Honeycomb structure equipped with coating and method for manufacturing same

Abstract

Provided is a honeycomb structure equipped with a coating, the honeycomb structure having applied thereto a coating that can contribute to suppression of falling-off of a functional-material-containing layer. This honeycomb structure equipped with a coating comprises: an outer peripheral wall; a partition wall disposed on the inner-peripheral side of the outer peripheral wall, the partition wall partitioning and forming a plurality of cells that form a flow path extending from a first end surface to a second end surface; a functional-material-containing layer covering the partition wall; a first coating that covers a partition wall portion constituting the first end surface and an in-cell partition wall portion near the first end surface, said portions being part of the partition wall, and penetrates into said partition wall portions; and a second coating that covers a partition wall portion constituting the second end surface and an in-cell partition wall portion near the second end surface, said portions being part of the partition wall, and penetrates into said partition wall portions.

Description

Coated honeycomb structure and manufacturing method thereof

[0001] The present invention relates to a coated honeycomb structure.The present invention also relates to a coated honeycomb structure.

[0002] Conventionally, honeycomb structures have been known that include an outer peripheral wall and partition walls disposed on the inner peripheral side of the outer peripheral wall to define a plurality of cells that form flow paths extending from a first end face to a second end face. Some honeycomb structures have various functions imparted by forming a functional material-containing layer on the surface of the partition walls, the functional material containing a functional material such as an exhaust gas purification catalyst, a carbon dioxide (CO2) adsorbent, and a moisture absorbent.

[0003] A honeycomb structure having such a functional material-containing layer may be further coated. Patent Document 1 describes a honeycomb catalyst for purifying exhaust gases, comprising a honeycomb catalyst carrier made of porous cordierite ceramic and a catalyst layer formed on the surface of the honeycomb catalyst carrier, characterized in that the inlet-side open end face and at least a portion of the adjacent end face of the honeycomb catalyst carrier are formed with a surface layer (coating) that is smoother than the catalyst layer. Patent Document 1 also describes that the surface layer is coated with a glassy material and that the length of the surface layer is within 30 millimeters in the axial direction from the open end face of the honeycomb catalyst carrier. It also describes that this configuration smooths the area near the inlet-side open end face, preventing collected black smoke particles from accumulating and clogging the opening.

[0004] According to Patent Document 1, such a honeycomb catalyst for purifying exhaust gas can be manufactured by applying a material that becomes low-expansion glass when fired to the open end face and adjacent end face of a honeycomb catalyst carrier made of porous cordierite ceramic, baking and impregnating the material to form a smooth surface layer, and then applying activated alumina and catalytic metal to the areas other than the surface layer to form a catalyst layer.

[0005] Japanese Patent Application Publication No. 4-293550

[0006] A conventional problem with honeycomb structures having a functional material-containing layer is that the functional material-containing layer peels off and falls off from the partition wall surface of the honeycomb structure. For example, when a moisture-absorbent-containing layer is formed on the partition wall surface as the functional material-containing layer and the moisture absorption and desorption cycle is repeated, cracks eventually occur in the moisture-absorbent-containing layer due to the expansion and contraction of the moisture-absorbent. As the cracks progress, the moisture-absorbent-containing layer eventually peels off and falls off from the partition wall surface.

[0007] Coating a honeycomb structure is considered to be an effective means for preventing the functional material-containing layer from falling off. Therefore, for example, forming a surface layer of a glassy material as described in Patent Document 1 is considered. However, in Patent Document 1, glass is baked and impregnated to form a surface layer (coating) on ​​the honeycomb structure. Baking and impregnation is a process that involves high temperatures of over 100°C, and some functional materials are prone to performance degradation when exposed to such high temperatures. Therefore, it is desirable to develop a technology that can form a coating without requiring high temperatures of over 100°C.

[0008] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide, in one embodiment, a coated honeycomb structure having a coating that can contribute to suppressing shedding of the functional material-containing layer. Also, an object of the present invention is to provide, in another embodiment, a method for manufacturing such a coated honeycomb structure.

[0009] The present inventors have conducted extensive research to solve the above problems and have devised the present invention, as exemplified below. [Aspect 1] A coated honeycomb structure comprising: an outer peripheral wall; partition walls disposed on the inner peripheral side of the outer peripheral wall and defining a plurality of cells that form flow paths extending from a first end face to a second end face; a functional material-containing layer covering the partition walls; a first coating covering, of the partition walls, partition wall portions that form the first end face and intra-cell partition wall portions near the first end face and penetrating into these partition wall portions; and a second coating covering, of the partition walls, partition wall portions that form the second end face and intra-cell partition wall portions near the second end face and penetrating into these partition wall portions. [Aspect 2] The coated honeycomb structure according to Aspect 1, wherein the functional material-containing layer covers the partition wall portions that form the first end face, the intra-cell partition wall portions from the first end face to the second end face, and the partition wall portion that forms the second end face. [Embodiment 3] A coated honeycomb structure according to embodiment 1 or 2, wherein the first coating penetrates into the portion of the functional material-containing layer that covers the partition wall portion constituting the first end face and the portion of the functional material-containing layer that covers the partition wall portion within the cell near the first end face, and the second coating penetrates into the portion of the functional material-containing layer that covers the partition wall portion constituting the second end face and the portion of the functional material-containing layer that covers the partition wall portion within the cell near the second end face. [Embodiment 4] A coated honeycomb structure according to any one of Embodiments 1 to 3, wherein the first coating covering the partition wall portions within the cells near the first end face has an average coating length extending from the first end face in the length direction of the cells of 300 μm or more and 0.2% to 2.5% of the length of the honeycomb structure, and the second coating covering the partition wall portions within the cells near the second end face has an average coating length extending from the second end face in the length direction of the cells of 300 μm or more and 0.2% to 2.5% of the length of the honeycomb structure.[Aspect 5] A coated honeycomb structure according to Aspect 3 or Aspect 4 dependent on Aspect 3, wherein the average thickness of the first coating penetrating into the portion of the functional material-containing layer covering the intracellular partition wall portion near the first end face is 0 to 80 μm based on the surface of the functional material-containing layer, and the average thickness of the second coating penetrating into the portion of the functional material-containing layer covering the intracellular partition wall portion near the second end face is 0 to 80 μm based on the surface of the functional material-containing layer. [Aspect 6] A coated honeycomb structure according to any of Aspects 1 to 5, wherein at least one of the first coating and the second coating contains an adhesive resin. [Aspect 7] A coated honeycomb structure according to Aspect 6, wherein at least one of the first coating and the second coating contains an epoxy resin. [Embodiment 8] The coated honeycomb structure according to any one of Embodiments 1 to 7, wherein the average penetration depth of the first coating that has penetrated into the partition wall portion that constitutes the first end face is 100 μm to 200 μm, and the average penetration depth of the second coating that has penetrated into the partition wall portion that constitutes the second end face is 100 μm to 200 μm. [Aspect 9] A method for manufacturing a coated honeycomb structure, comprising: Step A of preparing a honeycomb structure including an outer peripheral wall, partition walls disposed on an inner peripheral side of the outer peripheral wall and defining a plurality of cells each forming a flow path extending from a first end face to a second end face, and a functional material-containing layer covering the partition walls; Step B of penetrating a first coating liquid containing an adhesive resin into the partition wall portion constituting the first end face and the intracellular partition wall portion near the first end face of the partition walls; Step C of penetrating a second coating liquid containing an adhesive resin into the partition wall portion constituting the second end face and the intracellular partition wall portion near the second end face of the partition walls; and Step D of heating the first coating liquid and the second coating liquid after Steps B and C. [Aspect 10] A method for manufacturing a coated honeycomb structure according to Aspect 9, wherein Step D is performed in an atmosphere of 100°C or less. [Aspect 11] A method for manufacturing a coated honeycomb structure according to Aspect 9 or 10, wherein the adhesive resin is a curable resin.[Aspect 12] The manufacturing method of the honeycomb structure with coating according to any one of Aspects 9 to 11, wherein the viscosities at 25°C measured by a single cylindrical rotational viscometer conforming to JIS Z8803:2011 of the first coating liquid and the second coating liquid are 500 mPa·s to 20,000 mPa·s.

[0010] The honeycomb structure with coating according to an embodiment of the present invention can contribute to suppressing the peeling-off of the functional material-containing layer, and thus contributes to extending the lifespan of the honeycomb structure having the functional material-containing layer.

