JP5476048B2 - Manufacturing method of honeycomb structure - Google Patents

Description

  The present invention relates to a method for manufacturing a honeycomb structure. More specifically, the present invention relates to a method for manufacturing a honeycomb structure capable of manufacturing a large honeycomb structure having a large size with high dimensional accuracy.

  In general, a honeycomb structure used for a catalyst carrier for automobile exhaust gas purification is manufactured by obtaining a honeycomb formed body by extrusion molding and firing the obtained honeycomb formed body in order to improve mass productivity.

  In such a method for manufacturing a honeycomb structure using extrusion molding, since the moldability of the clay used for extrusion molding is low, the cells around the outer peripheral wall may be crushed by the weight of the obtained honeycomb molded body (cellyore). In other words, there is a problem that a sasker-like defect occurs on the outer periphery. Further, since the forming accuracy of the obtained honeycomb formed body is low, it has been necessary to grind the outer peripheral portion of the fired honeycomb structure and dispose the outer peripheral coat layer made of the outer peripheral coat material on the outer peripheral surface. . In particular, the problem of dimensional accuracy becomes more serious in, for example, a large honeycomb structure having an end face diameter of 229 mm or more.

  Although it is possible to improve the roundness of the honeycomb structure as a final product by arranging the outer peripheral coat layer as described above, the manufacturing process becomes very complicated and the manufacturing cost increases.

For this reason, for example, a cordierite raw material batch for extrusion molding contains 65% by weight or more of a flat and plate-like cordierite raw material having crystal water composed of talc, kaolin and aluminum hydroxide, and each BET specific surface area of the cordierite-forming raw material, talc 7~18m ² / g, kaolin 14~22m ² / g, aluminum hydroxide using those 6~18m ² / g thin wall cordierite A method for manufacturing a honeycomb structure is disclosed (see Patent Document 1). Also, the cordierite raw material batch for extrusion molding contains at least 65% by weight of a cordierite raw material having crystal water composed of talc, kaolin, and aluminum hydroxide, and has an average particle size of 5 μm or more and a BET ratio. A production method in which 10% by weight or more of kaolin having a surface area of 10 m ² / g or less is also disclosed (see Patent Document 2).

Japanese Patent No. 3150928 Japanese Patent No. 3340689

  However, the manufacturing method of the honeycomb structure described in Patent Documents 1 and 2 described above is a manufacturing method for manufacturing a relatively small honeycomb structure having a thin partition wall and is deformed by its own weight. It has been difficult to apply to a method for manufacturing a large honeycomb structure that is liable to cause erosion. For this reason, there is a demand for development of a manufacturing method capable of manufacturing a large honeycomb structure having a relatively large size with high dimensional accuracy.

  The present invention has been made in view of the above-mentioned problems of the prior art, and a manufacturing method capable of manufacturing a large honeycomb structure having a relatively large size with high dimensional accuracy. Is to provide.

  As a result of intensive studies to solve the problems of the prior art as described above, the inventor has achieved fluidity while maintaining the rheometer hardness at a certain value or more in the process of preparing the clay for extrusion molding. It was conceived that the above problems could be solved by preparing an excellent clay, and the present invention was completed. Specifically, the present invention provides the following method for manufacturing a honeycomb structure.

[1] A clay preparation step in which a forming raw material containing a ceramic raw material is mixed and kneaded to obtain a clay, a molding step in which the obtained clay is extruded into a honeycomb shape to obtain a honeycomb formed body, and A honeycomb structure having a porous partition wall for partitioning and forming a plurality of cells serving as fluid flow paths, and an outer wall disposed so as to surround the partition wall, by drying and firing the formed honeycomb molded body. A honeycomb structure for preparing the clay that has an extrusion stress of 25 MPa or less at the time of extrusion molding in a state in which the rheometer hardness is adjusted to 2.0 kgf in the clay preparation step. Method.

[2] The honeycomb according to [1], wherein the ceramic raw material is a ceramic raw material in which the proportion of particles of 1 μm or less in the particle size distribution is 20% by volume or more and the proportion of particles of 10 μm or more is 30% by volume or more. Manufacturing method of structure.

[3] As the ceramic raw material, kaolin particles having an average particle diameter of 1 μm or less and a BET specific surface area of 17 m ² / g or more, and an average particle diameter of 5 μm or more and a BET specific surface area of 7 m ² / g or less. The method for manufacturing a honeycomb structured body according to [1] or [2], wherein at least certain kaolin particles are used.

[4] The method for manufacturing a honeycomb structure according to [3], wherein the kaolin particles are contained in the ceramic raw material in an amount of 2 to 40% by mass.

[5] The honeycomb structure according to any one of [1] to [4], wherein at least talc particles having an average particle diameter of 25 μm or more and a BET specific surface area of 2 m ² / g or less are used as the ceramic raw material. Manufacturing method.

[6] The method for manufacturing a honeycomb structured body according to [5], wherein 1 to 30% by mass of the talc particles are contained in the ceramic raw material.

[7] As the ceramic raw material, at least calcined kaolin and raw kaolin are used, and the ratio of the amount of the calcined kaolin used to the amount of the raw kaolin used is 25/75 to 75/25 in terms of mass. The method for manufacturing a honeycomb structure according to any one of [1] to [6].

[8] The method for manufacturing a honeycomb structure according to any one of [1] to [7], wherein the forming raw material contains 0.1 to 2% by mass of a water-absorbing polymer.

[9] The method for manufacturing a honeycomb structure according to any one of [1] to [8], wherein 1 to 4% by mass of a (meth) acrylic acid polymer is contained in the forming raw material.

[10] A method of manufacturing a cylindrical honeycomb structure having an end face diameter of 229 mm or more, and manufacturing the roundness of the outer peripheral portion to 1 mm or less without grinding the outer peripheral portion of the honeycomb structure. The method for manufacturing a honeycomb structure according to any one of [1] to [9].

  According to the method for manufacturing a honeycomb structure of the present invention, the honeycomb structure can be manufactured with high dimensional accuracy. In particular, the method for manufacturing a honeycomb structure of the present invention performs drying and firing because the honeycomb formed body obtained by extrusion molding is not easily deformed even when manufacturing a large honeycomb structure having a large size. High dimensional accuracy can be maintained even after. For this reason, a honeycomb structure with high roundness can be easily and inexpensively manufactured without grinding the outer peripheral portion and disposing the outer peripheral coat layer, which has been performed by the conventional method for manufacturing a honeycomb structure. can do.

