Columnar honeycomb structure and method for manufacturing the same

Abstract

To suppress deterioration of mechanical strength of a columnar honeycomb structure containing a sintering aid and cordierite as a main component.SOLUTION: Provided is a columnar honeycomb structure that has a first cell and a second cell alternately arranged adjacent to each other with a partition wall therebetween, and sealing portions. The structure contains cordierite as a main component and one or more of sintering aids selected from ceria, zirconia, and titania, wherein when an average porosity of a portion in a range B from the deepest portion of the sealing portion of the first bottom face in the extending direction of the second cells to the first bottom face in a region of the partition wall in a range A from the deepest portion of the sealing portion of a second bottom face in an extending direction of the first cell to the second bottom face is defined as P1 (%), and when an average porosity of a portion of the partition wall in a range C from the deepest portion of the sealing portion of the second bottom face in the extending direction of the first cell to the deepest portion of the sealing portion of the first bottom face in the extending direction of the second cell is P2 (%), the relationship -4≤P1-P2≤7 is satisfied.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a columnar honeycomb structure and a method for manufacturing the same.

Background Art

[0002] Exhaust gas discharged from internal combustion engines such as diesel engines contains a large amount of particulate matter (PM) mainly composed of carbon, which causes environmental pollution. Therefore, generally, an exhaust system of a diesel engine or the like is equipped with a filter (Diesel Particulate Filter: DPF) for collecting particulate matter. In recent years, particulate matter discharged from gasoline engines has also been regarded as a problem, and gasoline engines are also being equipped with filters (Gasoline Particulate Filter: GPF).

[0003] As a filter, there is known a wall-flow type columnar honeycomb structure in which an outer peripheral side wall, a plurality of first cells arranged on the inner peripheral side of the outer peripheral side wall, extending from a first bottom surface to a second bottom surface, the first bottom surface being open and having a blind seal portion on the second bottom surface, and a plurality of second cells arranged on the inner peripheral side of the outer peripheral side wall, extending from the first bottom surface to the second bottom surface, having a blind seal portion on the first bottom surface, and the second bottom surface being open, are alternately and adjacently arranged with a partition wall interposed therebetween.

[0004] Patent Document 1 describes an invention aimed at providing a honeycomb filter capable of suppressing an increase in pressure loss, having a large maximum soot deposition amount, and achieving high durability. The honeycomb filter includes a cylindrical honeycomb structure having a porous partition wall that forms a plurality of cells extending from one end face, which serves as a fluid flow path, to the other end face, and blind seal portions disposed at one open end of a predetermined one of the cells and the other open end of the remaining cells. The porosity of the partition wall is 46% or less, and the permeability of the honeycomb structure is 0.8 μm 2The above conditions are met, and the pore volume fraction of pores with a diameter of 40 μm or more is 7.5% or less, and the pore volume fraction of pores with a diameter of 10 μm or less is 25% or less, and the thermal expansion coefficient of the honeycomb structure at 40°C to 800°C is 1.0 × 10⁻⁶. -6 It has the characteristic of being below / ℃.

[0005] Furthermore, Patent Document 1 describes a structure in which the partition wall is made of a porous material mainly composed of cordierite. The partition wall contains at least one selected from the group consisting of cerium oxide, zirconium oxide, and yttrium oxide, wherein the content of cerium oxide is 3.0% by mass or less, the content of zirconium oxide is 2.5% by mass or less, and the content of yttrium oxide is 2.0% by mass or less. Patent Document 1 states that by configuring it in this way, it is possible to suppress the formation of pores unrelated to gas permeability and to produce a honeycomb structure with low porosity while maintaining permeability. It also states that when the porosity of the honeycomb structure is reduced, the heat capacity of the honeycomb filter increases, which improves the durability of the honeycomb filter and can improve the maximum amount of soot deposited. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] International Publication No. 2013 / 047908 [Overview of the project] [Problems that the invention aims to solve]

[0007] As described in Patent Document 1, adding a small amount of ceria (cerium oxide) or the like to a honeycomb filter mainly composed of cordierite is advantageous in suppressing the formation of pores unrelated to gas permeability and in producing a low-porosity honeycomb structure while maintaining permeability. However, the honeycomb filter described in Patent Document 1 does not have sufficient strength because the pore sealing portion is not fired, and the pore sealing portion is easily damaged by ash or the like during use. Furthermore, there is a risk that the pore sealing portion may detach if strong pressure is applied.

[0008] On the other hand, it was found that even if the sealing portion was fired, honeycomb filters mainly composed of cordierite with sintering aids such as cerium oxide added did not have sufficient mechanical strength. For this reason, it was difficult to adopt a high porosity in honeycomb filters with sintering aids such as cerium oxide added.

[0009] The present invention has been made in view of the above circumstances, and in one embodiment, aims to suppress the decrease in mechanical strength of a columnar honeycomb structure containing a sintering aid and mainly composed of cordierite. In another embodiment, the present invention aims to provide a method for manufacturing a columnar honeycomb structure with improved mechanical strength. [Means for solving the problem]

[0010] The inventors of this invention diligently investigated the above problem and found that during firing, the sintering aid moves from the partition wall to the pore sealing area, causing a localized increase in the porosity of the partition wall near the pore sealing area, resulting in a decrease in strength. The sintering aid gathers towards the small pores due to capillary action and seals them, but it also moves to the pore sealing material in the process. Furthermore, because the sintering aid has the effect of sealing pores, more pore-forming material than usual is used to maintain porosity, and it was found that the partition wall in the area where the sintering aid has been removed has an even higher porosity.

[0011] As a result of discovering this phenomenon, the inventors concluded that suppressing the migration of the sintering aid from the partition wall to the sealing area and thereby suppressing the increase in porosity of the partition wall near the sealing area would lead to suppressing the decrease in mechanical strength, and found that adding the sintering aid to the sealing area is also effective. The present invention was completed based on this finding and is illustrated below.

[0012] [Aspect 1] A columnar honeycomb structure comprising an outer peripheral wall, a plurality of first cells arranged on the inner peripheral side of the outer peripheral wall, extending from a first bottom surface to a second bottom surface, having an opening on the first bottom surface and a sealing portion on the second bottom surface, and a plurality of second cells arranged on the inner peripheral side of the outer peripheral wall, extending from a first bottom surface to a second bottom surface, having a sealing portion on the first bottom surface and an opening on the second bottom surface, wherein the plurality of first cells and the plurality of second cells are arranged alternately adjacent to each other with a partition wall in between, The outer periphery, side walls, partitions, and seals are fired, and the main component is cordierite, along with one or more sintering aids selected from ceria, zirconia, and titania. Of the partition walls, the average porosity of the portion in area A from the deepest point in the direction in which the first cell of the sealing portion of the second bottom surface extends to the second bottom surface, and the average porosity of the portion in area B from the deepest point in the direction in which the second cell of the sealing portion of the first bottom surface extends to the first bottom surface, is defined as P1 (%). If P2 (%) is the average porosity of the portion C in the partition wall, from the deepest point in the direction in which the first cell of the sealing portion of the second bottom surface extends to the deepest point in the direction in which the second cell of the sealing portion of the first bottom surface extends, then -4 ≤ P1 - P2 ≤ 7. Columnar honeycomb structure. [Aspect 2] A columnar honeycomb structure according to embodiment 1, satisfying -2 ≤ P1 - P2 ≤ 5. [Aspect 3] A columnar honeycomb structure according to embodiment 1 or 2 that satisfies 55 ≤ P2 ≤ 70. [Aspect 4] A columnar honeycomb structure according to any of embodiments 1 to 3, wherein S1 (%) is the average total content of one or more sintering aids selected from ceria, zirconia, and titania in the parts of the partition wall in range A and in the parts of range B, and S2 (%) is the average total content of one or more sintering aids selected from ceria, zirconia, and titania in the parts of the partition wall in range C, and D50 (μm) is the cumulative 50% pore diameter of the partition wall in the volume-based cumulative pore diameter distribution measured by the mercury intrusion method, such that (S2-S1) / D50 × 100 ≤ 6. [Aspect 5] The columnar honeycomb structure described in any of embodiments 1 to 4, wherein the portion of the partition wall in range C satisfies the relationship (D90-D10) / D50≦1.2 in the volume-based cumulative pore diameter distribution measured by the mercury intrusion method, where the cumulative 10% pore diameter (D10), cumulative 50% pore diameter (D50), and cumulative 90% pore diameter (D90) from the small pore side. [Aspect 6] A method for manufacturing a columnar honeycomb structure comprising an outer peripheral wall, a plurality of first cells arranged on the inner peripheral side of the outer peripheral wall, extending from a first bottom surface to a second bottom surface, having an opening on the first bottom surface and a sealing portion on the second bottom surface, and a plurality of second cells arranged on the inner peripheral side of the outer peripheral wall, extending from a first bottom surface to a second bottom surface, having a sealing portion on the first bottom surface and an opening on the second bottom surface, wherein the plurality of first cells and the plurality of second cells are arranged alternately adjacent to each other with a partition wall in between, A process to obtain a columnar honeycomb molded body having an outer peripheral wall and a columnar honeycomb molded body that is positioned on the inner periphery of the outer peripheral wall, extending from the first bottom surface to the second bottom surface, and having openings on both the first and second bottom surfaces, by kneading a raw material composition containing a cordierite material, a dispersion medium, a pore-forming material, and a binder, in addition to one or more sintering aids selected from ceria, zirconia, and titania, and then extruding the said clay to obtain a columnar honeycomb molded body, After drying the columnar honeycomb molded body, a step is to fill the openings on the first and second bottom surfaces where the sealing portions are to be formed with a slurry for forming sealing portions, which contains a cordierite raw material, a dispersion medium, a pore-forming material, and a binder, as well as one or more sintering aids selected from ceria, zirconia, and titania. A step of firing the columnar honeycomb formed body filled with the slurry for forming the eye-sealing part; including; Regarding the sintering aid in the raw material composition, when the total addition amount per 100 parts by mass of the cordierite-forming raw material is C1 parts by mass, and regarding the sintering aid in the slurry for forming the eye-sealing part, when the total addition amount per 100 parts by mass of the cordierite-forming raw material is C2 parts by mass, -8 ≦ C1 - C2 ≦ 1 is satisfied. Manufacturing method. [Aspect 7] The manufacturing method according to Aspect 6, which satisfies -6 ≦ C1 - C2 ≦ 0. [Aspect 8] The manufacturing method according to Aspect 6 or 7, which satisfies 1 ≦ C2 ≦ 10. [Aspect 9] For both the sintering aid in the raw material composition and the sintering aid in the slurry for forming the eye-sealing part, the median diameter (D50) in the volume-based cumulative particle size distribution determined by the laser diffraction / scattering method is 0.1 to 10 μm. The manufacturing method according to any one of Aspects 6 to 8. [Effects of the Invention]

