JP2019093381A - Honeycomb structure - Google Patents

Abstract

To provide a honeycomb structure excellent in thermal shock resistance.SOLUTION: There is provided a honeycomb structure 4 having porous partition walls 1 disposed so as to surround a plurality of cells 2, wherein a value of a porosity of the partition walls 1 in wall parts 16 for partitioning two cells 2 is defined as a porosity A and a value of a porosity of the partition walls 1 in an intersection point 15 which is a portion for connecting two or more wall parts 16 is defined as a porosity B, A/B, which is a value obtained by dividing the porosity A by the porosity B, is 0.5 to 0.95 and the porosity A is 10 to 40%.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a honeycomb structure. More specifically, the present invention relates to a honeycomb structure excellent in thermal shock resistance.

  In recent years, awareness of environmental issues has been increasing throughout society, and in the technical field of burning fuel and generating power, various technologies for removing harmful components such as nitrogen oxides from exhaust gas generated at the time of fuel combustion Is being developed. For example, various techniques have been developed for removing harmful components such as nitrogen oxides from exhaust gases emitted from automobile engines. In removing such harmful components in the exhaust gas, it is common to use a catalyst to cause a chemical reaction of the harmful components to convert them into relatively harmless other components. And, a honeycomb structure is used as a catalyst carrier for supporting a catalyst for exhaust gas purification.

  Conventionally, as such a honeycomb structure, one having a honeycomb structure portion having porous partition walls for forming a plurality of cells serving as a flow path of fluid extending from the inflow end face to the outflow end face has been proposed (for example, , Patent Documents 1 to 4).

International Publication No. 2002/011884 Unexamined-Japanese-Patent No. 2004-270569 JP 2004-289925 A JP, 2010-227818, A

  Patent Document 1 discloses a honeycomb structure in which in the cross section perpendicular to the cell extending direction of the honeycomb structure, the thickness of the partition wall in the outer peripheral portion is larger than that in the central portion. In Patent Document 1, such a honeycomb structure has a negative surface due to an increase in pressure loss and a decrease in thermal shock resistance, and a positive surface due to an improvement in isostatic strength and high accuracy of partition wall shape and honeycomb structure external shape. Is said to be able to achieve a balance of

  Here, when the honeycomb structure is used as a catalyst carrier or the like for exhaust gas purification, it may be used in a state of being stored in a can such as a metal case. Hereinafter, storing a honeycomb structure in a can such as a metal case is sometimes referred to as canning. The metal case is sometimes called a metal can. The honeycomb structure described in Patent Document 1 has improved strength in the outer peripheral portion of the honeycomb structure, so that it has certain effects on suppressing breakage in the outer peripheral portion, for example, at the above-described canning time and the like. It is guessed that. However, the honeycomb structure described in Patent Document 1 can be a countermeasure for suppressing the occurrence of cracks due to thermal shock load since the shape of the partition wall in the central portion of the cross section is the same as that of the conventional honeycomb structure. There was a problem of not being.

  Patent Document 2 shows a relationship of Pi <Po, where Pi is the porosity of the partition wall in the center of the cross section perpendicular to the axial direction of the honeycomb structure, and Po is the porosity of the partition in the outer peripheral portion of the cross section. A honeycomb structure is disclosed. Such a honeycomb structure can increase the heat capacity of the central portion by making the porosity of the central portion smaller than the porosity of the outer peripheral portion. However, in the case of focusing only on the central portion, the problem is that the problem is that the partition wall in the wall part that divides the two cells becomes the crack initiation point when the crack is generated due to thermal shock load. was there.

  In Patent Document 3, the shape of the cell is substantially square, the intersection of the partition is R-shaped or C-shaped, and the value of the ratio of the diagonal distance of the intersection to the average thickness of the partition is 1.6. It is the above, and the honeycomb structure whose aperture ratio of a cell is 55% or more is disclosed. Such a honeycomb structure can strengthen the intersections of the partition walls, but the problem is that the partition walls in the wall part separating the two cells become the starting point of the generation of the cracks, but there is no problem. there were.

  In Patent Document 4, a cross-point pore, which is a ratio of a cross-point porosity, which is a porosity at a cross-point where the partition walls cross each other, is a ratio between a cross-point porosity, which is a porosity at a partition cross-point A honeycomb structure having a ratio / intermediate porosity of 0.5 to 0.95 is disclosed. Although such a honeycomb structure can also strengthen the partition wall intersection, there is no problem in that the middle of the partition between the adjacent partition intersections becomes the crack initiation point. there were. In particular, since the honeycomb structure described in Patent Document 4 has a structure in which the strength of the partition intermediate portion that substantially divides the two cells becomes weaker when a thermal shock load is applied, the heat of the entire honeycomb structure is obtained. Considering impact, it is considered to act in a disadvantageous direction with respect to thermal shock resistance.

  The present invention has been made in view of the problems of the prior art. The present invention provides a honeycomb structure excellent in thermal shock resistance.

  According to the present invention, a honeycomb structure shown below is provided.