1 is a perspective view schematically showing a honeycomb structure manufactured by one embodiment of a method for manufacturing a honeycomb structure of the present invention.

  Hereinafter, embodiments of the method for manufacturing a honeycomb structure of the present invention will be specifically described. However, the present invention broadly encompasses a method for manufacturing a honeycomb structure having the invention-specific matters, and is not limited to the following embodiments.

[1] Manufacturing method of honeycomb structure:
One embodiment of a method for manufacturing a honeycomb structure according to the present invention is a porous structure in which a plurality of cells 2 penetrating from one end face 11 to the other end face 12 and serving as fluid flow paths are formed as shown in FIG. 1 and a peripheral wall 4 disposed so as to surround the outer periphery of the partition wall 3 that defines the cell 2.

  In the method for manufacturing a honeycomb structure of the present embodiment, a clay preparation step in which a forming raw material containing a ceramic raw material is mixed and kneaded to obtain a clay (hereinafter, sometimes referred to as “a clay preparation step (1)”) A molding step of extruding the obtained clay into a honeycomb shape to obtain a honeycomb molded body (hereinafter sometimes referred to as “molding step (2)”), and drying the obtained honeycomb molded body, A firing step (hereinafter, referred to as “firing step (3)” is performed by firing to obtain a honeycomb structure having porous partition walls that form a plurality of cells serving as fluid flow paths and outer walls disposed so as to surround the partition walls. ) ”, And in the above-described clay preparation step (1), a clay having an extrusion stress of 25 MPa or less at the time of extrusion molding in a state in which the rheometer hardness is adjusted to 2.0 kgf. To be prepared. In the method for manufacturing a honeycomb structure of the present embodiment, such a clay is subjected to extrusion molding in a state where the rheometer hardness is 2.0 kgf or more and the extrusion stress is 25 MPa or less. A molded body is produced.

  In the conventional method for manufacturing a honeycomb structure, the extrusion stress during extrusion molding is reduced, in other words, the fluidity of the clay is improved to improve the moldability. As a result, the honeycomb formed body obtained is too soft and is likely to be deformed, for example, by its own weight, especially when manufacturing a large honeycomb structure. It was significantly reduced. That is, in the case of obtaining a honeycomb formed body by extrusion forming a molding clay, it is necessary to adjust the hardness (rheometer hardness) of the clay so that the extrusion stress at the time of extrusion molding is 25 MPa or less, for example. Since the clay prepared by the conventional manufacturing method has an extrusion stress of 25 MPa or less, the hardness (rheometer hardness) of the clay is extremely low (soft). The hardness was also low.

  The method for manufacturing a honeycomb structure according to the present embodiment uses a clay that has a rheometer hardness of a certain value (2.0 kgf) or more, and that can make the extrusion stress 25 MPa or less. By forming, the honeycomb structure can be manufactured with high dimensional accuracy. In particular, even when manufacturing a large honeycomb structure having a large size, the honeycomb molded body obtained by extrusion molding is not easily deformed, so that high dimensional accuracy can be maintained even after drying and firing. it can. That is, the extrusion stress at the time of extrusion molding can be reduced, and the honeycomb formed body obtained by molding can be made excellent in shape retention while maintaining good moldability. For this reason, a honeycomb structure with high roundness can be easily and inexpensively manufactured without grinding the outer peripheral portion and disposing the outer peripheral coat layer, which has been performed by the conventional method for manufacturing a honeycomb structure. can do.

  In addition, rheometer hardness (kgf) is taken as the average value of the first peak of the load measured by conducting the penetration test of 4 places about the extruded clay of thickness 50mm. The plunger used for the penetration test is a circle with a diameter of 3 mm, and the penetration speed is 20 mm / min. Such rheometer hardness can be measured by “FUDOH rheometer RT-2008D • D (trade name)” manufactured by Rheotech.

  Moreover, the extrusion stress at the time of extrusion molding is a value measured by a method based on JIS K7199. That is, the extrusion pressure (extrusion load) applied to the clay when the clay is extruded from the slit die by the cylinder at a constant volume flow rate is measured. More specifically, the inner diameter of the cylinder through which the clay is extruded is 25 mm in diameter, the cross-sectional shape of the slit die is 0.1 × 2.5 mm, the cylinder is filled with the cylinder, and the cylinder piston is moved at a speed of 1 mm / min. Then, the thin plate is extruded from the exit of the slit die. The value of the pressure sensor attached to the piston tip at this time is defined as the extrusion pressure. According to the above method, the formability of a part (partition wall) of the honeycomb formed body obtained by extrusion molding can be modeled, and the fluidity can be evaluated. In addition, it means that the fluidity | liquidity of a clay is so good that extrusion stress is low. The said measurement can be performed by "Autograph AG-5000A (brand name)" by Shimadzu Corporation.

  In addition, the clay that satisfies the rheometer hardness and extrusion stress described above is the type of ceramic raw material, the particle size, the particle size distribution, and the other contained in the forming raw material to be included in the forming raw material used for preparing the clay. It can be prepared by appropriately selecting the kind of additive.

  In addition, if the clay is such that the rheometer hardness of the obtained honeycomb formed body is less than 2.0 kgf, the shape retention of the obtained honeycomb formed body is lowered, and the obtained honeycomb formed body is easily deformed. End up. For this reason, the honeycomb formed body is deformed during the drying and firing processes, and the dimensional accuracy of the obtained honeycomb structure is lowered.

  Further, if the clay is such that the extrusion stress at the time of extrusion molding exceeds 25 MPa, the fluidity of the clay is remarkably lowered, and extrusion molding may become difficult or defective molding may occur.

  The clay prepared in the clay preparation step (1) preferably has a rheometer hardness of 2 kgf or more, preferably 2.0 to 2.2 kgf. Thereby, the rheometer hardness of the obtained honeycomb molded body can be 2.0 kgf or more, and a molded body excellent in shape retention can be obtained.

  Moreover, this clay is preferably prepared so that the extrusion stress during extrusion molding is 25 MPa or less, and is preferably prepared so as to be 18 to 25 MPa.

  Hereinafter, the method for manufacturing a honeycomb structured body of the present embodiment will be described more specifically for each step.