[0013] According to one embodiment of the present invention, it is possible to suppress a decrease in the mechanical strength of a columnar honeycomb structure body containing a sintering aid such as ceria and having cordierite as a main component. Thereby, for example, even if the porosity of the partition wall is increased to achieve further low pressure loss, it is possible to secure the mechanical strength required for the product. In addition, by adding a sintering aid such as ceria, the pore size distribution can be sharpened, in other words, pores with high uniformity of pore size can be obtained. A sharp pore size distribution is considered to be advantageous in improving the balance between low pressure loss and collection performance. [Brief Description of the Drawings]

[0014] [Figure 1] It is a perspective view schematically showing a wall flow type columnar honeycomb structure body. [Figure 2] It is a schematic cross-sectional view when the wall flow type columnar honeycomb structure body is observed from a cross-section parallel to the extending direction of the cells. [Figure 3] This is an example of a porosity profile when the porosity (%) is measured along the thickness direction D of the partition wall from one surface to the other. [Figure 4] This is a conceptual diagram illustrating a method for identifying the position of one surface of a partition wall on a cross-sectional image. [Figure 5] This is a schematic magnified view of the area near the sealing portion when the partition wall of a columnar honeycomb structure is observed in a cross-section parallel to the direction in which the cells extend. [Figure 6] This is a schematic magnified view of a section of a columnar honeycomb structure, observed in a cross-section perpendicular to the direction in which the cells extend. [Figure 7] This is a schematic diagram illustrating an example of a method for forming an eye seal using a squeegee. [Modes for carrying out the invention]

[0015] Next, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following embodiments, and it should be understood that appropriate design changes, improvements, etc., can be made based on the ordinary knowledge of those skilled in the art, without departing from the spirit of the invention.

[0016] (1. Columnar honeycomb structure) Figures 1 and 2 illustrate schematic perspective and cross-sectional views, respectively, of a columnar honeycomb structure 100 applicable as a wall-flow type automotive exhaust gas filter and / or catalyst carrier. This columnar honeycomb structure 100 comprises an outer peripheral wall 102, a plurality of first cells 108 arranged on the inner peripheral side of the outer peripheral wall 102, extending parallel from a first bottom surface 104 to a second bottom surface 106, with the first bottom surface 104 being open and the second bottom surface 106 having a sealing portion 109, and a plurality of second cells 110 arranged on the inner peripheral side of the outer peripheral wall 102, extending parallel from a first bottom surface 104 to a second bottom surface 106, with the first bottom surface 104 having a sealing portion 109 and the second bottom surface 106 being open. In this columnar honeycomb structure 100, the first cells 108 and the second cells 110 are arranged alternately adjacent to each other with a partition wall 112 in between.

[0017] For example, when exhaust gas containing particulate matter such as soot is supplied to the first bottom surface 104 on the upstream side of the columnar honeycomb structure 100, the exhaust gas is introduced into the first cell 108 and proceeds downstream within the first cell 108. Since the second bottom surface 106 on the downstream side of the first cell 108 is sealed, the exhaust gas permeates through the porous partition wall 112 that separates the first cell 108 and the second cell 110 and flows into the second cell 110. Since the particulate matter cannot pass through the partition wall 112, it is collected and deposited within the first cell 108. After the particulate matter is removed, the clean exhaust gas that has flowed into the second cell 110 proceeds downstream within the second cell 110 and flows out from the second bottom surface 106 on the downstream side.

[0018] There are no restrictions on the shape of the base of the columnar honeycomb structure 100, but it can be a round shape such as a circle, ellipse, racetrack shape, or oval shape, a polygonal shape such as a triangle or square shape, or other irregular shapes. The columnar honeycomb structure 100 shown in the figure has a circular base and is cylindrical overall.

[0019] There are no particular restrictions on the height of the columnar honeycomb structure (length from the first base to the second base), and it can be set appropriately according to the application and required performance. For example, the height of the columnar honeycomb structure can be 40 mm to 450 mm. There are also no particular restrictions on the relationship between the height of the columnar honeycomb structure and the maximum diameter of each base (referring to the maximum length of the diameter passing through the centroid of each base of the columnar honeycomb structure). Therefore, the height of the columnar honeycomb structure may be longer than the maximum diameter of each base, or shorter than the maximum diameter of each base.

[0020] The outer periphery side walls, partitions, and sealing portions of the columnar honeycomb structure are fired and each contains cordierite as its main component. This means that the total mass percentage of cordierite (2MgO·2Al2O3·5SiO2) in 100% by mass of the material constituting each of the outer periphery side walls, partitions, and sealing portions is 50% by mass or more. Preferably, the mass percentage of cordierite in 100% by mass of the material constituting each of the outer periphery side walls, partitions, and sealing portions is 70% by mass or more, and more preferably 80% by mass or more. The mass percentage of cordierite is measured by X-ray diffraction (XRD).

[0021] From the viewpoint of sharpening the pore size distribution, the outer peripheral side walls and partitions of the columnar honeycomb structure preferably contain one or more sintering aids selected from ceria, zirconia, and titania, and more preferably contain at least ceria. Furthermore, from the viewpoint of suppressing a decrease in mechanical strength, the pore sealing portion of the columnar honeycomb structure preferably contains one or more sintering aids selected from ceria, zirconia, and titania, and more preferably contain at least ceria.

[0022] When the partition wall contains one or more sintering aids selected from ceria, zirconia, and titania, it is desirable that the difference between the porosity (%) near the sealed portion of the partition wall and the porosity (%) at a location away from the sealed portion of the partition wall be small in order to suppress a decrease in the mechanical strength of the columnar honeycomb structure. Specifically, it is preferable that P1-P2≦7 be satisfied, more preferable that P1-P2≦5 be satisfied, and even more preferable that P1-P2≦4 be satisfied. The advantage is that the decrease in the mechanical strength of the columnar honeycomb structure is suppressed by having an upper limit of P1-P2 of 7 or less. However, if P1-P2 is made too small, the disadvantage of a decrease in the mechanical strength of the honeycomb structure due to the difference in rigidity may occur, so it is preferable that -4≦P1-P2 be satisfied, more preferable that -2≦P1-P2 be satisfied, and even more preferable that 0≦P1-P2 be satisfied. Therefore, for example, it is preferable that -4 ≤ P1 - P2 ≤ 7 be satisfied, more preferably that -2 ≤ P1 - P2 ≤ 5 be satisfied, and even more preferably that 0 ≤ P1 - P2 ≤ 3 be satisfied.

