JP2020060164A - Honeycomb structure - Google Patents

Abstract

To provide a honeycomb structure capable of reducing pressure loss in an initial stage of inflow of exhaust gas and maintaining mechanical strength.SOLUTION: A honeycomb structure 10 includes: a porous cell partition wall 11 that defines a plurality of cells each serving as an exhaust gas flow passage; exhaust gas introduction cells 12 each having an opened end surface on the exhaust gas inlet side and a sealed end surface on the exhaust gas outlet side; and exhaust gas discharge cells 13 each having an opened end surface on the exhaust gas outlet side and a sealed end surface on the exhaust gas inlet side. In the honeycomb structure, each of the exhaust gas introduction cell and the exhaust gas discharge cell comprises: an inner region 10B having a fixed cross sectional shape vertical to the longitudinal direction; and an end region 10A, 10C of which cross sectional shape vertical to the longitudinal direction is expanded or contracted toward the end surface. The arithmetic average roughness Ra on the cell partition wall surface in the end region in accordance with JISB0601 is larger than that on the cell partition wall surface in the inner region.SELECTED DRAWING: Figure 1

Description

The present invention relates to a honeycomb structure.

The exhaust gas discharged from an internal combustion engine such as a gasoline engine or a diesel engine contains particulates such as soot (hereinafter, also referred to as PM), and in recent years, this PM may be harmful to the environment or the human body. It's a problem. Moreover, since harmful gas components such as CO, HC or NOx are also contained in the exhaust gas, there is concern about the effect of these harmful gas components on the environment or the human body.

Therefore, titanic acid is used as an exhaust gas purifying apparatus for collecting PM in exhaust gas by connecting with an internal combustion engine and purifying harmful gas components such as CO, HC or NOx contained in the exhaust gas. Various honeycomb structures made of porous ceramics such as aluminum, cordierite, and silicon carbide have been proposed.

Further, in these honeycomb filters, in order to improve fuel efficiency of an internal combustion engine and eliminate troubles during operation due to an increase in pressure loss, various filters having a honeycomb structure with low pressure loss have been proposed.

Patent Document 1 has a plurality of first flow paths that are open at one end surface and closed at the other end surface, and a plurality of second flow paths that are closed at the one end surface and open at the other end surface. A central partition wall in which the cross-sectional area of each of the first flow paths and the second flow path is constant in the axial direction, and a cross-sectional area of each of the first flow paths from the central partition wall toward the other end surface. A honeycomb structure including: the other end side inclined partition wall, which is reduced and has a larger cross-sectional area of each of the second flow paths, wherein the other end side inclined partition wall has an axial length of 4 mm or more. A honeycomb structure is disclosed.

Patent Document 1 does not describe at all that the effect of reducing the pressure loss of the honeycomb structure during passage of exhaust gas can be obtained by changing the characteristics of the other end side inclined partition wall with respect to the central partition wall.

Republished 2016-098835

The present inventor pays attention to the other end side inclined partition wall (cell partition wall of the end region of the present invention), and by changing the characteristics of the other end side inclined partition wall (cell partition wall of the end region) with respect to the central partition wall, From the standpoint that it is possible to reduce the pressure loss of the honeycomb structure, as a result of various studies, by adjusting the surface roughness on the cell partition surface of the end region, the pressure loss, especially the initial pressure loss. The inventors have found that it is possible to reduce the above, and have completed the present invention.

That is, the honeycomb structure of the present invention is a porous cell partition wall partitioning and forming a plurality of cells to be a flow path of the exhaust gas, the exhaust gas inlet side end face is opened and the exhaust gas outlet side end face is sealed A honeycomb structure having an introduction cell and an exhaust gas discharge cell in which an end surface on the exhaust gas outlet side is opened and an end surface on the exhaust gas inlet side is sealed,
The exhaust gas introduction cell and the exhaust gas discharge cell, the exhaust gas introduction cell and an internal region having a constant cross-sectional shape perpendicular to the longitudinal direction of the exhaust gas discharge cell, and vertical to the longitudinal direction of the exhaust gas introduction cell and the exhaust gas discharge cell A cross-sectional shape that is enlarged or reduced as it approaches the end surface,
The arithmetic mean roughness (Ra) according to JIS B 0601 on the cell partition surface of the end region is larger than the arithmetic mean roughness (Ra) according to JIS B 0601 on the cell partition surface of the inner region. Characterize.

