JP2008169105A - Method for manufacturing honeycomb structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing honeycomb structure which does not develop deformation or cracks. <P>SOLUTION: The method for manufacturing a honeycomb structure comprises a raw material composition-producing step of mixing at least inorganic particles and mineral fibers and/or whiskers and an inorganic binder solution to produce a raw material composition, a molding step of manufacturing a pillar-shaped honeycomb molding in which many cells are arranged side-by-side in the longitudinal direction separated by cell walls by an extrusion molding using the raw material composition, and a firing step of subjecting the honeycomb molding to firing to manufacture a honeycomb fired body, wherein the amount of the inorganic binder solution to be mixed is 30-60 wt.% based on the total amount of the inorganic particles and the mineral fibers and/or the whiskers and the inorganic binder solution, and the concentration of the inorganic binder solution is 35-50 wt.%. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a method for manufacturing a honeycomb structure.

Conventionally, a honeycomb catalyst in which a catalyst component is supported on a honeycomb structure used for exhaust gas purification of a vehicle is a monolithic and low thermal expansion cordierite honeycomb structure on the surface of a high specific surface area material such as activated alumina and platinum. It is manufactured by carrying | supporting this catalyst metal. In addition, such a honeycomb catalyst carries an alkaline earth metal such as Ba as a NOx storage agent for NOx treatment in an oxygen-excess atmosphere such as a lean burn engine and a diesel engine. By the way, in order to further improve the purification performance, it is necessary to increase the contact probability between the exhaust gas, the catalyst noble metal and the NOx storage agent. For that purpose, it is necessary to make the carrier have a higher specific surface area, to reduce the particle size of the noble metal and to disperse it highly. Therefore, for example, as a honeycomb structure made of a high specific surface area material, a honeycomb structure obtained by extrusion molding inorganic particles and inorganic fibers together with an inorganic binder is known (see, for example, Patent Documents 1 to 3).
JP 2005-218935 A JP 2005-349378 A Japanese Patent Laid-Open No. 5-213681

However, as disclosed in Patent Documents 1 to 3, when a honeycomb structure is manufactured through a process of extruding inorganic particles and inorganic fibers together with an inorganic binder, heat treatment (drying treatment, degreasing is performed on the extruded molded body. When a treatment, a firing treatment, etc.) are performed, cracks and deformation may occur in the molded body and the fired body.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the occurrence of cracks and deformation as described above is attributable to the composition of the raw material composition to be extruded, that is, the raw material composition. In the inorganic binder solution used in preparing the composition, when the amount of solid content is small, the amount of solvent such as water is relatively large, and as a result, the amount of solvent such as water contained in the raw material composition When the heat treatment such as the extrusion molding process and the subsequent drying process is performed using such a raw material composition, the molded body shrinks greatly, and thus cracks and deformation as described above occur. I found out.
Furthermore, in order to prevent the occurrence of cracks and deformation as described above, it has been found that the concentration of the inorganic binder contained in the inorganic binder solution may be adjusted within a predetermined range, and the present invention has been completed.

That is, the method for manufacturing a honeycomb structure of the present invention includes a raw material composition preparation step of preparing a raw material composition by mixing at least inorganic particles and inorganic fibers and / or whiskers and an inorganic binder solution;
A molding step of producing a columnar honeycomb molded body in which a large number of cells are arranged in parallel in the longitudinal direction across the cell wall by extrusion molding using the raw material composition,
A honeycomb structure manufacturing method including a firing step of subjecting the honeycomb formed body to a firing treatment to produce a honeycomb fired body,
The blending amount of the inorganic binder solution is 30 to 60% by weight with respect to the total amount of the inorganic particles and the inorganic fibers and / or the whiskers and the inorganic binder solution, and
The concentration of the inorganic binder solution is 35 to 50% by weight.

In the method for manufacturing a honeycomb structured body of the present invention, the inorganic binder solution is desirably at least one selected from the group consisting of alumina sol, silica sol, titania sol, sepiolite suspension and attapulgite suspension.

In the method for manufacturing a honeycomb structure of the present invention, an inorganic binder solution having a predetermined concentration is compounded in the raw material composition in a predetermined compounding amount. Thus, the honeycomb structure can be manufactured without deformation and cracks.

Hereinafter, the manufacturing method of the honeycomb structure of the present invention will be described in detail.
A method for manufacturing a honeycomb structure of the present invention includes a raw material composition manufacturing step of mixing at least inorganic particles and inorganic fibers and / or whiskers and an inorganic binder solution to prepare a raw material composition;
A molding step of producing a columnar honeycomb molded body in which a large number of cells are arranged in parallel in the longitudinal direction across the cell wall by extrusion molding using the raw material composition,
A honeycomb structure manufacturing method including a firing step of subjecting the honeycomb formed body to a firing treatment to produce a honeycomb fired body,
The blending amount of the inorganic binder solution is 30 to 60% by weight with respect to the total amount of the inorganic particles and the inorganic fibers and / or the whiskers and the inorganic binder solution, and
The concentration of the inorganic binder solution is 35 to 50% by weight.
In addition, in this invention, the density | concentration of an inorganic binder means the percentage of the weight for an inorganic binder with respect to the total weight of an inorganic binder solution.
Further, in this specification, the columnar shape includes an arbitrary shape such as a columnar shape, an elliptical columnar shape, or a polygonal columnar shape.