[0011] It is a schematic perspective view of the honeycomb structure with coating according to an embodiment of the present invention. It is a schematic cross-sectional view parallel to the extending direction of the cells of the honeycomb structure with coating according to an embodiment of the present invention. It is a partial enlarged view of the region surrounded by the thick frame in FIG. 2-1. It is a schematic cross-sectional view (X-X line cross-section in FIG. 2-1) orthogonal to the extending direction of the cells of the honeycomb structure with coating according to an embodiment of the present invention. It is a schematic cross-sectional view parallel to the extending direction of the cells of the honeycomb structure with coating according to another embodiment of the present invention. It is a schematic diagram for explaining the mechanism by which the peeling-off of the functional material-containing layer covering the partition wall by the coating is suppressed. It is a graph showing the result of obtaining the relationship between the film thickness of the coating and the pressure loss increase rate by simulation.

[0012] Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. The present invention is not limited to the following embodiments, and it should be understood that those obtained by appropriately making changes, improvements, etc. to the following embodiments based on the ordinary knowledge of those skilled in the art without departing from the gist of the present invention also fall within the scope of the present invention.

[0013] (1. Coated Honeycomb Structure) The coated honeycomb structure according to the embodiment of the present invention can be incorporated into a vehicle compartment purification system in various vehicles such as automobiles. Examples of vehicles include, but are not limited to, automobiles and trains. Examples of automobiles include, but are not limited to, gasoline-powered vehicles, diesel-powered vehicles, gas-fueled vehicles using CNG (compressed natural gas) or LNG (liquefied natural gas), fuel cell vehicles, electric vehicles, and plug-in hybrid vehicles. The honeycomb structure can also be applied to a system that absorbs carbon dioxide from the atmosphere.

[0014] As shown in FIGS. 1 to 4 , a coated honeycomb structure 100 according to an embodiment of the present invention includes an outer peripheral wall 11 and partition walls 14 disposed on the inner peripheral side of the outer peripheral wall 11 to define a plurality of cells 13 that form flow paths extending in parallel from a first end face 12 a to a second end face 12 b. The coated honeycomb structure 100 also includes a functional material-containing layer 20 that coats the partition walls 14. The coated honeycomb structure 100 can also include a first coating 15 that coats, of the partition walls 14, partition wall portions 140 a that constitute the first end face 12 a and intra-cell partition wall portions 141 a near the first end face, and that penetrates into the interiors of these partition wall portions 140 a, 141 a, and a second coating 16 that coats, of the partition walls 14, partition wall portions 140 b that constitute the second end face 12 b and intra-cell partition wall portions 141 b near the second end face, and that penetrates into the interiors of these partition wall portions 140 b, 141 b. Hereinafter, each of the constituent members of the coated honeycomb structure 100 will be described in detail.

[0015] (1-1. Honeycomb Structure) Here, the portion of the coated honeycomb structure 100 excluding the functional material-containing layer 20 and coatings such as the first coating 15 and second coating 16 (including the third coating and fourth coating, if any, described later) is referred to as the "honeycomb structure." The outer shape of the honeycomb structure is not particularly limited. For example, the outer shape of the cross section perpendicular to the extension direction of the cells 13 can be polygonal (quadrilateral (rectangle, square), pentagon, hexagon, heptagon, octagon, etc.) or rounded (circular, oval, egg, elliptical, oval, rounded rectangle, etc.). In the embodiment shown in FIG. 3, it is square. Note that the end faces (first end face 12a and second end face 12b) have the same shape as the cross section. Furthermore, when the cross section and end faces are polygonal, the corners may be chamfered.

[0016] The shape of the cells 13 is not particularly limited, but can be polygonal (quadrilateral (rectangle, square), pentagon, hexagon, heptagon, octagon, etc.) or round (circular, oval, egg, elliptical, oval, rounded rectangle, etc.) in a cross section perpendicular to the extension direction of the cells 13. These shapes may be used alone or in combination of two or more. Among these shapes, quadrilaterals and hexagons are preferred. In the embodiment shown in Figure 3, the shape is square. By providing cells 13 of such a shape, it is possible to reduce pressure loss when air flows through.

[0017] The honeycomb structure may be provided as a honeycomb bonded body by preparing a plurality of honeycomb segments, each having a honeycomb structure, and bonding the peripheral side surfaces of the plurality of honeycomb segments together via a bonding layer. Using a honeycomb bonded body makes it possible to increase the total cross-sectional area of ​​the cells 13, which is important for ensuring air flow while suppressing cracking. The bonding layer can be formed using a bonding material. The bonding material is not particularly limited, but may be a paste made by adding a solvent such as water to a ceramic raw material. The bonding material may contain a material having PTC (Positive Temperature Coefficient) properties or may contain the same material as the peripheral wall 11 and the partition walls 14. In addition to bonding the honeycomb segments together, the bonding material can also be used as an outer coating material after bonding the honeycomb segments.

[0018] In this specification, the thickness of the partition walls 14 refers to the length of a line segment connecting the centers of gravity of adjacent cells 13 across the partition walls 14 in a cross section perpendicular to the extension direction of the cells 13. The thickness of the partition walls 14 refers to the average thickness of all the partition walls 14. In this specification, the cell density refers to a value obtained by dividing the number of cells by the area of ​​one end face of the honeycomb structure (the total area of ​​the partition walls 14 and the cells 13 excluding the peripheral wall 11). In this specification, the cell opening ratio refers to a value obtained by dividing the total area of ​​the cells 13 defined by the partition walls 14 in a cross section perpendicular to the extension direction of the cells 13 by the area of ​​one end face (the total area of ​​the partition walls 14 and the cells 13 excluding the peripheral wall 11). Note that the cell opening ratio is calculated for the honeycomb structure, and the functional material-containing layer 20, the first coating 15, and the second coating 16 (third coating and fourth coating) are not taken into consideration.

[0019] From the viewpoint of ensuring the amount of functional material supported, the upper limit of the partition wall thickness is preferably 0.500 mm or less, more preferably 0.200 mm or less, and even more preferably 0.150 mm or less. Furthermore, from the viewpoint of ensuring the strength of the honeycomb structure, the lower limit of the partition wall thickness is preferably 0.010 mm or more, more preferably 0.020 mm or more, and even more preferably 0.030 mm or more. Therefore, the partition wall thickness is, for example, preferably 0.010 to 0.500 mm, more preferably 0.020 to 0.200 mm, and even more preferably 0.030 to 0.150 mm.

[0020] From the viewpoint of suppressing an increase in pressure loss and ensuring the amount of functional material supported, the upper limit of the cell density is 100 cells / cm. 2 Preferably, the number of cells per square centimeter is 70 or less. 2 More preferably, 65 cells / cm or less. 2 From the viewpoint of ensuring the strength of the substrate, the lower limit of the cell density is preferably 10 cells / cm or less. 2 Therefore, the cell density is preferably 10 to 100 cells / cm. 2 Preferably, the density is 10 to 70 cells / cm 2 More preferably, the density is 10 to 65 cells / cm 2 It is even more preferable that:

[0021] From the viewpoint of ensuring the strength of the substrate, the upper limit of the cell opening ratio is preferably 0.94 or less, more preferably 0.92 or less, and even more preferably 0.90 or less. From the viewpoint of keeping the pressure loss low, the lower limit of the cell opening ratio is preferably 0.80 or more, more preferably 0.83 or more, and even more preferably 0.85 or more. Therefore, the cell opening ratio is, for example, preferably 0.80 to 0.94, more preferably 0.83 to 0.92, and even more preferably 0.85 to 0.90.

[0022] From the viewpoints of ensuring the strength of the honeycomb structure, reducing the pressure loss when the gas passes through the cells, ensuring the amount of functional material carried, and ensuring the contact area with the gas flowing through the cells, it is desirable to suitably combine the thickness of the partition walls 14, the cell density, and the cell opening ratio. Therefore, in a preferred embodiment, for example, the thickness of the partition walls is 0.010 to 0.500 mm, and the cell density is 10 to 100 cells / cm. 2 The cell aperture ratio is 0.80 to 0.94.

[0023] The thickness of the peripheral wall 11 is not particularly limited, but is preferably determined based on the following viewpoints. First, from the viewpoint of reinforcing the honeycomb structure, the thickness of the peripheral wall 11 is preferably 0.05 mm or more, more preferably 0.06 mm or more, and even more preferably 0.08 mm or more. In this specification, the thickness of the peripheral wall 11 refers to the length in the normal direction of the side surface of the honeycomb structure from the boundary between the peripheral wall 11 and the outermost cell 13 or partition wall 14 in a cross section perpendicular to the extension direction of the cells 13.