[0023] P1 refers to the average porosity (%) of the portion of the partition wall 112, specifically the portion in range A from the deepest part in the direction in which the first cell 108 of the sealing portion 109 of the second bottom surface 106 extends to the second bottom surface 106, and the portion in range B from the deepest part in the direction in which the second cell 110 of the sealing portion 109 of the first bottom surface 104 extends to the first bottom surface 104. P2 refers to the average porosity (%) of the portion in range C of the partition wall 112, from the deepest part in the direction in which the first cell 108 of the sealing portion 109 of the second bottom surface 106 extends to the deepest part in the direction in which the second cell 110 of the sealing portion 109 of the first bottom surface 104 extends.

[0024] From the viewpoint of achieving low pressure loss, it is preferable that P2 satisfies 55 ≤ P2, more preferably 57 ≤ P2, and even more preferably 59 ≤ P2. Furthermore, from the viewpoint of ensuring mechanical strength, it is preferable that P2 ≤ 70, more preferably 57 ≤ P2 ≤ 68, and even more preferably 59 ≤ P2 ≤ 66. Therefore, for example, it is preferable that 55 ≤ P2 ≤ 70, more preferably 57 ≤ P2 ≤ 68, and even more preferably 59 ≤ P2 ≤ 66.

[0025] P1 and P2 are measured using the following procedure. First, the measurement procedure for P2 is described. Three samples of the septum (cross section size (length 20 mm × width 2 mm) × depth 0.3 mm) are taken from the septum area in the above range C, without bias, and with the cross section exposed parallel to the direction in which the cells extend. Next, the corresponding cross section of each sample is observed with an X-ray microscope and CT scanned. The obtained 3D cross section image is then binarized based on brightness to separate it into numerous voxels (a cube with a size of one voxel = length in the wall direction (Y direction) of the septum: 0.8 μm, length in the thickness direction (X direction) of the septum: 0.8 μm, and length in the depth direction (Z direction) of the septum: 0.8 μm) into a spatial part and a solid part. The measurement conditions for the X-ray microscope are a magnification of 4x. The binarization process will be performed using Otsu's binarization method.

[0026] Next, for a predetermined region of any one partition wall on the 3D cross-sectional image (length in the wall direction (Y direction): 340 μm, length in the thickness direction (X direction): encompassing the entire thickness and having at least 50 μm of space on each side of the partition wall, length in the depth direction (Z direction): 300 μm), a porosity (%) profile is obtained at 0.8 μm intervals along the thickness direction (X direction) of the partition wall from one surface to the other, based on binarized voxel data (see Figure 3). The porosity of a 0.8 μm thickness is calculated for a 0.8 μm thickness region (length in the wall direction (Y direction): 340 μm, length in the thickness direction (X direction): 0.8 μm, length in the depth direction (Z direction): 300 μm) according to the formula: porosity = (number of voxels in the space) / (total number of voxels in the region) × 100 (%). By performing this calculation at 0.8 μm intervals from the left edge of the screen across the entire predetermined region, a profile of porosity (%) is obtained at 0.8 μm intervals along the thickness direction (X direction) of the partition wall from one surface to the other.

[0027] In this case, the position of one surface of the partition wall is determined as the position of the mode of the distance M measured in the thickness direction D (X direction) from a line segment parallel to the wall surface direction of the partition wall to the surface of the partition wall being measured, as shown in Figure 4. This distance M is measured at 0.8 μm intervals over a length of 340 μm in the wall surface direction of the partition wall (Y direction perpendicular to the thickness direction (X direction)) on the binarized image. The position of the other surface of the partition wall is determined in the same manner.

[0028] In this way, a porosity profile of any one septum is obtained from each sample, and the average porosity of that septum is determined from that profile. Then, the average value of the three septum samples in the range C is taken as the average porosity P2 (%).

[0029] Next, the measurement procedure for P1 will be described. Six samples are taken in total, three from each of the septum locations in the above-mentioned ranges A and B, with cross-sections exposed parallel to the direction of cell extension (cross-sectional size (20 mm long x 2 mm wide) x 0.3 mm deep). Then, using the same method as for P2 measurement, the relevant cross-sections of each sample are observed with an X-ray microscope and CT scanned. The resulting 3D cross-sectional images are then binarized based on brightness to separate them into numerous voxels consisting of spatial and physical parts.

[0030] Next, for a predetermined region of any one partition wall on the 3D cross-sectional image (length in the wall direction (Y direction): 340 μm, length in the thickness direction (X direction): encompassing the entire thickness and having at least 50 μm of space on each side of the partition wall, length in the depth direction (Z direction): 300 μm), a porosity (%) profile is obtained at 0.8 μm intervals along the thickness direction (X direction) of the partition wall from one surface to the other, based on binarized voxel data, using the same method as for measuring P2. However, in the above ranges A and B, one surface 112a of the partition wall is adjacent to the cell space, while the other surface 112b is adjacent to the eye seal portion 109. It is difficult to determine the boundary between the eye seal portion 109 and the partition wall 112. Therefore, the position of the surface 112c of the partition wall 112 in the area C where the eye sealing portion 109 of the other surface 112b of the partition wall 112 is not adjacent is identified by the method described above, and a straight line L is drawn along the surface 112c to define the boundary with the eye sealing portion. Figure 5 shows a schematic partial enlargement view of the vicinity of the eye sealing portion when the partition wall of the columnar honeycomb structure is observed in a cross section parallel to the direction in which the cells extend.

[0031] In this way, a porosity profile of any one septum is obtained from each sample, and the average porosity of that septum is determined from that profile. Then, the average value of the six septum samples in ranges A and B is taken as the average porosity P1 (%).

[0032] In a columnar honeycomb structure mainly composed of cordierite and containing the above-mentioned sintering aid, in order to suppress the decrease in mechanical strength, it is advantageous to suppress the migration of the sintering aid from the partition walls to the pore sealing areas and to suppress the local decrease in porosity near the pore sealing areas of the partition walls. Since the migration of the sintering aid is thought to be due to the difference in the concentration of the sintering aid between the pore sealing areas and the partition walls, it can be suppressed by adding the same amount of sintering aid to the pore sealing areas as to the partition walls, preferably in a larger amount than the partition walls. It is preferable to appropriately set this concentration difference according to the cumulative 50% pore diameter (D50) of the partition walls, as described later.

[0033] Specifically, it is preferable that the following relationship is satisfied between the average value S1 (%) of the total content of one or more sintering aids selected from ceria, zirconia, and titania near the pore sealing portion of the partition wall, the average value S2 (%) of the total content of the sintering aids at locations away from the pore sealing portion of the partition wall, and the cumulative 50% pore diameter (D50) (μm) of the partition wall. Specifically, it is preferable that (S2-S1) / D50×100≦6, more preferably (S2-S1) / D50×100≦4, and even more preferably (S2-S1) / D50×100≦2. The advantage is obtained that the reduction in the mechanical strength of the columnar honeycomb structure is suppressed by having the upper limit of (S2-S1) / D50×100 be 6 or less. There is no specific lower limit set for (S2-S1) / D50×100, but if it is made too small the effect of suppressing the decrease in mechanical strength saturates. On the other hand, considering the range of S2 shown below, it is common to satisfy -6≦(S2-S1) / D50×100, typically -4≦(S2-S1) / D50×100, and more typically -2≦(S2-S1) / D50×100. Therefore, for example, it is preferable to satisfy -6≦(S2-S1) / D50×100≦6, more preferably -4≦(S2-S1) / D50×100≦4, and even more preferably -2≦(S2-S1) / D50×100≦2.

[0034] S1 refers to the average value (%) of the total content of one or more sintering aids selected from ceria, zirconia, and titania in the portion of the partition wall 112 from the deepest part in the direction in which the first cell 108 of the sealing portion 109 of the second bottom surface 106 extends to the second bottom surface 106 (area A), and in the portion of the first bottom surface 104 from the deepest part in the direction in which the second cell 110 of the sealing portion 109 of the first bottom surface 104 (area B). S2 refers to the average value (%) of the total content of one or more sintering aids selected from ceria, zirconia, and titania in the area C of the partition wall 112, from the deepest part in the direction in which the first cell 108 of the sealing portion 109 of the second bottom surface 106 extends to the deepest part in the direction in which the second cell 110 of the sealing portion 109 of the first bottom surface 104 extends.

