WO2005068396A1

WO2005068396A1 - Honeycomb structure and method for producing the same

Info

Publication number: WO2005068396A1
Application number: PCT/JP2005/000112
Authority: WO
Inventors: Hiroyuki Suenobu; Yasushi Noguchi; Tomoo Nakamura
Original assignee: Ngk Insulators, Ltd.
Priority date: 2004-01-13
Filing date: 2005-01-07
Publication date: 2005-07-28
Also published as: JPWO2005068396A1; DE112005000172T5; DE112005000172B4

Abstract

A honeycomb structure comprises pores having diameters the variation by portion of which is small and an increased average pore diameter. A method for producing a honeycomb structure (1) of cordierite comprises a firing step of firing a honeycomb molding is also disclosed. The firing step includes a temperature rise substep at which the temperature rise rate is 40°C/hr or above from 1200°C to 1250°C, 2-40°C/hr from 1250°C to 1300°C, and 40°C/hr or above from 1300°C to 1400°C when the atmospheric temperature is elevated. The honeycomb structure has a porosity of 50-70%, an average pore diameter of 15-30 μm, an average pore diameter difference of 5 μm or less between the central part and the peripheral part, thermal expansion coefficients of 1.0×10-6/°C or less at the central part and the peripheral part, and A-axis compression strengths of 1.5 Mpa or above at the central part and the peripheral part.

Description

Specification

Honeycomb structure and manufacturing method thereof

Technical field

The present invention relates to a honeycomb structure and a method for producing the same, and more particularly, to a honeycomb structure that can be used as a filter, a catalyst carrier, and the like, and a method for suitably producing the honeycomb structure. About the method.

Background art

[0002] In recent years, a honeycomb structure has been used as a filter (DPF) for capturing fine particles emitted from the power of a diesel engine in order to comply with the increasingly stricter vehicle emission regulations. In order to remove nitrogen oxides, sulfur oxides, hydrogen chloride, hydrocarbons and carbon oxides contained in automobile exhaust gas, a catalyst-supported two-cam structure is used. I have.

[0003] In such a honeycomb structure, it is required to increase the pore diameter or increase the porosity for the purpose of reducing pressure loss and the like. In addition, there is a need for larger honeycomb structures for purifying exhaust gas from large vehicles.

[0004] However, the conventional method for manufacturing a honeycomb structure has a problem in that, when the average pore diameter of the honeycomb structure is increased, for example, when the honeycomb structure is used for a DPF, the collection efficiency is reduced. Was. This problem tended to be even greater when trying to increase the porosity or size. Also, if the isostatic strength and the thermal shock resistance were reduced due to the increase in porosity and size, there was also a problem.

[0005] In the firing step in the conventional method for manufacturing a honeycomb structure, a heating rate of 400 to 1200 ° C is controlled within a predetermined range for the purpose of improving isostatic strength and reducing pressure loss. (For example, see Patent Document 1). In order to obtain a honeycomb structure having a high water absorption and a low coefficient of thermal expansion, the temperature was raised between 1100 and 1200 ° C at a rate of 60 ° C or less, and the temperature between 1200 ° C and 1300 ° C was reduced to 80 ° C. It is disclosed that the temperature is raised at a rate of not less than ° CZhr (for example, see Patent Document 2).

[0006] Further, in order to obtain a nod-cam structure having excellent thermal shock resistance and heat resistance, a predetermined It is disclosed that using a raw material having a particle size of 1 to 100 ° C, a heating rate of 250 ° CZhr or less up to 1100 ° C and a heating rate of 30 to 300 ° CZhr at 1100 ° C or more (for example, Patent Reference 3).

[0007] However, in such a conventional manufacturing method, for example, when a honeycomb structure for a filter such as a DPF is manufactured, the trapping efficiency associated with increasing the average pore diameter of the honeycomb structure is increased. It was difficult to suppress the decrease in the amount.

Patent Document 1: Japanese Patent Application Laid-Open No. 2003-277162

Patent Document 2: Japanese Patent No. 2981034

Patent Document 3: Japanese Patent Publication No. 57-28390

Disclosure of the invention

[0008] The present invention provides a method for manufacturing a honeycomb structure capable of increasing the overall average pore diameter and reducing dispersion depending on the location of the pore diameter. A feature is to provide a nod-cam structure in which variation in the hole diameter depending on the place is reduced.