[1] A honeycomb structure having porous partition walls disposed so as to surround a plurality of cells serving as fluid channels extending from the first end face to the second end face,
The value of the porosity of the partition wall in the wall part separating the two cells is taken as porosity A,
The porosity B of the partition wall at the intersection, which is a portion connecting two or more of the walls, is taken as porosity B.
A / B which is a value obtained by dividing the porosity A by the porosity B is 0.5 to 0.95,
The honeycomb structure whose said porosity A is 10 to 40%.

[2] The honeycomb structure according to [1], wherein the arithmetic mean of the porosity A and the porosity B is 15 to 45%.

[3] The honeycomb structure according to [1] or [2], wherein the shape of the cells in a cross section orthogonal to the extending direction of the cells of the honeycomb structure body is a quadrangle or a hexagon.

[4] The honeycomb structure according to any one of the above [1] to [3], wherein the thickness of the partition wall is 40 to 200 μm.

  The honeycomb structure of the present invention is excellent in thermal shock resistance. That is, the honeycomb structure of the present invention can effectively suppress the occurrence of cracks due to thermal shock, as compared with the conventional honeycomb structure having the same degree of porosity. In particular, the thermal shock resistance of the whole honeycomb structure is improved by setting the porosity of the partition walls to 10 to 40% and appropriately reducing the porosity B of the partition walls at the intersections connecting two or more wall portions. be able to. That is, when the porosity of the partition walls is 40% or less, it is difficult for the catalyst for exhaust gas purification to permeate into the pores formed in the partition walls. For this reason, when the conventional honeycomb structure is used as a catalyst carrier under severe thermal conditions, such as directly under an automobile engine, the thickness of the partition wall is thinner than the intersection of the partition walls, Cracks may occur early on the wall of the partition wall. And the crack which arose in the wall part of the partition is easy to progress to a bigger crack, and there is concern that the defect of a honeycomb structure may aggravate. Here, although the thermal shock resistance of the honeycomb structure can be improved by, for example, increasing the thickness of the wall portion of the partition wall, the pressure loss of the honeycomb structure can be obtained by increasing the thickness of the partition wall. Invite the rise of The honeycomb structure of the present invention relatively lowers the porosity A of the partition wall in the wall portion where the crack is more likely to be generated, and the above-mentioned A / B is 0.5 to 0.95. It is possible to effectively suppress the occurrence of cracks at both of the intersection points. Further, in the honeycomb structure of the present invention, in the cross section orthogonal to the extending direction of the cells, it is not necessary to partially change the thickness of the partition wall or partially change the shape of the cells. It is hard to raise secondary problems such as the rise of

It is the perspective view seen from the first end face side which shows typically the first embodiment of the honeycomb structure of the present invention. It is a top view which shows typically the 1st end surface of the honeycomb structure shown in FIG. It is the enlarged plan view which expanded a part of 1st end surface of the honeycomb structure shown in FIG. It is sectional drawing which shows typically the A-A 'cross section of FIG. It is a top view which shows a part of 1st end surface which shows typically 2nd embodiment of the honeycomb structure of this invention. It is the perspective view seen from the 1st end surface side which shows typically 3rd embodiment of the honeycomb structure of this invention. It is a top view which shows typically the 1st end face of a 4th embodiment of the honeycomb structure of the present invention. It is a graph which shows the relationship between the operating time (second) of an engine, and an engine speed (rpm) in the test of a thermal shock resistance.

  Hereinafter, embodiments of the present invention will be described. However, the present invention is not limited to the following embodiments. Therefore, it should be understood that appropriate modifications, improvements, and the like can be added to the following embodiments based on the ordinary knowledge of those skilled in the art without departing from the spirit of the present invention.

(1) Honeycomb structure (first embodiment):
As shown in FIGS. 1 to 4, the first embodiment of the honeycomb structure of the present invention is a honeycomb structure 100 including a honeycomb structure portion 4 having porous partition walls 1. Here, FIG. 1 is a perspective view schematically showing the first embodiment of the honeycomb structure of the present invention as viewed from the first end face side. FIG. 2 is a plan view schematically showing a first end face of the honeycomb structure shown in FIG. FIG. 3 is an enlarged plan view of a part of the first end face of the honeycomb structure shown in FIG. FIG. 4 is a cross-sectional view schematically showing a cross section AA 'in FIG.

  The partition walls 1 of the honeycomb structure portion 4 are disposed so as to surround a plurality of cells 2 serving as fluid channels extending from the first end surface 11 to the second end surface 12. That is, the plurality of cells 2 are partitioned by the porous partition walls 1. The honeycomb structure portion 4 may further have an outer peripheral wall 3 disposed on the outer peripheral portion so as to surround the partition wall 1.

  The honeycomb structure 100 of the present embodiment can be suitably used as a catalyst carrier for supporting a catalyst for exhaust gas purification. A catalyst support is a porous structure that supports the particulates of the catalyst. Therefore, in each of the cells 2 formed in the honeycomb structure portion 4, the end portions on the first end surface 11 side and the second end surface 12 side are not sealed by the plugging portion or the like. The cells 2 communicate with the second end face 12 side.