[1-1] Clay preparation step (1):
First, in the method for manufacturing a honeycomb structure of the present embodiment, the extrusion stress at the time of extrusion molding in a state where the rheometer hardness is adjusted to 2.0 kgf is mixed with a molding raw material containing a ceramic raw material and kneaded. The following kneaded clay is prepared (kneaded material preparing step (1)).

  More specifically, for example, a binder, a surfactant, water or the like is added to the ceramic raw material to obtain a forming raw material. Examples of the ceramic raw material include kaolin, talc, calcined kaolin, alumina, aluminum hydroxide, and silica. In particular, a ceramic material containing at least two or more inorganic raw materials selected from the group consisting of kaolin, talc, calcined kaolin, alumina, aluminum hydroxide, and silica in a proportion that will give a chemical composition of cordierite is a preferred example. Can be mentioned.

  In the present invention, the term “kaolin” simply refers to kaolin produced as a mineral (also referred to as raw kaolin). On the other hand, “calcined kaolin” refers to the above-described raw kaolin calcined at a predetermined temperature, for example, 1000 to 1100 ° C.

  In the method for manufacturing a honeycomb structure of the present embodiment, as the ceramic raw material, a ceramic raw material in which the proportion of particles of 1 μm or less in the particle size distribution is 20% by volume or more and the proportion of particles of 10 μm or more is 30% by volume or more. Is preferably used. By comprising in this way, the honeycomb molded body obtained by extrusion molding becomes difficult to deform, and high dimensional accuracy can be maintained even after drying and firing. For example, if the ratio of particles of 1 μm or less in the particle size distribution is less than 20% by volume, the bearing effect cannot be produced because there are few fine particles, and the fluidity may not be improved. If it is less than 30% by volume, there are too many fine particles, so that the particles may aggregate and the fluidity may not be improved. The bearing effect refers to an effect that the entire particles are easy to flow when the fine particles are present around the coarse particles.

  In addition, the ratio of the particle | grains of each particle diameter in the above-mentioned particle size distribution produces the graph which shows the particle size distribution of a particle diameter (micrometer) on a horizontal axis, and a ratio (volume%) on a vertical axis | shaft, for example, The ratio (volume%) can be read.

Further, as ceramic raw materials, kaolin particles having an average particle diameter of 1 μm or less and a BET specific surface area of 17 m ² / g or more, and kaolin having an average particle diameter of 5 μm or more and a BET specific surface area of 7 m ² / g or less. It is preferable to use at least particles. By comprising in this way, a bearing effect can be produced by the combination of particle size large and small, fluidity | liquidity can be improved, and the moisture content required for clay preparation can be reduced. For example, when the average particle diameter of kaolin particles is 1 μm or less and the BET specific surface area is less than 17 m ² / g, fine particles do not exist densely around the coarse particles, and thus the fluidity may not be improved. When the average particle diameter is 5 μm or more and the BET specific surface area exceeds 7 m ² / g, the interaction with the fine particles is not generated and the fluidity may not be improved.

  Such kaolin particles having a specific average particle diameter and BET specific surface area are preferably contained in the ceramic raw material in an amount of 2 to 40% by mass, and more preferably 20 to 35% by mass. When the content of such kaolin particles is less than 2% by mass, the extrusion stress is unlikely to be 25 MPa or less. On the other hand, when the content exceeds 40% by mass, cracks (cracks) occur when the honeycomb formed body is fired. Sometimes.

  The above average particle diameter is the median diameter value of the particle size distribution measured with a laser diffraction / scattering particle size distribution measuring apparatus.

  The BET specific surface area can be measured by, for example, a BET specific surface area measuring instrument using the BET flow method as a measurement principle. As a specific measuring method, for example, a sample (for example, ceramic particles) is placed in an adsorption cell, and after the gas molecules adsorbed on the sample surface are removed by evacuating the inside of the cell while heating, Measure the mass. Next, nitrogen gas is passed through the adsorption cell in which the sample from which the gas molecules have been removed is enclosed. As a result, when nitrogen is adsorbed on the sample surface and the flow rate of the inflowing gas is further increased, gas molecules form a plurality of layers on the sample surface. Here, the above process is plotted as a change in adsorption amount with respect to a change in pressure, and a graph is created. From the obtained graph, the adsorption amount of the gas molecules adsorbed only on the sample surface is obtained from the BET adsorption isotherm. Since the adsorption occupation area of nitrogen molecules is known in advance, the surface area of the sample can be calculated from the amount of adsorption of gas molecules.

In the method for manufacturing a honeycomb structured body of the present embodiment, it is preferable to use at least talc particles having an average particle diameter of 25 μm or more and a BET specific surface area of 2 m ² / g or less as the ceramic raw material. By comprising in this way, the bearing effect by microparticles | fine-particles can be produced, fluidity | liquidity can be improved, and the moisture content required for clay preparation can be reduced. For example, when the average particle diameter of the talc particles is 25 μm or more and the BET specific surface area exceeds 2 m ² / g, the interaction with the particles is not generated and the fluidity may not be improved.

  Such talc particles having a predetermined average particle diameter and BET specific surface area are preferably contained in the ceramic raw material in an amount of 1 to 30% by mass, and more preferably 20 to 25% by mass. When the content of such talc particles is less than 1% by mass, the extruding load stress is unlikely to be 25 MPa or less. On the other hand, when the content exceeds 30% by mass, the proportion of coarse particles increases, and the honeycomb formed body ( Alternatively, defects may occur in the partition walls constituting the fired honeycomb structure. Such talc particles are more preferably used in combination with the kaolin particles described above. By using the talc particles and kaolin particles in combination, the fluidity can be greatly improved by the interaction between the coarse particles and the fine particles.

  Moreover, it is preferable to use at least calcined kaolin and raw kaolin as the ceramic raw material, and the ratio of the amount of the calcined kaolin used to the amount of the raw kaolin used is 25/75 to 75/25 in terms of mass. . With this configuration, the honeycomb structure can be manufactured with higher dimensional accuracy and high yield. The ratio of the amount of the calcined kaolin used is more preferably 40/60 to 60/40. The raw kaolin is particularly preferably kaolin particles having the specific average particle diameter and BET specific surface area described above. If the ratio of the amount of calcined kaolin used is less than 25/75, the moldability of the clay may be difficult to improve, while the ratio of the amount of calcined kaolin used is more than 75/25, When the honeycomb formed body is fired, cracks may occur.

  By using the ceramic raw material described above as the ceramic raw material, a clay having a rheometer hardness of 2.0 kgf or more and an extrusion stress of 25 MPa or less at the time of extrusion molding can be well prepared.

