Manufacturing method of honeycomb structure

Abstract

To provide a honeycomb structure in which the generation of defects is suppressed.SOLUTION: A honeycomb structure production method has: a step of passing silicon carbide powder and metallic silicon powder through a sieve to obtain raw material powder; a step of mixing and kneading the raw material powder, a binder and a dispersion medium to obtain a green body; a molding step of extruding the green body from a nozzle formed with a slit corresponding to a partition wall of the honeycomb structure to obtain a honeycomb molded body with the partition wall for partitioning and forming cells made into a flow passage of a fluid; and a firing step of firing the honeycomb molded body. An opening of the sieve is 30 to 100% of a slit width of the nozzle, and in the molding step, the green body is passed through a screen having an opening of 70 to 150% of the slit width of the nozzle to execute the extrusion.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a honeycomb structure. [Background technology]

[0002] Catalyst carriers, which have a catalyst supported on a carrier, are used to treat harmful substances in exhaust gases emitted from vehicle engines. During treatment, if the catalyst temperature is low when the engine is started, the catalyst does not heat up to the required temperature, resulting in insufficient purification of exhaust gases. To solve this problem, development is underway on exhaust gas treatment devices that use electrically heated catalysts (EHCs), which heat the conductive carrier by passing electricity through it, thereby raising the temperature of the catalyst supported on the carrier to its activation temperature before or during engine start.

[0003] Patent Document 1 discloses a ceramic honeycomb structure as the carrier. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6438939 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in a ceramic honeycomb structure, if the partition walls that define the cells that serve as fluid flow paths have defects such as cuts (broken ribs), cracks, burrs, or small holes, it may be difficult to ensure excellent electrical heat generation properties, for example.

[0006] In view of the above, an object of the present invention is to provide a honeycomb structure in which the occurrence of the above defects is suppressed. [Means for solving the problem]

[0007] A method for manufacturing a honeycomb structure according to an embodiment of the present invention includes a step of passing silicon carbide powder and metal silicon powder through a sieve to obtain raw material powder, a step of mixing and kneading the raw material powder with a binder and a dispersion medium to obtain a puddle, a molding step of extruding the puddle from a die having slits corresponding to the partition walls of the honeycomb structure to obtain a honeycomb molded body having partition walls that define cells that serve as fluid flow paths, and a firing step of firing the honeycomb molded body, wherein the opening of the sieve is 30% to 100% of the slit width of the die, and the molding step includes a step of passing the puddle through a screen having openings that are 70% to 150% of the slit width of the die to perform the extrusion. In one embodiment, the extrusion pressure when the moldable material is extruded from the die is 20 MPa or less. In one embodiment, a pro-shear mixer is used to mix the raw material powder, the binder, and the dispersion medium. In one embodiment, a mixture of the raw material powder, the binder, and the dispersion medium is kneaded in a kneader at a kneading blade rotation speed of 20 rpm to 40 rpm for 50 minutes or longer. In one embodiment, the dispersion medium is added to the raw material powder and the binder in at least two or more divided portions, and the mixing and kneading is carried out for each addition. In one embodiment, the clay is left in an environment of 15°C to 35°C for 12 hours or more, and then the extrusion is carried out. In one embodiment, the forming tool used for the extrusion is made of a stainless steel material. In one embodiment, the forming tool used in the extrusion is surface-treated, and the surface treatment is at least one of DLC treatment and chrome plating. The surface treatment may be performed at least on a portion located downstream of the screen in the extrusion direction. In one embodiment, the average primary particle size of the silicon metal powder is less than 10 μm. In one embodiment, the silicon carbide powder has a particle size distribution in which the ratio of particle diameter D90 to particle diameter D10 (D90 / D10) is 2.0 or more. In one embodiment, the slit width of the die is 155 μm or less. [Effects of the Invention]

[0008] According to the embodiment of the present invention, a honeycomb structure in which the occurrence of defects is suppressed can be obtained. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a perspective view showing a schematic configuration of a honeycomb structure according to one embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view of the honeycomb structure shown in FIG. [Figure 3] FIG. 2 is a perspective view showing an example of use of the honeycomb structure shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to these embodiments. In addition, in order to clarify the description, the drawings may show the width, thickness, shape, etc. of each part more schematically than in the embodiment, but these are merely examples and do not limit the interpretation of the present invention.