[0009] The present inventors have investigated the cause of a decrease in the collection efficiency of a cordierite-made no-cam structure having a high porosity used in a DPF. As a result, it was found that the pore diameter at the center of the honeycomb structure became larger than the pore diameter at the outer periphery, soot and the like leaked from the center, and the collection efficiency was reduced. .

[0010] Furthermore, as a result of a detailed study of the cause of the variation in the pore diameter, a large exothermic reaction occurred in the process of forming cordierite between 1250 and 1300 ° C in the heating process of the firing process, and the center of the honeycomb structure was heated. The temperature rise rate of the central part suddenly increased, and the difference in the pore diameter, the coefficient of thermal expansion, and the A-axis compressive strength occurred due to the difference between the temperature rise rate in the central part and the temperature rise rate in the outer peripheral part. I found that.

[0011] Furthermore, when studies were conducted to suppress such a phenomenon, the exothermic reaction was allowed to proceed gently by setting the heating rate between 1250 and 1300 ° C to 40 ° CZhr or less, It has been found that the difference in the rate of temperature rise between the central portion and the outer peripheral portion of the honeycomb structure is reduced, and the difference in the pore diameter between the central portion and the outer peripheral portion can be reduced. Furthermore, by setting the heating rate between 1200-1250 ° C and 1300-1400 ° C to 40 ° CZhr or more, the difference in pore diameter between the center and the outer periphery is reduced. It has been found that it is possible to increase the average pore diameter of the whole while keeping it small. Also, a honeycomb structure having a small variation in pore diameter depending on the location, a small thermal expansion coefficient in the central portion and a small outer peripheral portion, and a small variation in the A-axis compression strength depending on the location and a high isostatic strength are obtained. Succeeded.

[0012] That is, the present invention is a method for producing a cordierite-made honeycomb structure, comprising a step of firing a molded body in a shape of a cordierite, wherein in the firing step, the temperature of the atmosphere is increased. In addition, the rate of temperature rise from 1200 ° C to 1250 ° C is 40 ° CZhr or more, and the rate of temperature rise from 1250 ° C to 1300 ° C is 2 ° C-40 ° CZhr, and 1300 ° C to 1400 ° An object of the present invention is to provide a method for manufacturing a honeycomb structure including a heating step in which a heating rate up to C is 40 ° CZhr or more.

In the present invention, a honeycomb structure having a porosity of 50% to 70%, an average pore diameter of 15 to 30 μm, and a difference in average pore diameter between a central portion and an outer peripheral portion of 5 μm or less is manufactured. It is preferable to do so. It is also preferable to manufacture a honeycomb structure having a diameter of 100 mm or more and a length of 100 mm or more. Furthermore, A-axis compression strength of the central portion and it is preferable that the thermal expansion coefficient of the outer peripheral portion to produce a hard second cam structure is not more than 1. OX 10- ⁶ Z ° C instrument center portion and the peripheral portion is 1. It is more preferable to manufacture a honeycomb structure having a pressure of 5 MPa or more, and it is particularly preferable to manufacture a honeycomb structure having an isostatic strength of 1. OMPa or more.

[0014] Further, it is preferable that the plugging slurry is pressed into a molded body before firing and then fired.

Further, the present invention relates to a cordierite honeycomb structure having a porosity of 50 to 70%, an average pore diameter of 15 to 30 m, and a difference in average pore diameter between the center portion and the outer peripheral portion of 5 to 5. m or less, the thermal expansion coefficient of the center portion and the peripheral portion 1. OX 10- ⁶ Z ° C or less, and a-axis compression strength of the central portion and the peripheral portion Ha 1. is 5MPa or more - providing a cam structure Things. More preferably, the honeycomb structure has an isostatic strength of 1. OMPa or more.

By controlling the heating rate in the firing step as described above, the average pore diameter of the honeycomb structure can be increased, and the difference in pore diameter between the central portion and the outer peripheral portion can be reduced. Further, even if the porosity of the honeycomb structure is increased or the size thereof is increased, it is possible to suppress the variation of the pore diameter depending on the location. Furthermore, thermal expansion over the entire honeycomb structure A smaller coefficient A-axis compressive strength can be improved, and isostatic strength can be improved.

[0017] Further, the porosity of the honeycomb structure, the average pore diameter, the difference between the average pore diameter of the central part and the average pore diameter, the thermal expansion coefficient of the central part and the peripheral part, and the A-axis compressive strength of the central part and the peripheral part, Preferably, by further setting the isostatic strength within a predetermined range, for example, when used as a DPF, pressure loss can be reduced, collection efficiency can be increased, and durability against heat and pressure can be improved.