Hereinafter, the manufacturing method of the honeycomb structure of the present invention will be described in the order of steps.
(1) In the method for manufacturing a honeycomb structure of the present invention, first, a raw material composition manufacturing step is performed in which a raw material composition including at least inorganic particles, inorganic fibers and / or whiskers, and an inorganic binder solution is manufactured.

As said raw material composition, what added the organic binder and the shaping | molding adjuvant suitably according to the moldability further as needed can be used.

In the method for manufacturing a honeycomb structure of the present invention, an inorganic binder solution having a lower limit of 35% by weight and an upper limit of 50% by weight is used as the inorganic binder solution.
By manufacturing a honeycomb structure using such a raw material composition containing an inorganic binder solution, cracks and deformation do not occur in the honeycomb formed body and the honeycomb fired body during the manufacturing process.
On the other hand, when the concentration of the inorganic binder solution is less than 35% by weight, the amount of the solvent such as water contained in the raw material composition increases, and therefore, good moldability is obtained when the raw material composition is extruded. Although it can be ensured, cracks and deformation may occur in the honeycomb formed body and the honeycomb fired body in the manufacturing process of the honeycomb structure. On the other hand, when the concentration of the inorganic binder solution exceeds 50% by weight, the extrusion molding of the raw material composition is inferior in moldability, and a molded article having a desired shape may not be produced.
The desirable upper limit of the concentration of the inorganic binder solution is 45% by weight.

As the inorganic binder solution, an inorganic sol, a clay binder suspension, or the like can be used. Specific examples of the inorganic sol include alumina sol, silica sol, titania sol, and the like. In addition, examples of the clay-based binder include double-chain structured clays such as clay, kaolin, montmorillonite, sepiolite, and attapulgite. These may be used alone or in combination of two or more.
Among these, at least one selected from the group consisting of alumina sol, silica sol, titania sol, sepiolite suspension and attapulgite suspension is desirable.

As for the average particle diameter of the inorganic binder contained in the inorganic binder solution, the lower limit is desirably 10 nm and the upper limit is desirably 50 nm. This is because a honeycomb structure having a large specific surface area and excellent strength can be manufactured through a manufacturing process described later.
When the average particle diameter of the inorganic binder is less than 10 nm or exceeds 50 nm, the strength of the manufactured honeycomb structure may be insufficient.
The reason is considered as follows.
That is, in the method for manufacturing a honeycomb structure of the present invention, the inorganic binder is considered to play a role of mainly bonding the inorganic particles, the inorganic fibers, and the whiskers, and between the inorganic fibers (whiskers) and the inorganic particles. It is considered that the adhesive function is exhibited by being in contact with inorganic fibers (whiskers) and inorganic particles at the same time, interposing between inorganic particles and simultaneously in contact with different inorganic particles.
Here, when the average particle diameter is less than 10 nm, it is difficult to contact the inorganic fibers (whiskers) and the inorganic particles at the same time, or to contact different inorganic particles at the same time, and a sufficient adhesive force can be obtained. On the other hand, if the average particle diameter exceeds 50 nm, the number of adhesion points decreases, and as a result, the strength is considered insufficient.
Furthermore, when the average particle diameter of the inorganic binder exceeds 50 nm, the specific surface area of the manufactured honeycomb structure is not sufficiently increased, which is disadvantageous when the honeycomb structure is used as a catalyst carrier.
Moreover, as for the more desirable average particle diameter of the inorganic binder, the lower limit is 20 nm and the upper limit is 40 nm.

In addition, the average particle diameter of the said inorganic binder can be measured by the following methods, for example.
Specifically, when the inorganic binder is a silica sol, the silica sol is first dried and the BET specific surface area is measured.
Then, assuming that the silica particles in the silica sol are dense spherical particles, the following calculation formula (1) is used.
BET specific surface area = (6000 / ρ) / particle diameter (1)
(Wherein ρ is the true density of silica (2.2 g / cm ³ ))
The average particle diameter of the inorganic binder can be directly measured using, for example, a TEM (transmission electron microscope).

In the method for manufacturing the honeycomb structure, the lower limit of the blending amount of the inorganic binder solution with respect to the total amount of the inorganic particles and the inorganic fibers and / or whiskers and the inorganic binder solution is 30% by weight, The upper limit is 60% by weight.
When the blending amount of the inorganic binder solution is less than 30% by weight, the amount of the inorganic binder contained in the manufactured honeycomb structure decreases, and thus the strength of the honeycomb structure may be lowered. On the other hand, the inorganic binder solution This is because if the blending amount exceeds 60% by weight, the moldability of the raw material composition tends to deteriorate.
The desirable upper limit of the blending amount of the inorganic binder solution with respect to the total amount of the inorganic particles, the inorganic fibers and / or whiskers, and the inorganic binder solution is 50% by weight.