  As shown in FIG. 2 and FIG. 3, the honeycomb structure portion 4 is a portion at which the porosity A of the partition wall 1 in the wall portion 16 partitioning the two cells 2 and two or more wall portions 16 are connected. The porosity B of the partition wall 1 in the present invention has a different value. More specifically, the value of the porosity of the partition wall 1 in the wall portion 16 dividing the two cells 2 is taken as the porosity A. Further, the porosity B of the partition wall 1 at the intersection 15 connecting two or more wall portions 16 is referred to as “porosity B”. In this case, “porosity A / porosity B”, which is a value obtained by dividing the porosity A by the porosity B, is 0.5 to 0.95. Hereinafter, “porosity A / porosity B” may be simply referred to as “A / B”. Here, the “intersection portion 15 connecting two or more wall portions 16” is, for example, a case where the partition walls 1 are formed in a lattice shape in a plane orthogonal to the extending direction of the cells 2 of the honeycomb structure portion 4. And the intersections of the partition walls 1 and the like. For example, although illustration is omitted, a portion where two wall portions are connected so as to be bent is also an intersection portion connecting two or more wall portions. As shown in FIGS. 2 and 3, the wall portion 16 and the intersection portion 15 are elements constituting the partition wall 1, and are appropriately described as “the wall portion 16 of the partition wall 1” and “the intersection portion 15 of the partition wall 1”. Sometimes.

  The honeycomb structure 100 of the present embodiment is excellent in thermal shock resistance. That is, the honeycomb structure 100 of the present invention can effectively suppress the occurrence of cracks due to thermal shock, as compared with the conventional honeycomb structure having the same degree of porosity. In particular, when the porosity of the partition wall 1 is 40% or less, the heat resistance of the whole honeycomb structure 100 is achieved by appropriately reducing the porosity B of the partition wall 1 at the intersection 15 connecting two or more wall portions 16. Impact resistance can be improved. That is, when the porosity of the partition wall 1 is 40% or less, it is difficult for the catalyst for exhaust gas purification to penetrate into the pores formed in the partition wall 1. For example, when a conventional honeycomb structure is used as a catalyst carrier under severe thermal conditions, such as directly under an automobile engine, the partition walls are thinner than the intersections of the partition walls, so Cracks occur early on the wall of the And the crack which arose in the wall part of the partition is easy to progress to a bigger crack, and there is concern that the defect of a honeycomb structure may aggravate. Here, although the thermal shock resistance of the honeycomb structure can be improved by, for example, increasing the thickness of the wall portion of the partition wall, the pressure loss of the honeycomb structure can be obtained by increasing the thickness of the partition wall. Invite the rise of In the honeycomb structure 100 of the present embodiment, the porosity A of the partition wall 1 in the wall portion 16 in which the crack is more easily generated is made relatively low, and the above-described A / B is set to 0.5 to 0.95. It is possible to effectively suppress the occurrence of cracks in both the wall portion 16 and the intersection portion 15 of the partition wall 1. In the honeycomb structure 100 of the present embodiment, it is necessary to partially change the thickness of the partition wall 1 or partially change the shape of the cell 2 in a cross section perpendicular to the extending direction of the cell 2. As a result, there are no secondary problems such as an increase in pressure loss.

  Hereinafter, in the present specification, the value of the porosity of the partition wall 1 in the wall portion 16 dividing the two cells 2 may be simply referred to as “porosity A”. Moreover, the value of the porosity of the partition 1 in the intersection part 15 which connects two or more wall parts 16 may only be called "porosity B." When the cross-sectional shape of two cells 2 is a polygon, for example, "the wall part 16 which divides two cells 2" is a part which comprises each side in each cross-sectional shape.

  In the present invention, each of the porosity A and the porosity B of the partition wall 1 is a value obtained by the following method. First, a sample piece for performing measurement of the porosity A and the porosity B is cut out from the honeycomb structure 100. About the cut-out part of each sample piece, it is set as ten places in total at five each in each of the 1st end face 11 side and the 2nd end face 12 side of honeycomb structure 100. The cutout position at each end surface is taken as the first cutout position at the center position of each end surface. Then, at each end face, the remaining four points are cut out at four points which are intermediate points between the center position and the outer peripheral edge of the honeycomb structure 100 on the X axis and Y axis passing through the center position and orthogonal to each other. It will be the place.

  The sample piece for measuring the porosity A is cut out so that the central part of the wall part 16 which divides the two cells 2 may be included in each of ten places mentioned above. The length of one side of the sample piece for measuring the porosity A is the thickness of the wall portion 16 constituting the partition 1 and the length of the other side is 100 μm in the extending direction of the partition 1 in each end face. The other side has a length of 20 mm in the cell 2 extending direction.

  The sample piece for measuring the porosity B is cut out so that the central part of the intersection part 15 of the partition 1 may be included in each of ten places mentioned above. The sample piece for measuring the porosity B has a square with a side length of 100 μm centering on the center of the intersection 15 connecting two or more walls 16 as an end face, and the axial length is It is 20 mm in the extending direction of the cell 2.

  After the sample piece thus cut out and produced from the honeycomb structure 100 is embedded in an epoxy resin and solidified, the surface is polished. Then, each sample piece is cut out by 5 mm in the full length direction, and the cut surface is taken as an observation surface by a scanning electron microscope (hereinafter also referred to as "SEM"). SEM is an abbreviation of "Scanning Electron Microscope". As a scanning electron microscope, for example, a scanning electron microscope "Model No .: S3200-N" manufactured by Hitachi High-Technologies Corporation can be used.