Brief Description of Drawings

FIG. 1 (a) is a schematic perspective view showing one example of a honeycomb structure according to the present invention.

FIG. 1 (b) is a partially enlarged plan view enlarging a portion b in FIG. 1 (a).

FIG. 1 (c) is a partially enlarged view schematically showing a part of a cross section parallel to the axial direction of the honeycomb structure shown in FIG. 1 (a).

FIG. 2 is a schematic sectional view parallel to the axial direction showing another example of the honeycomb structure according to the present invention.

Explanation of symbols

[0019] 1 ... honeycomb structure, 2 ... partition, 2a ... partition at center, 2b ... partition at outer periphery, 3 ... cell, 4 ... plugging part, 5 ... center of gravity, 42 ... End face, 44 ··· End face.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in detail with reference to specific examples, but the present invention is not limited to these specific examples. In the following, the present invention will be described by taking a honeycomb structure for a DPF as an example.The features of the present invention are that the average pore diameter can be increased and the variation of the pore diameter depending on the location can be suppressed. It is possible to reduce the coefficient of thermal expansion, improve the material strength represented by A-axis compressive strength, improve the static strength, and improve the static strength over the entire honeycomb structure. This feature can be suitably applied to all cordierite porous honeycomb structures, such as a catalyst carrier that is not limited to a DPF honeycomb structure.

FIG. 1 (a) is a schematic perspective view showing an example of a cordierite-made honeycomb structure for a DPF, and FIG. 1 (b) is an enlarged view of a portion b in FIG. 1 (a). Fig. 1 (c) is a partially enlarged plan view. FIG. 2 is a partially enlarged view schematically showing a part of a cross section parallel to the axial direction of the honeycomb structure shown in FIG. 1 (a). The two-cam structure 1 shown in FIGS. 1 (a)-(c) includes a partition wall 2 arranged to form a plurality of cells 3 extending in an axial direction from one end face 42 to another end face 44. . Further, a plugging portion 4 is provided so as to plug the cell 3 on one of the end faces. By adopting such a configuration, the exhaust gas flowing into the cell 3 from one end face 42 passes through the porous partition 2, passes through the adjacent cell 3, and is discharged from the other end face 44. At this time, the partition 2 serves as a filter to capture PM such as soot. In the case where the honeycomb structure is used for a catalyst carrier or the like, a plugging portion is not required. The present invention provides a honeycomb structure having a plugging portion and a no-camera having no plugging portion. It is intended for both structures. A cordierite honeycomb structure means that 50% by mass or more of the substance constituting the partition walls is cordierite, and 70% by mass or more, particularly 90% by mass or more is cordierite. Is preferred.

[0022] Such a cordierite-made honeycomb structure can be manufactured by firing a honeycomb-shaped formed body containing a cordierite-shaped raw material as a firing raw material. The raw material for forming cordierite is a raw material that becomes cordierite upon firing, and has a SiO content of 42 to 56 mass

2

%, Al O power 30-45% by mass, MgO has a chemical composition within the range of 12-16% by mass

twenty three

It is a ceramic raw material that is blended as follows. Specifically, talc, kaolin, calcining power, alumina, aluminum hydroxide, silica, and the like include those containing a plurality of inorganic raw materials selected in proportions such that the above chemical composition is obtained. .

[0023] The honeycomb shaped body usually contains a processing aid and a dispersion medium in addition to the cordierite-forming raw material. Specific examples of processing aids include binders such as hydroxypropylmethylcellulose, methylcellulose, hydroxyethylcellulose, carboxymethylcellulose, polyvinylinoleanol, polyethylene terephthalate, polyethylene, and glycerin, ethylene blender, dextrin, fatty acid stone, and polyalcohol. And pore-forming agents such as graphite, wheat flour, starch, phenolic resin, polymethyl methacrylate, polyethylene, polyethylene terephthalate, unfoamed foamed resin, unfoamed foamed resin, and water-absorbing polymer. These may be included alone or in combination depending on the purpose. Water is usually used as the dispersion medium. [0024] It is preferable to dry such a formed body before firing. Drying is performed to remove water, a dispersion medium, and the like contained in the molded body. There is no particular limitation on the drying method.Generally, drying can be performed by hot air drying, microwave drying, dielectric drying, reduced pressure drying, vacuum drying, etc. Among them, hot air drying is particularly preferred in that the whole can be dried quickly and uniformly. It is preferable to carry out in a drying step in which drying is combined with microwave drying or dielectric drying. The drying temperature of hot air drying is preferably in the range of 80-150 ° C because it can be dried quickly!