Examples of the inorganic particles include alumina, silica, zirconia, titania, ceria, mullite, and zeolite. These may be used alone or in combination of two or more.
Of these, alumina particles and ceria particles are particularly desirable.

The desirable lower limit of the blending amount of the inorganic particles is 30% by weight with respect to the total amount of the inorganic particles, the inorganic fibers and / or whiskers, and the solid content of the inorganic binder solution (hereinafter referred to as the total amount of essential raw materials). The more desirable lower limit is 40% by weight, and the still more desirable lower limit is 50% by weight.
On the other hand, the desirable upper limit is 85% by weight, the more desirable upper limit is 80% by weight, and the more desirable upper limit is 75% by weight.
When the blending amount of the inorganic particles is less than 30% by weight, the amount of inorganic particles contributing to the improvement of the specific surface area is relatively small, so that the specific surface area of the manufactured honeycomb structure is small and the catalyst component is supported. In some cases, the catalyst component cannot be highly dispersed. On the other hand, if the amount exceeds 85% by weight, the amount of inorganic binder, inorganic fiber, and whisker that contributes to strength improvement is relatively reduced, so that the strength of the manufactured honeycomb structure tends to be lowered.

Moreover, as for the inorganic particle mix | blended with the said raw material composition, it is desirable that the average particle diameter of a secondary particle is 0.5-20 micrometers.
If the average particle diameter of the secondary particles is less than 0.5 μm, the manufactured honeycomb structure is densified, and when used as a catalyst carrier, the gas permeability may be inferior, whereas it exceeds 20 μm. And the specific surface area of the manufactured honeycomb structure tends to be small.
The average particle size of the primary particles of the inorganic particles is preferably 5 to 100 nm.
In the present specification, primary particles are particles constituting powders or aggregates, and are the smallest unit particles that exist without breaking bonds between molecules. Secondary particles refer to particles formed by aggregation of primary particles.

The inorganic particles (secondary particles) preferably have a specific surface area of 50 to 300 m ² / g.
When the specific surface area is less than 50 m ² / g, the specific surface area of the manufactured honeycomb structure tends to be small. On the other hand, when the specific surface area exceeds 300 m ² / g, the specific surface area of the inorganic particles (secondary particles) is increased. This is because the specific surface area of the honeycomb structure is not improved so much.
In the method for manufacturing a honeycomb structure of the present invention, the average aspect ratio of the inorganic particles (secondary particles) is preferably 1 to 5.

Examples of the inorganic fibers and whiskers include inorganic fibers and whiskers made of alumina, silica, silicon carbide, silica-alumina, glass, potassium titanate, aluminum borate or the like.
These inorganic fibers and whiskers may be used alone or in combination of two or more.
In the honeycomb structure manufacturing method of the present invention, inorganic fibers and whiskers are those having an average aspect ratio of more than 5.
Moreover, the desirable average aspect-ratio of the said inorganic fiber and a whisker is 10-1000.

With respect to the total amount of the inorganic fibers and / or whiskers, a desirable lower limit is 3% by weight, a more desirable lower limit is 5% by weight, and a further desirable lower limit is 8% by weight with respect to the total amount of the essential raw materials. On the other hand, the desirable upper limit is 50% by weight, the more desirable upper limit is 40% by weight, and the more desirable upper limit is 30% by weight.
When the total amount of the inorganic fibers and / or whiskers is less than 3% by weight, the strength of the manufactured honeycomb structure is lowered. On the other hand, when the total amount exceeds 50% by weight, the specific surface area is improved in the manufactured honeycomb structure. When the manufactured honeycomb structure is used as a catalyst carrier, the specific surface area of the honeycomb structure is small, and the catalyst component is highly dispersed when supporting the catalyst component. May not be possible.

The raw material composition may contain an organic binder, a dispersion medium, a molding aid and the like. The organic binder is not particularly limited, and examples thereof include methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, and polyethylene glycol.
These may be used alone or in combination of two or more.
The blending amount of the organic binder is desirably 1 to 10 parts by weight with respect to a total of 100 parts by weight of the solid content of the inorganic particles, the inorganic fibers, the whiskers, and the inorganic binder solution.

Although it does not specifically limit as said shaping | molding adjuvant, For example, ethylene glycol, dextrin, a fatty acid, fatty acid soap, polyalcohol etc. are mentioned.
In this, in order to improve a moldability more, it is good to mix | blend an oleic acid further.

The preparation of the raw material composition is not particularly limited, but it is preferable to mix and knead the raw materials. For example, the raw material composition may be mixed using a mixer or an attritor, or sufficiently kneaded with a kneader or the like. Also good.