  The water used for preparing the kneaded material is preferably 15 to 28% by mass, more preferably 18 to 22% by mass, based on the entire forming raw material. In addition, the amount of this water can determine the optimal mixing | blending ratio from the said range in consideration of the kind of ceramic raw material to be used, the value of rheometer hardness, and an extrusion stress.

  Moreover, in this clay preparation process (1), it is preferable to contain 0.1-2 mass% of water-absorbing polymers in a shaping | molding raw material, and it is still more preferable to contain 0.4-2 mass%. With this configuration, the honeycomb structure can be manufactured with higher dimensional accuracy and high yield. If the water-absorbing polymer content is less than 0.1% by mass, the moldability of the clay may be difficult to improve. On the other hand, if the water-absorbing polymer content exceeds 2% by mass, There is a need to increase the ratio of water required when preparing the soil, and the honeycomb formed body may not be sufficiently dried.

  As a water-absorbing polymer, for example, a water-absorbing polymer having a particle shape and an average particle diameter after water absorption of 2 to 200 μm can be mentioned as a suitable example. A water-absorbing polymer (for example, a water-absorbing resin) having a water absorption ratio of 15 to 20 times and an average particle diameter after water absorption of 10 to 30 μm can be used more suitably. Specific examples of the water-absorbing polymer include acrylic resins having the above characteristics.

  As described above, when a water-absorbing polymer having an average particle diameter after water absorption of 10 to 30 μm is used as the water-absorbing polymer, the thermal shock resistance of the resulting honeycomb structure can be improved. This is presumably because the resulting honeycomb structure has many 10 to 30 μm pores due to the 10 to 30 μm water-absorbing polymer, which alleviates the crack growth of thermal shock. For example, when the water-absorbing polymer has an average particle diameter after water absorption of less than 10 μm, the pores formed in the honeycomb structure also become smaller and the average pore diameter also becomes smaller. On the other hand, if the average particle diameter of the water-absorbing polymer after water absorption exceeds 30 μm, the pores formed in the honeycomb structure may become large and the strength may be lowered.

  The water-absorbing polymer used in the method for manufacturing a honeycomb structure of the present embodiment is a structure in which water is absorbed when mixed and kneaded with water together with a ceramic raw material and an organic binder, and moisture is retained in the polymer. It means a polymer having high strength and resistance to crushing. Since the water-absorbing polymer and the ceramic raw material are granulated when mixed and kneaded, the plasticity of the clay can be improved. In such a state, when forming the honeycomb formed body by extruding the kneaded material, the cross-section pressure bonding of the kneaded material extruded from the extrusion die (die) is sufficiently performed, so that the generation of defects can be suppressed. it can. In addition, the intersection pressure bonding refers to a bonding phenomenon of the clay that flows from the grooves in the four directions on the left, right, and top of the extrusion mold and merges at one point when the clay is extruded from the extrusion mold.

  As such a water-absorbing polymer, for example, a water-absorbing resin described in International Publication No. 2005/063360 pamphlet can be suitably used.

  When such a water-absorbing polymer is used, the honeycomb structure can be manufactured with higher dimensional accuracy by using in combination with the ceramic raw material having the specific average particle diameter or BET specific surface area described above. It becomes.

  Moreover, you may contain 1-4 mass% of (meth) acrylic-acid type polymers in a shaping | molding raw material. The (meth) acrylic acid polymer is more preferably contained in an amount of 2 to 4% by mass. With this configuration, the honeycomb structure can be manufactured with higher dimensional accuracy and high yield. If the content of the (meth) acrylic acid polymer is less than 1% by mass, the moldability of the clay may be difficult to improve, while the content of the (meth) acrylic acid polymer is 4% by mass. Even if it exceeds%, further improvement in formability may not be observed.

  The (meth) acrylic acid-based polymer described above is a polymer containing a structural unit derived from (meth) acrylic acid (salt) and a vinyl monomer represented by the following general formula (1).

R ¹ —O— (AO—) _p X (1)
(In the general formula (1), R ¹ is a (meth) acryloyl group, AO is an oxyalkylene group having 2 to 4 carbon atoms, X is hydrogen or an alkyl group having 1 to 12 carbon atoms, and p is 1 It is an integer of ~ 200.)

  In addition, as (meth) acrylic acid (salt), well-known (meth) acrylic acid (salt) can be used. Salts include alkali metal salts, alkaline earth metal salts, ammonium salts, organic amine salts and the like. These may be a mixture of two or more. In the present specification, “(meth) acryl” refers to acryl and methacryl. That is, “(meth) acrylic acid” means “acrylic acid and / or methacrylic acid”, and “acrylic acid (salt)” means “acrylic acid and / or acrylate”.

  Of the known (meth) acrylic acid (salt), from the viewpoint of extrusion moldability, (meth) acrylic acid, (meth) acrylic acid alkali metal salt, (meth) acrylic acid ammonium salt, (meth) acrylic acid organic Amine salts, more preferred are (meth) acrylic acid, (meth) acrylic acid sodium salt, (meth) acrylic acid ammonium salt, (meth) acrylic acid organic amine salt, most preferred are methacrylic acid, ammonium methacrylate salt, A preferred example is a methacrylic acid organic amine salt.

In the general formula (1), R ¹ is preferably a methacryloyl group. Thereby, the moldability at the time of extrusion molding can be improved.

  In the general formula (1), AO is preferably an oxyethylene group or an oxypropylene group, and more preferably an oxyethylene group. By comprising in this way, a moldability can be further improved at the time of extrusion molding.

  In the general formula (1), when p is 2 or more, the plurality of oxyalkylene groups (AO) having 2 to 4 carbon atoms may be the same or different. When a plurality of types of oxyalkylene groups are mixed, the bonding form may be any of a block form, a random form, and a mixture thereof.

  P in the general formula (1) is preferably an integer of 9 to 190, more preferably an integer of 21 to 150, and particularly preferably an integer of 30 to 100. By comprising in this way, a moldability can be further improved at the time of extrusion molding.

