JP2018167221A - Honeycomb structure - Google Patents

Abstract

To provide a honeycomb structure having an isostatic strength improved and a pressure loss well suppressed.SOLUTION: A honeycomb structure 100 includes partition walls 1 that partition a plurality of cells 2 extending from an inlet end of a fluid to an outlet end. The cells 2 have a hexagonal shape. The partition walls 1 have a tabular main bodies and intersections 5 where the partition walls cross each other. The intersections 5 are composed of thick intersections 14 reinforced by a thick wall and remaining ordinary intersections 15 without a thick wall. A standard hexagon is assumed to have one apex as a starting thick intersection 5 among the main bodies and intersections 5 and other five intersections 5 as apexes on the end face. A hexagonal net 21 having a net-like hexagonal shape is assumed to have hexagons sharing at least one side with the standard hexagon to form a hexagonal net work on the end face. The intersections of the partition walls at the locations the hexagonal net 21 pass are thick intersections 14.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a honeycomb structure. More specifically, the present invention relates to a honeycomb structure in which isostatic strength is improved and pressure loss is well suppressed.

  Conventionally, exhaust gas discharged from a diesel engine or the like has been purified by a honeycomb-structured filter having porous partition walls that define a plurality of cells extending from the inflow end surface to the outflow end surface. Specifically, the filter purifies harmful substances in the exhaust gas with a catalyst or collects particulate matter in the exhaust gas.

  And as this filter, the thing whose shape of the cell in the cross section orthogonal to the cell extending direction is a hexagon (hexagonal cell) is widely used from a viewpoint that a catalyst can be apply | coated uniformly. In particular, in the market, a filter with high purification efficiency and low pressure loss is required, and hexagonal cells are often employed in combination with the condition that the partition walls are thin and the cell density is low. However, a honeycomb structure having hexagonal cells has a problem that isostatic strength is lower than that of a honeycomb structure that adopts non-hexagonal cells (for example, a cell having a square shape in the cross section). Furthermore, when it is employed in combination with the above-described conditions that the partition walls are thin and the cell density is low, there is a problem that the isostatic strength of the honeycomb structure further decreases.

  Thus, a honeycomb structure having hexagonal cells with improved isostatic strength has been reported in a honeycomb structure having hexagonal cells (see, for example, Patent Documents 1 to 4). Specifically, the honeycomb structure disclosed in Patent Document 1 is formed by isolating the honeycomb structure by thickening or reinforcing partition walls that form cells that are located at a specific distance (range) from the outer peripheral wall. Static strength is improved. In the honeycomb structure described in Patent Document 2, the isostatic strength is improved by setting the intersection radius of the partition walls and the radius of curvature of the intersection portion of the partition walls and the outer peripheral wall to a specific range. The honeycomb structure described in Patent Document 3 is provided with a reinforced region that is substantially straight and has both ends in contact with the outer peripheral wall, and the isostatic strength is improved by thickening the partition walls of the reinforced region. The honeycomb structure described in Patent Document 4 has improved isostatic strength by disposing discontinuous partition reinforcing regions in a hexagonal lattice shape.

Japanese Patent No. 3229595 JP 2008-246472 A JP 2007-275873 A JP 2012-223719 A

  In the honeycomb structures of Patent Documents 1 to 4, there is a problem with pressure loss, which is a performance required as a filter. Specifically, since the honeycomb structure described in Patent Document 1 employs means such as thickening the partition walls, pressure loss, which is a performance required as a filter, is still high, and there is room for reduction of pressure loss. is there.

  Since the honeycomb structure described in Patent Document 2 has a curvature at all the intersections of the hexagonal cells for the purpose of suppressing catalyst peeling, the pressure loss increases.

  In the honeycomb structure described in Patent Document 3, the catalyst is clogged in the reinforced region (cells defined by the reinforced cell walls), and the pressure loss increases.

  Since the honeycomb structure described in Patent Document 4 has reinforced partition walls with a large thickness, it is difficult to sufficiently suppress pressure loss.

  As described above, in the honeycomb structure having hexagonal cells, there is a problem that pressure loss increases when isostatic strength is improved. Accordingly, there has been a strong demand for the development of a honeycomb structure in which pressure loss is well suppressed while improving isostatic strength.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide a honeycomb structure with improved isostatic strength and favorable suppression of pressure loss.

  In order to solve the above-described problems, the present invention provides the following honeycomb structure.