[0035] From the viewpoint of sharpening the pore size distribution, it is preferable that 1 ≤ S2, more preferably that 2 ≤ S2, and even more preferably that 3 ≤ S2. Also, from the viewpoint of suppressing a decrease in the melting point of the septa, it is preferable that S2 ≤ 10, more preferably that S2 ≤ 8, and even more preferably that S2 ≤ 6. Therefore, for example, it is preferable that 1 ≤ S2 ≤ 10, more preferably that 2 ≤ S2 ≤ 8, and even more preferably that 3 ≤ S2 ≤ 6.

[0036] Furthermore, from the viewpoint of suppressing the movement of sintering aids from the partitions to the sealing portion, the sealing portion of the columnar honeycomb structure preferably contains one or more sintering aids selected from ceria, zirconia, and titania, and more preferably contains at least ceria. If the average value of the total content of one or more sintering aids selected from ceria, zirconia, and titania in the sealing portion is S3 (%), then from the viewpoint of suppressing the movement of sintering aids from the partitions to the sealing portion, it is preferable that 1 ≤ S3, more preferably 2 ≤ S3, and even more preferably 3 ≤ S3. Furthermore, from the viewpoint of suppressing a decrease in the melting point of the sealing portion, it is preferable that S3 ≤ 10, more preferably S3 ≤ 8, and even more preferably S3 ≤ 6. Therefore, for example, it is preferable that 1 ≤ S3 ≤ 10, more preferably 2 ≤ S3 ≤ 8, and even more preferably 3 ≤ S3 ≤ 6.

[0037] The total content of sintering aids is measured by an energy-dispersive X-ray spectrometer (EDS) mounted on a scanning electron microscope (SEM). Specifically, a sample (size: 15mm × 15mm × 15mm) is taken from the measurement points of the outer peripheral sidewall, partition wall, and eye seal, exposing a cross-section parallel to the direction of cell extension. The polished surface, obtained by mirror polishing the cross-section with a diamond slurry, is used as the observation sample. This polished surface is observed and elementally mapped by SEM-EDS analysis at 200x magnification (field of view size: 700μm × 700μm). The area of ​​the solid portion excluding the spatial portion on the SEM image is set to 100%, and the area occupied by Ce is determined by image analysis; this is considered the ceria content. Similarly, the area of ​​the solid portion excluding the spatial portion on the SEM image is set to 100%, and the area occupied by Zr is determined by image analysis; this is considered the zirconia content. Excluding the voids on the screen, the area of ​​the solid material is considered 100%, and the area occupied by Ti is determined by image analysis; this is then considered the titania content.

[0038] The method for measuring S1 will now be explained. Using the method described above, two samples each of the septums in ranges A and B, where the cross-section parallel to the direction of cell extension is exposed, are taken without bias, for a total of four samples, and observation samples are prepared from each. Elemental mapping is performed on each observation sample using the SEM-EDS analysis described above, and the total content of one or more sintering aids selected from ceria, zirconia, and titania is determined. The average value of the total content across all observation samples is then defined as S1 (%).

[0039] The method for measuring S2 is described below. Using the method described above, two septum samples are taken from the septum area within range C, ensuring that the cross-section is exposed parallel to the direction of cell extension without bias, and observation samples are prepared from each sample. Elemental mapping is performed on each observation sample using the SEM-EDS analysis described above, and the total content of one or more sintering aids selected from ceria, zirconia, and titania is determined. The average value of the total content across all observation samples is then defined as S2 (%).

[0040] The method for measuring S3 is described below. Using the method described above, two samples each are taken from the seal area near the first and second base surfaces, ensuring that the cross-section is exposed parallel to the direction in which the cell extends, without bias. A total of four samples are taken from these samples and observation samples are prepared. Elemental mapping is performed on each observation sample using the SEM-EDS analysis described above, and the total content of one or more sintering aids selected from ceria, zirconia, and titania is determined. The average value of the total content across all observation samples is then defined as S3 (%).

[0041] In a columnar honeycomb structure, the average thickness of the partition walls is preferably 152 μm or more, more preferably 178 μm or more, and even more preferably 203 μm or more, from the viewpoint of ensuring strength. Furthermore, from the viewpoint of suppressing pressure loss, the average thickness of the partition walls is preferably 305 μm or less, more preferably 279 μm or less, and even more preferably 254 μm or less. Figure 6 shows a schematic partial enlargement view of the partition walls 112 of the columnar honeycomb structure 100 when observed in a cross section perpendicular to the direction in which the cells extend. The thickness of the partition wall refers to the length that a line segment N crosses the partition wall when the centroids O of adjacent cells are connected by a line segment N in a cross section perpendicular to the direction in which the cells extend (the height direction of the columnar honeycomb structure). The thickness direction D of the partition wall refers to the direction parallel to the line segment N. The average thickness of the partition wall refers to the average value of the thicknesses of all partition walls.

[0042] In one embodiment, the average depth of the sealing portion of both the first and second bottom surfaces is 2 to 8 mm. The strength of the sealing portion can be ensured by having an average depth of 2 mm or more. Preferably, the average depth of the sealing portion is 3 mm or more. Furthermore, by having an average depth of 8 mm or less, it is possible to prevent the area of ​​the partition wall that collects particulate matter within the cell from becoming too small. Preferably, the average depth of the sealing portion is 7 mm or less. The depth of the sealing portion in the direction in which the cell extends is measured at 20 arbitrary locations on each bottom surface, and the average value is taken as the average depth of the sealing portion on each bottom surface.

[0043] There are no particular restrictions on the cell density (number of cells per unit cross-sectional area) of a columnar honeycomb structure; for example, 6 to 2000 cells / square inch (0.9 to 311 cells / cm²) is possible. 2 ), more preferably 50 to 1000 cells / square inch (7.8 to 155 cells / cm²). 2 ), particularly preferably 100-600 cells / square inch (15.5-92.0 cells / cm²) 2 ) can be expressed as follows. Here, the cell density is calculated by dividing the total number of cells (including sealed cells) by the area of ​​one of the bases of the columnar honeycomb structure, excluding the outer side walls.

[0044] A sharp pore size distribution in the partition wall is desirable for achieving a balance between low pressure drop and collection performance. Specifically, in the partition wall, particularly in the portion of the partition wall within range C, it is preferable that the cumulative pore size distribution based on volume, measured by the mercury intrusion method, satisfies the relationship (D90-D10) / D50≦1.2 for the cumulative 10% pore size (D10), the cumulative 50% pore size (D50), and the cumulative 90% pore size (D90) from the small pore side, more preferably (D90-D10) / D50≦1.1, and even more preferably (D90-D10) / D50≦1.0. The lower limit of (D90-D10) / D50 is 0, but from the viewpoint of ease of manufacture, it is usually satisfied with 0.5≦(D90-D10) / D50.

[0045] In this specification, the partitions D10, D50, and D90 are measured using a mercury porosimeter by the mercury intrusion method specified in JIS R1655:2003. The mercury intrusion method is a method in which a sample is immersed in mercury under vacuum, uniform pressure is applied, and mercury is injected into the sample while the pressure is gradually increased, and the pore size distribution is calculated from the pressure and the volume of mercury injected into the pores. As the pressure is gradually increased, mercury is injected into the pores in order from the largest diameter, increasing the cumulative volume of mercury, and finally, when all pores are filled with mercury, the cumulative volume reaches an equilibrium amount. The cumulative volume at this time is the total pore volume (cm³). 3 The value is ( / g). Then, the pore diameter when 10% of the total pore volume of mercury is injected from the small pore side is the cumulative 10% pore diameter (D10), the pore diameter when 50% of the total pore volume of mercury is injected from the small pore side is the cumulative 50% pore diameter (D50), and the pore diameter when 90% of the total pore volume of mercury is injected from the small pore side is the cumulative 90% pore diameter (D90).

[0046] Six samples (0.3g each) are taken from the septum within the columnar honeycomb structure, without bias, including the central and outer peripheral areas in the radial direction. The pore size distribution of each sample is measured to determine D10, D50, and D90, and the average value is taken as the measured value.