[0011] A. Honeycomb structure FIG. 1 is a perspective view showing a schematic configuration of a honeycomb structure according to one embodiment of the present invention, and FIG. 2 is a cross-sectional view of the honeycomb structure shown in FIG. 1. The honeycomb structure 10 has partition walls 14 that define a plurality of cells 12 that extend in the longitudinal direction and can serve as fluid flow paths, and an outer peripheral wall 16 that surrounds the partition walls 14. The outer peripheral wall 16 extends in the longitudinal direction. Each of the plurality of cells 12 defines a space that extends in the longitudinal direction. The cross-sectional shape of each cell 12 perpendicular to the longitudinal direction is approximately square in the illustrated example, but may be other shapes such as a polygon (e.g., a triangle, a pentagon, or a hexagon), a circle, or an ellipse. The cross-sectional shape of the outer peripheral wall 16 perpendicular to the longitudinal direction is typically circular, but may also be polygonal or elliptical.

[0012] The thickness of the partition walls 14 is, for example, from the viewpoint of use as a catalyst carrier, preferably 310 μm or less, more preferably 250 μm or less, and even more preferably 230 μm or less. On the other hand, the thickness of the partition walls 14 is, for example, from the viewpoint of strength, preferably 100 μm or more, more preferably 130 μm or more, and even more preferably 150 μm or more. The number of cells 12 per unit area in a cross section perpendicular to the longitudinal direction is, for example, 50 cells / cm. 2 ~150 cells / cm 2 and preferably 75 cells / cm 2 ~150 cells / cm 2 is.

[0013] From the viewpoint of strength, the thickness of the outer peripheral wall 16 is preferably 0.1 mm or more, for example, whereas the thickness of the outer peripheral wall 16 is, for example, 1 mm or less, and preferably 0.7 mm or less.

[0014] The honeycomb structure 10 is preferably made of a silicon-silicon carbide composite material. The silicon-silicon carbide composite material may be a material in which a plurality of silicon carbide particles are bonded together by metal silicon. When the honeycomb structure 10 is made of a silicon-silicon carbide composite material, the ratio of the "mass of metal silicon as a binder" contained in the honeycomb structure 10 to the sum of the "mass of silicon carbide particles as aggregate" contained in the honeycomb structure 10 and the "mass of metal silicon as a binder" contained in the honeycomb structure 10 is preferably 10% by mass to 40% by mass, and more preferably 15% by mass to 35% by mass. The electrical resistivity of the honeycomb structure 10 at 400°C is preferably 0.1 Ωcm to 200 Ωcm.

[0015] The porosity of the partition walls 12 of the honeycomb structure 10 is preferably 35% to 60%. The average pore diameter of the partition walls 12 of the honeycomb structure 10 is preferably 2 μm to 15 μm. With such an average pore diameter, for example, the above-mentioned electrical resistivity can be satisfactorily achieved. The porosity and the average pore diameter can be measured by a mercury porosimeter.

[0016] B. Manufacturing method A method for manufacturing a honeycomb structure according to an embodiment of the present invention includes, in this order, a step of passing silicon carbide powder and metal silicon powder through a sieve to obtain raw material powder; a step of mixing and kneading the raw material powder with a binder and a dispersion medium to obtain a clay; a molding step of extruding the clay from a die having slits corresponding to the partition walls of the honeycomb structure to obtain a honeycomb molded body having partition walls that define cells that serve as fluid flow paths; and a firing step of firing the honeycomb molded body.

[0017] B-1. Raw material powder As described above, silicon carbide powder and metal silicon powder are sieved to obtain raw powder. The sieve opening is 100% or less, or may be 90% or less, or 80% or less, of the slit width of the die described below. For example, the sieve opening may be 150 μm or less, or may be 125 μm or less, or may be 100 μm or less. By using such a sieve, foreign matter, coarse particles, and agglomerated particles in the raw powder can be captured, effectively preventing the occurrence of defects caused by these. In addition, the residue captured by the screen described below can be reduced, and the screen can be made finer. Meanwhile, the sieve opening is 30% or more, preferably 40% or more, and more preferably 50% or more, of the slit width of the die described below. For example, the sieve opening may be 30 μm or more, or may be 40 μm or more, or may be 50 μm or more.