[1] In a cross section orthogonal to the cell extending direction, including a porous partition wall defining a plurality of cells extending from an inflow end surface that is one end surface serving as a fluid flow path to an outflow end surface that is the other end surface The cell has a hexagonal shape, and the partition wall is composed of a plate-shaped partition wall main body and an intersection portion where the partition wall main bodies intersect each other, and the intersection portion of the partition wall is reinforced by being thickened. A thick intersection point and a normal intersection point that is an intersection point other than the thick intersection point and is not thick, and of the partition wall body and the intersection point, only the intersection point is reinforced thickly. , Assuming a reference hexagon that is a hexagon starting from one of the intersections on the end face, the starting point being one of the vertices, and the other five intersections being vertices; At least one side outside the square When the hexagonal mesh, which is a net-like figure having a hexagonal mesh, is assumed on the end face by arranging a shared hexagon, the intersection of the partition walls at a position where the hexagonal mesh passes, The intersecting point of the partition that is the thick-walled intersection or the partition of the partition at the position where the hexagonal mesh passes and the intersection of the partition that forms the cell at the position where the hexagonal mesh passes A honeycomb structure in which at least one of the intersection portions is the thick intersection portion.

[2] The honeycomb structure according to [1], wherein a distance between opposing sides of the hexagonal mesh constituting the hexagonal mesh is 10 to 60 mm.

[3] In a cross section orthogonal to the cell extending direction, when an inscribed circle having the maximum area is drawn inside the thick intersection point, the thick intersection point has a diameter of the inscribed circle. The honeycomb structure according to [1] or [2], which satisfies a range of 0.10 to 0.40 mm.

[4] The honeycomb structure according to any one of [1] to [3], wherein only the intersection portion of the partition wall at a position through which the hexagonal mesh passes is the thick intersection portion.

[5] The honeycomb structure according to any one of [1] to [4], wherein the thick-walled intersection is a curved concave surface.

[6] The honeycomb structure according to [5], wherein a radius of a circle circumscribing the curved concave surface is 0.10 to 0.40 mm at the thick intersection point.

  In the honeycomb structure of the present invention, only a specific intersection portion among a plurality of intersection portions is thick (thick intersection portion), so that isostatic strength is improved and pressure loss is well suppressed. Is.

1 is a perspective view schematically showing an embodiment of a honeycomb structure of the present invention. It is a top view which shows typically a state when a hexagonal net | network is assumed on one end surface in one Embodiment of the honeycomb structure of this invention. [Fig. 3] Fig. 3 is a plan view schematically showing an enlarged one end face in one embodiment of a honeycomb structure of the present invention. FIG. 4 is a plan view schematically showing a further enlarged end surface shown in FIG. 3. FIG. 6 is a plan view schematically showing an enlarged one end face in another embodiment of a honeycomb structure of the present invention. FIG. 10 is an enlarged plan view schematically showing one end face of still another embodiment of a honeycomb structure of the present invention. FIG. 10 is an enlarged plan view schematically showing one end face of still another embodiment of a honeycomb structure of the present invention. FIG. 10 is an enlarged plan view schematically showing one end face of still another embodiment of a honeycomb structure of the present invention.

  Next, embodiments for carrying out 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 is understood that design changes, improvements, and the like can be added as appropriate based on the ordinary knowledge of those skilled in the art without departing from the spirit of the present invention. Should.

(1) Honeycomb structure:
One embodiment of the honeycomb structure of the present invention is a honeycomb structure 100 as shown in FIGS. The honeycomb structure 100 includes a porous partition wall 1 that partitions and forms a plurality of cells 2 extending from an inflow end surface 11 that is one end surface serving as a fluid flow path to an outflow end surface 12 that is the other end surface. In the honeycomb structure 100, the shape of the cell 2 in a cross section orthogonal to the extending direction of the cell 2 is a hexagon. In the honeycomb structure 100, the partition wall 1 includes a plate-shaped partition wall body 4 (see FIG. 4) and an intersection portion 5 where the partition wall bodies 4 intersect each other. The intersection portion 5 of the partition wall 1 includes a thick-walled intersection portion 14 reinforced by thickening, and a normal intersection portion 15 that is the intersection portion 5 other than the thick-walled intersection portion 14 and is not thick. Further, in the honeycomb structure 100, only the intersection portion 5 of the partition wall main body 4 and the intersection portion 5 is reinforced thickly. And when the honeycomb structure 100 assumes the hexagonal net | network 21 on the inflow end surface 11 as follows, the intersection part 5 of the partition 1 in the position which the hexagonal net | network 21 passes is the thick-walled intersection part 14 It is. Alternatively, the honeycomb structure 100 includes at least intersections 5 of the partition walls 1 at positions where the hexagonal mesh 21 passes and intersections 5 of the partition walls 1 which form cells 2 at positions where the hexagonal mesh 21 passes. One intersection 5 is a thick intersection 14. The hexagonal net 21 is a figure defined as follows. That is, first, on the end face of the honeycomb structure 100, one intersection point 5 is set as a starting point, this starting point is set as one of the vertices, and the other five intersection points 5 are respectively set as vertices. In FIG. 2, a thick broken line is assumed). Thereafter, a hexagon that shares at least one side is arranged outside the reference hexagon 23. In this way, a hexagonal mesh 21 (indicated by a broken line in FIG. 2), which is a net-like figure having a hexagonal mesh, is assumed on the inflow end face 11. In the honeycomb structure 100, only the intersection portion 5 at a position satisfying the above conditions is a thick intersection portion, and the other intersection portions 5 are normal intersection portions 15. That is, when all the intersection parts 5 are reinforced thickly, it does not correspond to the honeycomb structure of the present invention. The honeycomb structure 100 has an outer peripheral wall 26 on the outermost periphery. In FIG. 2, the reference hexagon 23 is indicated by a thick broken line for convenience of explanation, but is not distinguished from the hexagonal mesh 21 and constitutes the hexagonal mesh 21.