[0047] It is desirable to set the D50 of the partition wall to an appropriate range depending on the application. For example, when using a columnar honeycomb structure for filter applications, the D50 of the partition wall, particularly the portion of the partition wall in range C, is preferably 28 μm or less, more preferably 26 μm or less, and even more preferably 24 μm or less. When the D50 of the partition wall is within the above range, the collection efficiency of particulate matter is significantly improved. Furthermore, the D50 of the partition wall is preferably 5 μm or more, more preferably 6 μm or more, and even more preferably 7 μm or more. When the D50 of the partition wall is within the above range, the increase in pressure loss can be suppressed.

[0048] One measure of the mechanical strength of a columnar honeycomb structure is its isostatic fracture strength. In measuring the isostatic fracture strength of a columnar honeycomb structure, the structure is submerged in water in a pressure vessel, and the water pressure is gradually increased to apply isotropic pressure to the structure. As the water pressure in the pressure vessel gradually increases, fracture eventually occurs in the partition walls and outer side walls of the columnar honeycomb structure. The pressure value (fracture strength) at which fracture occurs is the isostatic fracture strength. Isostatic fracture strength is measured according to the automotive standard (JASO M505-87) issued by the Society of Automotive Engineers of Japan.

[0049] When applying a columnar honeycomb structure as an exhaust gas filter and / or catalyst support for automobiles, the lower limit of the isostatic fracture strength is preferably 0.5 MPa or higher, more preferably 1.0 MPa or higher, and even more preferably 1.5 MPa or higher. There is no specific upper limit set for the isostatic fracture strength, but it is usually 3.0 MPa or lower, and typically 2.5 MPa or lower.

[0050] When a columnar honeycomb structure is used as a catalyst support, a catalyst can be coated onto the surface of the partition wall according to the purpose. Examples of catalysts, though not limited to them, include oxidation catalysts (DOC) for increasing exhaust gas temperature by oxidative combustion of hydrocarbons (HC) and carbon monoxide (CO), PM combustion catalysts for assisting the combustion of PM such as soot, SCR catalysts and NSR catalysts for removing nitrogen oxides (NOx), and three-way catalysts capable of simultaneously removing hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx). The catalyst may appropriately contain, for example, noble metals (Pt, Pd, Rh, etc.), alkali metals (Li, Na, K, Cs, etc.), alkaline earth metals (Mg, Ca, Ba, Sr, etc.), rare earth metals (Ce, Sm, Gd, Nd, Y, La, Pr, etc.), transition metals (Mn, Fe, Co, Ni, Cu, Zn, Sc, Ti, Zr, V, Cr, etc.).

[0051] (2. Manufacturing method) A method for manufacturing a columnar honeycomb structure according to one embodiment of the present invention is described below as an example. First, a raw material composition containing a cordierite raw material, a dispersion medium, a pore-forming material, and a binder, in addition to one or more sintering aids selected from ceria, zirconia, and titania, is kneaded to form a clay body. Then, the clay body is extruded to obtain a columnar honeycomb molded body having an outer peripheral side wall and a columnar honeycomb molded body that is positioned on the inner circumferential side of the outer peripheral side wall, extending from a first bottom surface to a second bottom surface, with both the first and second bottom surfaces having openings. Additives such as dispersants and other ceramic raw materials may be added to the raw material composition as needed. When extruding, a die having a desired overall shape, cell shape, partition wall thickness, cell density, etc., can be used.

[0052] Corgielite-forming raw materials are raw materials that become cordierite upon calcination, and can be provided, for example, in powder form. The cordierlite-forming raw materials preferably have a chemical composition of alumina (Al2O3) (including the portion of aluminum hydroxide converted to alumina): 30-45% by mass, magnesia (MgO): 11-17% by mass, and silica (SiO2): 42-57% by mass.

[0053] From the viewpoint of sharpening the pore size distribution, the total amount of one or more sintering aids selected from ceria, zirconia, and titania added is preferably 2 parts by mass or more, more preferably 3 parts by mass or more, and even more preferably 4 parts by mass or more, per 100 parts by mass of cordierite raw material. From the viewpoint of suppressing a decrease in the melting point of the outer peripheral sidewalls and partitions, the total amount of one or more sintering aids selected from ceria, zirconia, and titania added is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 6 parts by mass or less, per 100 parts by mass of cordierite raw material.

[0054] From the viewpoint of improving compositional uniformity in the partition walls and outer side walls of the columnar honeycomb structure, the upper limit of the median diameter (D50) in the volume-based cumulative particle size distribution determined by laser diffraction and scattering is preferably 10 μm or less, more preferably 8 μm or less, and even more preferably 6 μm or less. Furthermore, from the viewpoint of preventing internal defects due to aggregation, the lower limit of the median diameter (D50) in the volume-based cumulative particle size distribution determined by laser diffraction and scattering is preferably 0.1 μm or more, more preferably 0.3 μm or more, and even more preferably 0.5 μm or more. Therefore, for example, the median diameter (D50) of the sintering aid in the raw material composition is preferably 0.1 to 10 μm, more preferably 0.3 to 8 μm, and even more preferably 0.5 to 6 μm.

[0055] Examples of dispersion media include water, or a mixed solvent of water and an organic solvent such as alcohol, but water is particularly suitable.

[0056] The content of the dispersion medium in the columnar honeycomb molded body before the drying process is preferably 20 to 110 parts by mass, more preferably 25 to 100 parts by mass, and even more preferably 30 to 90 parts by mass, per 100 parts by mass of the cordierite raw material. A dispersion medium content of 20 parts by mass or more per 100 parts by mass of the cordierite raw material offers the advantage of easily stabilizing the quality of the columnar honeycomb structure. A dispersion medium content of 90 parts by mass or less per 100 parts by mass of the cordierite raw material reduces shrinkage during drying and suppresses deformation. In this specification, the dispersion medium content of the columnar honeycomb molded body refers to the value measured by the drying loss method.

[0057] The pore-forming material is not particularly limited as long as it becomes pore after firing, and examples include wheat flour, starch, foamed resin, superabsorbent resin, silica gel, carbon (e.g., graphite), ceramic balloons, polyethylene, polystyrene, polypropylene, nylon, polyester, acrylic resin, phenol, etc. The pore-forming material may be used alone or in combination of two or more types. From the viewpoint of increasing the porosity of the columnar honeycomb structure after firing, the content of the pore-forming material is preferably 3 parts by mass or more, more preferably 6 parts by mass or more, and even more preferably 9 parts by mass or more, per 100 parts by mass of the cordierite raw material. From the viewpoint of ensuring the strength of the columnar honeycomb structure after firing, the content of the pore-forming material is preferably 30 parts by mass or less, more preferably 27 parts by mass or less, and even more preferably 24 parts by mass or less, per 100 parts by mass of the cordierite raw material.

[0058] Examples of binders include organic binders such as methylcellulose, hydroxypropoxylmethylcellulose, hydroxypropylmethylcellulose, hydroxyethylcellulose, hydroxyethylmethylcellulose, carboxymethylcellulose, and polyvinyl alcohol. Furthermore, from the viewpoint of increasing the strength of the columnar honeycomb molded body before firing, the binder content is preferably 4 parts by mass or more, more preferably 4.5 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of the cordierite raw material. From the viewpoint of suppressing cracking due to abnormal heat generation during the firing process, the binder content is preferably 9 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 7 parts by mass or less, per 100 parts by mass of the cordierite raw material. The binder may be used alone or in combination of two or more types.

[0059] Dispersants such as ethylene glycol, dextrin, fatty acid soap, and polyether polyol can be used. One type of dispersant may be used alone, or two or more types may be used in combination. The dispersant content is preferably 0 to 2 parts by mass per 100 parts by mass of cordierite raw material.

[0060] For drying columnar honeycomb molded articles, conventional drying methods such as hot air drying, microwave drying, dielectric drying, reduced pressure drying, vacuum drying, and freeze-drying can be used. Among these, a drying method combining hot air drying with microwave drying or dielectric drying is preferred because it can dry the entire columnar honeycomb molded article quickly and uniformly.

[0061] After drying the columnar honeycomb molded body, pore seals are formed on both bottom surfaces of the columnar honeycomb molded body. Each pore seal can be formed by filling the openings in the first and second cells to be formed with a pore seal forming slurry, and then drying and firing the filled slurry. In addition to the cordierite forming raw material, dispersion medium, pore-forming material, and binder, the pore seal forming slurry may contain one or more sintering aids selected from ceria, zirconia, and titania.