[0025] The firing can be performed by placing the honeycomb-shaped formed body in a firing furnace, raising the ambient temperature, and maintaining the temperature at a predetermined temperature for a predetermined time. In the temperature range from the temperature starting temperature to 1200 ° C, the effect of the heating rate on the pore diameter is small.There is no particular limitation on the heating rate, and there is no firing crack. Good,. Such a heating rate varies depending on the shape of the molded body and the like, and can be appropriately selected by those skilled in the art.For example, the heating rate is 500 ° CZhr or less, further 300 ° CZhr or less, particularly 200 ° CZhr or less. It is preferable to set the heating rate. On the other hand, from the viewpoint of productivity, it is preferably 2 ° CZhr or more, more preferably 5 ° CZhr or more, particularly preferably 10 ° CZhr or more.

[0026] Then, the temperature is raised from 1200 to 1250 ° C at a rate of 40 ° CZhr or more, and the temperature is raised from 1250 to 1300 ° C at a rate of 2 ° C to 40 ° CZhr. Then, the temperature is raised from 1300 to 1400 ° C at a rate of 40 ° C or more.

[0027] As described above, by setting the heating rate in the temperature range of 1250 to 1300 ° C to 40 ° CZhr or less, the difference in pore diameter between the central portion and the outer peripheral portion of the honeycomb structure can be reduced. it can. In order to make the difference in pore diameter smaller, the heating rate should be less than 40 ° CZhr, more preferably 30 ° CZhr or less, particularly preferably 20 ° CZhr or less. preferable. On the other hand, if the heating rate is too low, the productivity will decrease, so the heating rate must be 2 ° C Zhr or more, preferably 3 ° C Zhr or more, and 5 ° CZhr or more. Is more preferred.

[0028] On the other hand, in a temperature range of 1200 to 1400 ° C, increasing the heating rate can increase the diameter of the shrimp. Therefore, the pore diameter can be increased as a whole by setting the heating rate in the temperature range of 1200-1250 ° C and 1300-1400 ° C to 40 ° CZhr or more. In addition, as mentioned above, the heating rate in the temperature range of 1250-1300 ° C was set to 40 ° C By setting Zhr or less, it is possible to obtain a honeycomb structure with less variation in pore diameter depending on the location.For example, when such a honeycomb structure is used as a DPF, low pressure loss and high It is possible to achieve both the collection efficiency. From the viewpoint of further increasing the overall pore diameter, the heating rate in the temperature range of 1200 to 1250 ° C and 1300 to 1400 ° C is preferably 45 ° CZhr or more, more preferably 50 ° CZhr or more. Is more preferable.

[0029] Further, by controlling the temperature in this manner, the material strength represented by the A-axis compressive strength, which reduces the thermal expansion coefficient over the entire honeycomb structure, is improved, and the isostatic strength is improved. Can be improved. This is because by suppressing the rapid rise in temperature due to the exothermic reaction in the cordierite generation process, it is possible to suppress the formation of pores of non-uniform diameter due to non-uniform temperature distribution and the formation of non-uniform cordierite crystals. It is considered possible. Accordingly, pores having a more uniform diameter and cordierite in a better crystalline state can be formed, the thermal expansion coefficient is reduced over the entire honeycomb structure, the A-axis compressive strength is improved, and It is considered that the static strength can be improved.

[0030] The maximum temperature of firing is preferably about 1400 to 1440 ° C, and it is preferable to maintain the maximum temperature in this range for 2 to 20 hours. 1400 ° C—There is no particular limitation on the heating rate in the maximum temperature range. However, if the heating rate is too high, melting of the honeycomb structure may occur due to overshooting. It is preferable to be not more than ° CZhr. In addition, the heating rate means an average heating rate in each temperature range.