  Examples of X in the general formula (1) include linear alkyl groups having 1 to 12 carbon atoms and branched alkyl groups having 3 to 12 carbon atoms. As the linear alkyl group, a methyl group, an ethyl group, an n-butyl group, an n-hexyl group, an n-octyl group, an n-decyl group, an n-undecyl group, an n-dodecyl group, and the like are preferable. Is preferably an isopropyl group, a t-butyl group, a 2-ethylhexyl group, an isodecyl group, an isododecyl group, or the like. Among these, a linear alkyl group is more preferable, and a methyl group, an ethyl group, an n-butyl group, an n-hexyl group, and an n-octyl group are particularly preferable. By comprising in this way, the moldability at the time of extrusion molding can further be improved.

  Examples of the vinyl monomer represented by the general formula (1) include alkyl polyoxyalkylene (meth) acrylate and polyoxyalkylene glycol mono (meth) acrylate.

  The weight average molecular weight (Mw) of the (meth) acrylic acid polymer is preferably 42,000 to 240,000, and more preferably 50,000 to 150,000. The weight average molecular weight (Mw) of the above (meth) acrylic acid polymer is a weight average molecular weight determined by gel permeation chromatography (GPC) method (standard substance: polyethylene glycol). When the weight average molecular weight is less than 42,000, the viscosity is lowered and the fluidity is improved. However, the shape retention may be lowered, and when the weight average molecular weight exceeds 240,000, the viscosity is increased. Although shape retention is improved, fluidity may be reduced.

  The (meth) acrylic acid polymer is preferably a 40% water-soluble polymer. By comprising in this way, the moldability at the time of extrusion molding can further be improved. The “40% water-soluble polymer” refers to an aqueous solution containing 40% by mass of a polymer.

  As such a (meth) acrylic acid polymer, for example, a vinyl polymer (vinyl polymer (P)) described in JP 2008-137829 A can be suitably used.

  When such a (meth) acrylic acid polymer is used, a honeycomb structure can be produced with higher dimensional accuracy by using in combination with the above-mentioned ceramic raw material having a specific average particle diameter or BET specific surface area. It becomes possible to do.

  Such molding raw materials are mixed and kneaded to prepare a clay. There is no restriction | limiting in particular as a method of knead | mixing a shaping | molding raw material and preparing a clay, For example, the method of using a kneader, a vacuum clay kneader, etc. can be mentioned.

[1-2] Molding step (2):
Next, in the method for manufacturing a honeycomb structure of the present embodiment, the obtained clay is extruded into a honeycomb shape to obtain a honeycomb formed body (forming step (2)).

  There is no restriction | limiting in particular about the method of extruding a kneaded material, It can carry out according to the shaping | molding method performed in the manufacturing method of a conventionally well-known honeycomb structure. For example, a method of forming a honeycomb formed body by extrusion molding using a die having a desired cell shape, partition wall thickness, and cell density can be cited as a suitable example. As the material of the die, a cemented carbide which does not easily wear is preferable.

  The partition wall thickness of the formed honeycomb body is preferably 0.05 to 0.45 mm after firing, and more preferably 0.06 to 0.43 mm after firing. If it is thinner than 0.05 mm, the strength of the resulting honeycomb structure may be reduced. If it is thicker than 0.45 mm, when the honeycomb structure is used as a filter such as DPF, the exhaust gas passes through the cell. The pressure loss may increase.

The cell density of a cross section perpendicular to the central axis of the honeycomb formed body is preferably 8-155 cells / cm ^2, more preferably from 16 to 140 cells / cm ^2. If it is less than 8 cells / cm ² , the strength of the resulting honeycomb structure may be reduced. If it is greater than 155 cells / cm ² , the exhaust gas is not contained in the cell when the honeycomb structure is used as a filter such as a DPF. Pressure loss when passing through may increase.

  The cell shape of the honeycomb formed body is not particularly limited, but in a cross section perpendicular to the central axis, it is preferably a polygon such as a triangle, a quadrangle, a pentagon, a hexagon, a circle, or an ellipse, and other irregular shapes. There may be.

  Further, the outer shape of the honeycomb formed body is not particularly limited, and examples thereof include a cylindrical shape of a bottom surface such as a cylindrical shape, an elliptical cylindrical shape, and a rectangular cylindrical shape, and a cylindrical shape having an indefinite bottom shape. Further, the size of the honeycomb formed body is not particularly limited, but the length in the central axis direction is preferably 100 to 360 mm. For example, when the honeycomb molded body has a cylindrical outer shape, the diameter of the end face is preferably 40 to 360 mm. The method for manufacturing a honeycomb structure of the present embodiment is particularly effective as a method for manufacturing a honeycomb structure having a relatively large size, that is, a columnar honeycomb structure having an end face diameter of 229 mm or more.

  In the conventional method for manufacturing a honeycomb structure, it is difficult to manufacture a cylindrical honeycomb structure having an end face diameter of 229 mm or more with high dimensional accuracy, and the partition wall and the outer peripheral wall are integrated to manufacture the honeycomb structure. However, when the roundness of the outer peripheral portion is reduced and used in a DPF or the like, the outer peripheral portion must be ground and peeled off once, and an outer peripheral coat layer must be separately provided on the outer peripheral portion. It was. In the method for manufacturing a honeycomb structure of the present embodiment, the roundness of a cylindrical honeycomb structure having an end face diameter of 229 mm or more can be suppressed to 1 mm or less. The “roundness” refers to a value obtained by subtracting the minimum outer diameter (mm) from the maximum outer diameter (mm) of the honeycomb structure obtained by firing.

[1-3] Firing step (3):
Next, the obtained honeycomb molded body is dried and fired to form a honeycomb structure having a porous partition wall for partitioning a plurality of cells serving as a fluid flow path, and an outer wall disposed so as to surround the partition wall A body is obtained (firing step (3)).

  There is no restriction | limiting in particular about the method of drying, For example, well-known drying methods, such as hot air drying, microwave drying, dielectric drying, reduced pressure drying, vacuum drying, freeze-drying, can be used. Especially, the drying method which combined hot air drying and microwave drying or dielectric drying is preferable at the point which can dry the whole honeycomb molded object rapidly and uniformly.

  In the firing step (3), it is preferable to calcine before firing the dried honeycomb formed body. The “calcination” means an operation for burning and removing organic substances (organic binder, dispersant, pore former, etc.) in the honeycomb formed body. In general, since the combustion temperature of the organic binder is about 100 to 300 ° C, the calcining temperature may be about 200 to 500 ° C. Although there is no restriction | limiting in particular as a calcination time, Usually, it is about 10 to 100 hours.

  After performing drying and calcination as described above as necessary, the honeycomb formed body is fired (also referred to as main firing) to produce a honeycomb structure.