[0062] For example, the slurry for forming the pore seal contains 30 to 60 parts by mass of dispersion medium, 5 to 20 parts by mass of pore-forming material, and 0.2 to 2.0 parts by mass of binder, per 100 parts by mass of cordierite raw material. In a preferred embodiment, the slurry for forming the pore seal contains 35 to 50 parts by mass of dispersion medium, 8 to 16 parts by mass of pore-forming material, and 0.2 to 1.5 parts by mass of binder, per 100 parts by mass of cordierite raw material.

[0063] The total amount of one or more sintering aids selected from ceria, zirconia, and titania added to the slurry for forming the eye seals should be adjusted according to the total amount of one or more sintering aids selected from ceria, zirconia, and titania added to the raw material composition for obtaining the columnar honeycomb molded body described above. Specifically, if the total amount of sintering aids added to the raw material composition for obtaining the columnar honeycomb molded body is C1 parts by mass per 100 parts by mass of cordierite raw material, and the total amount of sintering aids added to the slurry for forming the eye seals is C2 parts by mass per 100 parts by mass of cordierite raw material, then from the viewpoint of suppressing the movement of the sintering aids from the partitions to the eye seals, it is preferable that C1-C2≦1 be satisfied, more preferably that C1-C2≦0 be satisfied, and even more preferably that C1-C2≦-1 be satisfied. However, if C1-C2 is made too small, the effect of suppressing the movement of the sintering aid from the partition wall to the sealing portion will saturate, while the melting point of the partition wall tends to decrease. Therefore, it is preferable to satisfy -8 ≤ C1-C2, more preferably -6 ≤ C1-C2, and even more preferably -4 ≤ C1-C2. Accordingly, for example, it is preferable to satisfy -8 ≤ C1-C2 ≤ 1, more preferably -6 ≤ C1-C2 ≤ 0, and even more preferably -4 ≤ C1-C2 ≤ -1.

[0064] If C1 and C2 satisfy the above relationship, there are no particular restrictions on C2 itself, but it is common for 1 ≤ C2 ≤ 10, typical for 1.5 ≤ C2 ≤ 8, and more typical for 2.0 ≤ C2 ≤ 6.

[0065] From the viewpoint of compositional uniformity, the upper limit of the median diameter (D50) in the volume-based cumulative particle size distribution determined by laser diffraction-scattering is preferably 10 μm or less, more preferably 8 μm or less, and even more preferably 6 μm or less. Furthermore, from the viewpoint of preventing internal defects due to aggregation, the lower limit of the median diameter (D50) in the volume-based cumulative particle size distribution determined by laser diffraction-scattering is preferably 0.1 μm or more, more preferably 0.3 μm or more, and even more preferably 0.5 μm or more. Therefore, for example, the median diameter (D50) of the sintering aid in the slurry for forming the sealant is preferably 0.1 to 10 μm, more preferably 0.3 to 8 μm, and even more preferably 0.5 to 6 μm.

[0066] Examples of dispersion media include water, or a mixed solvent of water and an organic solvent such as alcohol, but water is particularly suitable.

[0067] The pore-forming material is not particularly limited as long as it becomes pore-forming after firing. Examples include wheat flour, starch, foamed resin, superabsorbent resin, silica gel, carbon (e.g., graphite), ceramic balloons, polyethylene, polystyrene, polypropylene, nylon, polyester, acrylic resin, phenol, etc. The pore-forming material may be used alone or in combination of two or more types.

[0068] Examples of binders include organic binders such as methylcellulose, hydroxypropoxylmethylcellulose, hydroxypropylmethylcellulose, hydroxyethylcellulose, hydroxyethylmethylcellulose, carboxymethylcellulose, and polyvinyl alcohol. The binder may be used individually or in combination of two or more types.

[0069] The slurry for forming the sealant portion may contain a dispersant as appropriate. For example, the dispersant can be contained in an amount of 0.1 to 3 parts by mass, preferably 0.2 to 2 parts by mass, per 100 parts by mass of the cordierite raw material. Examples of dispersants include ethylene glycol, dextrin, fatty acid soap, and polyalcohol. The dispersant may be used alone or in combination of two or more types.

[0070] Filling the cell openings with slurry for forming the eye seal can be carried out, for example, by the following "squeegee method". As shown in Figure 7, a film 121 is attached to the upper bottom surface (the second bottom surface 106 in this case) of a dried columnar honeycomb molded body 600 fixed using a chuck 120, and a laser is irradiated onto the film 121 at positions corresponding to the arrangement conditions for the eye seal (for example, a "checkerboard pattern") to create a plurality of holes 126 in the film 121.

[0071] Subsequently, the slurry 124 for forming the seal portion is placed on the film 121, and the squeegee 122 is moved along the film 121 in the direction of the arrow in Figure 7. This fills the cells 125 that have opened at positions corresponding to the holes 126 in the film 121 with a certain amount of slurry 124 for forming the seal portion.

[0072] The depth of the sealing portion can be varied by the number of times the squeegee 122 is moved, the contact angle between the squeegee 122 and the film 121, the pressure the squeegee 122 applies to the film 121, and the viscosity of the slurry 124 for forming the sealing portion.

[0073] After filling with the slurry 124 for forming the pore seal, the film 121 is peeled off and the entire columnar honeycomb molded body 600 is dried. This dries the slurry 124 for forming the pore seal filled in the cell 125, forming the pore seal before firing. Drying can be carried out, for example, at a drying temperature of 100 to 230°C for about 60 to 150 seconds. After drying, the pore seal protrudes from the bottom surface of the columnar honeycomb molded body by the thickness of the film, so it can be scraped off as needed.

[0074] The material of the film is not particularly limited, but it is preferably polypropylene (PP), polyethylene terephthalate (PET), polyimide, or Teflon (registered trademark) because it is easy to heat-process to form pores. Furthermore, the film preferably has an adhesive layer, and the material of the adhesive layer is preferably an acrylic resin, a rubber-based material (for example, rubber mainly composed of natural rubber or synthetic rubber), or a silicone resin. For example, an adhesive film with a thickness of 20 to 50 μm can be suitably used.

[0075] In addition to the "squeegee method" described above, another method for filling the cell opening with the slurry for forming the sealing portion is the "press-in method." The "press-in method" involves immersing the bottom surface of a columnar honeycomb molded body, to which a film has been attached and perforated, into a liquid tank containing the slurry for forming the sealing portion, thereby filling the cell with the slurry. In this case, the depth of the sealing portion can be varied by the depth to which the columnar honeycomb molded body is immersed in the slurry for forming the sealing portion.

[0076] The columnar honeycomb molded body, filled with a slurry for forming the pore seal, then undergoes a degreasing process and a firing process to produce a columnar honeycomb structure. The combustion temperature of the binder is approximately 200°C, and the combustion temperature of the pore-forming material is approximately 300 to 1000°C. Therefore, the degreasing process can be carried out by heating the honeycomb molded body to a range of approximately 200 to 1000°C. The heating time is not particularly limited, but is usually around 10 to 100 hours. The honeycomb molded body after the degreasing process is called a calcined body. The firing process depends on the material composition of the columnar honeycomb structure, but for example, it can be carried out by heating the calcined body to 1300 to 1450°C and holding it for 3 to 24 hours. [Examples]

[0077] The following examples illustrate the present invention and its advantages, but the present invention is not limited to these examples.

[0078] <Comparative Example 1-1> (1) Fabrication of columnar honeycomb molded body A clay base was prepared by kneading a raw material composition obtained by adding 80 parts by mass of a dispersion medium, 25 parts by mass of a pore-forming material, 5 parts by mass of a binder, and 1 part by mass of a dispersant to 100 parts by mass of cordierite-forming raw material. Alumina, aluminum hydroxide, kaolin, talc, and silica were used as cordierite-forming raw materials. Water was used as the dispersion medium, water-absorbent resin and silica gel were used as pore-forming materials, methylcellulose was used as the binder, and ethylene glycol was used as the dispersant.

[0079] This clay was fed into an extrusion molding machine and extruded through a die of a predetermined shape to obtain a cylindrical columnar honeycomb molded body. The obtained columnar honeycomb molded body was dielectric dried and hot air dried, then both bottom surfaces were cut to the predetermined dimensions, and it was further hot air dried at 70°C for 2 hours.

[0080] (2) Formation of the eye sealing portion A slurry for forming the pores was prepared by mixing 100 parts by mass of cordierite raw material with 40 parts by mass of dispersion medium, 10 parts by mass of pore-forming material, 2 parts by mass of binder, and 1 part by mass of dispersant, and then kneading the mixture. Alumina, aluminum hydroxide, kaolin, talc, and silica were used as the cordierite raw material. Water was used as the dispersion medium, foamed resin as the pore-forming material, methylcellulose as the binder, and ethylene glycol as the dispersant. Using the aforementioned "squeegee method," this slurry for forming the pores was filled into both bottom surfaces so that the first and second cells were arranged alternately adjacent to each other. After that, drying was carried out under atmospheric conditions at 180°C for 200 seconds.