  FIG. 1 is a perspective view schematically showing one embodiment of a honeycomb structure of the present invention. FIG. 2 is a plan view schematically showing a state when a hexagonal mesh is assumed on one end face in one embodiment of the honeycomb structure of the present invention. Fig. 3 is an enlarged plan view schematically showing one end face in one embodiment of the honeycomb structure of the present invention. FIG. 4 is a plan view schematically showing the end face shown in FIG. 3 further enlarged. In FIG. 2, the cells and the partition walls are not shown. In FIG. 3, a part of the end face of the honeycomb structure is selected and enlarged. The same applies to FIGS.

  In such a honeycomb structure 100, by making the intersection portion 5 at a specific position the thick intersection portion 14, the isostatic strength is improved and the increase in pressure loss is well suppressed. ing.

  That is, the present invention assumes the above-mentioned “hexagonal mesh 21” in the honeycomb structure in which the shape of the cell 2 is “hexagonal” in the cross section orthogonal to the extending direction of the cell 2, and further this hexagonal mesh 21. By arranging the thick intersection point 14 in relation to the above, the above effect can be obtained. Furthermore, the figure assumed on the inflow end face 11 needs to be a net-like shape, and further, this net-like figure needs to be a hexagonal shape.

  In the honeycomb structure 100, as shown in FIG. 2, in the hexagonal mesh constituting the hexagonal mesh 21, the distance D between opposing sides is preferably 10 to 60 mm, and preferably 20 to 50 mm. Is more preferable. By setting it as such a range, the increase in a pressure loss can be suppressed favorably, fully improving isostatic strength. When the distance between the opposing sides is less than 10 mm, the effect of suppressing an increase in pressure loss becomes insufficient, and the fuel consumption may be deteriorated. If it exceeds 60 mm, the isostatic strength cannot be sufficiently improved, and the honeycomb structure may be damaged during canning. The “distance between the opposing sides” is an average value of the distances between the three sets of opposing sides (the distance connecting the centers of the opposing sides and the center). For example, when the hexagon which comprises a hexagonal net | network is a regular hexagon, it is the distance between the parallel sides which oppose.

  When the inscribed circle 27 (see FIG. 4) having the largest area is drawn inside the thick intersection point 14 in the cross section perpendicular to the extending direction of the cells 2, the honeycomb structure 100 has a thick intersection point 14. The diameter of the inscribed circle 27 preferably satisfies the range of 0.10 to 0.40 mm. When the diameter of the inscribed circle 27 of the thick-walled intersection portion 14 satisfies the above range, the isostatic strength is further improved and the pressure loss is further suppressed. If the diameter of the inscribed circle 27 of the thick intersection 14 is less than 0.10 mm, the isostatic strength cannot be sufficiently improved, and the honeycomb structure may be damaged during canning. If it exceeds 0.40 mm, the pressure loss increases, so that fuel consumption may be deteriorated. The diameter of the inscribed circle at the thick intersection point can be measured by analyzing an image obtained by photographing the end face of the honeycomb structure. Specifically, for the diameter of the inscribed circle, a plurality (10) of thick-walled intersections in the end face of the honeycomb structure are arbitrarily selected. Draw a tangent circle, measure its diameter, and calculate the average value.