[0018] The silicon carbide powder and the metal silicon powder may be sieved using the same sieve (e.g., a sieve with the same mesh size), or different sieves (e.g., sieves with different mesh sizes). In one embodiment, the sieve used for sieving is selected depending on the particle sizes of the silicon carbide powder and the metal silicon powder. Specifically, it is preferable to sieve the silicon carbide powder using a sieve with mesh sizes of 60% or less of the slit width of the die described below. In order to achieve the particle size distribution described below and from the standpoint of cost, the silicon carbide powder before sieving may contain coarse particles. By using such a sieve, for example, coarse particles can be captured, thereby achieving the particle size distribution described below. Since agglomerated particles of silicon metal tend to pass through a screen (described later) and have a large effect on the occurrence of defects, the silicon metal powder is preferably sieved using a sieve with an opening size of 75% or less of the slit width of the die (described later), more preferably 70% or less, and even more preferably 65% or less. The lower limit of the opening size of each sieve is as described above.

[0019] The average particle size (average particle size after sieving) is preferably 3 μm to 50 μm, more preferably 3 μm to 40 μm. In one embodiment, from the viewpoint of the packing property (specifically, porosity and density) of the obtained honeycomb silicon carbide powder structure, the particle size distribution of the silicon carbide powder (particle size distribution after sieving) is such that the ratio of particle size D90 to particle size D10 (D90 / D10) is preferably 2.0 or more, more preferably 2.3 or more. Meanwhile, D90 / D10 is preferably 3.5 or less, more preferably 3.0 or less.

[0020] The average primary particle size of the metal silicon powder is preferably less than 10 μm, while the average primary particle size of the metal silicon powder is preferably 1 μm or more.

[0021] The raw material powder may contain powders other than silicon carbide powder and metal silicon powder.

[0022] B-2. Clay The raw material powder, binder, and dispersion medium are mixed and kneaded to obtain a clay. The blending ratio of silicon carbide powder and metal silicon powder in the raw material powder can be set to any appropriate ratio. The blending ratio of metal silicon powder is preferably 10 to 40 parts by mass, and more preferably 15 to 35 parts by mass, per 100 parts by mass of the total of silicon carbide powder and metal silicon powder. This range allows, for example, to obtain a honeycomb structure that satisfies the above-mentioned electrical resistivity.

[0023] Any suitable binder can be used as the binder. Typically, a cellulose-based binder is used. Specific examples of the cellulose-based binder include methyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxybutyl cellulose, hydroxyethyl methyl cellulose, and hydroxypropyl methyl cellulose. These may be used alone or in combination of two or more.

[0024] The blending ratio of the binder is preferably 1 to 15 parts by mass, and more preferably 6 to 10 parts by mass, per 100 parts by mass of the total of the silicon carbide powder and the metal silicon powder.

[0025] Specific examples of the dispersion medium include water and alcohol. Preferably, water is used. The blending ratio of the dispersion medium is preferably 20 to 80 parts by mass, more preferably 30 to 50 parts by mass, per 100 parts by mass of the total of the silicon carbide powder and the metal silicon powder.

[0026] The clay may contain additives, such as pore-forming materials and dispersants such as surfactants. The additives are added in an amount of, for example, 0 to 20 parts by mass per 100 parts by mass of the silicon carbide powder and metal silicon powder combined.

[0027] The raw material powder, the binder, the dispersion medium, and, if necessary, the additives are mixed and kneaded to obtain a clay. The method of mixing and kneading is not particularly limited, and any appropriate mixer or kneader can be used to perform the mixing and kneading.

[0028] Examples of the mixer include a Sigma kneader, a Banbury kneader, and a ribbon mixer. Other examples include a Plosser mixer and a Henschel mixer. Among these, a Plosser mixer is preferably used. A Plosser mixer can effectively break down agglomerates of the raw material powder, reducing the residue trapped in the screen described below and achieving finer meshes of the screen. It can also improve the fluidity of the resulting clay.

[0029] Examples of the kneader include a Sigma kneader, a Banbury mixer, and a screw-type kneading extruder. For example, kneading using a kneader is preferably carried out under conditions of a kneading blade (e.g., a screw) rotation speed of 20 to 40 rpm for 50 minutes or more. Under such conditions, the residue captured by the screen described below can be reduced, and the fluidity of the resulting clay can be improved.

[0030] In the mixing and kneading process, the order in which the raw materials are added is not particularly limited, but it is preferable to add the dispersion medium to the raw material powder and binder in at least two or more separate batches. Specifically, it is preferable to add the dispersion medium in multiple batches and mix and knead after each addition. This method of addition can reduce the residue captured by the screen described below and improve the fluidity of the resulting clay.