  In the present invention, “firing” means an operation for sintering and densifying the honeycomb formed body obtained by extruding the kneaded clay to ensure a predetermined strength. Here, “sintering the honeycomb formed body” means sintering the forming raw material contained in the honeycomb formed body. For example, the firing temperature is preferably 1400 to 1440 ° C, and more preferably 1410 to 1430 ° C. Moreover, it can also be set as one baking by performing calcination and main baking continuously.

  As described above, according to the method for manufacturing a honeycomb structure of the present embodiment, a honeycomb structure as shown in FIG. 1 can be manufactured with high dimensional accuracy.

  In the method for manufacturing a honeycomb structure of the present embodiment, plugging is performed on the opening of the cell of the honeycomb structure, and one end and the other end of the cell are alternately plugged. A plugged honeycomb structure can also be manufactured. The method for plugging the openings of the cells of the honeycomb structure is not particularly limited. For example, a mask is disposed in one opening of a predetermined cell, and the plugging slurry is applied to the openings of the remaining cells. A filling method can be mentioned. By drying and firing the plugged slurry thus filled, a honeycomb structure in which the cell openings are plugged can be manufactured. The plugging method described above can be performed in accordance with a plugging method performed by a conventionally known method for manufacturing a honeycomb structure.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. Various evaluations and measurements in the examples were performed by the following methods.

[1] Rheometer hardness (kgf):
About the 50 mm-thick extrusion forming clay, a penetration test was conducted at four locations using “FUDOH Rheometer RT-2008D • D (trade name)” manufactured by Rheotech Co., Ltd., and the load was measured. The value of the first peak of each measured load was determined, and the average value of these values was defined as rheometer hardness (kgf). The plunger was a circle with a diameter of 3 mm, and the penetration speed was 20 mm / min.

[2] Extrusion stress (MPa):
It was measured by “Autograph AG-5000A (trade name)” manufactured by Shimadzu Corporation by a method based on JIS K7199. The inner diameter of the cylinder through which the clay is extruded is 25 mm in diameter, the cross-sectional shape of the slit die is 0.1 × 2.5 mm, and the cylinder piston is pushed at a speed of 1 mm / min, and the clay is made into a thin plate from the outlet of the slit die. The value of the pressure sensor attached to the piston tip at the time of extrusion was measured as extrusion stress (MPa).

[3] Roundness (mm):
A value obtained by subtracting the minimum outer diameter (mm) from the maximum outer diameter (mm) of the obtained honeycomb structure (maximum outer diameter−minimum outer diameter (mm)) was measured to obtain the roundness of the honeycomb structure. A honeycomb structure having a roundness of 1 mm or less was considered to have good roundness.

[4] Dryability:
The molded body was dried with a dielectric dryer for 20 minutes, and whether or not the outer wall was crushed when the molded body was gripped by hand was evaluated according to the following criteria.
○: No crushing and good drying properties.
Δ: Not crushed by normal force, but may be crushed when firmly grasped.
X: It will be crushed when grabbed with normal force.

[5] Bulkhead defect:
A molded body was prepared, dried, and visually checked for the presence or absence of partition wall defects in the cross section, and evaluated according to the following criteria.
○: No partition wall defect was confirmed.
Δ: No partition wall defect was confirmed, but deformation of the partition wall was confirmed.
X: Separation of partition walls was confirmed.

[6] Firing crack:
The presence or absence of cracks when the honeycomb structure was fired was visually evaluated according to the following criteria. In addition, it fired on two conditions of 40 hours and 60 hours, and evaluated each honeycomb structure.
○: No crack.
Δ: Continuous cracks within 5 cells.
X: There are continuous cracks of 6 cells or more.

[7] Particle size of ceramic material:
The particle size of each component (particle) constituting the ceramic material was measured with a laser diffraction / scattering particle size distribution measuring apparatus (“LA-920” (trade name) manufactured by Horiba, Ltd.). The particle diameter of each component (particle) was the median diameter (50% diameter) of the particle size distribution.

[8] BET specific surface area of ceramic material:
The BET specific surface area of each component (particle) constituting the ceramic material was measured with a BET specific surface area measuring device (“Macsorb HM model-1208” (trade name) manufactured by Mounttech).

[9] Coefficient of thermal expansion (× 10 ⁻⁶ / ° C.):
Car standards established by the Japan Automobile Engineers Association Standards Council: Measurements were made in accordance with the method described in the test method (JASO M 505-87) for ceramic monolith carriers for automobile exhaust gas purification catalysts. The thermal expansion coefficient is a value measured in the central axis direction of the honeycomb structure.

[10] Porosity (%):
The total pore volume was measured by the method described in “JASO Automotive Standard Automotive Exhaust Gas Purification Catalyst Ceramic Monolith Carrier Test Method M505-87 6.3”, and from the total pore volume obtained, the cordierite true The porosity (%) was calculated with a specific gravity of 2.52 g / cm ³ .

[11] Average pore diameter (μm):
The median pore diameter was measured by the method described in “JASO Automotive Standard Automotive Exhaust Gas Purification Catalyst Ceramic Monolith Carrier Test Method M505-87 6.3”, and the obtained median pore diameter was determined as the average pore diameter (μm). did.

[12] Thermal shock resistance (° C):
The honeycomb structure is heated for 30 minutes in an electric furnace set to a predetermined temperature, the heated honeycomb structure is taken out from the electric furnace to a room temperature of 25 ° C., and the occurrence of cracks on the outer periphery of the taken-out honeycomb structure is visually observed. Confirmed. The temperature of the electric furnace was increased from 650 ° C. to 50 ° C., and when the electric furnace was taken out to room temperature from the electric furnace, the highest temperature at which no cracks were formed on the outer periphery was defined as the thermal shock resistance temperature.

[13] Isostatic strength (MPa):
The honeycomb structure was inserted into a rubber tube having the same diameter as that of the honeycomb structure, an equal pressure was applied by water pressure, and the pressure (MPa) at which partial fracture occurred was measured. In each example, 10 honeycomb structures were produced, the pressure was measured on the 10 honeycomb structures, and the average value of the obtained measured values was defined as isostatic strength.