[0024] The length of the honeycomb structure in the direction in which the cells 13 extend and the cross-sectional area perpendicular to the direction in which the cells 13 extend are not particularly limited and may be adjusted according to the required size of the coated honeycomb structure 100. For example, the honeycomb structure may have a length of 20 to 350 mm in the direction in which the cells 13 extend and a cross-sectional area perpendicular to the flow path direction of 12.25 to 625 cm. 2 There are no particular limitations on the relationship between the length of the cells of the honeycomb structure in the extension direction and the maximum diameter of each end face (the maximum length of the diameters passing through the center of gravity of each end face of the honeycomb structure). Therefore, the length of the cells 13 of the honeycomb structure in the extension direction may be longer than the maximum diameter of each end face, or the length of the cells 13 of the honeycomb structure in the extension direction may be shorter than the maximum diameter of each end face.

[0025] Although there are no particular restrictions on the materials of the partition walls 14 and the outer peripheral wall 11 that constitute the honeycomb structure, for example, ceramics can be used. In one embodiment, the partition walls 14 and the outer peripheral wall 11 contain one or more materials selected from cordierite, silicon carbide, a silicon-silicon carbide composite material, silicon nitride, mullite, alumina, aluminum titanate, and barium titanate (BaTiO).

[0026] (1-2. Functional Material-Containing Layer) The functional material-containing layer 20 is provided so as to cover the partition walls 14 of the honeycomb structure. For example, the functional material-containing layer 20 may be provided so as to cover the partition wall portions 141 inside the cells 13 (intra-cell partition wall portions), or may be provided so as to cover the partition wall portions 140a constituting the first end face 12a, or may be provided so as to cover the partition wall portions 140b constituting the second end face 12b. In a preferred embodiment, the functional material-containing layer 20 covers the partition wall portions 140a constituting the first end face 12a, the partition wall portions 141 inside the cells 13 from the first end face 12a to the second end face 12b (intra-cell partition wall portions), and the partition wall portions 140b constituting the second end face 12b.

[0027] The functional material-containing layer 20 may be provided so as to cover the outer peripheral wall portion 111 inside the cell 13, the outer peripheral wall portion 110a constituting the first end face 12a, or the outer peripheral wall portion 110b constituting the second end face 12b. In a preferred embodiment, the functional material-containing layer 20 covers the outer peripheral wall portion 111 inside the cell 13, the outer peripheral wall portion 110a constituting the first end face 12a, and the outer peripheral wall portion 110b constituting the second end face 12b.

[0028] Therefore, in one embodiment, the functional material-containing layer 20 covers the partition wall portion (internal cell partition wall portion) 141 inside the cell 13, the partition wall portion 140a constituting the first end face 12a, and the partition wall portion 140b constituting the second end face 12b, as well as the outer peripheral wall portion 111 inside the cell 13, the outer peripheral wall portion 110a constituting the first end face 12a, and the outer peripheral wall portion 110b constituting the second end face 12b (see Figure 2-1).

[0029] In another embodiment, as shown in FIG. 4 , the functional material-containing layer 20 covers the partition wall portion (internal cell partition wall portion) 141 inside the cell 13 and the outer peripheral wall portion 111 inside the cell 13, but does not cover the partition wall portion 140 a constituting the first end face 12 a, the partition wall portion 140 b constituting the second end face 12 b, the outer peripheral wall portion 110 a constituting the first end face 12 a, or the outer peripheral wall portion 110 b constituting the second end face 12 b.

[0030] The functional material contained in the functional material-containing layer 20 is not particularly limited as long as it can exhibit the desired function, but an adsorbent, a catalyst, or the like can be used. The adsorbent preferably has the function of adsorbing one or more components to be removed from the air, such as water vapor, carbon dioxide, and odor components. It is also preferable that the adsorbent has the function of adsorbing harmful volatile components. The components to be removed can be purified by using a catalyst. Furthermore, an adsorbent and a catalyst may be used in combination to enhance the ability of the adsorbent to capture the components to be removed.

[0031] The adsorbent preferably has the function of being able to adsorb components to be removed, such as water vapor, carbon dioxide, and harmful volatile components (e.g., aldehydes, odor components, etc.), at -20 to 40°C and desorb them at high temperatures of 60°C or higher. Examples of adsorbents having such a function include zeolite, silica gel, activated carbon, alumina, silica, low-crystalline clay, and amorphous aluminum silicate complexes. The type of adsorbent may be selected appropriately depending on the type of component to be removed. One type of adsorbent may be used alone, or two or more types may be used in combination.

[0032] The catalyst preferably has a function capable of promoting the oxidation-reduction reaction. Examples of catalysts having such a function include metal catalysts such as Pt, Pd, and Ag, and oxide catalysts such as CeO2 and ZrO2. One type of catalyst may be used alone, or two or more types may be used in combination.

[0033] Harmful volatile components contained in the air of a vehicle cabin, etc., include, for example, volatile organic compounds (VOCs), odor components, etc. Specific examples of harmful volatile components include ammonia, acetic acid, isovaleric acid, nonenal, formaldehyde, toluene, xylene, paradichlorobenzene, ethylbenzene, styrene, chlorpyrifos, di-n-butyl phthalate, tetradecane, di-2-ethylhexyl phthalate, diazinon, acetaldehyde, and N-methylcarbamate-2-(1-methylpropyl)phenyl.

[0034] The average thickness of the functional material-containing layer 20 is not particularly limited and may be determined depending on the size of the cells 13. For example, from the viewpoint of ensuring sufficient contact with gas, the average thickness of the functional material-containing layer 20 is preferably 20 μm or more, more preferably 25 μm or more, and even more preferably 30 μm or more. On the other hand, from the viewpoint of preventing peeling of the functional material-containing layer 20 from the partition walls 14 and the outer peripheral wall 11, the average thickness of the functional material-containing layer 20 is preferably 400 μm or less, more preferably 380 μm or less, and even more preferably 350 μm or less. Therefore, the average thickness of the functional material-containing layer 20 is, for example, preferably 20 to 400 μm, more preferably 25 to 380 μm, and even more preferably 30 to 350 μm.

[0035] The average thickness of the functional material-containing layer 20 is measured by the following procedure. As shown in FIG. 2-1 , a cross section of the honeycomb structure passing through the central axis O extending in the extension direction of the cells 13 and parallel to the extension direction of the cells 13 is cut out, and a cross-sectional image at approximately 50x magnification is obtained using a scanning electron microscope or the like. The position of the central axis O is the center of gravity of the cross section perpendicular to the extension direction of the cells 13 of the honeycomb structure (see FIG. 3 ). For each functional material-containing layer 20 visible in the cross-sectional image, the average thickness is calculated by dividing the cross-sectional area of ​​the functional material-containing layer 20 present in the region between both ends of the coating length (the length in the extension direction of the cells 13 or the length perpendicular to the extension direction of the cells 13, depending on the position of the functional material-containing layer) by the coating length. This calculation is performed uniformly for multiple functional material-containing layers 20 visible in the cross section, and the overall average value is the average thickness of the functional material-containing layer 20 throughout the coated honeycomb structure.

[0036] When the functional material-containing layer 20 is provided on each of the intra-cell partition wall portions 141, the partition wall portion 140a constituting the first end face 12a, the partition wall portion 140b constituting the second end face 12b, the outer peripheral wall portion 111 inside the cell 13, the outer peripheral wall portion 110a constituting the first end face 12a, and the outer peripheral wall portion 110b constituting the second end face 12b, the preferred range of the average thickness of the functional material-containing layer 20 on each portion is the same as the average thickness of the functional material-containing layer 20 on the entire coated honeycomb structure described above. The average thickness of the functional material-containing layer 20 on these portions can be measured by the same procedure as described above.

[0037] From the viewpoint of the functional material exerting the desired function, the amount of the functional material-containing layer 20 is preferably 50 g / L or more and 500 g / L or less, more preferably 100 g / L or more and 400 g / L or less, and even more preferably 150 g / L or more and 350 g / L or less, relative to the volume of the coated honeycomb structure 100. The volume of the honeycomb structure is a value determined by the external dimensions of the honeycomb structure.

[0038] (1-3. Coating) In one embodiment, the coated honeycomb structure 100 comprises a first coating 15 that coats the partition wall portion 140a constituting the first end face 12a and the intra-cell partition wall portion 141a near the first end face of the partition walls 14 and penetrates into the interior of these partition wall portions 140a, 141a, and a second coating 16 that coats the partition wall portion 140b constituting the second end face 12b and the intra-cell partition wall portion 141b near the second end face of the partition walls 14 and penetrates into the interior of these partition wall portions 140b, 141b.