[0031] Prior to the extrusion (molding step) described below, the clay is preferably placed in an environment of 15°C or higher, more preferably in an environment of 15 to 35°C. The time for placing the clay in an environment of 15°C or higher is, for example, 6 hours or more, preferably 12 hours or more, and more preferably 18 hours or more. By carrying out such a step, gases that may be contained in the clay (e.g., gases derived from the raw materials) are released, and deterioration of the clay can be prevented. Furthermore, a honeycomb structure having desired properties (e.g., density and average pore diameter) can be manufactured.

[0032] The clay is preferably subjected to a degassing treatment before the extrusion (molding process) described below. By performing the degassing treatment, a clay with good moldability can be obtained, and a honeycomb structure with reduced defects can be obtained. For example, a kneader equipped with a vacuum pressure reducing device such as a vacuum pump (a so-called vacuum clay kneader) can be used to obtain a degassed clay.

[0033] As the kneader, a kneading extruder that kneads the raw materials with a screw and then continuously extrudes the resulting clay into a die (described later) can be used, thereby enabling continuous kneading and molding. For example, mixing is performed using a blast share mixer or the like, and molding is performed using a kneading extruder equipped with a vacuum pressure reduction device.

[0034] B-3. Molding The clay is extruded from a die having slits formed therein corresponding to the partition walls of the honeycomb structure, to obtain a honeycomb formed body having partition walls that define cells that serve as fluid flow paths.

[0035] The die has slits formed therein that have a shape complementary to the partition walls of the honeycomb structure. Specifically, the honeycomb structure 10 shown in Fig. 1 has a large number of approximately square cells 12, and the partition walls 14 have a lattice pattern. When manufacturing such a honeycomb structure, a die is used that has slits formed therein that have a shape complementary to the lattice pattern of the partition walls (lattice-like).

[0036] The slit width of the slits can be set to any appropriate width depending on the thickness of the partition walls of the desired honeycomb structure. For example, from the viewpoint of use as a catalyst carrier, the slit width is preferably 155 μm or less, more preferably 140 μm or less. According to an embodiment of the present invention, a honeycomb structure in which the occurrence of defects is suppressed can be obtained by using a die with such a slit width. On the other hand, from the viewpoint of the strength of the obtained honeycomb structure, the slit width is, for example, 120 μm or more.

[0037] Examples of the extruder for extruding the clay include a ram extruder and a twin-screw kneading extruder. For example, from the viewpoint of obtaining a uniform honeycomb molded body, a twin-screw kneading extruder is preferably used.

[0038] In an embodiment of the present invention, the molding step includes passing the clay through a screen (mesh) with a predetermined mesh size and then extruding the clay. Specifically, the clay is extruded after passing through the screen. The screen may be located inside the extrusion molding machine, upstream of the die in the extrusion direction. By passing the clay through the screen, foreign matter and hard clay (agglomerates) can be captured, effectively preventing defects caused by these.

[0039] The opening of the screen is 150% or less of the slit width of the die, preferably 140% or less, more preferably 130% or less, even more preferably 120% or less, and particularly preferably 110% or less. On the other hand, from the viewpoint of preventing screen breakage, the opening of the screen is preferably 50% or more of the slit width of the die, more preferably 70% or more.

[0040] The tool (molding tool) used for extrusion is preferably made of SUS (stainless steel). The molding tool may also be surface-treated. Examples of surface treatments include DLC treatment and chrome plating. Forming a surface-treated layer on the molding tool can improve the peel resistance of the molding tool surface and reduce residues captured by the screen. Surface treatment on the portion (molding tool) located downstream of the screen in the extrusion direction can effectively prevent foreign matter (e.g., foreign matter containing metal) from being mixed into the honeycomb molded body.

[0041] The extrusion pressure when extruding the clay from the die is preferably 20 MPa or less, more preferably 10 MPa or less. By improving the fluidity of the clay, such an extrusion pressure can be achieved well, and a honeycomb structure in which the occurrence of defects is effectively suppressed can be obtained. Note that the extrusion pressure refers to the extrusion pressure at an extrusion speed of 20 mm / sec.