  In the honeycomb structure 100, as described above, the intersection portion 5 (only the intersection portion 5) of the partition wall 1 at the position where the hexagonal mesh 21 passes may be the thick intersection portion 14, or the following In this way, the thick intersection 14 may be arranged. That is, the intersection 5 of the partition 1 at a position where the hexagonal mesh 21 passes, and at least one intersection 5 of the intersection 5 of the partition 1 which forms a cell 2 where the hexagonal mesh 21 passes. However, the thick-walled intersection 14 may be used. Among these, in the honeycomb structure 100, it is preferable that only the intersection portion 5 of the partition wall 1 at the position where the hexagonal mesh 21 passes is the thick intersection portion 14. That is, the thick intersection point 14 may be arranged in any way, but is preferably arranged only at a position where the hexagonal mesh 21 passes. Thus, by arranging the thick-walled intersection 14 only at the position where the hexagonal mesh 21 passes, the isostatic strength is further improved and the pressure loss is further suppressed. “The intersection (or cell) of the partition wall at the position where the hexagonal mesh passes” refers to the intersection where the hexagonal mesh overlaps the locus of the hexagonal mesh when the hexagonal mesh is drawn on the end face of the honeycomb structure. (Or cell).

  In the honeycomb structure 100 shown in FIG. 3 and the honeycomb structure 101 shown in FIG. 5, only the intersection portion 5 of the partition wall 1 at a position where the hexagonal mesh 21 passes is a thick intersection portion 14. . FIG. 5 is a plan view schematically showing an enlarged one end face in another embodiment of the honeycomb structure of the present invention.

  In the honeycomb structure 102 shown in FIG. 6, the intersection portion 5 of the partition wall 1 at a position through which the hexagonal mesh 21 passes and the intersection portion 5 of the partition wall 1 that partitions the cell 2 at a position through which the hexagonal mesh 21 passes. The at least one intersection portion 5 is a thick intersection portion 14. In other words, when a “cell in a position where the hexagonal mesh passes” is a hexagonal mesh passage cell, at least one of the six intersection portions of the partition walls defining the hexagonal mesh passage cell is a thick intersection portion. It is. Note that the honeycomb structure 103 shown in FIG. 7 and the honeycomb structure 104 shown in FIG. 8 also satisfy the above-mentioned conditions at the thick intersection 14 as in the honeycomb structure 102 shown in FIG.

  FIG. 6 is a plan view schematically showing an enlarged one end face in still another embodiment of the honeycomb structure of the present invention. FIG. 7 is a plan view schematically showing an enlarged one end face in still another embodiment of the honeycomb structure of the present invention. FIG. 8 is a plan view schematically showing an enlarged one end face in still another embodiment of the honeycomb structure of the present invention.

  The reference hexagon may be a hexagon (that is, a figure having six vertices), but is preferably a hexagon having three sets of parallel sides facing each other, and more preferably a regular hexagon. By doing in this way, isostatic strength is further improved and the increase in pressure loss is suppressed more satisfactorily. The hexagon arranged outside the reference hexagon is the same shape as the reference hexagon, and is preferably a hexagon that shares at least one side with the reference hexagon. When assuming the reference hexagon, after determining the starting point, when determining the other five vertices (intersection points) other than this starting point, these “other five vertices” can be selected as appropriate, but as described above It is preferable to select the reference hexagon to be a regular hexagon.

  In the honeycomb structure of the present invention, the shape of the thick intersection point is not particularly limited as long as it is reinforced by thickening compared to the normal intersection point which is not thick. That is, it can be said that the thick intersection portion is an intersection portion whose area is larger than that of the normal intersection portion in a cross section orthogonal to the cell extending direction.

  In the thick intersection point, the surface exposed to the cell is preferably a curved concave surface. That is, it is preferable that the thick intersection point has an arc shape in a cross section orthogonal to the cell extending direction. By doing so, the isostatic strength is further improved.

  Further, in the thick intersection point, the radius of the circle circumscribing the curved concave surface is preferably 0.10 to 0.40 mm, and more preferably 0.15 to 0.35 mm. Isostatic strength is further improved when the thick-walled intersection meets the above conditions. If the radius of the thick-walled intersection is less than 0.10 mm, the isostatic strength cannot be sufficiently improved, and the honeycomb structure may be damaged during canning. If it exceeds 0.40 mm, the pressure loss increases, so that fuel consumption may be deteriorated.

  The thickness of the partition wall (i.e., the partition wall body) is preferably 38 to 254 [mu] m, and more preferably 50 to 216 [mu] m. If it is thinner than 38 μm, the isostatic strength of the honeycomb structure may be lowered. If it is thicker than 254 μm, the initial pressure loss of the honeycomb structure may increase. The thickness of the partition wall (partition wall main body) 1 is determined so that the inner wall of the adjacent intersection portion 5 is the same as the inner circle of the intersection portion 5 in the cross section perpendicular to the cell 2 extending direction. The thickness T (see FIG. 4) at the center position of the straight line connecting the centers O of the tangent circles shall be said. The thickness of a partition is the value measured by the method observed with a microscope, and is an average value when measuring 15 places.