[0031] When a honeycomb structure having a relatively high porosity is manufactured, the problem of variation depending on the pore diameter tends to increase. However, such a sintering process increases the average pore diameter and increases the central portion. And a honeycomb structure having a small difference in average pore diameter between the outer peripheral portion and the outer peripheral portion. The porosity of the honeycomb structure manufactured by the present invention is preferably 50 to 70%, the average pore diameter is 15 to 30 m, and the difference between the average pore diameter at the center and the average pore diameter at the outer periphery is 5 m or less. This range is preferable, particularly in the case of a honeycomb structure for a DPF, since both low pressure loss and high collection efficiency can be achieved. Further, c having the characteristics of such a range - the cam structure, the thermal expansion coefficient of the center portion and the peripheral portion 1. 0 X 10- ⁶ Z ° C or less, the A-axis compressive strength 1. 5 MPa or more, § The isostatic strength can be set to 1. OMPa or more, and it is preferable to manufacture such a honeycomb structure. Here, the average pore diameter and porosity of the honeycomb structure mean the average pore diameter and porosity of the entire partition 2 shown in FIG. 1 (c), respectively. The average pore diameter, porosity, coefficient of thermal expansion, and A-axis compressive strength at the center of the honeycomb structure 1 are shown in FIG. When a similar shape S with a volume of 1Z64 is drawn, it means the average pore diameter, porosity, coefficient of thermal expansion, and A-axis compressive strength of the part of the bulkhead 2a at the center that enters the similar shape S, The average pore diameter, porosity, coefficient of thermal expansion, and A-axis compressive strength of the outer peripheral portion are the same as the volume of the honeycomb structure 1 at the center of the volume center point 5 of the knob-cam structure 1 shown in FIG. Mean average pore diameter, porosity, coefficient of thermal expansion, and A-axis compressive strength of the part of the partition wall 2b at the outer peripheral portion located outside the similar shape S ′. FIG. 2 is a cross-sectional view schematically showing a cross section parallel to the axial direction of the honeycomb structure.

[0033] The porosity and the pore diameter are values measured with a mercury intrusion porosimeter, and are values measured in the range of 40 to 800 ° C in accordance with the thermal expansion coefficient miS R1618. The A-axis compressive strength is a value measured by a compression tester conforming to JIS B7733 in accordance with the automotive standard JASO standard M505-87 issued by the Society of Automotive Engineers of Japan. The isostatic strength is indicated by a pressure value when the honeycomb structure is broken, and is a value measured according to JASO standard M505-87.

[0034] Another preferred embodiment to which the present invention is applied is a large honeycomb structure. Even when the size of the honeycomb structure is increased, the difference in the pore size, the coefficient of thermal expansion, and the material strength represented by the A-axis compressive strength between the central part and the outer peripheral part tends to increase. It is preferable to reduce the difference. In this case, examples of a preferable application object include a diameter of 100 mm or more, a length of 100 mm or more, more preferably a diameter of 140 mm or more, and a length of 150 mm or more, particularly preferably a diameter of 140 mm to 350 mm and a length of 150 mm to 400 mm. The honeycomb structure of the above.

[0035] The method for forming a honeycomb-shaped formed body in the present invention is not particularly limited. However, it can be formed by, for example, the following method. The above-mentioned raw material, processing aid and dispersion medium are mixed and kneaded to obtain a kneaded material, which is then formed into a honeycomb shape. Mixing can be performed using a general mixer. The kneading can be performed using a kneading machine such as a general kneader, a pressure kneader, a single-screw continuous extruder, a twin-screw continuous kneading extruder, a vacuum kneader and the like. it can. The molding may be performed by any known method such as extrusion molding, injection molding, and press molding. However, extrusion molding is preferred for forming the honeycomb structure. It is also preferable that the kneading step and the forming step are continuously performed by an extruder such as a biaxial continuous kneading extruder.

In the case of manufacturing a honeycomb structure for a filter such as a DPF, a plugging portion is formed. The plugging portion can be formed as follows. A ceramic powder is prepared, and a binder, a dispersant, and a dispersion medium such as water or glycerin are added to the mixture to form a slurry, which is placed in a container having an open top. At one end face of the molded body in the shape of a honeycomb, openings of predetermined cells are masked with a film or the like. Then, by immersing the masked end face of the molded body downward, immersing the molded body in the slurry in the container, and further pressing the upper force, the slurry can be packed at a predetermined depth in the unmasked cell. .