In the present invention, the arithmetic average surface roughness (Ra) of the cell partition wall surface can be measured by a stylus type surface roughness meter, and specifically, a contact type surface roughness measuring instrument SURFCOM1400D manufactured by Tokyo Seimitsu Co., Ltd. is used. , 0.5 mm can be obtained by measuring with a measurement length of 0.5 mm. Specifically, the obtained honeycomb structure is cut at a predetermined location to facilitate the measurement, and then the measurement is performed. For the measurement, randomly select 6 points and take the average value.

The end face of the exhaust gas introduction cell on the exhaust gas outlet side and the end face of the exhaust gas discharge cell on the exhaust gas inlet side are sealed by filling a part including the end face with a sealant. Rather than being present, it means that the cross-sectional shape perpendicular to the longitudinal direction of the cell is reduced as it approaches the end face in the end region, the area of the cross section becomes 0 at the end face, and the cell is closed.

In the end region of the exhaust gas introduction cell and the end region of the exhaust gas discharge cell in the honeycomb structure of the present invention, the cross-sectional shape perpendicular to the longitudinal direction of the exhaust gas introduction cell and the exhaust gas discharge cell is enlarged or reduced as it approaches the end face. Since the arithmetic mean roughness (Ra) on the cell partition wall surface in the end region is larger than the arithmetic mean roughness (Ra) on the cell partition wall surface in the inner region, in the initial process of inflowing exhaust gas, PM easily adheres to the cell partition wall surface in the above-mentioned end region, the amount of PM flowing into the cell partition wall in the inner region can be reduced, and pressure loss in the initial process of inflow of exhaust gas (hereinafter referred to as initial pressure loss That is) can be reduced.

In the honeycomb structure of the present invention, the arithmetic mean roughness (Ra) according to JIS B 0601 on the cell partition surface of the end region is 5 to 15 μm, and JIS B on the cell partition surface of the end region is The arithmetic average roughness (Ra) according to 0601 is preferably 1 to 5 μm larger than the arithmetic average roughness (Ra) according to JIS B 0601 on the cell partition wall surface in the internal region.
In the honeycomb structure of the present invention, the arithmetic mean roughness (Ra) according to JIS B 0601 on the cell partition surface of the end region is 5 to 15 μm, and JIS B on the cell partition surface of the end region is If the arithmetic mean roughness (Ra) according to 0601 is 1 to 5 μm larger than the arithmetic mean roughness (Ra) according to JIS B 0601 on the cell partition wall surface in the internal region, PM is at the end portion. Adhesion is more likely to occur due to the cell partition wall surface in the region, and the initial pressure loss can be sufficiently reduced.

In the honeycomb structure of the present invention, from the arithmetic mean roughness (Ra) according to JIS B 0601 on the cell partition wall surface in the end region, from the arithmetic mean roughness (Ra) according to JIS B 0601 on the cell partition wall surface in the inner region. When the value obtained by subtracting (Ra) is less than 1 μm, the arithmetic mean roughness (Ra) on the cell partition wall surface in the end region is compared with the arithmetic mean roughness (Ra) on the cell partition wall surface in the inner region. Since it is not sufficiently large, it is difficult to reduce the initial pressure loss, and from the arithmetic mean roughness (Ra) according to JIS B 0601 on the cell partition wall surface in the above-mentioned end region, from the JIS B 0601 on the cell partition wall surface in the above inner region. It is difficult to form a rough surface having a value obtained by subtracting the arithmetic average roughness (Ra) according to 0601 above 5 μm on the cell partition wall surface in the end region.

In the honeycomb structure of the present invention, the porosity of the cell partition walls in the internal region is preferably 35 to 65%.
In the honeycomb structure of the present invention, when the porosity of the cell partition walls in the inner region is 35 to 65%, the porosity of the cell partition walls in the end region is caused by the inner region together with the effect of increasing the surface roughness of the cell partition walls. Initial pressure loss can be suppressed, and sufficient mechanical strength can be maintained.

If the porosity of the cell partition walls in the inner region is less than 35%, the proportion of the pores of the cell partition walls in the inner region is too small, so that the exhaust gas is less likely to pass through the cell partition walls in the inner region and the pressure loss increases. On the other hand, when the porosity of the cell partition walls in the inner region exceeds 65%, the mechanical properties of the cell partition walls in the inner region are not sufficient, and cracks or the like are likely to occur during reproduction.

In the honeycomb structure of the present invention, it is desirable that the average pore diameter of the pores of the cell partition wall in the end region is 5 to 30 μm.