[0081] (3) Firing Next, the material was degreased by heating at approximately 200°C under an atmospheric atmosphere, and then fired at 1400°C for 10 hours under an atmospheric atmosphere to obtain a columnar honeycomb structure with a sealed section. The number of columnar honeycomb structures required for the following tests was manufactured.

[0082] (4) Specifications of columnar honeycomb structure The specifications of the resulting columnar honeycomb structure are as follows: Overall shape: Cylindrical shape with a diameter of 132mm and a height of 152mm. Cell shape in a cross-section perpendicular to the flow direction of the cell: square Cell density (number of cells per unit cross-sectional area): 300 cells / square inch (47 cells / cm²) 2 ) Average thickness of the partition: 8.5 mil (216 μm) (Nominal value based on the specifications of the nozzle) Average depth of the sealing area: 5mm X-ray diffraction measurements were performed on the outer periphery side walls, partitions, and pore seals of the columnar honeycomb structure using a PANalytical X'pert PRO instrument with Cu Kα radiation in the range of 2θ = 8 to 100°. Analysis of the cordierite crystal phase ratio, obtained by analyzing the data using the Rietveld analysis program RIETAN, revealed a ratio of 75 to 94 mass%.

[0083] <Comparative Examples 1-2 to 1-6, Examples 1-1 to 1-9> Three types of sintering aids were prepared: ceria, zirconia, and titania. These were in powder form, and the median diameter (D50) in the volume-based cumulative particle size distribution, determined by laser diffraction and scattering, is shown below. • Celia: 1μm Zirconia: 1 μm • Titania: 1 μm

[0084] A columnar honeycomb structure was obtained under the same manufacturing conditions as Comparative Example 1-1, except that the amount of sintering aid C1 (parts by mass) per 100 parts by mass of cordierite raw material in the raw material composition for the honeycomb molded body, and the amount of sintering aid C2 (parts by mass) per 100 parts by mass of cordierite raw material in the slurry for forming the seal portion were as shown in Table 1. The number of columnar honeycomb structures required for the following tests were manufactured.

[0085] <Comparative Example 2-1> (1) Fabrication of columnar honeycomb molded body A clay base was prepared by kneading a raw material composition obtained by adding 80 parts by mass of a dispersion medium, 25 parts by mass of a pore-forming material, 5 parts by mass of a binder, and 1 part by mass of a dispersant to 100 parts by mass of cordierite-forming raw material. Alumina, aluminum hydroxide, kaolin, talc, and silica were used as cordierite-forming raw materials. Water was used as the dispersion medium, water-absorbent resin and silica gel were used as pore-forming materials, methylcellulose was used as the binder, and ethylene glycol was used as the dispersant.

[0086] This clay was fed into an extrusion molding machine and extruded through a die of a predetermined shape to obtain a cylindrical columnar honeycomb molded body. The obtained columnar honeycomb molded body was dielectric dried and hot air dried, then both bottom surfaces were cut to the predetermined dimensions, and it was further hot air dried at 70°C for 2 hours.

[0087] (2) Formation of the eye sealing portion To 100 parts by mass of cordierite-forming raw material, 40 parts by mass of dispersion medium, 10 parts by mass of pore-forming material, 2 parts by mass of binder, and 1 part by mass of dispersant were added and kneaded to prepare a slurry for forming the pore seal. Alumina, aluminum hydroxide, kaolin, talc, and silica were used as the cordierite-forming raw material. Water was used as the dispersion medium, foamed resin as the pore-forming material, methylcellulose as the binder, and ethylene glycol as the dispersant. Using the aforementioned "squeegee method," this slurry for forming the pore seal was filled into both bottom surfaces so that the first and second cells were arranged alternately adjacent to each other.

[0088] (3) Firing Subsequently, drying was performed under atmospheric conditions at 180°C for 200 seconds. Next, degreasing was performed by heating at approximately 200°C under atmospheric conditions, and then firing at 1400°C for 10 hours under atmospheric conditions to obtain a columnar honeycomb structure with sealed sections. The number of columnar honeycomb structures required for the following tests was manufactured.

[0089] (4) Specifications of columnar honeycomb structure The specifications of the resulting columnar honeycomb structure are as follows: Overall shape: Cylindrical shape with a diameter of 132mm and a height of 152mm. Cell shape in a cross-section perpendicular to the flow direction of the cell: square Cell density (number of cells per unit cross-sectional area): 340 cells / square inch (53 cells / cm²) 2 ) Average thickness of the partition: 11 mil (279 μm) (Nominal value based on the specifications of the nozzle) Average depth of the sealing area: 5mm X-ray diffraction measurements were performed on the outer periphery side walls, partitions, and pore seals of the columnar honeycomb structure using a PANalytical X'pert PRO instrument with Cu Kα radiation in the range of 2θ = 8 to 100°. Analysis of the cordierite crystal phase ratio, obtained by analyzing the data using the Rietveld analysis program RIETAN, revealed a ratio of 75 to 94 mass%.

[0090] <Comparative Examples 2-2 to 2-6, Examples 2-1 to 2-9> Three types of sintering aids were prepared: ceria, zirconia, and titania. These were in powder form, and the median diameter (D50) in the volume-based cumulative particle size distribution, determined by laser diffraction and scattering, is shown below. • Celia: 1μm Zirconia: 1 μm • Titania: 1 μm

[0091] A columnar honeycomb structure was obtained under the same manufacturing conditions as Comparative Example 2-1, except that the amount of sintering aid C1 (parts by mass) per 100 parts by mass of cordierite raw material in the raw material composition for the honeycomb molded body, and the amount of sintering aid C2 (parts by mass) per 100 parts by mass of cordierite raw material in the slurry for forming the seal portion were as shown in Table 2. The number of columnar honeycomb structures required for the following tests were manufactured.

[0092] <Characteristic Evaluation> Various characteristics were evaluated for each of the columnar honeycomb structures obtained above.

[0093] (1. Porosity) The average porosity P1 (%) of the partition wall portion in the aforementioned ranges A and B (near the sealed portion) of the columnar honeycomb structure, and the average porosity P2 (%) of the partition wall portion in the aforementioned range C (a portion away from the sealed portion), were determined according to the method described above. Based on the measurement results, P1-P2 was calculated. The results are shown in Tables 1 and 2.

[0094] (2.SEM-EDS analysis) The average total content of sintering aids in the partition areas of the columnar honeycomb structure in the aforementioned ranges A and B (near the sealing area), S1 (%), S2 (%), S2 (%), S3

[0095] (3. Measurement of pore size distribution) The pore size distribution (D10, D50, and D90) of the septa of the columnar honeycomb structure was measured by mercury intrusion according to the method described above. Based on the measurement results, (D90-D10) / D50 was calculated. In addition, based on the results of SEM-EDS analysis, (S2-S1) / D50×100 was calculated. The results are shown in Tables 1 and 2.

[0096] (4. Measurement of isostatic fracture strength) The isostatic fracture strength of columnar honeycomb structures was measured according to the automotive standard (JASO M505-87) issued by the Society of Automotive Engineers of Japan. The results are shown in Tables 1 and 2.

[0097] [Table 1]

[0098] [Table 2]

[0099] (5. Discussion) Comparative Examples 1-1 and 2-1, which did not contain the specified sintering aid, exhibited excellent isostatic fracture strength, but had a broad pore size distribution. In contrast, Comparative Examples 1-2 to 1-7 and 2-2 to 2-7, which contained the specified sintering aid, showed a sharper pore size distribution. However, in these examples, the manufacturing conditions C1-C2 were inappropriate, resulting in a large average porosity P1 in the partition wall area near the seal, failing to satisfy -4 ≤ P1-P2 ≤ 7. Consequently, the isostatic fracture strength was significantly reduced.