[0039] The presence of the first coating 15 and the second coating 16 can prevent the functional material-containing layer 20 covering the partition walls 14 from falling off. Although the present invention is not intended to be limited by theory, the mechanism by which the functional material-containing layer 20 covering the partition walls 14 can be prevented from falling off is presumed to be as follows. When the first coating 15 and the second coating 16 are provided, even if the functional material-containing layer 20 peels off from the partition walls 14, the first coating 15 and the second coating 16 act as a stopper, making it difficult for the functional material-containing layer 20 to fall off from the cells 13 (see (1) in Figure 5). This effect can be obtained even if the first coating 15 and the second coating 16 do not penetrate into the functional material-containing layer 20, but it is preferable that the first coating 15 and the second coating 16 penetrate into the functional material-containing layer 20 because a greater effect can be obtained. When the first coating 15 and the second coating 16 penetrate into the functional material-containing layer 20, the coatings prevent the functional material-containing layer 20 from peeling off in the first stage, and even if the functional material-containing layer 20 peels off in the second stage, the first coating 15 and the second coating 16 act as stoppers, thereby increasing the effect of preventing the layer from falling off (see (2) in Figure 5).

[0040] The same applies to the case where the functional material-containing layer 20 is provided so as to cover the partition wall portion 140a that constitutes the first end face 12a. In the first stage, the coating prevents the functional material-containing layer 20 from peeling off, and even if the functional material-containing layer 20 peels off in the second stage, the first coating 15 and the second coating 16 act as stoppers to prevent the functional material-containing layer 20 from falling off (see (2) in Figure 5).

[0041] Therefore, in a preferred embodiment, the first coating 15 penetrates into the functional material-containing layer 20 in the portions covering the partition wall portions 140a constituting the first end face 12a and the portions covering the intra-cell partition wall portions 141a near the first end face. In addition to penetrating, the first coating 15 may also coat the portions of the functional material-containing layer 20 covering the partition wall portions 140a constituting the first end face 12a and the portions covering the intra-cell partition wall portions 141a near the first end face. Furthermore, in a preferred embodiment, the second coating 16 penetrates into the functional material-containing layer 20 in the portions covering the partition wall portions 140b constituting the second end face 12b and the portions covering the intra-cell partition wall portions 141b near the second end face. In addition to penetrating, the second coating 16 may also coat the portion of the functional material-containing layer 20 that covers the partition portion 140b constituting the second end face 12b, and the portion of the functional material-containing layer 20 that covers the intra-cell partition portion 141b near the second end face.

[0042] In one embodiment, the coated honeycomb structure 100 is provided with a third coating 17 that coats the outer peripheral wall portion 110a constituting the first end face 12a of the outer peripheral wall 11 and the outer peripheral wall portion (cell inner and outer peripheral wall portion) 111a inside the cell 13 near the first end face, and penetrates into the interior of these outer peripheral wall portions 110a, 111a, and a fourth coating 18 that coats the outer peripheral wall portion 110b constituting the second end face 12b of the outer peripheral wall 11 and the outer peripheral wall portion (cell inner and outer peripheral wall portion) 111b inside the cell 13 near the second end face, and penetrates into the interior of these outer peripheral wall portions 110b, 111b.

[0043] The presence of the third coating 17 and the fourth coating 18 can suppress the falling off of the functional material-containing layer 20 that covers the outer peripheral wall 11. The mechanism for suppressing the falling off is the same as the mechanism for suppressing the falling off of the functional material-containing layer 20 that covers the partition wall 14, as described above.

[0044] Here, the vicinity of the first end face refers to a range of coordinate values ​​from 0 to 0.05×L when the length in the extension direction of the cells 13 from the first end face 12a to the second end face 12b of the honeycomb structure is L, and the coordinate value of the first end face 12a is 0 and the coordinate value of the second end face 12b is L. Furthermore, the vicinity of the second end face refers to a range of coordinate values ​​from 0.95×L to L.

[0045] In this specification, when A covers B, this includes both the case where A partially covers B and the case where A completely covers B. Therefore, for example, when the first coating 15 covers the intra-cell partition wall portion 141 a near the first end face, this includes both the case where the first coating 15 partially covers and the case where the first coating 15 completely covers the intra-cell partition wall portion 141 a near the first end face. Similarly, when the second coating 16 covers the intra-cell partition wall portion 141 b near the second end face, this includes both the case where the second coating 16 partially covers and the case where the second coating 16 completely covers the intra-cell partition wall portion 141 b near the second end face.

[0046] [Average Coating Length] From the viewpoint of enhancing the effect of suppressing shedding of the functional material-containing layer 20 coating the partition walls 14 and from the viewpoint of ensuring the functionality of the functional material-containing layer, the average coating length M1 of the first coating 15 (second coating 16) coating the intra-cell partition wall portion 141a near the first end face (inter-cell partition wall portion 141b near the second end face) extending from the first end face 12a (second end face 12b) in the length direction of the cells 13 is preferably 300 μm or more and 0.2% to 2.5% of the length of the honeycomb structure (the length from the first end face 12a to the second end face 12b). The average coating length M1 of the first coating 15 (second coating 16) extending from the first end face 12a (second end face 12b) in the length direction of the cells 13 is more preferably 750 to 3000 μm and 0.5% to 2% of the length of the honeycomb structure. The average coating length M1 of the first coating 15 (second coating 16) extending from the first end face 12a (second end face 12b) in the longitudinal direction of the cell 13 is 1000 to 2000 μm, and it is even more preferable that it is 1% to 1.5% of the length of the honeycomb structure.

[0047] Similarly, from the viewpoint of enhancing the effect of suppressing the shedding of the functional material-containing layer 20 coating the outer peripheral wall 11, the average coating length M2 of the third coating 17 (fourth coating 18) coating the cell inner and outer peripheral wall portion 111a near the first end face (cell inner and outer peripheral wall portion 111b near the second end face) extending in the length direction of the cell 13 from the first end face 12a (second end face 12b) is preferably 300 μm or more and 0.2% to 2.5% of the length of the honeycomb structure. The average coating length M2 of the third coating 17 (fourth coating 18) extending in the length direction of the cell 13 from the first end face 12a (second end face 12b) is more preferably 750 to 3000 μm and 0.5% to 2% of the length of the honeycomb structure. The average coating length M2 of the third coating 17 (fourth coating 18) extending from the first end face 12a (second end face 12b) in the longitudinal direction of the cell 13 is 1000 to 2000 μm, and it is even more preferable that it is 1% to 1.5% of the length of the honeycomb structure.

[0048] The average coating length of each of the first coating 15, the second coating 16, the third coating 17, and the fourth coating 18 is measured by the following procedure. As shown in FIG. 2-1 , an arbitrary cross section is cut out that passes through the central axis O extending in the cell extension direction of the honeycomb structure and is parallel to the extension direction of the cells 13, and cross-sectional images of each of the first coating 15, the second coating 16, the third coating 17, and the fourth coating 18 are obtained at approximately 50x magnification using a scanning electron microscope or the like. The position of the central axis O is the position of the center of gravity in the cross section perpendicular to the extension direction of the cells 13 of the honeycomb structure (see FIG. 3 ). The coating lengths of the first coating 15, the second coating 16, the third coating 17, and the fourth coating 18 that can be visually observed in the cross section in the cell extension direction are measured uniformly, and the average values ​​for each are calculated.

[0049] [Average Thickness of Coating] The first coating 15 (second coating 16) may not only penetrate into the portion of the functional material-containing layer 20 that covers the partition wall portion 140a constituting the first end face 12a (the partition wall portion 140b constituting the second end face 12b), but may also coat that portion. In this case, from the viewpoint of enhancing the effect of suppressing shedding of the functional material-containing layer 20 and suppressing an increase in pressure loss, the average thickness T1 of the first coating 15 (second coating 16) covering that portion is preferably 0 to 80 μm, more preferably 0 to 50 μm, and even more preferably 0 to 30 μm, based on the surface of the functional material-containing layer 20 (in the extension direction of the cells 13). Here, the average thickness T1 of the first coating 15 (second coating 16) being 0 means that the first coating 15 (second coating 16) has only penetrated but has not yet covered the surface of the functional material-containing layer 20.

[0050] The first coating 15 (second coating 16) may not only penetrate into the portion of the functional material-containing layer 20 that covers the intra-cell partition wall portion 141a near the first end face (the intra-cell partition wall portion 141b near the second end face), but may also coat that portion. In this case, from the viewpoint of enhancing the effect of suppressing shedding of the functional material-containing layer 20 and suppressing an increase in pressure loss when gas is flowed through the cells 13, the average thickness T2 of the first coating 15 (second coating 16) covering that portion is preferably 0 to 80 μm, more preferably 0 to 50 μm, and even more preferably 0 to 30 μm, based on the surface of the functional material-containing layer 20 (in a direction perpendicular to the extension direction of the cells 13). Here, the average thickness T2 of the first coating 15 (second coating 16) being 0 means that the first coating 15 (second coating 16) has only penetrated but has not yet covered the surface of the functional material-containing layer 20.