In the honeycomb structure of the present invention, when the average pore diameter of the pores of the cell partition walls in the end region is 5 to 30 μm, PM can be collected with high collection efficiency while keeping the initial pressure loss low. it can.

If the average pore diameter of the pores of the cell partition walls in the end region is less than 5 μm, the pores are too small, and the pressure loss when exhaust gas permeates the cell partition walls increases. On the other hand, if the average pore diameter of the pores of the cell partition wall in the above-mentioned end region exceeds 30 μm, the pore diameter becomes too large, and the PM trapping efficiency decreases.

In the honeycomb structure of the present invention, the length in the longitudinal direction of the cells in the end region is preferably 1 to 10 mm.
In the honeycomb structure of the present invention, when the lengthwise length of the cells in the end regions is 1 to 10 mm, the effect of increasing the arithmetic average roughness (Ra) on the cell partition wall surface in the end regions is exhibited. Therefore, the initial pressure loss can be further reduced.

In the honeycomb structure of the present invention, when the length in the longitudinal direction of the cells in the end regions is less than 1 mm, the end regions are too small, and therefore the arithmetic mean roughness (Ra) on the cell partition surface of the end regions is increased. ) Is difficult to be exerted, and the initial pressure loss cannot be sufficiently reduced. On the other hand, when the length of the cells in the end region in the longitudinal direction exceeds 10 mm, the honeycomb structure having such a structure is Manufacturing becomes difficult.

In the honeycomb structure of the present invention, it is desirable that the cross-sectional shape of the cells in the inner region, which is perpendicular to the longitudinal direction, be quadrangular.
In the honeycomb structure of the present invention, the cross-sectional shape perpendicular to the longitudinal direction of the cells in the internal region is a quadrangle, and in manufacturing the honeycomb structure, in the end region, a cross-section perpendicular to the longitudinal direction of the cells. The shape can be easily expanded or reduced as it approaches the end face, and a honeycomb structure having a sufficiently low pressure loss can be realized.

In the honeycomb structure of the present invention, it is desirable that the honeycomb structure is made of one honeycomb fired body having an outer peripheral wall on the outer periphery.
In the honeycomb structure of the present invention, as compared with the honeycomb structure in which a large number of honeycomb segments are combined by using an adhesive, the opening ratio at the end face can be increased due to the absence of the adhesive layer, thus reducing the initial pressure loss. You can demonstrate more.

In the honeycomb structure of the present invention, the honeycomb fired body is preferably made of cordierite or aluminum titanate.
In the honeycomb structure of the present invention, when the honeycomb fired body is made of cordierite or aluminum titanate, since the ceramic is a material having a low coefficient of thermal expansion, when large thermal stress occurs during regeneration or the like. Even in this case, the honeycomb structure is resistant to cracks.

1 (a) is a perspective view schematically showing an example of the honeycomb structure of the present invention, and FIG. 1 (b) is a sectional view taken along the line AA in FIG. 1 (a). c) is an end view as seen from one end surface side. FIG. 2A is a perspective view schematically showing the unsealed honeycomb molded body produced by the molding process, and FIG. 2B is the unsealed honeycomb molded body shown in FIG. 2A. FIG. 6 is a sectional view taken along line BB of FIG. FIG. 3 is an explanatory view schematically showing a state of a remolding step of the unsealed honeycomb molded body. FIG. 4 is a cross-sectional view schematically showing a state of a remolding step of the unsealed honeycomb molded body. FIG. 5: is sectional drawing which shows the pressure loss measuring method typically. FIG. 6 is a graph showing the arithmetic average roughness (Ra) of the cell partition wall surface in the end region and the inner region of the honeycomb structure obtained in Example 1.

(Detailed Description of the Invention)
[Honeycomb structure]
First, the honeycomb structure of the present invention will be described.

The honeycomb structure of the present invention is a porous cell partition wall that partitions and forms a plurality of cells that are channels of exhaust gas, and an exhaust gas introduction cell in which the end surface on the exhaust gas inlet side is opened and the end surface on the exhaust gas outlet side is closed. And a honeycomb structure including an exhaust gas discharge cell in which an end surface on the exhaust gas outlet side is opened and an end surface on the exhaust gas inlet side is sealed,
The exhaust gas introduction cell and the exhaust gas discharge cell, the exhaust gas introduction cell and an internal region having a constant cross-sectional shape perpendicular to the longitudinal direction of the exhaust gas discharge cell, and vertical to the longitudinal direction of the exhaust gas introduction cell and the exhaust gas discharge cell The cross-sectional shape is enlarged or reduced as it approaches the end face, and the arithmetic mean roughness (Ra) in accordance with JIS B 0601 on the cell partition surface of the end region is the cell of the inner region. It is characterized in that it is larger than the arithmetic average roughness (Ra) according to JIS B 0601 (hereinafter, simply referred to as arithmetic average roughness (Ra)) on the partition wall surface.