[0042] B-4. Firing The honeycomb formed body is fired to obtain a honeycomb structure. Specifically, the raw material powder is sintered and densified by firing, thereby obtaining a honeycomb structure having a predetermined strength. Any appropriate firing conditions can be adopted. The firing temperature is, for example, 1350°C to 1500°C. The firing time is, for example, 20 hours to 80 hours. Firing may be performed continuously or in multiple stages at different temperatures. When firing is performed in multiple stages, the firing time is the total of the firing times for each stage.

[0043] It is preferable to dry the honeycomb formed body before subjecting it to a firing treatment. Examples of drying methods include hot air drying, microwave drying, dielectric drying, reduced pressure drying, vacuum drying, and freeze drying. These may be used alone or in combination of two or more. In a preferred embodiment, microwave drying or dielectric drying is combined with hot air drying. In this embodiment, the entire honeycomb formed body can be dried quickly and uniformly. The hot air drying temperature is preferably 50°C to 150°C.

[0044] Furthermore, the honeycomb formed body may be calcined before being subjected to a firing treatment. Calcination can promote the removal of organic substances (e.g., binders, pore-forming materials, dispersants, etc.) contained in the honeycomb formed body. The calcination temperature can be determined, for example, according to the combustion temperature of the organic substances contained in the honeycomb formed body. The calcination temperature is, for example, 200°C to 1000°C. The calcination time is, for example, 10 hours to 100 hours. Note that calcination and firing may be carried out consecutively. Specifically, calcination may be carried out during the temperature rise process of firing.

[0045] C. Usage example Fig. 3 is a perspective view showing an example of use of the honeycomb structure shown in Fig. 1. A pair of electrode layers 18, 18 facing each other with the honeycomb structure 10 interposed therebetween are disposed on the side surface (peripheral wall 16) of the honeycomb structure 10. Each of the pair of electrode layers 18, 18 is formed in a strip shape extending in the extension direction of the cells 12 of the honeycomb structure 10. Although not shown, each of the pair of electrode layers 18, 18 is provided with a metal electrode terminal, one of which can be connected to the positive pole of a power source and the other of which can be connected to the negative pole of the power source.

[0046] Although not shown, a catalyst is carried on the partition walls 14, and CO, NO in the exhaust gas passing through the cells 12 are removed. x It is possible to convert hydrocarbons and the like into harmless substances through a catalytic reaction. The catalyst may preferably contain a noble metal (e.g., platinum, rhodium, palladium, ruthenium, indium, silver, gold), aluminum, nickel, zirconium, titanium, cerium, cobalt, manganese, zinc, copper, tin, iron, niobium, magnesium, lanthanum, samarium, bismuth, barium, or a combination thereof. [Example]

[0047] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The methods for measuring each property are as follows, unless otherwise specified. 1. Average particle size and particle size distribution (D90 / D10) of silicon carbide powder Measurement was performed using a laser diffraction / scattering method. Specifically, particle size distribution was measured using a laser diffraction / scattering particle size distribution analyzer (Horiba Ltd.'s "LA-960V2") to determine the average particle size (D50), D90, and D10. 2. Average primary particle size of metal silicon powder The particle size was measured by the laser diffraction scattering method. Specifically, the particle size distribution was measured using a laser diffraction / scattering particle size distribution analyzer (LA-960V2 manufactured by Horiba, Ltd.) to determine the average primary particle size (D50).

[0048] [Example 1] Silicon carbide powder was passed through a sieve with a mesh size of 75 μm (56% of the slit width described below), and metal silicon powder was passed through a sieve with a mesh size of 91 μm (67% of the slit width described below). The sieved silicon carbide powder and metal silicon powder were mixed in a mass ratio of 70:30 to obtain a raw material powder. The average particle size of the silicon carbide powder after sieving was 33 μm, and D90 / D10 was 2.5. The average primary particle size of the metal silicon powder after sieving was 2 μm.

[0049] Hydroxypropyl methylcellulose, a pore-forming material, and water were added to the obtained raw material powder, and the mixture was mixed in a Proshare mixer to obtain a wet powder (mixture). During mixing, water was added in two batches. The obtained wet powder was kneaded in a Banbury kneader at 35 rpm for 75 minutes to obtain a clay. The clay was then placed in a 25°C environment for 12 hours and then molded into a cylindrical shape using a vacuum kneader (continuous kneading extrusion molding machine). Here, when the total amount of silicon carbide powder and the amount of metal silicon powder was 100 parts by mass, 8 parts by mass of hydroxypropyl methylcellulose, 2 parts by mass of a pore-forming material, and 35 parts by mass of water were blended.