Example 1
First, a cordierite forming raw material having a cordierite theoretical composition (2MgO · 2Al ₂ O ₃ · 5SiO ₂ ) was prepared as a forming raw material containing a ceramic material. Specifically, kaolin, talc, and other cordierite forming raw materials are selected so that SiO ₂ is 42 to 56 mass%, Al ₂ O ₃ is 30 to 45 mass%, and MgO is 12 to 16 mass%. Each raw material was mixed to prepare a cordierite forming raw material. In Example 1, as kaolin, as shown in Table 1, kaolin A (particle diameter 5.8 μm, BET specific surface area 6.5 m ² / g) 3 mass%, kaolin B (particle diameter 0.5 μm, BET ratio) Surface area 17.5 m ² / g) 8% by mass, as shown in Table 2, talc A (particle diameter 8 μm, BET specific surface area 8.3 m ² / g) 15% by mass, talc B (particle diameter 10.9 μm, BET (Specific surface area 5.2 m ² / g) 24 mass%, calcined kaolin 33 mass%, alumina 11 mass%, aluminum hydroxide 5 mass%, and silica 1 mass% were mixed to prepare a cordierite forming raw material. Table 3 shows the formulation of the cordierite forming raw material. Table 1 shows the particle diameter and BET specific surface area of kaolin used in each example, and Table 2 shows the particle diameter and BET specific surface area of talc used in each example.

  With respect to 100 parts by mass of such a cordierite forming raw material (ceramic raw material), the dispersion medium (water) is 25 to 30 parts by mass, the surfactant is 2 parts by mass, and the molding aid is 0.05 to 5 parts by mass. The added forming raw material was mixed and kneaded to obtain a clay that was plasticized so as to be extruded. A kneader was used for preparing the kneaded material. As shown in Table 4, the ratio of particles of 1 μm or less in the particle size distribution of the cordierite forming raw material (ceramic raw material) was 22% by volume, and the ratio of particles of 10 μm or more was 32% by volume. Moreover, the ratio (calcined kaolin / raw kaolin) of the usage-amount of calcined kaolin with respect to raw kaolin (kaolin A and B) was 75/25.

  The kneaded material thus obtained was extruded to produce a cylindrical honeycomb molded body having an end face diameter of 229 mm and a height of 300 mm. Moreover, the extrusion stress (MPa) in a state where the rheometer hardness (kgf) of the obtained clay was 2.0 kgf was measured according to the method described above. Table 5 shows the measurement results. In Example 1, the rheometer hardness of the clay actually subjected to extrusion molding is 2.0 kgf. In addition, the extrusion stress (MPa) at 2.0 kgf was prepared by changing the rheometer hardness of the clay to prepare three types of clay, measuring the extrusion stress in each clay, and obtaining the extrusion stress and rheology obtained. It calculated from the relational expression (linear formula) with meter hardness.

Next, the obtained honeycomb formed body was dried and then fired to manufacture a honeycomb structure. The drying was performed for 20 minutes in a dielectric dryer, and the baking was held at a maximum temperature of 1430 ° C. for 5 to 15 hours, and the baking was performed for a total of 40 to 60 hours. Moreover, in each manufacturing process, the dryness mentioned above, the defect | deletion of a partition, and the baking crack were evaluated. The results are shown in Table 5. The honeycomb structure obtained by firing had a partition wall thickness of 0.165 mm and a cell density of 62 cells / cm ² .

(Examples 2 to 19)
As the ceramic raw material, kaolin A and B shown in Table 1 and talc A to D shown in Table 2 were used, except that the clay was prepared using each forming raw material so as to have the formulation shown in Table 3. A honeycomb structure was produced by the same method as in Example 1. The extrusion stress (MPa) in a state where the rheometer hardness (kgf) of the obtained clay is 2.0 kgf is measured according to the method described above, and in each manufacturing process, drying properties, partition wall defects, and Evaluation of firing cracks was performed. The evaluation results are shown in Table 5. In Examples 2 to 19 as well, the rheometer hardness of the clay that was actually extruded was 2.0 kgf.

  In Examples 9 to 19, a water-absorbing polymer was added in the amount shown in Table 3 to the forming raw material. This water-absorbing polymer was a particulate polyacrylic ammonium salt having a water absorption ratio of 15 to 20 times and a particle diameter after water absorption of 10 to 30 μm.

  Furthermore, in Examples 16 to 19, the methacrylic acid polymer was added to the forming raw material in the amount shown in Table 3. This methacrylic acid polymer is a polymer having an ammonium methacrylate salt in the main chain and a weight average molecular weight (Mw) of 45,000. In addition, said Mw is the weight average molecular weight by a gel permeation chromatography (GPC) method (standard substance: polyethyleneglycol).

(Comparative Examples 1-7)
As the ceramic raw material, kaolins A to C shown in Table 1 and talc A to D shown in Table 2 were used, except that the kneaded material was prepared using each forming raw material so as to have the compounding recipe shown in Table 6. A honeycomb structure was produced by the same method as in Example 1. The extrusion stress (MPa) in a state where the rheometer hardness (kgf) of the obtained clay is 2.0 kgf is measured according to the method described above, and in each manufacturing process, drying properties, partition wall defects, and Evaluation of firing cracks was performed. Table 7 shows the evaluation results. In addition, when actually extruding using the clay in Comparative Examples 1 to 5, a dispersion medium was added and the one prepared to have an extrusion stress of 25 MPa was used. The rheometer hardness (kgf) of the clay was 1.4 kgf.

(Discussion 1)
As shown in Table 6 and Table 7, the manufacturing methods of Examples 1 to 19 can prepare clay with an extrusion stress of 25 MPa or less in a state where the rheometer hardness is adjusted to 2.0 kgf. It was possible to extrude the clay well. Further, the roundness of the obtained honeycomb structure was 1 mm or less, and high dimensional accuracy could be maintained even after the drying and firing processes. Regarding the drying property, in Example 14, the amount of the prepared water was large and drying was somewhat insufficient, but in all other cases, good results could be obtained. Moreover, about the defect | deletion of a partition, since many coarse particles were used in Example 3, a part of particle | grains might be clogged in a shaping | molding metal mold | die, and the other could have obtained a favorable result. . In addition, with regard to firing cracks, Examples 2, 7, and 8 have a large amount of raw kaolin (80 or more), so some firing cracks occurred due to shrinkage due to moisture dehydration in the raw kaolin. Could get. In addition, Examples 2, 7, and 8 were also improved by increasing the firing time, and good results could be obtained.