1 (a) is a perspective view schematically showing an example of the honeycomb structure of the present invention, and FIG. 1 (b) is a sectional view taken along the line AA in FIG. 1 (a). c) is an end view as seen from one end surface side.
The honeycomb structure 10 shown in FIGS. 1 (a) and 1 (b) has a porous cell partition wall 11 for partitioning and forming a plurality of cells 12 and 13 serving as exhaust gas flow paths, and an end face 10a on the exhaust gas inlet side. An exhaust gas introduction cell 12 that is opened and has an end face 10b on the exhaust gas outlet side sealed, and an exhaust gas discharge cell 13 that has an end face 10b on the exhaust gas outlet side opened and the end face 10a on the exhaust gas inlet side are sealed, The introduction cell 12 and the exhaust gas discharge cell 13 are perpendicular to the longitudinal direction of the exhaust gas introduction cell 12 and the exhaust gas discharge cell 13 and the internal region 10B having a constant sectional shape perpendicular to the longitudinal direction of the exhaust gas introduction cell 12 and the exhaust gas discharge cell 13. The cross-sectional shape is enlarged or reduced as it approaches the end face, and the end regions 10A and 10C are sealed.
As shown in FIGS. 1A and 1B, when the honeycomb structure 10 is made of a single honeycomb fired body, the honeycomb fired body is also a honeycomb structure.

In the honeycomb structure 10 of the present invention, the arithmetic mean roughness (Ra) of the cell partition surface in the end regions 10A and 10C is larger than the arithmetic mean roughness (Ra) of the cell partition surface in the inner region 10B.
Therefore, in the honeycomb structure 10 of the present invention, in the initial process of the inflow of exhaust gas, PM easily adheres to the cell partition surface of the end region, and the amount of PM flowing into the cell partition of the inner region is reduced. It is possible to reduce the initial pressure loss.

In the honeycomb structure of the present invention, the arithmetic mean roughness (Ra) according to JIS B 0601 on the cell partition surface of the end region is 5 to 15 μm, and JIS B on the cell partition surface of the end region is The arithmetic average roughness (Ra) according to 0601 is preferably 1 to 5 μm larger than the arithmetic average roughness (Ra) according to JIS B 0601 on the cell partition wall surface in the internal region.

In the honeycomb structure of the present invention, the arithmetic mean roughness (Ra) according to JIS B 0601 on the cell partition surface of the end region is 5 to 15 μm, and JIS B on the cell partition surface of the end region is If the arithmetic mean roughness (Ra) according to 0601 is 1 to 5 μm larger than the arithmetic mean roughness (Ra) according to JIS B 0601 on the cell partition wall surface in the internal region, PM is at the end portion. Adhesion is more likely to occur due to the cell partition wall surface in the region, and the initial pressure loss can be sufficiently reduced.

In the honeycomb structure of the present invention, the porosity of the cell partition walls in the internal region is preferably 35 to 65%.

In the honeycomb structure of the present invention, when the porosity of the cell partition walls in the inner region is 35 to 65%, the porosity of the cell partition walls in the end region is caused by the inner region together with the effect of increasing the surface roughness of the cell partition walls. Initial pressure loss can be suppressed, and sufficient mechanical strength can be maintained.

In the honeycomb structure of the present invention, it is desirable that the average pore diameter of the pores of the cell partition wall in the end region is 5 to 30 μm.
In the honeycomb structure of the present invention, when the average pore diameter of the pores of the cell partition walls in the end region is 5 to 30 μm, PM can be collected with high collection efficiency while keeping the pressure loss low. ..
In the honeycomb structure of the present invention, the porosity and the average pore diameter are measured by a mercury intrusion method under the conditions of a contact angle of 130 ° and a surface tension of 485 mN / m.