[0037] The above steps can be performed for other end faces. It is preferable that the plugging portions are arranged on both ends of the respective cells so that the cells have a checkered pattern at both end surfaces, and the cells do not have the plugging portions at both end surfaces. There is no particular limitation on the ceramic constituting the plugging portion, but in consideration of the adhesiveness to the surrounding partition walls, it is preferable that the material be a raw material. Further, such a step is preferably performed on the formed body rather than on the honeycomb structure after firing. In the case of performing on a molded body, a plugging portion is formed in a subsequent firing step. In the case of performing the honeycomb structure after firing, the sealing structure must be formed by further heating the honeycomb structure, and the number of steps is increased as compared with the case of performing the formed body. Further, in the case of performing on a molded body, since firing is performed in a state in which the end face portion is reinforced, occurrence of breakage in the firing step is suppressed. Furthermore, after the firing, the honeycomb structure and the plugged portion are more strongly bonded by the cordierite-dyeing reaction, so that the plugged portion is pressed by the exhaust gas from the engine or the pressure exerted during backwashing. The hardness of the cam structure can be prevented from falling off.

[0038] A honeycomb structure that can be suitably manufactured by the above-described manufacturing method has a porosity of 50 to 70%, an average pore diameter of 15 to 30 m, and a difference in average pore diameter between the central portion and the outer peripheral portion of 5 m. Ri der hereinafter, further center and the thermal expansion coefficient of the outer peripheral portion are both 1. 0 X 10- ⁶ Z ° C or less, preferably 0. 9 X 10- ⁶ Z ° C or less, more preferably 0. 8 X the honeycomb structure is less than 10- ⁶ Z ° C can be mentioned. Such a honeycomb structure exhibits low pressure loss, high collection efficiency, and good Shows thermal shock resistance. Further, the A-axis compressive strength of both the central portion and the outer peripheral portion is preferably 1.5 MPa or more, more preferably 1.7 MPa or more, and particularly preferably OMPa or more. Such a honeycomb structure exhibits a high isostatic strength because there is no particularly weak portion in the structure. The isostatic strength is preferably 1.OMPa or more, more preferably 1.2 MPa, particularly preferably 1.5 MPa. Such a honeycomb structure suppresses breakage during cabling and actual use, and exhibits good durability.

[0039] There is no particular limitation on the shape of the honeycomb structure of the present invention. For example, the shape of the cross section perpendicular to the axial direction can be any shape such as a circle, an ellipse, a racetrack, and a polygon. The shape of the cell is not particularly limited. For example, the cross-sectional shape may be any of a polygon such as a triangle, a quadrangle, and a hexagon, a circle, or an ellipse. The cell density is not particularly limited, but is, for example, about 50-600 cells Z square inch (7.8-93 cells Zcm ² ), preferably about 100-500 cells Z square inch (15.5-77.5 cells Zcm ² ). It can be. The thickness of the partition wall is not particularly limited, but may be, for example, about 50 to 650 μm, preferably about 75 to 500 m, and more preferably about 100 to 450 μm.

[0040] Further, the catalyst may be supported on the porous partition walls of the honeycomb structure. Examples of the catalyst include non-metallic perovskite-type catalysts such as noble metal-based Pt, Pd, and Rh. At least one of these can be supported on a no- or two-cam structure. The catalyst can be supported by a conventionally known method such as a push coat method.

Example

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

[0042] (Evaluation method)

Average pore diameter: measured with a mercury intrusion porosimeter manufactured by Micromeritics. Porosity: The total pore volume was measured with a mercury intrusion porosimeter manufactured by Micromeritics Co., and the true specific gravity of cordierite was set to 2.52 gZcc.

Coefficient of thermal expansion: Samples cut out from 2a and 2b in Fig. 2 were measured according to JIS R1618. It was measured in the range of 0-800 ° C.

A-axis compressive strength: A sample of A-axis compressive strength is cut out from each of 2a and 2b in Fig. 2 by a method based on JASO standard M505-87, and the breaking load is calculated using a compression tester conforming to JIS B7733. Was divided by the area of the pressed surface to obtain the A-axis compressive strength.

Isostatic strength: Measured by the following method in accordance with JASO standard M505-87. After covering both end surfaces of the honeycomb structure with metal plates of the same diameter as the end surface of the honeycomb structure, further covering the outer peripheral surface of the two-cam structure with rubber tubes of the same diameter, and fixing the metal plate, the rubber tube Rubber tape was adhered to the surrounding area, and the honeycomb structure was sealed so that water did not enter. In this state, the two-cam structure was submerged in water, and the water pressure was increased until the hard-cam structure was broken, to obtain a broken water pressure isostatic strength.