  Then, the observation surface of the produced sample piece is observed by SEM, and a SEM image is acquired. In the case of measurement of the porosity A of the partition 1, the said SEM image is acquired about the partition 1 in each observation surface of 10 above-described sample pieces. It is assumed that the SEM image is observed at a magnification of 100 times. Moreover, in the case of the measurement of the porosity B of the partition 1, the said SEM image is acquired about the intersection part 15 of the partition 1 in each observation surface of ten sample pieces mentioned above. Next, for each image, “area S1 of partition 1” and “area S2 of pore portion (void portion)” are calculated using image analysis software. And the porosity of the partition 1 imaged by each image is calculated by "calculation formula (1): S2 / (S1 + S2)." As the values of S1 and S2, the average value of the porosity of each of ten places is used.

  In the honeycomb structure 100 whose porosity is to be measured, when an exhaust gas purification catalyst (not shown) is supported on the surface of the partition 1 and the inside of the pores of the partition 1, the catalyst is supported. The porosity is determined on the assumption that the portion is the pore portion of the partition wall 1. That is, in the method of measuring the porosity A and the porosity B described above, after the SEM image is taken, the area where the catalyst is determined to be present from the color information in the obtained SEM image is identified as the pore portion of the partition wall 1 The porosity is determined.

  If A / B, which is a value obtained by dividing the porosity A by the porosity B, is less than 0.5, a crack tends to be easily formed at the intersection 15 of the partition wall 1 and sometimes develops into two or more continuous cracks. There are also concerns. When the above A / B exceeds 0.95, the partition wall 1 in the wall portion 16 separating the two cells 2 may easily be cracked.

  A / B which is a value obtained by dividing the porosity A by the porosity B is preferably 0.50 to 0.95, and more preferably 0.55 to 0.90. With this configuration, the occurrence of cracks can be suppressed more effectively.

  The value of the porosity B is not particularly limited, but is preferably 20 to 50%, and more preferably 20 to 45%. When the value of the porosity A is less than 20%, it may be difficult to support the catalyst on the partition walls 1. In addition, when the value of the porosity A exceeds 50%, the isostatic strength of the honeycomb structure 100 may be reduced.

  The arithmetic mean of the porosity A and the porosity B is preferably 15 to 45%, and more preferably 15 to 40%. When the arithmetic mean of the porosity A and the porosity B is less than 15%, it may be difficult to support the catalyst on the partition walls 1. When the arithmetic mean of the porosity A and the porosity B exceeds 45%, the isostatic strength of the honeycomb structure 100 may be lowered.

  There is no particular limitation on the shape of each cell 2 (hereinafter, also simply referred to as “cell shape”) in a cross section orthogonal to the extending direction of the cells 2 of the honeycomb structure part 4. For example, the shape of the cell 2 is preferably a polygon, and more preferably a square or a hexagon. In addition, the shape of each cell 2 may be a shape in which a corner of a polygon is formed in a curved shape, for example, a substantially square in which a corner of a square is formed in a curved shape.

  The thickness of the partition wall 1 is preferably 40 to 200 μm, more preferably 45 to 185 μm, and particularly preferably 50 to 170 μm. When the thickness of the partition walls 1 is less than 40 μm, the isostatic strength of the honeycomb structure 100 may be reduced. When the thickness of the partition wall 1 exceeds 200 μm, pressure loss may increase, which may cause reduction in engine output and fuel efficiency. The thickness of the partition wall 1 is a value measured by a method of observing a cross section orthogonal to the axial direction of the honeycomb structure 100 with an optical microscope.

  The entire shape of the honeycomb structure 100 is not particularly limited. For example, the overall shape of the honeycomb structure 100 shown in FIGS. 1 to 4 is a cylindrical shape in which the first end face 11 and the second end face 12 are circular. In addition, for example, as the entire shape of the honeycomb structure 100, the first end face 11 and the second end face 12 may be in a substantially circular columnar shape such as an oval shape, a racetrack shape, or an oval shape. Further, as the overall shape of the honeycomb structure 100, the first end face 11 and the second end face 12 may be polygonal prisms such as a quadrangle or a hexagon.

  There is no particular limitation on the material constituting the partition wall 1, but in terms of strength, heat resistance, durability and the like, the main component is preferably an oxide or non-oxide various ceramic, metal or the like. Specifically, for example, cordierite, mullite, alumina, spinel, silicon carbide, silicon nitride, and aluminum titanate can be considered as the ceramic. As the metal, Fe-Cr-Al based metal, metallic silicon, etc. can be considered. It is preferable to have as a main component 1 type or 2 types or more selected from these materials. From the viewpoint of high strength, high heat resistance, etc., one or more selected from the group consisting of alumina, mullite, aluminum titanate, cordierite, silicon carbide and silicon nitride may be the main component Particularly preferred. Further, silicon carbide or a silicon-silicon carbide composite material is particularly suitable from the viewpoint of high thermal conductivity, high heat resistance, and the like. Here, “main component” means a component that constitutes 50% by mass or more of the partition wall 1. It is preferable that 70 mass% or more is contained in the material which comprises the partition 1, and, as for the said component, it is still more preferable that 80 mass% or more is contained.