In the honeycomb structure of the present invention, the length of the cells in the end region in the longitudinal direction is preferably 1 to 10 mm.
In the honeycomb structure of the present invention, when the lengthwise length of the cells in the end regions is 1 to 10 mm, the effect of increasing the arithmetic mean roughness (Ra) on the cell partition wall surface in the end regions is exhibited. It is easy and the initial pressure loss can be further reduced.

The shape of the honeycomb structure of the present invention is not limited to a columnar shape, and examples thereof include a prismatic shape, an elliptic cylindrical shape, an oblong cylindrical shape, and a round chamfered prismatic shape (for example, a round chamfered triangular pillar). .

In the honeycomb structure of the present invention, the cross-sectional shape of the inner region perpendicular to the longitudinal direction of the cells is not limited to a quadrangle, and may be a triangle, a hexagon, or an octagon, but a quadrangle is preferable.

In the honeycomb structure of the present invention, the density of cells in a cross section perpendicular to the longitudinal direction of the honeycomb fired body is preferably 31 to 155 cells / cm ² (200 to 1000 cells / inch ² ).

In the honeycomb structure of the present invention, when the outer peripheral coat layer is formed on the outer peripheral surface of the honeycomb fired body, the thickness of the outer peripheral coat layer is preferably 0.1 to 2.0 mm.

The honeycomb structure of the present invention may be composed of one honeycomb fired body having an outer peripheral wall on the outer periphery, or may be provided with a plurality of honeycomb fired bodies, and the plurality of honeycomb fired bodies are adhesive. However, it is preferable that the honeycomb fired body has one outer peripheral wall having an outer peripheral wall.

The material constituting the honeycomb structure of the present invention is not particularly limited, and examples thereof include carbide ceramics such as silicon carbide, titanium carbide, tantalum carbide, and tungsten carbide, and nitrides such as aluminum nitride, silicon nitride, boron nitride, and titanium nitride. Examples include ceramics, alumina, zirconia, cordierite, mullite, oxide ceramics such as aluminum titanate, and silicon-containing silicon carbide, but the honeycomb structure is composed of one honeycomb fired body having an outer peripheral wall on the outer periphery. In this case, cordierite or aluminum titanate is preferable.

When the honeycomb fired body is made of cordierite or aluminum titanate, since the ceramic is a material having a low coefficient of thermal expansion, even when a large thermal stress occurs during regeneration, cracks and the like This is because the honeycomb structure does not easily occur.

Next, a method for manufacturing the honeycomb structure of the present invention will be described.
In the following, a method for manufacturing a honeycomb structure made of aluminum titanate will be described as an example, but the manufacturing target of the present invention is not limited to aluminum titanate.
(Mixing process)
First, additives such as magnesia powder and silica powder are added to alumina powder and titania powder and mixed to obtain a mixed powder.

In the above-mentioned mixed powder, silica and magnesia also have a role as a firing aid, but as the firing aid, in addition to silica and magnesia, oxides of Y, La, Na, K, Ca, Sr, and Ba are used. It may be used. If necessary, the following additives are added to these mixed powders to obtain a raw material composition. Examples of the molding aid include ethylene glycol, dextrin, fatty acid, fatty acid soap, and polyalcohol. Examples of the organic binder include hydrophilic organic polymers such as carboxymethyl cellulose, polyvinyl alcohol, methyl cellulose and ethyl cellulose. Examples of the dispersion medium include a dispersion medium composed of only water or a dispersion medium composed of 50% by volume or more of water and an organic solvent. Examples of the organic solvent include alcohols such as benzene and methanol. Examples of the pore-forming agent include balloons, which are minute hollow spheres, spherical acrylic particles, graphite, and starch. Examples of balloons include alumina balloons, glass micro balloons, shirasu balloons, fly ash (FA) balloons, and mullite balloons.

Further, the raw material composition may further contain other components. Examples of other components include plasticizers, dispersants, and lubricants. Examples of the plasticizer include polyoxyalkylene compounds such as polyoxyethylene alkyl ether and polyoxypropylene alkyl ether. Examples of the dispersant include sorbitan fatty acid ester. Examples of the lubricant include glycerin.

(Molding process)
The molding step is a step of molding the raw material composition obtained in the mixing step to produce an unsealed honeycomb molded body. The unsealed honeycomb molded body can be produced by, for example, extruding the raw material composition using an extrusion die. That is, the unsealed honeycomb molded body is manufactured by extruding the tubular outer peripheral wall of the honeycomb structure and the wall portion constituting the partition wall at one time. Further, in the extrusion molding, a molded body corresponding to the shape of a part of the honeycomb structure may be molded. That is, a honeycomb molded body having the same shape as the honeycomb structure may be manufactured by molding a molded body corresponding to a part of the shape of the honeycomb structure and combining the molded bodies.