[0051] The third coating 17 (fourth coating 18) may not only penetrate into the portion of the functional material-containing layer 20 that covers the outer peripheral wall portion 110a that constitutes the first end face 12a (the outer peripheral wall portion 110b that constitutes the second end face 12b), but may also coat that portion. In this case, from the perspective of enhancing the effect of suppressing shedding of the functional material-containing layer 20 and suppressing an increase in pressure loss, the average thickness T3 of the third coating 17 (fourth coating 18) that covers that portion is preferably 0 to 80 μm, more preferably 0 to 50 μm, and even more preferably 0 to 30 μm, based on the surface of the functional material-containing layer 20 (in the extension direction of the cells 13). Here, the average thickness T3 of the third coating 17 (fourth coating 18) being 0 means that the third coating 17 (fourth coating 18) has only penetrated but has not yet covered the surface of the functional material-containing layer 20.

[0052] The third coating 17 (fourth coating 18) may not only penetrate into the portion of the functional material-containing layer 20 that covers the cell inner and outer peripheral wall portion 111a near the first end face (the cell inner and outer peripheral wall portion 111b near the second end face), but may also coat that portion. In this case, from the perspective of enhancing the effect of suppressing shedding of the functional material-containing layer 20 and suppressing an increase in pressure loss when gas is flowed through the cells 13, the average thickness T4 of the third coating 17 (fourth coating 18) covering that portion is preferably 0 to 80 μm, more preferably 0 to 50 μm, and even more preferably 0 to 30 μm, based on the surface of the functional material-containing layer 20 (in a direction perpendicular to the extension direction of the cells 13). Here, the average thickness T4 of the third coating 17 (fourth coating 18) being 0 means that the third coating 17 (fourth coating 18) has only penetrated but has not yet covered the surface of the functional material-containing layer 20.

[0053] The average thicknesses (T1, T2, T3, T4) of the first coating 15, the second coating 16, the third coating 17, and the fourth coating 18 are measured by the following procedure. As shown in FIG. 2-1 , an arbitrary cross section is cut out that passes through the central axis O extending in the flow direction of the honeycomb structure and is parallel to the extension direction of the cells 13, and cross-sectional images of the first coating 15, the second coating 16, the third coating 17, and the fourth coating 18 are obtained at approximately 50 magnifications using a scanning electron microscope or the like. The position of the central axis O is the position of the center of gravity in the cross section perpendicular to the extension direction of the cells 13 of the honeycomb structure (see FIG. 3).

[0054] When measuring the average thickness T1, the average thickness is calculated by dividing the cross-sectional area of ​​the first coating 15 (second coating 16) present in the region sandwiched between both ends of the coating length (the length perpendicular to the extension direction of the cells 13) covering the portion of the functional material-containing layer 20 that covers the partition wall portion 140a constituting the first end face 12a (the partition wall portion 140b constituting the second end face 12b) of the first coating 15 (second coating 16) visible in the cross section by the coating length. This calculation is performed evenly for the multiple first coatings 15 (second coatings 16) visible in the cross section, and the overall average value is taken as the average thickness T1.

[0055] When measuring the average thickness T2, the average thickness is calculated by dividing the cross-sectional area of ​​the first coating 15 (second coating 16) present in the region sandwiched between both ends of the coating length (the length in the extension direction of the cells 13) covering the portion of the functional material-containing layer 20 that covers the intra-cell partition wall portion 141a near the first end face (the intra-cell partition wall portion 141b near the second end face) for the first coating 15 (second coating 16) visible in the cross section by the coating length. This calculation is performed evenly for multiple first coatings 15 (second coatings 16) visible in the cross section, and the overall average value is taken as the average thickness T2.

[0056] The average thicknesses T3 and T4 can also be measured in the same manner as above.

[0057] [Average Penetration Depth of Coating] From the viewpoint of enhancing the effect of suppressing the shedding of the functional material-containing layer 20, the average value D1 of the penetration depth (in the extension direction of the cells 13) of the first coating 15 (second coating 16) that has penetrated into the interior of the partition portion 140a (partition portion 140b) that constitutes the first end face 12a (second end face 12b) is preferably 100 μm to 200 μm, more preferably 150 μm to 200 μm, and even more preferably 190 μm to 200 μm.

[0058] Similarly, from the viewpoint of enhancing the effect of suppressing the shedding of the functional material-containing layer 20, the average penetration depth D2 (in a direction perpendicular to the extension direction of the cells 13) of the first coating 15 (second coating 16) that has penetrated into the interior of the cell partition portion 141a near the first end face (the interior cell partition portion 141b near the second end face) is preferably 100 μm to 200 μm, more preferably 150 μm to 200 μm, and even more preferably 190 μm to 200 μm.

[0059] Furthermore, from the viewpoint of enhancing the effect of suppressing the falling off of the functional material-containing layer 20, the average value D3 of the penetration depth (in the extension direction of the cells 13) of the third coating 17 (fourth coating 18) that penetrates into the interior of the outer wall portion 110a that constitutes the first end face 12a (the outer wall portion 110b that constitutes the second end face 12b) is preferably 100 μm to 200 μm, more preferably 150 μm to 200 μm, and even more preferably 190 μm to 200 μm.

[0060] Similarly, from the viewpoint of enhancing the effect of suppressing the falling off of the functional material-containing layer 20, the average penetration depth D4 (in a direction perpendicular to the extension direction of the cells 13) of the third coating 17 (fourth coating 18) that has penetrated into the cell inner and outer peripheral wall portion 111a near the first end face (cell inner and outer peripheral wall portion 111b near the second end face) is preferably 100 μm to 200 μm, more preferably 150 μm to 200 μm, and even more preferably 190 μm to 200 μm.

[0061] The average values ​​(D1, D2, D3, D4) of the penetration depths of the first coating 15, the second coating 16, the third coating 17, and the fourth coating 18 are measured by the following procedure. As shown in FIG. 2-1 , an arbitrary cross section is cut out that passes through the central axis O extending in the flow direction of the honeycomb structure and is parallel to the extension direction of the cells 13, and cross-sectional images of the first coating 15, the second coating 16, the third coating 17, and the fourth coating 18 are obtained at approximately 50x magnification using a scanning electron microscope or the like. The position of the central axis O is the position of the center of gravity in the cross section perpendicular to the extension direction of the cells 13 of the honeycomb structure (see FIG. 3).

[0062] When measuring the average penetration depth D1, for the first coating 15 (second coating 16) visible in the cross section, the average thickness is calculated by dividing the cross-sectional area of ​​the first coating 15 (second coating 16) that is sandwiched between both ends of the coating length (the length perpendicular to the extension direction of the cells 13) that covers the partition wall portions 140a (partition wall portions 140b) that constitute the first end face 12a (the partition wall portions 140b) by the coating length. This calculation is performed evenly for the multiple first coatings 15 (second coatings 16) visible in the cross section, and the overall average value is taken as the average penetration depth D1.

[0063] When measuring the average penetration depth D2, for the first coating 15 (second coating 16) visible in the cross section, the average thickness is calculated by dividing the cross-sectional area of ​​the first coating 15 (second coating 16) present in the intra-cell partition wall portion 141a (inter-cell partition wall portion 141b) between both ends of the coating length (the length in the extension direction of the cells 13) covering the intra-cell partition wall portion 141a near the first end face (the intra-cell partition wall portion 141b near the second end face) by the coating length. This calculation is performed evenly for multiple first coatings 15 (second coatings 16) visible in the cross section, and the overall average value is taken as the average penetration depth D2.

[0064] The average values ​​D3 and D4 of the penetration depth can also be measured in the same manner as above.

[0065] [Coating Material] From the viewpoint of enhancing the effect of suppressing shedding of the functional material-containing layer 20, it is preferable that at least one of, and preferably both of, the first coating 15 and the second coating 16 contain an adhesive resin, and more preferably a cured resin. Similarly, it is preferable that at least one of, and preferably both of, the third coating 17 and the fourth coating 18 contain an adhesive resin, and more preferably a cured resin.

[0066] In a preferred embodiment, at least one, and preferably both, of the first coating 15 and the second coating 16 contains an adhesive resin in an amount of preferably 5% by weight or more, and more preferably 50% by weight or more. Similarly, at least one, and preferably both, of the third coating 17 and the fourth coating 18 contains an adhesive resin in an amount of preferably 5% by weight or more, and more preferably 50% by weight or more.

[0067] Examples of adhesive resins include, but are not limited to, epoxy resins, acrylic resins, phenolic resins, silicone resins, polyvinyl alcohol, and polyvinyl acetals (e.g., polyvinyl butyral). These may be used alone or in combination of two or more. From the viewpoint of the crack resistance and adhesive strength of the coating, curable resins such as epoxy resins and phenolic resins are preferably used as adhesive resins. Curable resins generally exist in the coating in a cured state, i.e., as a cured resin.