[0050] The obtained cylindrical clay was extruded using an extrusion molding machine (continuous kneading extrusion molding machine) to obtain a honeycomb molded body having the same shape as the honeycomb structure shown in Figure 1. Specifically, the honeycomb molded body was obtained by extruding it from a die in which slits (slit width: 135 μm) having a shape complementary to the partition walls of the desired honeycomb structure were formed. Here, a screen with an opening of 125 μm (93% of the slit width) was placed inside the continuous kneading extrusion molding machine, and the clay that passed through the screen was extruded from the die (extrusion pressure: 10 MPa at an extrusion speed of 20 mm / sec). In this way, a honeycomb molded body was obtained.

[0051] The obtained honeycomb molded body was dried by high-frequency dielectric heating, and then dried using a hot air dryer at 120°C for 2 hours. Thereafter, the honeycomb molded body was fired in an argon atmosphere at 1450°C for 60 hours (including heating and cooling times), and further fired by holding at 1050°C for 6 hours in an air atmosphere, and then cooled to obtain a honeycomb structure.

[0052] [Example 2] In preparing the raw material powder, the silicon carbide powder was passed through a sieve with a mesh size of 50 μm (37% of the slit width described below), the metal silicon powder was passed through a sieve with a mesh size of 75 μm (56% of the slit width described below), and a screen with a mesh size of 105 μm (78% of the slit width) was placed inside the continuous kneading extrusion molding machine. A honeycomb structure was obtained in the same manner as in Example 1. The silicon carbide powder after sieving had an average particle size of 28 μm, and D90 / D10 was 3.0. The metal silicon powder after sieving had an average primary particle size of 2 μm.

[0053] [Example 3] In preparing the raw material powder, the silicon carbide powder was passed through a sieve with a mesh size of 125 μm (93% of the slit width described below), the metal silicon powder was passed through a sieve with a mesh size of 75 μm (56% of the slit width described below), and a screen with a mesh size of 105 μm (78% of the slit width) was placed inside the continuous kneading extrusion molding machine. A honeycomb structure was obtained in the same manner as in Example 1. The silicon carbide powder after sieving had an average particle size of 29 μm and a D90 / D10 ratio of 3.1.

[0054] [Example 4] A honeycomb structure was obtained in the same manner as in Example 1, except that in preparing the raw material powder, the metal silicon powder was passed through a sieve with an opening of 75 μm (56% of the slit width described below).

[0055] [Example 5] A honeycomb structure was obtained in the same manner as in Example 1, except that in preparing the raw material powder, the metal silicon powder was passed through a sieve with a mesh size of 91 μm (67% of the slit width described below), and a screen with a mesh size of 105 μm (78% of the slit width) was placed inside the continuous kneading extrusion molding machine.

[0056] [Example 6] A honeycomb structure was obtained in the same manner as in Example 1, except that in preparing the raw material powder, the silicon carbide powder was passed through a sieve with an opening of 50 μm (37% of the slit width described below). The silicon carbide powder after sieving had an average particle size of 28 μm and a D90 / D10 ratio of 3.0.

[0057] [Example 7] A honeycomb structure was obtained in the same manner as in Example 1, except that in preparing the raw material powder, the metal silicon powder was passed through a sieve with an opening of 75 μm (56% of the slit width described below), and a screen with an opening of 175 μm (130% of the slit width) was placed inside the continuous kneading extrusion molding machine.

[0058] [Comparative Example 1] A honeycomb structure was obtained in the same manner as in Example 1, except that in preparing the raw material powder, the silicon carbide powder was passed through a sieve with a mesh size of 150 μm (111% of the slit width described below) and the metal silicon powder was passed through a sieve with a mesh size of 150 μm (111% of the slit width described below). The silicon carbide powder after sieving had an average particle size of 30 μm, and D90 / D10 was 3.2. The metal silicon powder after sieving had an average primary particle size of 2 μm.

[0059] Comparative Example 2 A honeycomb structure was obtained in the same manner as in Example 1, except that a screen with an opening of 250 μm (185% of the slit width) was placed inside the continuous kneading extrusion molding machine.

[0060] Comparative Example 3 A honeycomb structure was obtained in the same manner as in Example 1, except that in preparing the raw material powder, the silicon carbide powder was passed through a sieve with an opening of 150 μm (111% of the slit width described below).