  In the honeycomb structure 100 of the present embodiment, a catalyst for exhaust gas purification may be supported on at least one of the surface of the partition walls 1 of the honeycomb structure portion 4 and the pores of the partition walls 1. By this configuration, CO, NOx, HC and the like in the exhaust gas can be made into harmless substances by catalytic reaction.

When carrying the catalyst on the honeycomb structure 100 of the present embodiment, the catalyst is a three-way catalyst, SCR catalyst, NO _X storage catalyst, it preferably comprises at least one member selected from the group consisting of oxidation catalyst. The three-way catalyst mainly refers to a catalyst that purifies hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NO _x ). As a three way catalyst, the catalyst containing platinum (Pt), palladium (Pd), rhodium (Rh) can be mentioned, for example. The SCR catalyst is a catalyst that selectively reduces the component to be purified. In particular, for the SCR catalyst mentioned above, it is preferable that _the NO _X selective reducing SCR catalyst for the selective reduction of NO _X in the exhaust gas. The _the NO _X selective reducing SCR catalyst for, can be mentioned catalyst for purifying by selective reduction of NO _X in the exhaust gas as a preferable example. Further, as the SCR catalyst, metal-substituted zeolite can be mentioned. Iron (Fe) and copper (Cu) can be mentioned as a metal which carries out metal substitution of zeolite. As a zeolite, beta zeolite can be mentioned as a suitable example. In addition, the SCR catalyst may be a catalyst containing at least one selected from the group consisting of vanadium and titania as a main component. Examples of the NO _x storage catalyst include alkali metals and alkaline earth metals. Examples of the alkali metal include potassium, sodium and lithium. As the alkaline earth metal, calcium and the like can be mentioned. As an oxidation catalyst, what contains a noble metal can be mentioned. Specifically, as the oxidation catalyst, one containing at least one selected from the group consisting of platinum, palladium and rhodium is preferable.

(2) Honeycomb Structure (Second to Fourth Embodiments):
Next, second to fourth embodiments of the honeycomb structure of the present invention will be described with reference to FIGS. 5 to 7. FIG. 5 is a plan view showing a part of a first end face schematically showing a second embodiment of the honeycomb structure of the present invention. FIG. 6 is a perspective view schematically showing a third embodiment of the honeycomb structure of the present invention as viewed from the first end face side. FIG. 7 is a plan view schematically showing the first end face of the fourth embodiment of the honeycomb structure of the present invention.

  As shown in FIG. 5, the second embodiment of the honeycomb structure of the present invention is a honeycomb structure 200 including a honeycomb structure portion 24 having porous partition walls 21. In the honeycomb structure 200 of the second embodiment, the shape of the cells 22 is “hexagonal”. The porosity of the partition 21 in the wall 36 separating the two cells 22 is the porosity A, and the porosity of the partition 21 in the intersection 35 connecting two or more walls 36 is the porosity. When it is set as the rate B, A / B which is a value which divided the porosity A by the porosity B is 0.5-0.95. The honeycomb structure 200 of the second embodiment configured in this manner can also obtain the same function and effect as the honeycomb structure 100 (see FIGS. 1 to 4) of the first embodiment described above. The honeycomb structure 200 of the second embodiment is preferably configured in the same manner as the honeycomb structure 100 of the first embodiment (see FIGS. 1 to 4) except that the shape of the cells 22 is different. In FIG. 5, reference numeral 31 denotes a first end face of the honeycomb structure portion 24.

  As shown in FIG. 6, the third embodiment of the honeycomb structure of the present invention is a honeycomb structure 300 provided with a honeycomb structure portion 44 of a segment structure. That is, in the honeycomb structure 300, each honeycomb structure portion 44 is constituted by the columnar honeycomb segments 46, and the side surfaces of the plurality of honeycomb segments 46 are joined by the joining layer 47. Thus, in the honeycomb structure 300 of the present embodiment, each of the plurality of honeycomb segments 46 is the honeycomb structure portion 44 in the honeycomb structure 300. Here, the “segment-structured honeycomb structure” refers to a honeycomb structure formed by bonding a plurality of individually manufactured honeycomb segments 46. A honeycomb structure 100 in which all the partition walls 1 of the honeycomb structure portion 4 are integrally formed as shown in FIGS. 1 to 4 may be referred to as an “integrated honeycomb structure”. The honeycomb structure of the present invention may be a "segment-structured honeycomb structure" or an "integral-type honeycomb structure".

  In the honeycomb structure 300, preferably, at least one honeycomb segment 46 is configured in the same manner as the honeycomb structure portion of the honeycomb structure of the first embodiment described above. Even with such a honeycomb structure 300, the same function and effect as those of the honeycomb structure of the first embodiment described above can be obtained. Each of the plurality of honeycomb segments 46 may have the same cell structure or may have different cell structures. In FIG. 6, reference numeral 51 denotes a first end face, and reference numeral 52 denotes a second end face.