[0068] (2. Coated Honeycomb Structure) Next, a method for manufacturing a coated honeycomb structure according to an embodiment of the present invention will be described by way of example.

[0069] In one embodiment, a manufacturing method of a coated honeycomb structure according to the present invention includes: step A of preparing a honeycomb structure including an outer peripheral wall 11, partition walls 14 arranged on the inner peripheral side of the outer peripheral wall 11 and defining a plurality of cells 13 that form flow paths extending from a first end face 12a to a second end face 12b, and a functional material-containing layer 20 that coats the partition walls 14; step B of penetrating a first coating liquid containing an adhesive resin into the interior of the partition wall portions 140a that constitute the first end face 12a of the partition walls 14 and the interior of the intra-cell partition wall portions 141a near the first end face; step C of penetrating a second coating liquid containing an adhesive resin into the interior of the partition wall portions 140b that constitute the second end face 12b of the partition walls 14 and the interior of the intra-cell partition wall portions 141b near the second end face; and step D of heating the first coating liquid and the second coating liquid after steps B and C.

[0070] (2-1. Step A) In step A, a honeycomb structure is prepared, including an outer peripheral wall 11, partition walls 14 disposed on the inner peripheral side of the outer peripheral wall 11 and defining a plurality of cells 13 that form flow paths extending from the first end face 12a to the second end face 12b, and a functional material-containing layer 20 that covers the partition walls 14. To this end, first, a raw material composition containing a pore-forming material, a binder, and a dispersion medium is mixed with a ceramic raw material, and the mixture is kneaded to prepare a clay. The clay is then extruded to produce a honeycomb molded body. Additives such as a dispersant can be blended into the raw material composition as needed. During extrusion molding, a die having the desired overall shape, cell shape, partition wall thickness, cell density, etc. can be used.

[0071] The ceramic raw material is a raw material for the portion that remains after firing and forms the skeleton of the honeycomb structure as ceramic. The ceramic raw material can be provided, for example, in the form of powder. For example, when the ceramic is cordierite, a cordierite-forming raw material is used as the ceramic raw material. In this case, the cordierite-forming raw material is a raw material that becomes cordierite upon firing. The cordierite-forming raw material preferably has a chemical composition of 30 to 45 mass% alumina (Al2O3) (including aluminum hydroxide converted to alumina), 11 to 17 mass% magnesia (MgO), and 42 to 57 mass% silica (SiO2).

[0072] The pore-forming material is not particularly limited as long as it forms pores after firing, and examples thereof include wheat flour, starch, foamed resin, water-absorbent resin, silica gel, carbon (e.g., graphite), ceramic balloons, polyethylene, polystyrene, polypropylene, nylon, polyester, acrylic resin, and phenol. One type of pore-forming material may be used alone, or two or more types may be used in combination. From the viewpoint of increasing the porosity of the honeycomb structure after firing, the content of the pore-forming material is preferably 0.5 parts by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more, per 100 parts by mass of the ceramic raw materials. From the viewpoint of ensuring the strength of the honeycomb structure after firing, the content of the pore-forming material is preferably 10 parts by mass or less, more preferably 7 parts by mass or less, and even more preferably 4 parts by mass or less, per 100 parts by mass of the ceramic raw materials.

[0073] Examples of binders include organic binders such as methyl cellulose, hydroxypropoxyl methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, and polyvinyl alcohol. Furthermore, from the viewpoint of increasing the strength of the honeycomb formed body, the binder content is preferably 4 parts by mass or more, more preferably 5 parts by mass or more, and even more preferably 6 parts by mass or more, per 100 parts by mass of the ceramic raw materials. From the viewpoint of suppressing cracks due to abnormal heat generation during the firing process, the binder content is preferably 9 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 7 parts by mass or less, per 100 parts by mass of the ceramic raw materials. The binder may be used alone or in combination of two or more types.

[0074] Examples of the dispersion medium include water and a mixed solvent of water and an organic solvent such as alcohol, with water being particularly preferred.

[0075] Examples of dispersants that can be used include ethylene glycol, dextrin, fatty acid soap, and polyether polyol. One type of dispersant may be used alone, or two or more types may be used in combination. The content of the dispersant is preferably 0 to 2 parts by mass per 100 parts by mass of the ceramic raw material.

[0076] Next, the obtained honeycomb molded body is dried. In the drying step, a conventionally known drying method such as hot air drying, microwave drying, dielectric drying, reduced pressure drying, vacuum drying, freeze drying, etc. Among them, a drying method that combines hot air drying with microwave drying or dielectric drying is preferred because it can dry the entire molded body quickly and uniformly.

[0077] Next, the dried honeycomb formed body is fired to manufacture a honeycomb structure. A degreasing process to remove the binder can also be performed before firing. The combustion temperature of the binder is about 200°C, and the combustion temperature of the pore-forming material is about 300 to 1000°C. Therefore, the degreasing process can be performed by heating the honeycomb formed body to a temperature in the range of about 200 to 1000°C. The heating time is not particularly limited, but is usually about 10 to 100 hours. The firing conditions can be appropriately determined depending on the material of the honeycomb formed body. For example, when the honeycomb formed body is mainly composed of a cordierite-forming raw material, the firing can be performed by heating it to, for example, 1300 to 1450°C and holding it for 3 to 24 hours.

[0078] The firing furnace is not particularly limited, but an electric furnace, a gas furnace, or the like can be used.

[0079] Next, a functional material-containing layer 20 is formed to cover the partition walls 14 of the honeycomb structure obtained in this manner. Furthermore, a functional material-containing layer 20 may be formed to cover the peripheral wall 11. The method for forming the functional material-containing layer 20 is not particularly limited, but it can be formed, for example, by the following method. The honeycomb structure is immersed in a slurry containing a functional material, an organic binder, and water for a predetermined period of time, and then excess slurry is removed by blowing and wiping. The slurry is then dried to form the functional material-containing layer 20 on the partition walls 14 and the peripheral wall 11. Drying can be performed while heating the honeycomb structure to a temperature of, for example, approximately 120 to 600°C. The series of steps of immersion, excess slurry removal, and drying may be performed only once, but by repeating them multiple times, a functional material-containing layer 20 of the desired thickness can be formed on the partition walls 14 and the peripheral wall 11. Areas where the functional material-containing layer 20 should not be formed may be masked with masking tape or the like. Furthermore, before forming the functional material-containing layer 20, the first end face 12a and the second end face 12b may be polished in advance.

[0080] (2-2. Steps B and C) Next, a first coating 15 and a second coating 16 are formed on the partition walls 14 of the honeycomb structure having the functional material-containing layer 20 obtained in this manner. Furthermore, a third coating 17 and a fourth coating 18 may be formed on the outer peripheral wall 11. Specifically, first, step B is performed in which a first coating liquid containing an adhesive resin is allowed to penetrate into the interior of the partition wall portion 140a constituting the first end face 12a of the partition walls 14 and the interior of the intra-cell partition wall portion 141a near the first end face, and step C is performed in which a second coating liquid containing an adhesive resin is allowed to penetrate into the interior of the partition wall portion 140b constituting the second end face 12b of the partition walls 14 and the interior of the intra-cell partition wall portion 141b near the second end face.

[0081] When carrying out step B, a first coating liquid containing an adhesive resin can be simultaneously permeated into the interior of the outer peripheral wall portion 110a constituting the first end face 12a and the cell inner and outer peripheral wall portions 111a near the first end face of the outer peripheral wall 11. Furthermore, when carrying out step C, a second coating liquid containing an adhesive resin can simultaneously be permeated into the interior of the outer peripheral wall portion 110b constituting the second end face 12b and the cell inner and outer peripheral wall portions 111b near the second end face of the outer peripheral wall 11.

[0082] In addition to the adhesive resin, a curing agent, a solvent, and an organic binder may be added to the first coating liquid and the second coating liquid as appropriate. Examples of the curing agent include polyaddition-type curing agents such as amine-based, acid anhydride-based, and phenol-based curing agents, polymerization-type catalysts that promote curing by ionic polymerization, and latent curing agents such as dicyandiamide. The curing agent is particularly advantageous when the adhesive resin is a curable resin.

[0083] The method for permeating these coating liquids into the interior of the partition walls 14 and the outer peripheral wall 11 is not particularly limited, but examples thereof include a method of immersing the vicinity of the first end face or the vicinity of the second end face of the honeycomb structure having the functional material-containing layer 20 in a coating liquid at 20 to 30°C for a predetermined time. After the honeycomb structure is pulled out of the coating liquid, excess coating liquid may be removed by blowing and wiping. Furthermore, the cycle of immersion and pulling out may be repeated multiple times.

