5 μm, the size is 34.3 mm × 34.3 mm × 305 mm, the number of cells (cell density) is 46.5 cells / cm ² , and the cell wall thickness is A honeycomb sintered body made of a 0.25 mm silicon carbide sintered body was manufactured.

(Examples 2 to 10, Reference Examples 1 to 5)
In the step (2) of Example 1, the drying conditions were changed to the conditions shown in Table 1, and the moisture content after drying (moisture residual ratio) with respect to the moisture content before drying was a value shown in Table 1. A honeycomb fired body was manufactured in the same manner as in Example 1 except that was manufactured.

(Comparative Example 1)
In the step (2) of Example 1, when the honeycomb formed body is dried using the drying device 10, the microwave radiating portions (14b, 14c, 14f) disposed on the upper side of the conveying member (belt conveyor 11). 14h), a honeycomb fired body was manufactured in the same manner as in Example 1, except that the microwave was radiated only and the honeycomb formed body was dried under the conditions shown in Table 1.
In this comparative example, microwaves are emitted from the upper side only to the honeycomb formed body.

In each Example, Reference Example and Comparative Example, after the honeycomb formed body was dried, the handling property of the formed body after drying was evaluated by the following method, and the warpage amount of the manufactured honeycomb fired body was measured. . The results are shown in Table 1.

(Handling evaluation)
The handling property of the honeycomb formed body was evaluated using a handling property evaluation jig (see FIGS. 6A and 6B).
The handling property evaluation jig 50 has a flat plate shape slightly larger than the side surface of the honeycomb formed body 1, and two plate-like bodies 51 in which the urethane layer 51 a is formed on the entire main surface of the jig 50. The thing which has the structure arrange | positioned so that may oppose was used.
At the time of evaluation, first, the honeycomb formed body 1 is interposed between the two plate-shaped bodies 51, and the above-mentioned plate-shaped body is applied to each of the parallel side faces of the honeycomb formed body 1 at a pressure of 2 kPa per side face. The honeycomb formed body 1 was sandwiched between the plate-like bodies 51 by pressing 51, and then the deformation amount of the honeycomb formed body 1 was measured, and the handling property was evaluated according to the following evaluation criteria.

As shown in FIG. 6B, the deformation amount of the honeycomb formed body is such that the two plate-like bodies are formed on the end face of the honeycomb formed body 1 in a state where the honeycomb formed body 1 is sandwiched between the two plate-like bodies 51. Before measuring the length of a portion equidistant from each main surface (the surface in contact with the honeycomb formed body) (the length of the portion sandwiched by arrows in FIG. 6B) and sandwiching it between the plate-like bodies 51 The amount of change from the length was taken as the amount of deformation of the honeycomb formed body.
The evaluation criteria were “◯” when there was no deformation, “Δ” when the deformation was less than 1 mm, and “X” when the deformation was 1 mm or more.

(Measurement of warpage)
The warpage amount of the honeycomb fired body was measured using a warpage amount measurement jig.
As a jig for measuring the amount of warpage, contact members having the same thickness are disposed at both ends of a straight square member having substantially the same length as the entire length of the honeycomb fired body, and the length of the square member is arranged at the center of the square member. A structure (scale for measuring the amount of warpage) having a configuration in which a scale slidable perpendicularly to the direction was attached was used.
At the time of measurement, the contact member is brought into contact with the vicinity of both ends of the dried honeycomb fired body, and then the warp amount measurement scale is moved to the fired body side, and the scale when the honeycomb fired body and the scale come into contact with each other. The amount of warpage was measured by reading the amount of movement.

As shown in Table 1, in the examples, the handleability of the honeycomb molded body was not deformed or the deformation amount was good at less than 1 mm, and the warpage amount of the honeycomb fired body was as small as 0.8 mm or less.
On the other hand, in Reference Examples 1 and 2, although the handleability of the honeycomb molded body was good, the warpage amount of the honeycomb fired body was relatively large at 1.1 mm. This is presumably because the drying of the honeycomb formed body rapidly progressed due to the high heating temperature (Reference Example 1) and the high hot air velocity (Reference Example 2).

In Reference Examples 3 to 5, although the amount of warpage of the honeycomb fired body was as small as 0.5 mm, the handleability of the honeycomb formed body was inferior. This is because the hot air temperature is low (Reference Example 3), the drying time is short (Reference Example 4), and the hot air speed is low (Reference Example 5). This is probably because they did not.
In Comparative Example 1, the honeycomb molded body had good handling properties, but the warpage of the honeycomb fired body was as large as 1.2 mm. This is presumably because the microwave was emitted only from the upper side of the honeycomb molded body, so that the drying did not proceed uniformly.

It is a top view which shows the outline | summary of the drying apparatus of this invention. (A) is the AA line fragmentary sectional view of the drying apparatus of this invention shown in FIG. 1, (b) is the partial BB sectional view of the drying apparatus of this invention shown in FIG. is there. It is sectional drawing which shows an example of the jig | tool for drying typically. 1 is a perspective view schematically showing an example of a honeycomb structure. FIG. (A) is sectional drawing which shows typically the honeycomb fired body which comprises a honeycomb structure, (b) is the AA sectional view taken on the line. (A) (b) is a schematic diagram for demonstrating the evaluation method of handling property, respectively.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Drying apparatus 11 Belt conveyor 13a-13i Microwave transmission part 14a-14i Microwave radiation | emission part 15a-15d Hot-air blowing part 15a'-15d 'Hot-air suction part 17 Microwave stirring blade 19 Drying furnace main body 20 Drying jig

Claims (7)

A plurality of microwave radiating units arranged alternately above and below the object to be dried, and a plurality of hot air blowing units,
A drying apparatus configured to emit microwaves alternately from above and below the object to be dried and to irradiate the object to be dried with hot air in parallel. A ceramic molded body is a method for drying a ceramic molded body, wherein the ceramic molded body is dried by passing through a drying device by a conveying member for a predetermined time,
The drying apparatus includes a plurality of microwave radiating units arranged alternately above and below the conveying member, and a plurality of hot air blowing units,
A method for drying a ceramic molded body, wherein microwaves are alternately emitted from the upper and lower sides of the ceramic molded body, and drying with hot air is also performed in parallel. The method for drying a ceramic molded body according to claim 2, wherein the moisture content of the ceramic molded body after drying is 30 wt% or more and less than 70 wt% of the moisture content before drying. The method for drying a ceramic molded body according to claim 2 or 3, wherein the temperature of the hot air is 40 to 80 ° C. By forming the ceramic raw material, a columnar honeycomb formed body in which a large number of cells are arranged in parallel in the longitudinal direction across the cell wall is manufactured, and this honeycomb formed body is placed on a conveying member and dried in a predetermined time. A honeycomb structure manufacturing method for manufacturing a honeycomb structure including a honeycomb fired body by firing a dried honeycomb formed body after performing a formed body drying step of passing through the apparatus and drying,
The drying apparatus includes a plurality of microwave radiating units arranged alternately above and below the conveying member, and a plurality of hot air blowing units,
A method for manufacturing a honeycomb structured body, wherein the honeycomb molded body is dried by alternately radiating microwaves from above and below the honeycomb molded body and performing drying with hot air in parallel. The method for manufacturing a honeycomb structured body according to claim 5, wherein the moisture content of the honeycomb formed body after drying is 30 wt% or more and less than 70 wt% of the moisture amount before drying. The method for manufacturing a honeycomb structured body according to claim 5 or 6, wherein the temperature of the hot air is 40 to 80 ° C.

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