  The outer peripheral wall 43 of the honeycomb structure 300 is preferably an outer peripheral coat layer formed of an outer peripheral coat material. The outer periphery coating material is a coating material for forming an outer periphery coating layer by coating the outer periphery of a joined body in which a plurality of honeycomb segments 46 are joined. Moreover, it is preferable that the bonded body obtained by bonding a plurality of honeycomb segments 46 is obtained by grinding the outer peripheral portion of the bonded body and arranging the above-described outer peripheral coat layer. Also in the integral type honeycomb structure 100 as shown in FIGS. 1 to 4, the outer peripheral wall 3 disposed on the outer periphery of the honeycomb structure portion 4 is formed by the outer peripheral coating material as described above. It may be a coat layer.

  In the honeycomb structure 300 shown in FIG. 6, the shape of the cells 42 is a quadrangle. However, the shape of each cell 42 in each honeycomb segment 46 is not limited to a quadrangle, and the shape of the cells in the honeycomb structure of the second embodiment described above can be adopted.

  As shown in FIG. 7, the fourth embodiment of the honeycomb structure of the present invention is a honeycomb structure 400 provided with a honeycomb structure portion 4 having an elliptical cross-sectional shape. Therefore, in the honeycomb structure 400, the entire shape of the honeycomb structure 400 is in the shape of a pillar having an elliptical end face. The honeycomb structure 400 of the fourth embodiment is configured in the same manner as the honeycomb structure 100 of the first embodiment (see FIGS. 1 to 4) except that the overall shape of the honeycomb structure 400 is different. preferable.

  In the honeycomb structure 400 shown in FIG. 7, the shape of the cell 2 is a quadrangle. However, the shape of the cell 2 is not limited to a quadrilateral.

(3) Manufacturing method of honeycomb structure:
Next, a method of manufacturing the honeycomb structure of the present invention will be described. Examples of the method for manufacturing a honeycomb structure of the present invention may include a step of producing a honeycomb formed body, and a step of drying and firing the obtained honeycomb formed body.

(3-1) Molding process:
The forming step is a step of extruding a clay obtained by kneading forming raw materials into a honeycomb shape to obtain a honeycomb formed body. The honeycomb formed body has a partition which partitions and forms a cell extending from the first end surface to the second end surface, and an outer peripheral wall formed so as to surround the outermost periphery of the partition. The part of the honeycomb structure constituted by the partition walls is the honeycomb structure part. In the forming step, first, the forming raw material is kneaded to form a clay. Next, the obtained clay is extruded to obtain a honeycomb formed body in which the partition walls and the outer peripheral wall are integrally formed.

  The forming raw material is preferably a ceramic raw material to which a dispersion medium and an additive are added. As an additive, an organic binder, a pore making material, surfactant, etc. can be mentioned. Water and the like can be mentioned as the dispersion medium. As the forming material, the same forming material as used in the conventionally known method for manufacturing a honeycomb structure can be used.

  As a method of knead | mixing a shaping | molding raw material and forming clay, the method of using a kneader, a vacuum soil kneader, etc. can be mentioned, for example.

  The extrusion molding can be performed using a die for extrusion molding in which a slit corresponding to the cross-sectional shape of the honeycomb formed body is formed. For example, as the die for extrusion molding, it is preferable to use a die having a slit corresponding to the shape of the cells in the honeycomb structures of the first to fourth embodiments described above.

  Here, in extrusion molding, it is preferable to increase the extrusion speed at the time of molding to increase the extrusion pressure. By performing extrusion molding by such a method, it is possible to make "the partition wall in the wall part which divides two cells" denser than the partition wall in the intersection. That is, in the obtained honeycomb structure, "the porosity B of the partition wall at the intersection portion" can be relatively increased. Accordingly, A / B, which is a value obtained by dividing the porosity A of the partition wall in the wall portion by the porosity B of the partition wall in the intersection portion, can be adjusted to a numerical range of 0.5 to 0.95.

(3-2) Firing step:
The firing step is a step of firing the honeycomb formed body obtained in the forming step to obtain a honeycomb structure. Before firing the honeycomb formed body, the obtained honeycomb formed body may be dried by, for example, microwave and hot air.

  The firing temperature when firing the honeycomb formed body can be appropriately determined depending on the material of the honeycomb formed body. For example, when the material of the honeycomb formed body is cordierite, the firing temperature is preferably 1380 to 1450 ° C., and more preferably 1400 to 1440 ° C. The firing time is preferably about 4 to 6 hours as a keeping time at the maximum temperature.

  Hereinafter, the present invention will be more specifically described by way of examples, but the present invention is not limited by these examples.

Example 1
0.5 parts by mass of a pore forming material, 33 parts by mass of a dispersion medium, and 5.6 parts by mass of an organic binder were added to 100 parts by mass of a cordierite-forming raw material, respectively, mixed and kneaded to prepare a clay. Alumina, aluminum hydroxide, kaolin, talc and silica were used as cordierite-forming materials. Water is used as the dispersion medium, a water-absorbing polymer having an average particle diameter of 10 to 50 μm is used as the pore forming material, methylcellulose is used as the organic binder, and dextrin is used as the dispersing agent did.

  Next, the clay was extruded using a predetermined mold to obtain a honeycomb molded body having a square cell shape and a cylindrical overall shape. At the time of extrusion molding, a die for extrusion molding having a slit corresponding to the cross-sectional shape of the honeycomb formed body is used, and in extrusion molding, the extrusion speed is compared with extrusion molding in Comparative Example 1 described later. The molding was carried out by raising the extrusion pressure.