Soot collection efficiency: Exhaust gas that generated soot by the soot generator was passed through the no-cam structures obtained in each of the examples and comparative examples until the soot was deposited by lgZL, and then passed through the hard-cam structure. The soot contained in the exhaust gas was collected by filter paper, and the weight of the soot (W was measured.) The exhaust gas that generated the soot was collected by filter paper for the same time without passing through the honeycomb structure. Then, the weight (W ² ) of the soot was measured, and the obtained weights (W ¹ ) and (W ² ) were substituted into the following equation (1) to determine the collection efficiency.

Equation (1): (W ² — w ^ / iw ^ x ioo

Soot collection pressure loss: Rings having an inner diameter of 130 mm were pressed against both end surfaces of the nod-cam structures obtained in the examples and comparative examples. Through this ring, soot generated by the soot generator was allowed to flow into the 130 mm diameter range of the honeycomb structure, and lgZL of soot was collected. Next, with the honeycomb structure cart collected, air of 2.27 Nm ³ Zmin was flown, the pressure difference before and after the honeycomb structure was measured, and the soot was collected. Was evaluated for pressure loss.

(Example 1)

The cordierite roll raw material, foamed resin, binder, and surfactant shown in Batch No. 1 of Table 1 were mixed with a professional shear mixer while spraying and adding water having a mixing ratio shown in Table 1. This was further kneaded in a single step to obtain a plastic clay. This plastic clay was formed into a cylindrical shape by a vacuum clay kneader, and charged into an extruder to form a honeycomb shape. Next Then, the obtained molded body was microwave-dried and then completely dried by hot air drying, and both end faces were cut to predetermined dimensions. Next, a slurry composed of a cordierite material having the same composition as that of Notch No. 1 was used, and cells were alternately plugged at both end faces. Finally, the temperature was raised from room temperature to 400 ° C under the conditions of 10 ° CZhr, and from 400 ° C to 1200 ° C under the condition of 50 ° CZhr. C-1250. C 50. CZhr, 1250 ° C—1300 ° C ^ 2 ° C / hr, 1300. C 1 Raise the temperature from 1400 ° C at 50 ° C / hr, then raise the temperature to the maximum temperature of 1420 ° C at 20 ° C Zhr and then at 1420 ° C to avoid melting of the product due to overshoot. After holding for 5 hours and firing, a honeycomb structure with a diameter of 144mm X length of 152mm, a partition wall thickness of 300m, a number of cells of 300 cells Z square inch (about 46.5 cells Zcm ² ) is obtained. Was.

(Examples 2 to 7 and Comparative Examples 1 to 6)

Each honeycomb structure was obtained in the same manner as in Example 1 except that the composition shown in Table 1 and the Z or the heating rate shown in Table 2 were used.

[0045] With respect to the obtained honeycomb structure, the porosity of the central portion and the outer peripheral portion, the average pore diameter of the central portion and the outer peripheral portion, the thermal expansion coefficient of the central portion and the outer peripheral portion, the central portion and the outer portion were determined by the above-described evaluation methods. The A-axis compression strength, isostatic strength, soot collection pressure loss, and soot collection efficiency of the outer periphery were evaluated. Table 2 shows the results.

[Table 1]

Koji I Lighting raw material

Batch No. Foam resin Binder Surfactant Water

Hydroxylation

Talc kaolin alumina aluminum silica

1 40 (25 m) 20 (5 / m) 15 (5 / m) 15 (5 j m) 10 (30 m) 2.0 (40 jUm) 6.0 0.2 34

2 40 (25 m) 20 (5 im) 15 (5jum) 10 (30 ^ m) 1.0 (40 m) 6.0 0.2 33

3 40 (25 / m) 20 (5 / m) 15 (5 / m) 15 (5 m) 10 (30 m) 0.5 (40 μm) 6.0 0.2 32

[Unit: parts by mass]

* Figures in parentheses indicate the average particle size of raw materials

[z [oo]

Zll000 / S00Zdf / X3d PI 96C890 / S00Z OAV Thermal expansion coefficient A-axis compressive strength

Heating rate (° C hr) Porosity (%) Pore diameter (m)

(i o "V ° o (MPa) Isostatic soot collection

No. Strength Pressure loss (kPa) Collection efficiency >>)