  The honeycomb structure 100 is one in which only the intersection portion 5 of the partition wall main body 4 and the intersection portion 5 is reinforced thickly. That is, in the honeycomb structure 100, the intersection portion 5 has a thick wall (thick intersection portion) as described above, but the partition wall body 4 does not have a thick wall. When the thick partition wall body 4 is provided, the initial pressure loss becomes too high. Note that “the partition wall body is thick” means that the partition wall body is thick (thick) when the thickness of the partition body is measured as described above. If the thickness T at the above-mentioned center position is the same, it is not thick. The phrase “the thickness T at the center position is the same” includes not only the case where the thickness T at the center position is uniform, but also the case where the thickness T is within a range of ± 10% of the average value.

Cell density of the honeycomb structure is not particularly limited, preferably from 15.5 to 186.0 cells / cm ^2, more preferably from 46.5 to 139.5 cells / cm ^2. If the cell density is less than 15.5 cells / cm ² , the isostatic strength of the honeycomb structure may be lowered. When the cell density is larger than 186.0 cells / cm ² , the cell cross-sectional area (area of the cross section perpendicular to the cell extending direction) is decreased, and thus the pressure loss may be increased.

  The porosity of the partition walls is preferably 20 to 80%, more preferably 25 to 70%. When the porosity is less than 20%, the initial pressure loss of the honeycomb structure may be increased. If the porosity is higher than 80%, the strength of the honeycomb structure may be lowered. The porosity is a value measured by a mercury porosimeter.

  The average pore diameter of the partition walls is preferably 1 to 30 μm, and more preferably 3 to 35 μm. When the average pore diameter is smaller than 1 μm, the initial pressure loss of the honeycomb structure may be increased. When the average pore diameter is larger than 30 μm, the isostatic strength of the honeycomb structure may be lowered. The average pore diameter is a value measured with a mercury porosimeter.

  As the material of the partition wall, ceramic is preferable, and cordierite, silicon carbide, silicon-silicon carbide based composite material, mullite, alumina, aluminum titanate, silicon nitride, and silicon carbide-cordierite because of excellent strength and heat resistance. More preferred is at least one selected from the group consisting of system composite materials. Among these, cordierite is particularly preferable.

  It is preferable that each thick-walled intersection in the honeycomb structure of the present invention is formed in the entire region (the entire region) from the inflow end surface to the outflow end surface of the honeycomb structure. By comprising in this way, durability of the whole direction of the cell of a honeycomb structure extending can be improved favorably.

(2) Manufacturing method of honeycomb structure:
A method for manufacturing the honeycomb structure of the present embodiment will be described. First, a kneaded material for producing a honeycomb structure is prepared, and this kneaded material is formed to produce a honeycomb formed body (forming step). At the time of forming, it is preferable that a thick-walled intersection is formed in at least a part of the cells serving as outflow cells in the obtained honeycomb structure to form a reinforced honeycomb formed body. On the other hand, at the time of molding, after forming a honeycomb molded body without forming thick-walled intersections in the cells, the honeycomb dried body obtained by drying the honeycomb molded body, or the honeycomb structure obtained by firing the honeycomb dried body In either case, a thick intersection point may be formed.

  Next, the obtained honeycomb formed body (or the dried honeycomb body after drying as necessary) can be fired to prepare a honeycomb structure (honeycomb structure manufacturing step).

(2-1) Molding process:
First, in the forming step, a ceramic forming raw material containing a ceramic raw material is formed to form a honeycomb formed body in which a plurality of cells serving as fluid flow paths are formed.

  The ceramic raw material contained in the ceramic forming raw material is preferably one containing at least one selected from the group consisting of cordierite forming raw material, cordierite, mullite, alumina, titania, silicon carbide, and aluminum titanate, More preferably, it is at least one selected from the group consisting of cordierite forming raw material, cordierite, mullite, alumina, titania, silicon carbide, and aluminum titanate, cordierite forming raw material, cordierite, mullite, alumina, Particularly preferred is one selected from the group consisting of titania, silicon carbide, and aluminum titanate. The cordierite forming raw material is a ceramic raw material blended so as to have a chemical composition that falls within the range of 42 to 56% by mass of silica, 30 to 45% by mass of alumina, and 12 to 16% by mass of magnesia. It is fired to become cordierite.

  The ceramic forming raw material is preferably prepared by mixing the ceramic raw material with a dispersion medium, an organic binder, an inorganic binder, a pore former, a surfactant and the like. The composition ratio of each raw material is not particularly limited, and is preferably a composition ratio in accordance with the structure and material of the honeycomb structure to be manufactured.