FIG. 2A is a perspective view schematically showing the unsealed honeycomb molded body produced by the molding process, and FIG. 2B is the unsealed honeycomb molded body shown in FIG. 2A. FIG. 6 is a sectional view taken along line BB of FIG.

As shown in FIGS. 2 (a) and 2 (b), due to the above-described molding process, the cells 22 and 23 have a square cross section perpendicular to the longitudinal direction, and the shape of the cells 22 and 23 at the end faces 20a ′ and 20b ′ is completely zero. An unsealed honeycomb molded body 20 'having the same rectangular shape and having cell partition walls 21 separating cells 22 and 23 and having a cylindrical shape as a whole is produced.

(Reforming process)
Thereafter, a taper jig is used to re-form the unsealed honeycomb molded body 20 ′ to form a portion corresponding to an end region of the honeycomb structure, thereby forming an exhaust gas introduction cell and an exhaust gas discharge cell. The cross-sectional shape of 22 and 23 perpendicular to the longitudinal direction is enlarged or reduced as it approaches the end face, and the sealed honeycomb molded body has a closed shape.

FIG. 3 is an explanatory view schematically showing a state of the remolding step of the unsealed honeycomb molded body, and FIG. 4 is a sectional view schematically showing a state of the remolding step of the unsealed honeycomb molded body. is there.
As shown in FIGS. 3 and 4, a taper including a support portion 33, a base portion 31 fixed on the support portion 33, and a large number of quadrangular pyramid-shaped tip portions 32 formed on the base portion 31. Using the jig 30, the corner portion 32c which is the boundary portion of the four flat surfaces 32b forming the quadrangular pyramid of the tip portion 32 forms the square of the cell partition wall 21 on the end surface 20a 'of the unsealed honeycomb molded body 20'. The taper jig 30 is arranged so as to be in contact with the center of the side 21a, and the taper jig 30 is pushed toward the central portion of the unsealed honeycomb molded body 20 '. The tip bottom surface 32a is welded to the tip forming surface 31a of the base 31.

At this time, the portion corresponding to the end region of the cell 22 into which the tip 32 is pushed has a shape in which the cross-sectional shape perpendicular to the longitudinal direction of the cell is enlarged as it approaches the end face, and the cell into which the tip 32 is pushed The portions corresponding to the end regions of the cells 23 existing on the upper, lower, left, and right sides of the cell 22 are reduced in shape as the cross-sectional shape perpendicular to the longitudinal direction of the cells 23 approaches the end surface, and become a sealed shape. Further, the shape of the sealed honeycomb formed body viewed from the end face is the same as the honeycomb structure 10 shown in FIG. 1C, and the square of the cell 12 on the end face 10a is rotated by 45 ° from the square of the cell 12 of the internal region 10B. It becomes the shape.

In the remolding step, the arithmetic mean roughness (Ra) of the four flat surfaces 32b forming the tip 32 is adjusted, the material of the tip is changed, the drying temperature of the tip is changed, and the tip is pushed. By changing the speed or the like at the time or by spraying water on the end face of the honeycomb molded body before pushing in the taper jig 30, the moisture content of the end portion of the honeycomb molded body is increased to improve the sealing honeycomb molded body. The arithmetic mean roughness (Ra) of the end region can be adjusted. Further, for example, by increasing the arithmetic average roughness (Ra) of the four flat surfaces 32b forming the tip portion 32, it is possible to increase the arithmetic average roughness (Ra) of the end region of the sealed honeycomb formed body. It is possible to increase the arithmetic average roughness (Ra) of the end region of the obtained honeycomb structure.

The sealed honeycomb molded body obtained by this remolding step uses a dryer such as a microwave dryer, a hot air dryer, a dielectric dryer, a vacuum dryer, a vacuum dryer, and a freeze dryer at 100 to 150 ° C. Then, it is dried in an air atmosphere, and degreased in an atmosphere of 250 to 400 ° C. and an oxygen concentration of 5% by volume.