[0084] The penetration depth can be controlled by adjusting the viscosity of the first coating liquid and the second coating liquid and the immersion time in the first coating liquid and the second coating liquid. Because it is easy to control the penetration depth within an appropriate range, the viscosity of the first coating liquid and the second coating liquid at 25°C, as measured using a single-cylindrical rotational viscometer in accordance with JIS Z8803:2011, is preferably 500 mP·s to 20,000 mP·s. The viscosity of the first coating liquid and the second coating liquid is more preferably 500 mP·s to 10,000 mP·s. The immersion time may be set appropriately depending on the required penetration depth of the coating, but can be, for example, 5 to 10 seconds.

[0085] (2-3. Step D) After steps B and C, step D is performed, in which the first coating liquid and the second coating liquid are heated. The ambient temperature during heating may be set appropriately depending on the type of adhesive resin contained in the first coating liquid and the second coating liquid. However, in order to prevent deterioration of the performance of the functional material contained in the honeycomb structure, step D is preferably performed in an atmosphere of 100°C or less, and more preferably in an atmosphere of, for example, 70 to 90°C. The heating time may be set appropriately depending on the type of adhesive resin, and can be, for example, 15 to 30 minutes.

[0086] The penetration of the coating liquid (step B or step C) and the heating of the coating liquid (step D) may be repeated multiple times.

[0087] (1. Fabrication of honeycomb structure with functional material-containing layer) [Honeycomb structure] First, a honeycomb structure was fabricated having the following design specifications: Cross section and end face shapes of honeycomb structure perpendicular to the cell extension direction: quadrangle Cell shape perpendicular to the cell extension direction: square Thickness of outer peripheral wall: 1 mm Thickness of partition wall: 0.127 mm Cell density: 36 cells / cm 2 Cell opening ratio: 0.86; Cross-sectional size perpendicular to the cell extension direction of the honeycomb structure: 40 mm x 40 mm; Length in the cell extension direction of the honeycomb structure: 40 mm; Material constituting the outer wall and partition walls: cordierite

[0088] [Functional Material-Containing Layer] Next, a slurry containing a solid organic compound (functional material) having an amino group, an organic binder, and water was applied to the honeycomb structure cells by suction, and dried at a temperature of about 70°C to form a functional material-containing layer covering the partition walls and outer peripheral wall. The design specifications for the functional material-containing layer were as follows: Average thickness of the functional material-containing layer: 0.13 mm Amount of the functional material-containing layer relative to the volume of the honeycomb structure: 250 g / L Portions where the functional material-containing layer was formed: Partition wall portions within the cells, partition wall portions constituting the first end face, partition wall portions constituting the second end face, and outer peripheral wall portions within the cells, outer peripheral wall portions constituting the first end face, and outer peripheral wall portions constituting the second end face.

[0089] (2. Preparation of Coated Honeycomb Structure) The coating conditions were changed for the above-mentioned honeycomb structure with a functional material-containing layer to prepare coated honeycomb structures according to the following examples and comparative examples.

[0090] Example 1: A room-temperature-curing, two-component epoxy resin adhesive was prepared as a coating liquid. The viscosity of this coating liquid at 25°C was measured using a single-cylindrical rotational viscometer in accordance with JIS Z8803:2011 and found to be 1000 mPa·s. This coating liquid was placed in a container with a flat bottom, and a honeycomb structure with a functional material-containing layer was immersed in the coating liquid at approximately 25°C to a depth of approximately 0.3 mm from the first end face side for 5 seconds. The honeycomb structure with a functional material-containing layer was then lifted out of the coating liquid and immersed again in the coating liquid at approximately 25°C to a depth of approximately 0.3 mm from the second end face side for 5 seconds.

[0091] Next, the honeycomb structure with the functional material-containing layer after immersion in the coating liquid was placed in a dryer heated to 70°C and held there for 20 minutes to promote hardening of the adhesive resin in the coating liquid, and then left in the air to harden.

[0092] Example 2: A coating liquid was prepared by mixing 5% by weight of polyvinyl butyral, a type of organic binder, and 95% by weight of organic solvent-based colloidal silica (solid content 50% by weight). The viscosity of this coating liquid at 25°C was measured using a single-cylindrical rotational viscometer in accordance with JIS Z8803:2011 and found to be 1500 mPa·s. This coating liquid was placed in a container with a flat bottom, and the honeycomb structure with the functional material-containing layer was immersed in the coating liquid at approximately 25°C to a depth of approximately 0.3 mm from the first end face side for 5 seconds. The honeycomb structure with the functional material-containing layer was then removed from the coating liquid and immersed in the coating liquid at approximately 25°C to a depth of approximately 0.3 mm from the second end face side for 5 seconds.

[0093] Next, the honeycomb structure with the functional material-containing layer after immersion in the coating liquid was placed in a dryer heated to 70° C. and held there for 20 minutes to dry the coating liquid, thereby obtaining a coated honeycomb structure.

[0094] Comparative Example 1: A coating liquid was prepared by mixing 45% by weight of organic solvent-based colloidal silica (solid content 50% by weight), 17.5% by weight of titania powder, and 37.5% by weight of fused silica powder. The viscosity of this coating liquid at 25°C was measured using a single-cylindrical rotational viscometer in accordance with JIS Z8803:2011 and found to be 300 mPa·s. This coating liquid was placed in a container with a flat bottom, and the honeycomb structure with the functional material-containing layer was immersed in the coating liquid at approximately 25°C to a depth of approximately 0.3 mm from the first end face side for 5 seconds. The honeycomb structure with the functional material-containing layer was then removed from the coating liquid and immersed in the coating liquid at approximately 25°C to a depth of approximately 0.3 mm from the second end face side for 5 seconds.

[0095] Next, the honeycomb structure with the functional material-containing layer after immersion in the coating liquid was placed in a dryer heated to 70° C. and held there for 20 minutes to dry the coating liquid, thereby obtaining a coated honeycomb structure.

[0096] Comparative Example 2: A coating liquid was prepared by mixing 12.5% ​​by weight of aqueous colloidal silica (solid content 43% by weight), 2.5% by weight of silicon carbide powder, 10% by weight of titania powder, 25% by weight of fused silica powder, and 50% by weight of water. The viscosity of this coating liquid at 25°C was measured using a single-cylindrical rotational viscometer in accordance with JIS Z8803:2011 and found to be 100 mPa·s. This coating liquid was placed in a container with a flat bottom, and the honeycomb structure with the functional material-containing layer was immersed in the coating liquid at approximately 25°C to a depth of approximately 0.3 mm from the first end face side for 5 seconds. The honeycomb structure with the functional material-containing layer was then removed from the coating liquid and immersed in the coating liquid at approximately 25°C to a depth of approximately 0.3 mm from the second end face side for 5 seconds.

[0097] Next, the honeycomb structure with the functional material-containing layer after immersion in the coating liquid was placed in a dryer heated to 70° C. and held there for 20 minutes to dry the coating liquid, thereby obtaining a coated honeycomb structure.

[0098] Comparative Example 3: Silicone (solid content 90% by mass) was prepared as a coating liquid. The viscosity of this coating liquid at 25°C was measured using a single-cylindrical rotational viscometer in accordance with JIS Z8803:2011 and found to be 100,000 mP·s. This coating liquid was placed in a container with a flat bottom, and the honeycomb structure with the functional material-containing layer was immersed in the coating liquid at approximately 25°C to a depth of approximately 0.3 mm from the first end face side for 3 seconds. The honeycomb structure with the functional material-containing layer was then lifted out of the coating liquid and immersed in the coating liquid at approximately 25°C to a depth of approximately 0.3 mm from the second end face side for 3 seconds.

[0099] Next, the honeycomb structure with the functional material-containing layer after immersion in the coating liquid was placed in a dryer heated to 70° C. and held there for 20 minutes to dry the coating liquid, thereby obtaining a coated honeycomb structure.