  When forming the ceramic forming raw material, it is preferable to first knead the forming raw material to form a kneaded material, and the obtained kneaded material is formed into a honeycomb shape. There is no restriction | limiting in particular as a method of kneading | mixing a shaping | molding raw material and forming a clay, For example, the method of using a kneader, a vacuum clay kneader, etc. can be mentioned. A method for forming a kneaded clay to form a honeycomb formed body is not particularly limited, and a conventionally known forming method such as extrusion molding or injection molding can be used. For example, a method of forming a honeycomb formed body by extrusion molding using a die having a desired cell shape, partition wall thickness, and cell density can be cited as a suitable example. As the material of the die, a cemented carbide which does not easily wear is preferable.

  As such a die, for example, it has two surfaces, and honeycomb-shaped slits are formed in a lattice shape on one surface and communicated with the slits on the other surface to introduce a forming raw material. A base made of a base body having holes formed therein can be mentioned. It is preferable that the corners of the base intersecting the slits are chamfered at the corners of the intersections where the slits intersect, which are the thick-walled intersections, on a curved or flat surface. By using such a die, a thick intersection can be selectively formed at a desired location during the formation of the honeycomb formed body. Moreover, you may provide a recessed part and a beam in the predetermined | prescribed intersection of the slit of a nozzle | cap | die so that an intersection part may become thick.

  The shape of the honeycomb formed body is not particularly limited, and is a cylindrical shape (columnar shape), a cross section orthogonal to the central axis is an elliptical shape, a racetrack shape, a triangular shape such as a triangular shape, a quadrangular shape, a pentagonal shape, a hexagonal shape or an octagonal shape. Examples include a shape (columnar shape). When the honeycomb structure to be manufactured is formed by joining a plurality of honeycomb segments, the shape of the honeycomb molded body is a triangle, a quadrangle, a pentagon, a hexagon, a cross section perpendicular to the central axis, A polygonal cylindrical shape (columnar shape) such as an octagon is preferable.

  After the above forming, the obtained honeycomb formed body may be dried. The drying method is not particularly limited, and examples thereof include hot air drying, microwave drying, dielectric drying, reduced pressure drying, vacuum drying, freeze drying and the like. Among them, dielectric drying, microwave drying or It is preferable to perform hot air drying alone or in combination.

  In the case where the thick-walled intersection is not formed at the time of forming the honeycomb molded body, after obtaining the honeycomb molded body in which the thick-walled intersection is not formed, the slurry that is the material of the thick-walled intersection is used. Is applied to a predetermined intersection of the intersections. Thereafter, the thick intersection point can be formed by drying and firing the slurry.

(2-2) Honeycomb structure manufacturing process:
Next, the obtained honeycomb formed body can be fired to obtain a honeycomb structure. When the honeycomb structure has a plugged portion, the honeycomb formed body is preferably fired after the plugged portion is disposed in the honeycomb formed body.

  Further, before firing (main firing) the honeycomb formed body, it is preferable to calcine the honeycomb formed body. The calcination is performed for degreasing, and the method is not particularly limited as long as the organic matter (organic binder, dispersant, pore former, etc.) therein can be removed. In general, the combustion temperature of the organic binder is about 100 to 300 ° C., and the combustion temperature of the pore former is about 200 to 800 ° C. Therefore, the calcining conditions are about 200 to 1000 ° C. in an oxidizing atmosphere, It is preferable to heat for about 100 hours.

  Firing of the honeycomb formed body (main firing) is performed in order to sinter and densify the forming raw material constituting the calcined formed body to ensure a predetermined strength. Since the firing conditions (temperature, time, atmosphere) vary depending on the type of molding raw material, appropriate conditions may be selected according to the type. For example, when a cordierite forming raw material is used, the firing temperature is preferably 1410 to 1440 ° C. In addition, the firing time is preferably 4 to 6 hours as a keep time at the maximum temperature.

(2-3) Plugging step:
In addition, when a plugging portion is provided at one end portion of a predetermined cell and the other end portion of the remaining cells (in the case of a plugged honeycomb structure), the following plugging step can be performed. . That is, plugging portions are formed by plugging the openings of predetermined cells on the inflow end face of the honeycomb formed body and the openings of the remaining cells on the outflow end face.

  Specifically, the plugged portion can be formed as follows. First, one end portion side is filled with a plugging material, and then the other end portion side is filled with a plugging material. As a method of filling the plugging material on one end side, a sheet is attached to one end face (for example, the inflow end face) of the honeycomb structure, and “cells to form plugging portions in the sheet” A masking process for opening a hole at a position overlapping with the sheet, and press-fitting the end of the honeycomb structure on the side where the sheet is attached into the container in which the plugging material is stored, And a press-fitting step of press-fitting into the cells of the honeycomb structure. When the plugging material is press-fitted into the cells of the honeycomb structure, the plugging material passes through the holes formed in the sheet and is filled only in the cells communicating with the holes formed in the sheet.