(2) Next, a forming step is performed to produce a columnar honeycomb formed body in which a large number of cells are arranged in parallel in the longitudinal direction with cell walls being separated by extrusion forming using the raw material composition.

(3) Next, if necessary, the honeycomb formed body is dried.
The drying treatment can be performed using, for example, a microwave dryer, a hot air dryer, a dielectric dryer, a vacuum dryer, a vacuum dryer, a freeze dryer, or the like.

(4) Next, if necessary, the honeycomb formed body that has been subjected to a drying treatment is subjected to a degreasing treatment.
In this case, the degreasing conditions are not particularly limited and are appropriately selected depending on the type and amount of the organic substance contained in the molded body, but are preferably about 400 ° C. and about 2 hours.

(5) Next, a firing process is performed in which a honeycomb formed body that has been subjected to a drying process or a degreasing process as necessary is subjected to a firing process to produce a honeycomb fired body.
The firing temperature in the firing treatment is not particularly limited, but is preferably 500 to 1200 ° C, and more preferably 600 to 1000 ° C.
If the firing temperature is less than 500 ° C., the adhesive function due to the inorganic binder is difficult to be exhibited, and sintering of inorganic particles and the like is difficult to proceed, so that the strength as the manufactured honeycomb structure may be reduced to 1200 ° C. Exceeds the above range, the sintering of inorganic particles proceeds too much, and the specific surface area per unit volume of the manufactured honeycomb structure becomes small. When the honeycomb structure is used as a catalyst carrier, the catalyst component to be supported is sufficient. May not be able to be highly dispersed.

By passing through such a process, it is possible to manufacture a columnar honeycomb fired body in which a large number of cells are arranged in parallel in the longitudinal direction with a cell wall therebetween.
The honeycomb fired body manufactured through such steps is itself a honeycomb structure, and in the method for manufacturing a honeycomb structure of the present invention, all the steps may be completed so far.
Moreover, a sealing material layer (coat layer) may be formed around the honeycomb fired body manufactured by the method described so far to obtain a finished product of the honeycomb structure. Hereinafter, such a honeycomb structure including one honeycomb fired body is also referred to as an integral honeycomb structure.
The method for forming the sealing material layer (coating layer) is as follows. When a honeycomb structure is manufactured from a honeycomb block formed by binding a plurality of honeycomb fired bodies described later, a sealing material layer (coating layer) is formed around the honeycomb block. The method is the same as that for forming the layer.

In the method for manufacturing a honeycomb structure of the present invention, the honeycomb fired body is manufactured by the above-described method, and then a honeycomb block in which a plurality of the honeycomb fired bodies are bundled is manufactured to manufacture the honeycomb structure. Good.
In this case, specifically, the following method may be used.
Hereinafter, a honeycomb structure formed by binding a plurality of honeycomb fired bodies is also referred to as a collective honeycomb structure.

That is, a sealing material paste to be a sealing material layer (adhesive layer) is applied to the obtained honeycomb fired body, the honeycomb fired body is sequentially bound, then dried and fixed, and the sealing material layer (adhesive layer) ) Through which a honeycomb fired body having a predetermined size is produced.
Further, after assembling a predetermined number of honeycomb fired bodies through spacers, a sealing material paste is injected into the gaps between the honeycomb fired bodies, and then dried and fixed to form a sealing material layer (adhesive layer). An aggregate of honeycomb fired bodies of a predetermined size that are bound together may be produced.

The sealing material paste for forming the adhesive layer is not particularly limited, for example, a mixture of an inorganic binder and ceramic particles, a mixture of an inorganic binder and inorganic fibers, What mixed the inorganic binder, the ceramic particle, and the inorganic fiber etc. can be used.
Further, an organic binder may be added to these sealing material pastes.

The organic binder is not particularly limited, and examples thereof include polyvinyl alcohol, methyl cellulose, ethyl cellulose, carboxymethyl cellulose and the like.
These may be used alone or in combination of two or more.

The thickness of the sealing material layer (adhesive layer) is preferably 0.5 to 5 mm.
If the thickness of the sealing material layer (adhesive layer) is less than 0.5 mm, sufficient bonding strength may not be obtained. If the thickness exceeds 5 mm, the sealing material layer (adhesive layer) does not function as a catalyst carrier. Since it is a part, the specific surface area per unit volume of the honeycomb structure is lowered, and when the catalyst component is supported, the honeycomb structure may not be sufficiently dispersed.
Further, when the thickness of the sealing material layer (adhesive layer) exceeds 5 mm, the pressure loss may increase.

Here, the number of honeycomb fired bodies to be bound may be determined as appropriate in accordance with the size of the honeycomb structure.
The aggregate of the honeycomb fired bodies in which the honeycomb fired bodies are bound through the sealing material layer (adhesive layer) is appropriately cut and polished as necessary to form honeycomb blocks.