[0100] (3. Measurement of Coating Length, Thickness, and Penetration Depth) The coated honeycomb structures according to the examples and comparative examples obtained above were subjected to the following measurements according to the procedures described above. The results are shown in Table 1. [Average coating length] The average coating length M1 of the first coating 15 that covers the intra-cell partition wall portions 141a near the first end face, extending from the first end face 12a in the length direction of the cells 13. The average coating length M1 of the second coating 16 that covers the intra-cell partition wall portions 141b near the second end face, extending from the second end face 12b in the length direction of the cells 13. [Average coating thickness] The average thickness T1 of the first coating 15 that covers the portion of the functional material-containing layer 20 that covers the partition wall portions 140a that constitute the first end face 12a. The average thickness T1 of the second coating 16 that covers the portion of the functional material-containing layer 20 that covers the partition wall portions 140b that constitute the second end face 12b. The average thickness T2 of the first coating 15 that covers the portion of the functional material-containing layer 20 that covers the intra-cell partition wall portions 141a near the first end face. Average thickness T2 of the second coating 16 covering the portion of the functional material-containing layer 20 covering the intra-cell partition wall portion 141b near the second end face [Average penetration depth of coating] Average value D1 of the penetration depth of the first coating 15 penetrating into the interior of the partition wall portion 140a constituting the first end face 12a Average value D1 of the penetration depth of the second coating 16 penetrating into the interior of the partition wall portion 140b constituting the second end face 12b Average value D2 of the penetration depth of the first coating 15 penetrating into the interior of the intra-cell partition wall portion 141a near the first end face Average value D2 of the penetration depth of the second coating 16 penetrating into the interior of the intra-cell partition wall portion 141b near the second end face

[0101]

[0102] (4. Evaluation of Coating Adhesion of Coated Honeycomb Structure) [Reference Example] First, the following cycle test was conducted on an uncoated honeycomb structure with a functional material-containing layer. 1. A flask containing 300 to 500 mmL of distilled water was placed in a water bath set to 90°C, and the flask was left to stand for 20 minutes to heat the water. 2. The flask was connected to a vacuum desiccator, and the vacuum desiccator was connected to a vacuum pump. A partition wall sample of the honeycomb structure with a functional material-containing layer, machined to a 15 mm square, was placed from the flask into the flow path of the desiccator. 3. The vacuum pump was started, and the pressure indicated by the desiccator was adjusted to -0.08 to -0.09 MPa. 4. Water vapor was introduced into the partition wall sample for 20 minutes. 5. The pressure was released, and the partition wall sample was removed from the flow path. 6. Air was passed through the removed partition wall sample at 8.0 to 10.0 m / s for 5 to 10 minutes to dry it. 7. After drying, the end faces of the partition wall samples were observed using a microscope at a magnification of about 30x. The above steps 1 to 7 were counted as one cycle, and the cycle was repeated. At the end of each cycle, the presence or absence of peeling of the functional material-containing layer was visually confirmed. As a result, at the end of the third cycle, peeling of the functional material-containing layer was observed from some cells.

[0103] [Example 1] A partition wall sample having a coating that had penetrated into the functional material-containing layer was collected from the coated honeycomb structure according to Example 1 obtained above, and the same cycle test as in the Reference Example was conducted. In this case, the presence or absence of coating peeling was confirmed at the end of each cycle. As a result, no cracks or peeling of the coating were observed by visual observation at the end of seven cycles.

[0104] [Example 2] The coated honeycomb structure according to Example 2 obtained above was also subjected to the same cycle test as in Example 1. As a result, at the end of seven cycles, no peeling of the coating was observed by visual observation, but the presence of cracks was confirmed in some parts of the coating.

[0105] [Comparative Example 1] The coated honeycomb structure according to Comparative Example 1 obtained above was also subjected to the same cycle test as in Example 1. As a result, at the end of three cycles, peeling of the coating and the presence of cracks were partially confirmed by visual observation.

[0106] [Comparative Example 2] The coated honeycomb structure according to Comparative Example 2 obtained above was also subjected to the same cycle test as in Example 1. As a result, at the end of three cycles, partial cracks in the coating were confirmed by visual observation. Furthermore, peeling of the coating was confirmed at the end of five cycles.

[0107] [Comparative Example 3] The coated honeycomb structure according to Comparative Example 3 obtained above was also subjected to the same cycle test as in Example 1. As a result, at the end of three cycles, peeling of the coating and the presence of cracks were partially confirmed by visual observation.

[0108] (5. Pressure Loss Evaluation) For the honeycomb structure according to the above-mentioned Reference Example (a honeycomb structure with a functional material-containing layer that was not coated), the pressure loss when gas was flowed through the cells from the first end face toward the second end face at a flow rate of 10 m / s was determined by a simulation based on the Fanning equation using Microsoft Excel software. Furthermore, using this as a reference, the rate of increase in pressure loss was calculated when the average thicknesses T1 and T2 of the glass coating were changed. The results are shown in Figure 6. From Figure 6, it can be seen that the rate of increase in pressure loss can be kept within 5% if the average thicknesses T1 and T2 of the glass coating are within approximately 0.08 mm.

[0109] 11: Peripheral wall 12a: First end face 12b: Second end face 13: Cell 14: Partition wall 15: First coating 16: Second coating 17: Third coating 18: Fourth coating 20: Functional material-containing layer 100: Coated honeycomb structure 110a: Peripheral wall portion constituting first end face 110b: Peripheral wall portion constituting second end face 111: Peripheral wall portion 111a: Cell inner and outer peripheral wall portion near first end face 111b: Cell inner and outer peripheral wall portion near second end face 140a: Partition wall portion constituting first end face 140b: Partition wall portion constituting second end face 141: Intra-cell partition wall portion 141a: Cell inner partition wall portion near first end face 141b: Cell inner partition wall portion near second end face

Claims

1. A coated honeycomb structure comprising: an outer peripheral wall; partition walls arranged on the inner peripheral side of the outer peripheral wall and defining a plurality of cells that form flow paths extending from a first end face to a second end face; a functional material-containing layer covering the partition walls; a first coating covering, of the partition walls, partition wall portions that form the first end face and intra-cell partition wall portions near the first end face and penetrating into the interiors of these partition wall portions; and a second coating covering, of the partition walls, partition wall portions that form the second end face and intra-cell partition wall portions near the second end face and penetrating into the interiors of these partition wall portions.

2. A coated honeycomb structure as described in claim 1, wherein the functional material-containing layer covers the partition wall portion constituting the first end face, the partition wall portion within the cells from the first end face to the second end face, and the partition wall portion constituting the second end face.

3. A coated honeycomb structure as described in claim 1, wherein the first coating penetrates into the portion of the functional material-containing layer that covers the partition wall portion that constitutes the first end face and the portion of the functional material-containing layer that covers the partition wall portion within the cell near the first end face, and the second coating penetrates into the portion of the functional material-containing layer that covers the partition wall portion that constitutes the second end face and the portion of the functional material-containing layer that covers the partition wall portion within the cell near the second end face.

4. A coated honeycomb structure according to claim 1, wherein the first coating covering the partition wall portions within the cells near the first end face has an average coating length extending from the first end face in the longitudinal direction of the cells of 300 μm or more and 0.2% to 2.5% of the length of the honeycomb structure, and the second coating covering the partition wall portions within the cells near the second end face has an average coating length extending from the second end face in the longitudinal direction of the cells of 300 μm or more and 0.2% to 2.5% of the length of the honeycomb structure.

5. A coated honeycomb structure as described in claim 3, wherein the average thickness of the first coating that penetrates into the portion of the functional material-containing layer that covers the partition wall portion within the cell near the first end face is 0 to 80 μm based on the surface of the functional material-containing layer, and the average thickness of the second coating that penetrates into the portion of the functional material-containing layer that covers the partition wall portion within the cell near the second end face is 0 to 80 μm based on the surface of the functional material-containing layer.

6. The coated honeycomb structure according to claim 1, wherein at least one of the first coating and the second coating contains an adhesive resin.

7. The coated honeycomb structure according to claim 6, wherein at least one of the first coating and the second coating contains an epoxy resin.

8. A coated honeycomb structure according to claim 1, wherein the average penetration depth of the first coating that has penetrated into the interior of the partition wall portion that constitutes the first end face is 100 μm to 200 μm, and the average penetration depth of the second coating that has penetrated into the interior of the partition wall portion that constitutes the second end face is 100 μm to 200 μm.

9. A method for manufacturing a coated honeycomb structure, comprising: step A of preparing a honeycomb structure having an outer peripheral wall, partition walls disposed on the inner peripheral side of the outer peripheral wall and defining a plurality of cells that form flow paths extending from a first end face to a second end face, and a functional material-containing layer covering the partition walls; step B of penetrating a first coating liquid containing an adhesive resin into the interior of the partition wall portions that form the first end face and the intra-cell partition wall portions near the first end face of the partition walls; step C of penetrating a second coating liquid containing an adhesive resin into the interior of the partition wall portions that form the second end face and the intra-cell partition wall portions near the second end face of the partition walls; and step D of heating the first coating liquid and the second coating liquid after steps B and C.

10. A method for producing a coated honeycomb structure according to claim 9, wherein step D is carried out in an atmosphere of 100°C or less.

11. The method for manufacturing a coated honeycomb structure according to claim 9, wherein the adhesive resin is a curable resin.

12. A method for manufacturing a coated honeycomb structure according to claim 9, wherein the viscosity of the first coating liquid and the second coating liquid at 25°C measured using a single cylindrical rotational viscometer in accordance with JIS Z8803:2011 is 500 mP·s to 20,000 mP·s.

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