  Further, the method of filling the plugging material on the other end portion (for example, the outflow end face) side of the honeycomb structure is the same as the method of filling the plugging material on the one end portion side of the honeycomb structure described above. It is preferable to adopt this method. Moreover, the plugging material may be simultaneously filled in both end portions of the honeycomb structure.

  This plugging step is preferably performed after the forming step and before firing the honeycomb formed body.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

Example 1
As a ceramic raw material, a cordierite forming raw material (alumina, talc, kaolin) was used. The mass ratio of alumina, talc, and kaolin was the mass ratio at which cordierite was obtained after firing. A ceramic raw material was obtained by mixing a ceramic raw material with a binder (methylcellulose) and water. The obtained ceramic forming raw material was kneaded using a kneader to obtain clay.

  Next, the obtained kneaded material was molded using a vacuum extrusion molding machine to obtain a honeycomb molded body. In the obtained honeycomb formed body, the shape of the cell in the cross section orthogonal to the cell extending direction was a hexagon.

Regarding the shape of the honeycomb formed body, the partition wall thickness in the honeycomb structure after firing the honeycomb formed body was 90 μm. The cell density was 116 cells / cm ² .

  The pore diameter of the partition walls of the honeycomb structure was 5 μm, and the porosity was 35%. The average pore diameter and porosity are values measured with a mercury porosimeter.

  Further, the overall shape of the honeycomb formed body was a cylindrical shape (the diameter of the end face was 110.0 mm, and the length in the cell extending direction was 97.1 mm). The honeycomb formed body was formed integrally with the entire shape (integrated structure).

  Further, in this honeycomb formed body, a predetermined intersection portion of the intersection portions of the partition walls was set as a thick intersection portion (see FIG. 5), and the remaining intersection portion was set as a normal intersection portion.

  In this example, the honeycomb formed body was arranged with thick-walled intersections as shown in FIG. That is, only the intersection portion at the position where the hexagonal mesh passes was defined as the thick intersection portion. In FIG. 5, the intersection indicated by the black circle is the thick intersection.

  Next, the honeycomb formed body was degreased by heating at 450 ° C. for 5 hours, and further fired by heating at 1425 ° C. for 7 hours to obtain a honeycomb structure.

  The obtained honeycomb structure was evaluated for “isostatic strength” and “pressure loss” as follows.

(Isostatic strength)
The measurement of isostatic strength was performed based on the isostatic fracture strength test prescribed | regulated by M505-87 of the automobile standard (JASO standard) by the Japan Society for Automotive Engineers. The isostatic fracture strength test is a test in which a honeycomb structure is placed in a rubber cylindrical container, covered with an aluminum plate, and isotropically compressed under water. That is, the isostatic fracture strength test is a test that simulates the compressive load applied when the honeycomb structure is gripped on the outer peripheral surface of the converter can. The isostatic strength measured by this isostatic fracture strength test is indicated by a pressure value (MPa) when the honeycomb structure breaks. The isostatic strength was evaluated based on the following evaluation criteria based on the isostatic strength of the honeycomb structure of Comparative Example 1. The ratio of “isostatic strength” (value of the ratio of the isostatic strength of each example and comparative example to the isostatic strength of the honeycomb structure of Comparative Example 1) is shown as “Isostatic ratio” in Table 1. .

  When the ratio of “isostatic strength” is 1.8 or more, since the isostatic strength is improved satisfactorily, it is evaluated as “excellent”. When the ratio of “isostatic strength” is 1.5 or more and less than 1.8, “good” is evaluated, and when it is more than 1.2 and less than 1.5, “good” is evaluated. When the ratio of “isostatic strength” is less than 1.2, the improvement in isostatic strength is not sufficient and it is evaluated as “impossible”. The results are shown in Table 1.

(Pressure loss (initial pressure loss))
Pressure loss was measured in a state where particulate matter such as soot and ash was not deposited on the partition walls of the honeycomb structure. Specifically, air at a constant flow rate of 25 ° C. flows into the honeycomb structure carrying the catalyst, the pressure at the inflow end face and the outflow end face of the honeycomb structure is measured, and the differential pressure is defined as the initial pressure loss. . The pressure loss was evaluated based on the following evaluation criteria based on the pressure loss of the honeycomb structure of Comparative Example 1. In addition, the ratio of “pressure loss” (the value of the ratio of pressure loss of each example and comparative example to the pressure loss of the honeycomb structure of comparative example 1) is described as “pressure loss ratio” in Table 1.