(Firing process)
The firing step is a step of firing the sealed honeycomb formed body obtained in the re-forming step at 1400 to 1600 ° C. In this firing step, the reaction with titania proceeds from the surface of alumina to form an aluminum titanate phase. The firing can be performed using a known single furnace, so-called batch furnace, or continuous furnace. The firing temperature is preferably in the range of 1450 to 1550 ° C. The firing time is not particularly limited, but the firing temperature is preferably maintained for 1 to 20 hours, more preferably 1 to 10 hours. In addition, it is preferable that the firing step be performed in an air atmosphere. The oxygen concentration may be adjusted by mixing an inert gas such as nitrogen gas or argon gas into the air atmosphere.

The arithmetic mean roughness (Ra) on the cell partition wall surface in the end region is the arithmetic mean roughness (Ra) on the cell partition wall surface in the inner region (Ra) through the above-mentioned mixing step, molding step, remolding step, and firing step. It is possible to produce a honeycomb structure of the present invention larger than Ra).

Hereinafter, examples in which the above embodiment is further embodied will be described.
(Example 1)
First, a raw material composition having the following composition was prepared.
Fine titania powder having D50 of 0.6 μm: 11.1% by weight, coarse titania powder having D50 of 13.0 μm: 11.1% by weight, alumina powder having D50 of 15.9 μm: 30.4% by weight, D50 of 1 .1 μm silica powder: 2.8% by weight, D50 3.8 μm magnesia powder: 1.4% by weight, D50 31.9 μm acrylic resin (pore forming material): 18.5% by weight, methylcellulose (organic A binder having a composition of 7.1% by weight, a molding aid (ester type nonion): 4.7% by weight, and ion-exchanged water (dispersion medium): 12.9% by weight are mixed with a mixer. A raw material composition was prepared.

The prepared raw material composition was put into an extrusion molding machine and extrusion-molded to prepare an unsealed honeycomb molded body 20 'in which cells were not sealed.

After the unsealed honeycomb molded body 20 'is manufactured, moisture is adhered until the water content of the end surface of the unsealed honeycomb molded body 20' becomes 35%, and remolding is performed to form the sealed honeycomb molded body of the present invention. The body was made. As the taper jig 30, the distance (V: valley width shown in FIG. 5) between the tip portions 32 for forming the end surface 20a of the unsealed honeycomb molded body 20 ′ is set to 0.13 mm, and the tip portion 32 is The angle α between the flat surface 32b of the quadrangular pyramid and the surface perpendicular to the tip forming surface 31a (tip bottom 32a) on which the tip 32 of the base 31 is formed is set to 12.5 ° (Fig. 3 and FIG. 4).

After that, the honeycomb structure was manufactured by holding and firing the sealed honeycomb molded body obtained through the remolding step at 1450 ° C. for 15 hours in the air atmosphere. The obtained honeycomb structure had a porosity of 57%, an average pore diameter of 17 μm, a size of 34 mm × 34 mm × 100 mm, a peripheral wall thickness of 0.3 mm, and a cell partition wall thickness of 0.40 mm on the end face. The thickness of the cell partition wall in the region was 0.25 mm, the number of cells (cell density) was 300 cells / inch ² , and the shape was a square pole. The porosity and the average pore diameter were measured by the methods described below.

(Comparative Example 1)
A honeycomb structure was manufactured in the same manner as in Example 1 except that moisture was not adhered to the end surface of the unsealed honeycomb molded body 20 'during the remolding.
The characteristics of the obtained honeycomb structure were the same as those in Example 1 except that the arithmetic mean roughness (Ra) of the cell partition wall surface in the end region described below was different.

[Measurement of Surface Roughness of Cell Partition Surface in Edge Area and Inner Area]
By cutting the honeycomb structure obtained in Example 1 and Comparative Example 1 to expose the cell partition walls of the end region and the inner region, using SURFCOM1400D, which is a contact surface roughness measuring machine manufactured by Tokyo Seimitsu Co., Six points were measured with a measurement length of 0.5 mm.

[Porosity and average pore size]
The honeycomb structures obtained in Example 1 and Comparative Example 1 were cut into a size of 10 mm × 10 mm × 10 mm to prepare a sample for pore measurement. The porosity and the average pore diameter were measured using a porosimeter (manufactured by Shimadzu Corporation, Autopore III 9420) by a mercury porosimetry using the sample for pore measurement. The contact angle was 130 ° and the surface tension was 485 mN / m under the mercury intrusion method.