  Next, the honeycomb formed body was dried by a hot air drier. The atmospheric temperature at the time of drying was 95 to 145 ° C.

  Next, the dried honeycomb molded body was fired to produce a honeycomb structure of Example 1. The atmosphere temperature at the time of firing was 1350 to 1440 ° C., and the firing time was 10 hours.

The honeycomb structure of Example 1 had a partition wall thickness of 70 μm and a cell density of 139.5 cells / cm ² . The cell shape in a cross section orthogonal to the cell extension direction of the honeycomb structure was a quadrangle. The column of “cell structure” in Table 1 shows the thickness of the partition wall, the cell density, and the cell shape.

  In the honeycomb structure of Example 1, the shape of the cross section orthogonal to the axial direction was a circle having a diameter of 105.7 mm, and the length in the cell extending direction (total length) was 81.2 mm. The shape of the honeycomb structure of Example 1 is shown in the column of “cross-sectional shape”, “diameter”, and “total length” in Table 1.

  About the honeycomb structure of Example 1, "porosity A of partition in the wall part which divides two cells 2" and "porosity B of partition in the intersection part which connects two or more wall parts" by the following method ", Was measured. Moreover, the average porosity and the porosity ratio were calculated | required from the value of the porosity A and the porosity B. The average porosity is the value of the arithmetic mean of porosity A and porosity B (ie, (A + B) / 2). The porosity ratio is the value of porosity A to porosity B (i.e., A / B). The respective results are shown in Table 2.

[Method of measuring porosity]
First, from the honeycomb structure, a sample piece for performing measurement of the porosity A and the porosity B was cut out. About the cut-out part of a sample piece, it makes a total of ten places five each in each of the 1st end face side (for example, inflow end face side) and the 2nd end face side (for example, outflow end face side) of a honeycomb structure. The cut-out point on each end face is the middle position between the center position and the outer peripheral edge of the honeycomb structure on the center position (first point) of each end face and the X axis and Y axis passing through the center position and orthogonal to each other. Four points (2 to 5), which are points, were used. The sample piece for measuring the porosity A was cut out so that the center part of the wall part which divides two cells may be included in each of ten places mentioned above. The length of one side of the sample piece for measuring the porosity A is the thickness of the wall constituting the partition wall, and the length of the other side is 100 μm in the extending direction of the partition wall in each end surface, The length was 20 mm in the cell extending direction. The sample piece for measuring the porosity B was cut out so that the center part of the intersection of a partition might be included in each of ten places mentioned above. The sample piece for measuring the porosity B had a square with a side length of 100 μm centering on the center of the intersection as an end face, and the axial length was 20 mm in the cell 2 extending direction. Next, the manufactured sample piece was embedded in epoxy resin and solidified, and then the surface was polished. And each sample piece was cut out 5 mm in the full length direction, the cut surface was observed by SEM, and the SEM image was acquired. As a scanning electron microscope, “model number: S3200-N” manufactured by Hitachi High-Technologies Corporation was used. In the case of measurement of the porosity A, a SEM image magnified 100 times was acquired for the central portion of the partition wall in each observation surface of the ten sample pieces. Moreover, in the case of the measurement of the porosity B, the SEM image expanded 100 times was acquired about the intersection part of the partition in each observation surface of 10 above-described sample pieces. After that, using image analysis software, for each image, “area S1 of partition wall” and “area S2 of pore portion (void portion)” are calculated, “calculation formula (1): S2 / (S1 + S2)” The porosity of the partition wall imaged by each image was computed by these. The average value of the porosity of ten places was used for the value of S1 and S2.

(Examples 2 to 20)
The cell structure, the cross-sectional shape, and the porosity A and the porosity B of the partition walls were changed as shown in Tables 1 and 2 to produce honeycomb structures of Examples 2 to 20. In Examples 5, 6, 13, and 14, the shape of the cell was hexagonal. In Examples 7 and 8, the cross-sectional shape of the honeycomb structure was elliptical.

  In Examples 19 and 20, silicon carbide (SiC) was used as a material for producing a honeycomb structure. The honeycomb structures of Examples 19 and 20 are honeycomb structures of a segment structure.

  At the time of preparation of the honeycomb structures of Examples 2 to 20, the extrusion pressure at the time of extrusion was adjusted, and the values of the porosity A and the porosity B of the partition wall were adjusted.

  The honeycomb structures of Examples 1 to 20 were evaluated for “heat-resistant shock resistance (robustness)” by the following method. The results are shown in Table 3.