[0100] On the other hand, in Examples 1-1 to 1-9 and Examples 2-1 to 2-9, the parts constituting the partition walls and outer peripheral side walls of the columnar honeycomb structure contained a predetermined sintering aid, satisfying -4 ≤ P1-P2 ≤ 7. Therefore, it was possible to sharpen the pore size distribution while suppressing the decrease in isostatic fracture strength. Furthermore, it can be seen that by optimizing P1-P2, isostatic fracture strength comparable to that of the examples before the addition of the predetermined sintering aid (Comparative Examples 1-1 and 2-1) can be obtained. [Explanation of symbols]

[0101] 100: Columnar honeycomb structure 102: Outer perimeter side wall 104: First bottom surface 106:Second bottom surface 108: Cell 1 109: Eye sealing part 110: Cell 2 112: Bulkhead 112a: surface 112b: Surface 112c: surface 120: Chuck 121: Film 122: Squeegee 124: Slurry for forming eye seals 125: Cell 126: Hole 600: Columnar honeycomb molded body

Claims

1. A columnar honeycomb structure comprising an outer peripheral wall, a plurality of first cells arranged on the inner peripheral side of the outer peripheral wall, extending from a first bottom surface to a second bottom surface, having an opening on the first bottom surface and a sealing portion on the second bottom surface, and a plurality of second cells arranged on the inner peripheral side of the outer peripheral wall, extending from a first bottom surface to a second bottom surface, having a sealing portion on the first bottom surface and an opening on the second bottom surface, wherein the plurality of first cells and the plurality of second cells are arranged alternately adjacent to each other with a partition wall in between, The outer periphery sidewalls, partitions, and sealant portions are fired and each contains cordierite as the main component and one or more sintering aids selected from ceria, zirconia, and titania. The average porosity of the portion of the partition wall, specifically the area A from the deepest point in the direction in which the first cell of the sealing portion of the second bottom surface extends to the second bottom surface, and the area B from the deepest point in the direction in which the second cell of the sealing portion of the first bottom surface extends to the first bottom surface, is P. 1 (%)year, The average porosity of the portion C within the partition wall, from the deepest point in the direction in which the first cell of the sealing portion of the second bottom surface extends to the deepest point in the direction in which the second cell of the sealing portion of the first bottom surface extends, is P. 2 (Assuming this is a percentage) 55 ≤ P² ≤ 70 and -4 ≤ P 1 -P 2 Satisfying ≤ 7, Columnar honeycomb structure.

2. A columnar honeycomb structure comprising an outer peripheral wall, a plurality of first cells arranged on the inner peripheral side of the outer peripheral wall, extending from a first bottom surface to a second bottom surface, having an opening on the first bottom surface and a sealing portion on the second bottom surface, and a plurality of second cells arranged on the inner peripheral side of the outer peripheral wall, extending from a first bottom surface to a second bottom surface, having a sealing portion on the first bottom surface and an opening on the second bottom surface, wherein the plurality of first cells and the plurality of second cells are arranged alternately adjacent to each other with a partition wall in between, The outer periphery sidewalls, partitions, and sealant portions are fired and each contains cordierite as the main component and one or more sintering aids selected from ceria, zirconia, and titania. Of the partition walls, the average porosity of the portion in area A from the deepest point in the direction in which the first cell of the sealing portion of the second bottom surface extends to the second bottom surface, and the average porosity of the portion in area B from the deepest point in the direction in which the second cell of the sealing portion of the first bottom surface extends to the first bottom surface, is defined as P1 (%). If P2 (%) is the average porosity of the portion C in the partition wall, from the deepest point in the direction in which the first cell of the sealing portion of the second bottom surface extends to the deepest point in the direction in which the second cell of the sealing portion of the first bottom surface extends, then -4 ≤ P1 - P2 ≤ 7 is satisfied. Let S1 (%) be the average total content of one or more sintering aids selected from ceria, zirconia, and titania in the parts of the partition wall in range A and in the parts of range B, and let S2 (%) be the average total content of one or more sintering aids selected from ceria, zirconia, and titania in the parts of the partition wall in range C, and let D50 (μm) be the cumulative 50% pore diameter of the partition wall in the volume-based cumulative pore diameter distribution measured by the mercury intrusion method, then (S2 - S1) / D50 × 100 ≤ 6. Columnar honeycomb structure.

3. A columnar honeycomb structure comprising an outer peripheral wall, a plurality of first cells arranged on the inner peripheral side of the outer peripheral wall, extending from a first bottom surface to a second bottom surface, having an opening on the first bottom surface and a sealing portion on the second bottom surface, and a plurality of second cells arranged on the inner peripheral side of the outer peripheral wall, extending from a first bottom surface to a second bottom surface, having a sealing portion on the first bottom surface and an opening on the second bottom surface, wherein the plurality of first cells and the plurality of second cells are arranged alternately adjacent to each other with a partition wall in between, The outer periphery sidewalls, partitions, and sealant portions are fired and each contains cordierite as the main component and one or more sintering aids selected from ceria, zirconia, and titania. Of the partition walls, the average porosity of the portion in area A from the deepest point in the direction in which the first cell of the sealing portion of the second bottom surface extends to the second bottom surface, and the average porosity of the portion in area B from the deepest point in the direction in which the second cell of the sealing portion of the first bottom surface extends to the first bottom surface, is defined as P1 (%). If P2 (%) is the average porosity of the portion C in the partition wall, from the deepest point in the direction in which the first cell of the sealing portion of the second bottom surface extends to the deepest point in the direction in which the second cell of the sealing portion of the first bottom surface extends, then -4 ≤ P1 - P2 ≤ 7 is satisfied. In the partition wall, the portion within range C satisfies the relationship (D90 - D10) / D50 ≤ 1.2 in the volume-based cumulative pore diameter distribution measured by the mercury intrusion method, where the cumulative 10% pore diameter (D10), cumulative 50% pore diameter (D50), and cumulative 90% pore diameter (D90) from the small pore side. Columnar honeycomb structure.

4. -2 ≤ P 1 -P 2 A columnar honeycomb structure according to any one of claims 1 to 3, satisfying ≤ 5.

5. 55 ≤ P 2 A columnar honeycomb structure according to claim 2 or 3, satisfying ≤ 70.

6. Of the partition walls, the average value of the total content ratio of one or more sintering aids selected from ceria, zirconia, and titania in the portion within the range A and the portion within the range B is defined as S 1 (%), and of the partition walls, the average value of the total content ratio of one or more sintering aids selected from ceria, zirconia, and titania in the portion within the range C is defined as S 2 (%). When the cumulative 50% pore diameter of the partition wall in the volume-based cumulative pore diameter distribution measured by the mercury intrusion method is D50 (μm), (S 2 -S 1 ) / D50 × 100 ≤ 6 is satisfied. The columnar honeycomb structure according to claim 1 or 3

7. The columnar honeycomb structure according to claim 1 or 2, wherein, in the portion of the partition wall within range C, the cumulative pore diameter distribution based on volume measured by the mercury intrusion method satisfies the relationship (D90 - D10) / D50 ≤ 1.2 for the cumulative pore diameters from the small pore side: D10, D50, and D90.

8. A method for manufacturing a columnar honeycomb structure according to any one of claims 1 to 3, A process to obtain a columnar honeycomb molded body having an outer peripheral wall and a columnar honeycomb molded body that is positioned on the inner periphery of the outer peripheral wall, extending from the first bottom surface to the second bottom surface, and having openings on both the first and second bottom surfaces, by kneading a raw material composition containing a cordierite material, a dispersion medium, a pore-forming material, and a binder, in addition to one or more sintering aids selected from ceria, zirconia, and titania, and then extruding the said clay to obtain a columnar honeycomb molded body, After drying the columnar honeycomb molded body, a step of filling the openings on the first and second bottom surfaces where the sealing portions are to be formed with a slurry for forming sealing portions, which contains a cordierite raw material, a dispersion medium, a pore-forming material, and a binder, as well as one or more sintering aids selected from ceria, zirconia, and titania, A step of firing the columnar honeycomb molded body filled with the slurry for forming the eye seal portion, Includes, Regarding the sintering aid in the raw material composition, the total amount added relative to 100 parts by mass of cordierite raw material is C 1 The total amount of the sintering aid in the slurry for forming the eye seal, relative to 100 parts by mass of the cordierite raw material, is C 2 If we consider the mass portion, then -8 ≤ C 1 -C 2 Satisfying ≤ 1, Manufacturing method.

9. -6 ≤ C 1 -C 2 The manufacturing method according to claim 8, satisfying ≤ 0.

10. 1 ≤ C 2 The manufacturing method according to claim 8, satisfying ≤ 10.

11. The manufacturing method according to claim 8, wherein both the sintering aid in the raw material composition and the sintering aid in the slurry for forming the seal portion have a median diameter (D50) of 0.1 to 10 μm in the volume-based cumulative particle size distribution determined by laser diffraction and scattering.

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