[0061] Comparative Example 4 A honeycomb structure was obtained in the same manner as in Example 1, except that in preparing the raw material powder, the metal silicon powder was passed through a sieve with an opening of 150 μm (111% of the slit width described below).

[0062] Comparative Example 5 In preparing the raw material powder, the silicon carbide powder was passed through a sieve with a mesh size of 150 μm (111% of the slit width described below), the metal silicon powder was passed through a sieve with a mesh size of 150 μm (111% of the slit width described below), and a screen with a mesh size of 250 μm (185% of the slit width) was placed inside the continuous kneading extrusion molding machine. A honeycomb structure was obtained in the same manner as in Example 1.

[0063] <Evaluation> A light transmittance test was conducted on 200 honeycomb structures obtained in the examples and comparative examples. Specifically, the obtained honeycomb structures were illuminated with a light-transmitting lamp and checked for the presence or absence of internal defects. The number of honeycomb structures in which internal defects were confirmed out of the total number of honeycomb structures inspected (200) was counted, and the defective rate was calculated. The evaluation results are shown in Table 1.

[0064] [Table 1]

[0065] The present invention is not limited to the above-described embodiment, and various modifications are possible. For example, the configurations shown in the above-described embodiment can be replaced with configurations that are substantially the same as those shown in the above-described embodiment, that have the same effects, or that can achieve the same purpose. [Industrial Applicability]

[0066] The honeycomb structure obtained by the manufacturing method according to the embodiment of the present invention can be suitably used for treating (purifying) exhaust gas from an internal combustion engine. [Explanation of symbols]

[0067] 10 Honeycomb structure 12 cells 14 Bulkhead 16 Peripheral wall 18 Electrode layer

Claims

1. A step of passing the silicon carbide powder and the metal silicon powder through a sieve to obtain a raw material powder; a step of mixing and kneading the raw material powder, a binder, and a dispersion medium to obtain a clay; a molding step of extruding the clay from a die having slits formed therein corresponding to the partition walls of the honeycomb structure to obtain a honeycomb formed body having partition walls that define cells that serve as fluid flow paths; a firing step of firing the honeycomb formed body, The mesh size of the sieve is 30% to 100% of the slit width of the die, The molding step includes a step of passing the clay through a screen having an opening size of 70% to 150% of the slit width of the die, and performing the extrusion. A method for manufacturing a honeycomb structure.

2. 2. The method for manufacturing a honeycomb structure according to claim 1, wherein an extrusion pressure when extruding the clay from the die is 20 MPa or less.

3. 3. The method for manufacturing a honeycomb structure according to claim 1, wherein a ploshear mixer is used to mix the raw material powder, the binder, and the dispersion medium.

4. 4. The method for manufacturing a honeycomb structure according to claim 3, wherein the mixture of the raw material powder, the binder and the dispersion medium is kneaded in a kneader under conditions of a kneading blade rotation speed of 20 rpm to 40 rpm for 50 minutes or more.

5. The method for manufacturing a honeycomb structure according to claim 1 , wherein the dispersion medium is added to the raw material powder and the binder in at least two or more divided portions, and the mixing and kneading are carried out for each addition.

6. 6. The method for manufacturing a honeycomb structure according to claim 1, wherein the extrusion is carried out after the clay is left in an environment of 15° C. to 35° C. for 12 hours or more.

7. The method for manufacturing a honeycomb structure according to claim 1 , wherein a forming jig or tool used for the extrusion is made of a stainless steel material.

8. The method for manufacturing a honeycomb structure according to any one of claims 1 to 7, wherein a forming jig or tool used for the extrusion is subjected to a surface treatment, and the surface treatment is at least one of DLC treatment and chrome plating.

9. The method for manufacturing a honeycomb structure according to claim 8, wherein the surface treatment is performed on at least a portion located downstream of the screen in the extrusion direction.

10. The method for manufacturing a honeycomb structure according to any one of claims 1 to 9, wherein the metal silicon powder has an average primary particle size of less than 10 µm.

11. 11. The method for manufacturing a honeycomb structure according to claim 1, wherein the silicon carbide powder has a particle size distribution in which a ratio (D90 / D10) of a particle diameter D90 to a particle diameter D10 is 2.0 or more.

12. The method for manufacturing a honeycomb structure according to any one of claims 1 to 11, wherein the die has a slit width of 155 µm or less.

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