Next, if necessary, a sealing material layer (coating layer) is formed on the outer peripheral surface of the honeycomb block by applying a sealing material paste for forming a coating layer, drying, and fixing.
By forming the sealing material layer (coat layer), the outer peripheral surface of the honeycomb block can be protected, and as a result, the strength of the honeycomb structure can be increased.

The sealing material paste for forming the coating layer is not particularly limited, and may be made of the same material as the sealing material paste for forming the adhesive layer, or may be made of a different material. May be.
Further, when the sealing material paste for forming the coating layer is made of the same material as the sealing material paste for forming the adhesive layer, the blending ratios of the two components are the same. May be different.

Although the thickness of the said sealing material layer (coat layer) is not specifically limited, It is desirable that it is 0.1-2 mm. If the thickness is less than 0.1 mm, the outer peripheral surface may not be protected and the strength may not be increased. If the thickness exceeds 2 mm, the specific surface area per unit volume as the honeycomb structure is reduced, and the catalyst component is loaded. May not be able to be sufficiently dispersed.

Further, in this manufacturing method, after the plurality of honeycomb fired bodies are bundled through the sealing material layer (adhesive layer) (provided that the sealing material layer (coating layer) is provided, the coating layer is formed). After) is preferably calcined.
Thereby, when an organic binder is contained in the sealing material layer (adhesive layer) or the sealing material layer (coat layer), the organic binder can be degreased and removed.
The conditions for calcining are appropriately determined depending on the type and amount of organic matter contained, but it is preferably about 700 ° C. and about 2 hours.

Next, the configuration of the honeycomb structure manufactured by the method for manufacturing a honeycomb structure of the present invention will be described with reference to the drawings.
FIG. 1 (a) is a perspective view schematically showing an example of a honeycomb fired body manufactured by the method for manufacturing a honeycomb structure of the present invention, and FIG. 1 (b) uses the honeycomb fired body shown in (a). 2 is a perspective view schematically showing an example of a honeycomb structure.

As shown in FIG. 1 (a), the honeycomb fired body 20 has a quadrangular prism shape, and a large number of cells 21 are arranged in the longitudinal direction (in the direction of arrow a in FIG. 1 (a)) with the cell walls 22 therebetween. It is installed.
As shown in FIG. 1B, the honeycomb structure 10 includes a ceramic block 15 in which a plurality of the honeycomb fired bodies 20 shown in FIG. 1A are bundled through a sealing material layer (adhesive layer) 14. The sealing material layer (coat layer) 13 is formed in the outer periphery.

In the honeycomb fired body, the thickness of the cell wall is not particularly limited, but a desirable lower limit is 0.05 mm, a more desirable lower limit is 0.10 mm, and a particularly desirable lower limit is 0.15 mm. is there. On the other hand, the desirable upper limit of the cell wall thickness is 0.35 mm, the more desirable upper limit is 0.30 mm, and the particularly desirable upper limit is 0.25 mm.

When the cell wall thickness is less than 0.05 mm, the strength of the honeycomb fired body may be reduced. On the other hand, when the cell wall thickness exceeds 0.35 mm, the honeycomb structure has a catalyst for purifying exhaust gas. When used as a carrier, the gas purification performance is reduced by the fact that the contact area with the exhaust gas is reduced and the gas does not penetrate deep enough to make it difficult for the catalyst carried inside the cell wall to come into contact with the gas. May fall.

Further, the cell density of the honeycomb fired body is preferably a lower limit of 15.5 cells / cm ² (100 cpsi), a more preferable lower limit of 46.5 cells / cm ² (300 cpsi), and a further preferable lower limit of 62 cells. / Cm ² (400 cpsi). On the other hand, the desirable upper limit of the cell density is 186 cells / cm ² (1200 cpsi), the more desirable upper limit is 170.5 cells / cm ² (1100 cpsi), and the more desirable upper limit is 155 cells / cm ² (1000 cpsi). is there.
When the cell density is less than 15.5 cells / cm ² , when the honeycomb structure is used as a catalyst carrier for purifying exhaust gas, the area of the cell wall in contact with the exhaust gas inside the honeycomb fired body becomes small. This is because when the number of particles / cm ² is exceeded, the pressure loss increases and it becomes difficult to fabricate the honeycomb fired body.

In addition, the lower limit of the cross-sectional area in the direction perpendicular to the longitudinal direction of the honeycomb fired body is desirably 5 cm ² and the upper limit is 50 cm ^{2. In} particular, the honeycomb structure binds a plurality of honeycomb fired bodies. If it is, it is desirable to be in the above range.
When the cross-sectional area is less than 5 cm ² , the area occupied by the sealing material layer (adhesive layer) for joining a plurality of honeycomb fired bodies is relatively large in the cross section perpendicular to the longitudinal direction of the honeycomb structure. When the honeycomb structure is used as a catalyst carrier, the area on which the catalyst can be supported becomes relatively small. On the other hand, if the cross-sectional area exceeds 50 cm ² , the honeycomb fired body is large, and thus there is a possibility that the thermal stress generated in the honeycomb fired body cannot be sufficiently suppressed.
A more desirable lower limit of the cross-sectional area is 6 cm ² , a particularly desirable lower limit is 8 cm ² , a more desirable upper limit is 40 cm ² , and a particularly desirable upper limit is 30 cm ² .