[Pressure loss]
FIG. 5: is sectional drawing which shows the pressure loss measuring method typically.
The pressure loss measuring device 210 includes a pipe 212 branched from an exhaust gas pipe 214 of a diesel engine 211 having a displacement of 1.6 liters and the honeycomb structure 10 obtained in Example 1 and Comparative Example 1 in a metal casing 213. It was fixed and arranged.
The end of the honeycomb structure 10 on the exhaust gas inlet side is arranged on the side close to the pipe 212 of the diesel engine 211. That is, the exhaust gas is arranged so that the exhaust gas flows into the cell having the open end on the exhaust gas inlet side.

FIG. 6 is a graph showing the arithmetic average roughness (Ra) of the cell partition wall surface in the end region and the inner region of the honeycomb structure obtained in Example 1.
As shown in FIG. 6, in the honeycomb structure obtained in Example 1, while the arithmetic mean roughness (Ra) on the cell partition wall surface in the inner region was 5.0 μm, the cell partition wall surface in the end region was formed. The arithmetic mean roughness (Ra) of was as high as 6.8 μm.
On the other hand, the arithmetic average roughness (Ra) of the surface roughness of the cell partition walls in the end region and the inner region of the honeycomb structure obtained in Comparative Example 1 was 5.0 μm.

When the diesel engine was operated and the initial pressure loss of the honeycomb structure 10 according to Example 1 and Comparative Example 1 was measured using the above-mentioned pressure loss measurement device, it was 2.4 kPa in Example 1. On the other hand, in Comparative Example 1, it was 2.8 kPa.

As is clear from the above results, the honeycomb structure according to Example 1 in which the surface roughness in the end region is rougher than that in the inner region has a smaller initial pressure loss than the honeycomb structure according to Comparative Example 1. It turned out.

10 Honeycomb Structures 10a, 10b End Faces 10A, 10C End Regions 10B Inner Region 11 Cell Partition 12 Exhaust Gas Introducing Cells 13 Exhaust Gas Emitting Cells 20 'Unsealed Honeycomb Molded Products 20a', 20b 'End Faces
21 Cell Partition Wall 21a One Side 22, 23 Cell 30 Taper Jig 31 Base 31a Tip Forming Surface 32 Tip 32a Tip Bottom 32b Flat 32c Corner 33 Support

Claims (8)

Porous cell partition walls partitioning and forming a plurality of cells that form the flow path of exhaust gas, an exhaust gas introduction cell in which the end surface on the exhaust gas inlet side is opened and the end surface on the exhaust gas outlet side is closed, and the end surface on the exhaust gas outlet side is A honeycomb structure provided with an exhaust gas discharge cell which is opened and whose end face on the exhaust gas inlet side is sealed,
The exhaust gas introduction cell and the exhaust gas discharge cell, the exhaust gas introduction cell and the internal region having a constant cross-sectional shape perpendicular to the longitudinal direction of the exhaust gas discharge cell, and vertical to the longitudinal direction of the exhaust gas introduction cell and the exhaust gas discharge cell A cross-sectional shape that is enlarged or reduced as it approaches the end surface,
The arithmetic mean roughness (Ra) according to JIS B 0601 on the cell partition surface of the end region is larger than the arithmetic mean roughness (Ra) according to JIS B 0601 on the cell partition surface of the inner region. A characteristic honeycomb structure. The arithmetic mean roughness (Ra) according to JIS B 0601 on the cell partition surface of the end region is 5 to 15 μm, and the arithmetic mean roughness on the cell partition surface of the end region according to JIS B 0601. The honeycomb structure according to claim 1, wherein (Ra) is larger by 1 to 5 μm than the arithmetic average roughness (Ra) according to JIS B 0601 on the cell partition wall surface of the internal region. The honeycomb structure according to claim 1 or 2, wherein the porosity of the cell partition walls in the internal region is 35 to 65%. The honeycomb structure according to any one of claims 1 to 3, wherein an average pore diameter of pores of the cell partition walls in the end region is 5 to 30 µm. The honeycomb structure according to any one of claims 1 to 4, wherein a length in a longitudinal direction of cells in the end region is 1 to 10 mm. The honeycomb structure according to any one of claims 1 to 5, wherein a cross-sectional shape of the cells in the inner region, which is perpendicular to the longitudinal direction of the cells, is a quadrangle. The honeycomb structure according to any one of claims 1 to 6, wherein the honeycomb structure is made of one honeycomb fired body having an outer peripheral wall on the outer periphery. The honeycomb structure according to claim 7, wherein the honeycomb fired body is made of cordierite or aluminum titanate.

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