  On the other hand, in the production methods of Comparative Examples 1 to 7, the extruding load of the clay in a state adjusted so that the rheometer hardness becomes 2.0 kgf exceeds 25 MPa. And the extrusion was formed with the hardness of the clay low (soft). For this reason, the rheometer hardness of the clays of Comparative Examples 1 to 7 during actual molding was less than 2.0 kgf, and the rheometer hardness of the honeycomb molded body was also less than 2.0 kgf accordingly. For this reason, distortion occurred in the honeycomb molded body, and the roundness of the honeycomb structure exceeded 1 mm as the final product.

(Examples 20 to 23)
Except for using a water-absorbing polymer having an average particle size (average particle size after water absorption) shown in Table 8 and using a clay constructed in the same manner as in Example 18, the extrusion die was changed. A honeycomb structure was manufactured in the same manner as in Example 18. The obtained honeycomb structure had a fired size of 110 mm in diameter, 100 mm in height, 0.064 mm in partition wall thickness, and a cell density of 62 cells / cm ² . In each manufacturing process, the above-described drying properties, partition wall defects, and firing cracks were evaluated. Further, the roundness, porosity, average pore diameter, thermal expansion coefficient, thermal shock resistance, and isostatic strength of the obtained honeycomb structure were measured. The results are shown in Table 8.

(Comparative Example 8)
A honeycomb structure was manufactured in the same manner as in Example 20 except that the clay having the same configuration as that of the clay used in Comparative Example 6 was used. In each manufacturing process, the above-described drying properties, partition wall defects, and firing cracks were evaluated. Further, the roundness, porosity, average pore diameter, thermal expansion coefficient, thermal shock resistance, and isostatic strength of the obtained honeycomb structure were measured. The results are shown in Table 8.

(Discussion 2)
As shown in Table 8, the manufacturing method of Examples 20 to 23 was a perfect circle even when a honeycomb structure with a partition wall thickness of 0.064 mm and a cell density of 62 cells / cm ² and a high aperture ratio was manufactured. The degree was less than 1 mm and high dimensional accuracy could be maintained. Further, the honeycomb structure obtained in Example 20 had a thermal shock resistance of 800 ° C. and was extremely excellent in thermal shock resistance. This is presumably due to the fact that the addition of a water-absorbing polymer having a particle diameter of 10 to 30 μm after water absorption resulted in the formation of a large number of 10 to 30 μm pores in the honeycomb structure and the relaxation of thermal shock cracks. Is done.

  On the other hand, in the manufacturing method of Comparative Example 8, distortion occurred in the honeycomb molded body, and the roundness of the honeycomb structure exceeded 1 mm as the final product. Since the cell was deformed, the isostatic strength was as small as 0.3 MPa. In addition, since no water-absorbing polymer having a predetermined particle size was added, the average pore size of the obtained honeycomb structure was reduced and the thermal shock resistance was also reduced by about 100 ° C. compared to Example 20. Met.

  In Example 22 using a water-absorbing polymer having an average particle diameter of 8 μm after water absorption, the improvement in thermal shock resistance was as small as 50 ° C. Further, in Example 23 using the water-absorbing polymer having an average particle diameter of 40 μm after water absorption, the isostatic strength is slightly low at 0.5 MPa, and it may not be possible to obtain sufficient strength in actual use. It turns out that there is sex.

  The method for manufacturing a honeycomb structure according to the present invention is applied to a filter for purifying exhaust gas discharged from various internal combustion engines, such as diesel engines, ordinary automobile engines, engines for large automobiles such as trucks and buses, and various combustion apparatuses. It can be suitably used as a method for producing a honeycomb structure to be used. In particular, the method for manufacturing a honeycomb structure of the present invention can manufacture a large honeycomb structure having a large size with high dimensional accuracy.

1: honeycomb structure, 2: cell, 3: partition, 4: outer peripheral wall, 11: one end face, 12: the other end face.

Claims (10)

A clay preparation step of mixing a kneading raw material containing ceramic raw materials and kneading to obtain a clay;
A molding step of extruding the obtained clay into a honeycomb shape to obtain a honeycomb molded body; and
The honeycomb formed body is dried and fired to form a honeycomb structure having porous partition walls that define a plurality of cells serving as fluid flow paths, and an outer wall disposed so as to surround the partition walls. A firing step to obtain
A method for manufacturing a honeycomb structure in which the clay is prepared so that an extrusion stress is 25 MPa or less during extrusion molding in a state where the rheometer hardness is adjusted to 2.0 kgf in the clay preparation step.   2. The honeycomb structure according to claim 1, wherein the ceramic raw material is a ceramic raw material having a particle size distribution of 1 μm or less in a particle size distribution of 20% by volume or more and 10 μm or more in a particle size distribution of 30% by volume or more. Method. As the ceramic raw material, kaolin particles having an average particle diameter of 1 μm or less and a BET specific surface area of 17 m ² / g or more, and kaolin particles having an average particle diameter of 5 μm or more and a BET specific surface area of 7 m ² / g or less The method for manufacturing a honeycomb structured body according to claim 1 or 2, wherein at least the above is used.   The method for manufacturing a honeycomb structured body according to claim 3, wherein the kaolin particles are contained in the ceramic raw material in an amount of 2 to 40 mass%. The method for manufacturing a honeycomb structured body according to any one of claims 1 to 4, wherein at least talc particles having an average particle diameter of 25 µm or more and a BET specific surface area of 2 m ² / g or less are used as the ceramic raw material.   The manufacturing method of the honeycomb structure according to claim 5, wherein the talc particles are contained in the ceramic raw material in an amount of 1 to 30% by mass.   The calcined kaolin and raw kaolin are used as the ceramic raw material, and the ratio of the amount of the calcined kaolin used to the amount of the raw kaolin used is 25/75 to 75/25 in terms of mass. The method for manufacturing a honeycomb structure according to any one of claims 6 to 10.   The method for manufacturing a honeycomb structure according to any one of claims 1 to 7, wherein the forming raw material contains 0.1 to 2% by mass of a water-absorbing polymer.   The method for manufacturing a honeycomb structured body according to any one of claims 1 to 8, wherein 1 to 4% by mass of a (meth) acrylic acid polymer is contained in the forming raw material. A method of manufacturing a cylindrical honeycomb structure having an end face diameter of 229 mm or more,
The method for manufacturing a honeycomb structure according to any one of claims 1 to 9, wherein the roundness of the outer peripheral portion is manufactured to 1 mm or less without grinding the outer peripheral portion of the honeycomb structure.

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