The shape of the cross section perpendicular to the longitudinal direction of the cells formed in the honeycomb fired body is not particularly limited, and may be a substantially triangular shape or a substantially hexagonal shape other than a quadrangle like the honeycomb fired body shown in FIG. Also good.

In the honeycomb structure, when a sealing material layer (adhesive layer) or a sealing material layer (coat layer) is formed, the cross section perpendicular to the longitudinal direction of the honeycomb structure is relative to the cross-sectional area of the honeycomb structure. Thus, the ratio of the total cross-sectional area of the honeycomb fired body is desirably 90% or more. This is because if it is less than 90%, the specific surface area of the honeycomb structure becomes small.

Moreover, the specific surface area per unit area of the honeycomb structure is desirably 25000 m ² / L or more.
This is because when the specific surface area is in the above range, it becomes easy to disperse and carry the catalyst over the entire honeycomb structure.
The desirable upper limit of the specific surface area is 70000 m ² / L in consideration of the dispersion limit of the catalyst (for example, platinum).

The bending strength of the honeycomb structure is preferably as large as possible. Specifically, for example, when the honeycomb fired body has a prismatic shape of 37 mm × 37 mm × 75 mm, it is preferably 3.0 Mpa or more.
This is because there is less risk of destruction due to thermal stress generated during use.

Further, the honeycomb structure manufactured by the method for manufacturing a honeycomb structure of the present invention is not limited to the aggregated honeycomb structure as shown in FIG. 1 (b), but an integrated honeycomb structure as shown in FIG. It may be a body.
FIG. 2 is a perspective view schematically showing another example of the honeycomb structure manufactured by the method for manufacturing a honeycomb structure of the present invention.
A honeycomb structure 30 shown in FIG. 2 has a columnar shape, and includes a single honeycomb fired body in which a large number of cells 31 are arranged in parallel in the longitudinal direction (in the direction of arrow b in FIG. 2) with cell walls 32 therebetween. Has been.
In such an integrated honeycomb structure, a sealing material layer (coat layer) may be formed around the honeycomb fired body.

Moreover, it is desirable that a catalyst be supported on the honeycomb structure having such a configuration. This is because the honeycomb structure can be suitably used as a catalyst carrier.
The catalyst is not particularly limited, and examples thereof include noble metals, alkali metals, alkaline earth metals, and oxides. These may be used alone or in combination of two or more.

Examples of the noble metal include platinum, palladium, and rhodium. Examples of the alkali metal include potassium and sodium. Examples of the alkaline earth metal include barium and the like. Examples of the oxide include perovskite (La _0.75 K _0.25 MnO _{3 and the} like), CeO _{2 and the} like.

The honeycomb structure on which the catalyst as described above is supported is not particularly limited, but can be used as a so-called three-way catalyst or NOx occlusion catalyst for purifying exhaust gas of automobiles, for example.
The timing for loading the catalyst is not particularly limited, and may be loaded after the honeycomb structure is manufactured, or may be loaded on the inorganic particles in the raw material composition.
Moreover, the catalyst loading method is not particularly limited, and for example, it can be carried out by an impregnation method or the like.

Heretofore, the manufacturing method of the honeycomb structure of the present invention and / or the honeycomb structure manufactured by this manufacturing method has been described mainly taking the case of using as a catalyst carrier as an example. The body can be used in addition to the catalyst carrier, for example, as an adsorbent for adsorbing a gas component or a liquid component.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.
(Example 1)
(1) 2250 g of γ-alumina particles (secondary particles having an average particle diameter of 2 μm) as inorganic particles, 680 g of aluminum borate whisker (fiber diameter of 0.5 to 1 μm, fiber length of 10 to 30 μm) as inorganic fibers, silica sol as an inorganic binder solution (Average particle diameter 15 nm, concentration 35% by weight) 2600 g was mixed. Further, 320 g of methylcellulose as an organic binder, 290 g of Unilube (manufactured by Nippon Oil & Fats Co., Ltd.) as a lubricant, and glycerin (Nippon Oil & Fats as a plasticizer) were mixed. 225 g) was added and further mixed and kneaded to prepare a raw material composition. Next, this raw material composition was subjected to extrusion molding with an extruder, and a honeycomb formed body was produced.

(2) Next, the honeycomb formed body was sufficiently dried using a microwave dryer and a hot air dryer, and further degreased by holding at 400 ° C. for 2 hours.
Thereafter, firing is performed by holding at 900 ° C. for 2 hours, prismatic shape (37 mm × 37 mm × 75 mm), cell density of 93 cells / cm ² (600 cpsi), cell wall thickness of 0.2 mm, cell cross-sectional shape Produced a square (square) honeycomb fired body.