[Heat resistance (robustness)]
The honeycomb structure was connected to an exhaust port (Exhaust port) of an in-line 4-cylinder gasoline engine having a displacement of 2.0 liters, and a metal can in which the honeycomb structure was held and accommodated was connected. In the evaluation of thermal shock resistance, a three-way catalyst was supported on the honeycomb structures of the respective examples and comparative examples so as to achieve a loading amount of 150 g / L. Then, a sample having a honeycomb structure supporting a three-way catalyst as a carrier was connected directly below the engine. Next, as shown in FIG. 8, the engine was operated under the condition that the engine high speed rotation and Idle were repeated. At this time, in each example, temperature control was performed so that the carrier temperature at the central portion at the 5 mm position on the inlet side of the honeycomb structure became 1050 ° C. as the maximum temperature and 100 ° C. or less as the minimum temperature. In the maximum temperature side, the engine high speed rotation was adjusted to adjust the temperature, and the minimum temperature was adjusted by introducing air at the time of cooling. The thermal shock resistance test was conducted by repeating the operation of this 20 minutes engine as one cycle (cycle) and repeating it 300 cycles. About the comparative example, the test was implemented on the conditions of the same engine speed as the same number of each Example, and the air introduction amount at the time of cooling. After finishing, I removed the metal can from the gasoline engine. Thereafter, the honeycomb structure as a carrier was taken out of the metal can, and the presence or absence of cracks in the "wall portion of partition wall" and the "intersection portion" was visually observed. About confirmation of the presence or absence of a crack, in the test mentioned above, it confirmed about all the places of the inflow end surface where temperature becomes the highest. And heat shock resistance was evaluated based on the following evaluation criteria. In Table 3, the observation result of the wall part of a partition and the observation result of the intersection part of a partition are each shown. Here, FIG. 8 is a graph showing the relationship between engine operation time (seconds) and engine rotational speed (rpm) in the thermal shock resistance test.
Evaluation A: no crack.
Evaluation C: Cracked.

Moreover, in evaluation of a thermal shock resistance, comprehensive determination was performed by the following method based on the evaluation result in two above-mentioned places. The results are shown in Table 3. In addition, in this comprehensive determination, the evaluation A is taken as pass, and the evaluation C is taken as failure.
Evaluation A: No cracks at both the wall and the intersection of the partition wall.
Evaluation C: Cracks in at least one of wall and intersection of partition wall.

(Comparative examples 1 to 22)
The cell structure, the cross-sectional shape, and the porosity A and porosity B of the partition walls were changed as shown in Table 4 and Table 5, to prepare honeycomb structures of Comparative Examples 1 to 22. The honeycomb structures of Comparative Examples 1 to 22 were also evaluated for “thermal shock resistance (robustness)” in the same manner as in Example 1. The results are shown in Table 6.

  In Comparative Examples 5, 6, 13, and 14, the cell shape was hexagonal. Moreover, about Comparative Examples 7 and 8, the cross-sectional shape of the honeycomb structure was made elliptical. In Comparative Examples 19 and 20, silicon carbide (SiC) was used as a material for producing a honeycomb structure. The honeycomb structures of Comparative Examples 19 and 20 are honeycomb structures having a segment structure. The honeycomb structure of Comparative Examples 1 to 20 is a honeycomb structure having the same structure as that of Examples 1 to 20 of the corresponding numbers except that the values of the porosity A and the porosity B are different. Further, the honeycomb structures of Comparative Examples 21 and 22 are honeycomb structures having the same structure (square cell shape) as the honeycomb structure of Comparative Example 1 except that the values of the porosity A and the porosity B are different. . In the heat shock resistance (robustness), the honeycomb structures of Comparative Examples 21 and 22 were measured under the same conditions as in Example 1.

(result)
The honeycomb structure of Examples 1 to 20 was able to obtain the result of “Evaluation A” satisfying the pass criteria in the comprehensive judgment of the thermal shock resistance. That is, in the honeycomb structures of Examples 1 to 20, in the evaluation of the thermal shock resistance, no cracks occurred in both the wall portion and the intersection portion of the partition wall.

  The honeycomb structures of Comparative Examples 1 to 22 resulted in “Evaluation C” which is rejected in the comprehensive judgment of the thermal shock resistance. That is, in the honeycomb structures of Comparative Examples 1 to 22, in the evaluation of the thermal shock resistance, cracks occurred in at least one of the wall portion and the intersection portion of the partition wall.

  The honeycomb structure of the present invention can be used as a catalyst carrier for supporting a catalyst for exhaust gas purification.

1, 21, 41: partition wall, 2, 22, 42: cell, 3, 43: outer peripheral wall, 4, 24, 44: honeycomb structure part, 11, 31, 51: first end face, 12, 52: second end face 15, 35: intersections, 16, 36: walls, 46: honeycomb segments, 47: bonding layers, 100, 200, 300, 400: honeycomb structures.

Claims (4)

A honeycomb structure portion having porous partition walls disposed so as to surround a plurality of cells serving as fluid channels extending from the first end face to the second end face;
The value of the porosity of the partition wall in the wall part separating the two cells is taken as porosity A,
The porosity B of the partition wall at the intersection, which is a portion connecting two or more of the walls, is taken as porosity B.
A / B which is a value obtained by dividing the porosity A by the porosity B is 0.5 to 0.95,
The honeycomb structure whose said porosity A is 10 to 40%.   The honeycomb structure according to claim 1, wherein an arithmetic mean of the porosity A and the porosity B is 15 to 45%.   The honeycomb structure according to claim 1 or 2, wherein the shape of the cells in a cross section orthogonal to the extending direction of the cells of the honeycomb structure portion is a quadrangle or a hexagon.   The honeycomb structure according to any one of claims 1 to 3, wherein a thickness of the partition wall is 40 to 200 m.

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