  When the ratio of “pressure loss” is 1.02 or less, the pressure loss is sufficiently suppressed and it is evaluated as “excellent”. When the ratio of “pressure loss” is larger than 1.02 and 1.05 or less, it is evaluated as “good”, and when it is larger than 1.05 and 1.10 or less, it is evaluated as “good”. When the ratio of “pressure loss” is larger than 1.10, the suppression of pressure loss is insufficient and it is evaluated as “impossible”. The results are shown in Table 1.

  In Table 1, “distance between opposing sides in the reference hexagon” indicates a distance between opposing sides in a hexagonal mesh constituting the hexagonal mesh. “Intersection R” indicates the radius of the circle circumscribing the curved concave surface at the intersection (the radius of curvature (R) of the intersection). “The diameter of the inscribed circle at the thick intersection point” means that the inscribed circle having the maximum area is drawn inside the thick intersection point in the cross section perpendicular to the cell extending direction. Indicates diameter. The “placement pattern of the thick intersection point” indicates the arrangement of the thick intersection point with a drawing number. That is, for example, in the first embodiment, “FIG. 5” indicates that the thick intersection point is arranged as shown in FIG. 5 (the circles indicate the positions of the thick intersection point). ). 3 and 6 to 8 also indicate the positions of the thick intersection points.

(Examples 2-7, Comparative Examples 1-3)
A honeycomb structure was manufactured in the same manner as in Example 1 except that the conditions were changed as shown in Table 1. In the same manner as in Example 1, the manufactured honeycomb structure was evaluated for “isostatic strength” and “pressure loss”. The results are shown in Table 1.

  In Comparative Example 1, the intersection portion was curved, and the radius of curvature (R) at the intersection point was 0.05 mm. In Comparative Example 1, since the “thick intersection point” did not exist, the “placement pattern of the thick intersection point” column was set to “−”. In Comparative Example 2, since all the intersections are thick intersections, the column “Pattern of thick intersections” is described as “all points reinforcement”. In Comparative Example 3, the “presence / absence of wall thickness of partition wall body” was “present”, and the partition wall body had a thick portion. In Comparative Example 3, specifically, in the cross section orthogonal to the cell extending direction, all three partition wall main bodies extending from all thick intersections among the intersections were thick.

  From Table 1, it was confirmed that the honeycomb structures of Examples 1 to 7 were improved in isostatic strength and well suppressed in an increase in pressure loss.

  The honeycomb structure of the present invention can be suitably used as a filter for purifying exhaust gas from automobiles and the like.

1: partition wall, 2: cell, 4: partition body, 5: intersection point, 11: inflow end surface, 12: outflow end surface, 14: thick intersection point, 15: normal intersection point, 21: hexagonal mesh, 23: reference Hexagon, 26: outer peripheral wall, 27: inscribed circle, 100, 101, 102, 103, 104: honeycomb structure.

Claims (6)

Comprising a porous partition wall defining a plurality of cells extending from an inflow end surface which is one end surface serving as a fluid flow path to an outflow end surface which is the other end surface;
The shape of the cell in a cross section perpendicular to the cell extending direction is a hexagon,
The partition wall is composed of a plate-shaped partition wall main body, and an intersection portion where the partition wall main bodies intersect each other,
The intersection part of the partition wall is composed of a thick-walled and reinforced thick intersection part, and a normal intersection part that is the intersection part other than the thick-walled intersection part and is not thick,
Of the bulkhead body and the intersection, only the intersection is reinforced thickly,
Assuming a reference hexagon that is a hexagon starting from one of the intersections on the end face, the starting point being one of the vertices, and the other five intersections being vertices, and then the reference hexagon When a hexagonal mesh that is a net-like figure having a hexagonal mesh is arranged on the end face by arranging a hexagon sharing at least one side outside
The intersection part of the partition wall at a position where the hexagonal mesh passes is the thick intersection part, or the intersection point part of the partition wall at a position where the hexagonal mesh passes, and the hexagonal shape. A honeycomb structure in which at least one of the intersection portions of the partition walls that define and form the cell at a position where the net passes is the thick intersection portion.   The honeycomb structure according to claim 1, wherein in the hexagonal mesh constituting the hexagonal mesh, a distance between opposing sides is 10 to 60 mm.   In the cross section orthogonal to the cell extending direction, when an inscribed circle having the maximum area is drawn inside the thick intersection, the thick intersection has a diameter of 0.10. The honeycomb structure according to claim 1 or 2, satisfying a range of ~ 0.40mm.   The honeycomb structure according to any one of claims 1 to 3, wherein only the intersection portion of the partition wall at a position where the hexagonal mesh passes is the thick intersection portion.   The honeycomb structure according to any one of claims 1 to 4, wherein the thick-walled intersection is a curved concave surface exposed to the cell.   The honeycomb structure according to claim 5, wherein a radius of a circle circumscribing the curved concave surface is 0.10 to 0.40 mm at the thick intersection portion.

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