(Examples 2 and 3)
A honeycomb fired body was manufactured in the same manner as in Example 1 except that silica sol (average particle diameter: 15 nm) having the concentration shown in Table 1 was used as the inorganic binder solution used when preparing the raw material composition.

Example 4
A honeycomb fired body was manufactured in the same manner as in Example 1 except that alumina sol (average particle size 15 nm, concentration 35% by weight) was used instead of silica sol when preparing the raw material composition.

(Example 5)
As inorganic particles, mixed particles of 50% by weight of γ alumina particles (secondary particles having an average particle diameter of 2 μm) and 50% by weight of β zeolite particles (secondary particles having an average particle diameter of 2 μm) are used instead of γ alumina particles. A honeycomb fired body was manufactured in the same manner as in Example 1 except that.

(Examples 6 and 7)
A honeycomb fired body was manufactured in the same manner as in Example 5 except that silica sol (average particle diameter: 15 nm) having the concentration shown in Table 1 was used as the inorganic binder solution used when preparing the raw material composition.

(Example 8)
A honeycomb fired body was manufactured in the same manner as in Example 5 except that alumina sol (average particle size 15 nm, concentration 35% by weight) was used instead of silica sol when preparing the raw material composition.

Example 9
As inorganic particles, instead of secondary particles of γ-alumina particles, 50% by weight of γ-alumina particles (secondary particles with an average particle size of 2 μm) and 50% by weight of CeO ₂ particles (secondary particles with an average particle size of 2 μm). A honeycomb fired body was manufactured in the same manner as in Example 1 except that the mixed particles were used.

(Examples 10 and 11)
A honeycomb fired body was manufactured in the same manner as in Example 9 except that silica sol (average particle diameter: 15 nm) having the concentration shown in Table 1 was used as the inorganic binder solution used when preparing the raw material composition.

(Example 12)
A honeycomb fired body was manufactured in the same manner as in Example 9 except that alumina sol (average particle size 15 nm, concentration 35 wt%) was used instead of silica sol when preparing the raw material composition.

(Example 13)
A honeycomb fired body was manufactured in the same manner as in Example 1 except that the raw material composition was prepared by the following method.
That is, 2970 g of γ-alumina particles (secondary particles having an average particle diameter of 2 μm) as inorganic particles, 900 g of aluminum borate whisker (fiber diameter of 0.5 to 1 μm, fiber length of 10 to 30 μm) as inorganic fibers, silica sol (inorganic binder solution) 1660 g of an average particle size of 15 nm and a concentration of 35% by weight was mixed. Further, 320 g of methyl cellulose as an organic binder, 290 g of Unilube (manufactured by NOF Corporation) as a lubricant, and glycerin (NOF Corporation) as a plasticizer were mixed. 225 g) was added and further mixed and kneaded to prepare a raw material composition.

(Examples 14 and 15)
A honeycomb fired body was manufactured in the same manner as in Example 13 except that silica sol (average particle diameter: 15 nm) having the concentrations shown in Table 1 was used as the inorganic binder solution used when preparing the raw material composition.

(Example 16)
A honeycomb fired body was manufactured in the same manner as in Example 1 except that the raw material composition was prepared by the following method.
That is, 1780 g of γ-alumina particles (secondary particles having an average particle diameter of 2 μm) as inorganic particles, 400 g of aluminum borate whisker (fiber diameter of 0.5 to 1 μm, fiber length of 10 to 30 μm) as inorganic fibers, and silica sol ( 3300 g of an average particle diameter of 15 nm and a concentration of 35% by weight were mixed. Further, 320 g of methylcellulose as an organic binder, 290 g of Unilube (manufactured by NOF Corporation) as a lubricant, and glycerin (NIPPON FATTY CO., LTD.) As a plasticizer were mixed. 225 g) was added and further mixed and kneaded to prepare a raw material composition.

(Examples 17 and 18)
A honeycomb fired body was manufactured in the same manner as in Example 16 except that silica sol (average particle diameter: 15 nm) having the concentrations shown in Table 1 was used as the inorganic binder solution used when preparing the raw material composition.

(Comparative Examples 1 and 2)
A honeycomb fired body was manufactured in the same manner as in Example 1 except that silica sol (average particle diameter: 15 nm) having the concentration shown in Table 1 was used as the inorganic binder solution used when preparing the raw material composition.

(Comparative Example 3)
A honeycomb fired body was manufactured in the same manner as in Example 4 except that alumina sol (average particle diameter: 15 nm) having the concentration shown in Table 1 was used as the inorganic binder solution used when preparing the raw material composition.

(Comparative Examples 4 and 5)
A honeycomb fired body was manufactured in the same manner as in Example 5 except that silica sol (average particle diameter: 15 nm) having the concentration shown in Table 1 was used as the inorganic binder solution used when preparing the raw material composition.

(Comparative Example 6)
A honeycomb fired body was manufactured in the same manner as in Example 8 except that alumina sol (average particle diameter: 15 nm) having the concentration shown in Table 1 was used as the inorganic binder solution used when preparing the raw material composition.

(Comparative Examples 7 and 8)
A honeycomb fired body was manufactured in the same manner as in Example 9 except that silica sol (average particle diameter: 15 nm) having the concentration shown in Table 1 was used as the inorganic binder solution used when preparing the raw material composition.

(Comparative Example 9)
A honeycomb fired body was manufactured in the same manner as in Example 12 except that alumina sol (average particle diameter: 15 nm) having the concentration shown in Table 1 was used as the inorganic binder solution used when preparing the raw material composition.

(Comparative Example 10)
A honeycomb fired body was manufactured in the same manner as in Comparative Example 1 except that the amount of the inorganic binder solution (silica sol) used in preparing the raw material composition was 2000 g.

In Examples 1 to 18 and Comparative Examples 1 to 10, as a silica sol having a concentration of 30% by weight, a snow tex 30 manufactured by Nissan Chemical Co., Ltd. was used, and the concentration was 35%, 40%, 50%, 60% As a silica sol having a weight%, one obtained by concentrating Snowtex 30 to a predetermined concentration was used. As the alumina sol having a concentration of 30% by weight and 35% by weight, a product obtained by concentrating alumina sol 520 (alumina concentration 20% by weight) manufactured by Nissan Chemical Co., Ltd. to a predetermined concentration was used.

Evaluation of honeycomb fired bodies In the manufacture of honeycomb fired bodies according to Examples and Comparative Examples, after the extruded honeycomb formed bodies were dried, the dried honeycomb formed bodies were evaluated for occurrence of cracks. Furthermore, the shape (presence or absence of deformation) of the manufactured honeycomb fired body was evaluated.
The results are shown in Table 1.

(Evaluation of occurrence of cracks)
The dried honeycomb formed body was visually observed to observe the presence or absence of cracks.

(Evaluation of honeycomb fired body shape)
About the manufactured honeycomb fired body, the flatness of the side surface thereof was measured by the following method, and the honeycomb fired body having a flatness of all side surfaces of 0.5 mm or less was evaluated as “◯”. A honeycomb fired body exceeding 5 mm was evaluated as “x”.
That is, the flatness of the honeycomb fired body was evaluated by plotting the position coordinates of the side face of the honeycomb fired body using a three-dimensional measuring machine (BH-V507, manufactured by Mitutoyo Corporation).

As is clear from the results shown in Table 1, cracks are generated when the honeycomb formed body is dried by using an inorganic binder solution having a concentration of 35 to 50% by weight in an amount of 30 to 60% by weight. This makes it possible to manufacture a honeycomb fired body having a desired shape without deformation.
On the other hand, when the concentration of the inorganic binder solution was less than 35% by weight, no deformation was observed in the shape of the honeycomb fired body, but cracks were observed when the honeycomb formed body was dried. When the concentration of the inorganic binder solution exceeded 50% by weight, no cracks were observed in the dried honeycomb formed body, but the manufactured honeycomb fired body was deformed.

Further, in the above-described examples and comparative examples, one honeycomb fired body was manufactured and evaluated as a honeycomb structure. A plurality of the honeycomb fired bodies were used, and FIG. It is considered that the same result is obtained when the aggregated honeycomb structure as shown in FIG.

(A) is a perspective view schematically showing an example of a honeycomb fired body manufactured by the method for manufacturing a honeycomb structure of the present invention, and (b) is a honeycomb using the honeycomb fired body shown in (a). It is a perspective view which shows an example of a structure typically. FIG. 6 is a perspective view schematically showing another example of a honeycomb structure manufactured by the method for manufacturing a honeycomb structure of the present invention.

Explanation of symbols

10, 30 Honeycomb structure 13 Sealing material layer (coat layer)
14 Sealing material layer (adhesive layer)
20 Honeycomb fired body 21, 31 Cell 22, 32 Cell wall

Claims (2)

A raw material composition preparation step of preparing a raw material composition by mixing at least inorganic particles and inorganic fibers and / or whiskers and an inorganic binder solution;
A molding step of producing a columnar honeycomb molded body in which a large number of cells are arranged in parallel in the longitudinal direction with cell walls being separated by extrusion molding using the raw material composition;
A honeycomb structure manufacturing method including a firing step of subjecting the honeycomb formed body to a firing treatment to produce a honeycomb fired body,
The blending amount of the inorganic binder solution is 30 to 60% by weight with respect to the total amount of the inorganic particles and the inorganic fibers and / or the whiskers and the inorganic binder solution, and
The method for manufacturing a honeycomb structure, wherein the concentration of the inorganic binder solution is 35 to 50% by weight. The method for manufacturing a honeycomb structure according to claim 1, wherein the inorganic binder solution is at least one selected from the group consisting of alumina sol, silica sol, titania sol, sepiolite suspension and attapulgite suspension.

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