1200. C ~ (MPa) (when Sue M g L is deposited) (when Sue H gZL is deposited)

1250 ° C Outer periphery center Outer periphery center Outer periphery center outer periphery

Example 1 1 50 to tn 2 50 66 65 19 18 0.3 0.3 2.9 2.9 1.9 4.7 93

ο ο

Example 2 1 50 15 ° ι 50 66 65 23 21 0.5 0.5 2.3 2.4 1.5 4.4 92 Example 3 1 50 30 ο 50 66 65 27 23 0.8 0.7 2.0 2.3 1.3 4.2 91

ο σ

Example 4 1 100 2 100 65 64 23 22 0.4 0.4 2.3 2.4 1.5 4.3 92 Example 5 1 100 30 100 65 64 30 26 0.9 0.8 1.7 2.1 1.1 3.7 90 Example 6 2 50 15 50 53 53 19 18 0.4 0.4 10.1 10.4 6.7 5.8 94 Example 7 3 50 15 50 45 45 18 18 0.3 0.3 15.6 15.7 10.4 7.0 95 Comparative example 1 1 50 50 50 66 65 43 24 1.2 1.0 0.8 2.3 0.5 3.6 75 Comparative example 2 1 30 50 50 66 65 36 19 1.2 1.1 1.1 2.8 0.7 3.5 83 Comparative Example 3 1 30 30 50 66 65 17 14 0.9 0.8 3.0 3.3 2.0 6.0 94 Comparative Example 4 1 30 50 30 66 66 32 14 1.1 1.0 1.4 3.2 0.9 5.6 88 Comparative Example 5 1 50 30 30 67 66 16 14 0.8 0.7 3.2 3.4 2.1 6.1 95 Comparative example 6 1 30 30 30 67 67 12 1 1 0.8 0.8 3.6 3.8 2.4 6.9 96

[0048] As shown in Table 2, the honeycomb structure having a relatively large average pore diameter and a small difference in the average pore diameter between the center portion and the outer peripheral portion was obtained by the manufacturing method of Example 17. I got it. On the other hand, in the production methods of Comparative Examples 1, 2, and 4, by increasing the heating rate from 1250 ° C to 1300 ° C, the difference in pore diameter between the central part and the outer peripheral part increased. . In the production methods of Comparative Examples 3, 5, and 6, the heating rate was reduced from 1200 ° C to 1250 ° C and from Z or 1300 ° C to 1400 ° C. The pore diameter of the entire cam structure has been reduced. Therefore, the temperature rise rate in the temperature range of 1250-1300 ° C is set to 40 ° C / hr or less, and 1200-1250. C and 1300-1400. By increasing the heating rate in the temperature range of C to 40 ° CZhr or more, the average pore diameter of the entire honeycomb structure is increased, and the difference between the average pore diameter of the central part and the average pore diameter of the peripheral part of the honeycomb structure is increased. It can be seen that can be reduced. Further, as shown in Example 16 by controlling the porosity and the average pore diameter within a predetermined range, the A-axis compressive strength at which the coefficient of thermal expansion is small over the entire honeycomb structure is reduced. A honeycomb structure for a filter, which has a high isostatic strength, a small pressure loss, and a high collection efficiency, which can be suitably used as a DPF, was obtained.

Industrial applicability

According to the production method of the present invention, a cordierite-nodal cam structure having a small variation in the average pore diameter depending on the location and a large overall average pore diameter can be produced. Such a honeycomb structure can be suitably used in various fields such as a filter such as a DPF and a catalyst carrier.

Claims

The scope of the claims

[1] A method for producing a cordierite-made honeycomb structure, which comprises a step of firing a molded body in a shape of cordierite, wherein in the firing step, the temperature is increased from 1200 ° C. The rate of temperature rise from 1250 ° C to 40 ° CZhr or more, the rate of temperature rise from 1250 ° C to 1300 ° C is 2 ° C-40 ° CZhr, and the rate of temperature rise from 1300 ° C to 1400 ° C A method for manufacturing a honeycomb structure including a temperature raising step of 40 ° C. Zhr or more.

[2] The honeycomb structure according to claim 1, wherein a honeycomb structure having a porosity of 50 to 70%, an average pore diameter of 15 to 30 μm, and a difference between an average pore diameter of a central part and an average pore diameter of an outer peripheral part of 5 μm or less is manufactured. The method for manufacturing a honeycomb structure of the present invention.

[3] The method for manufacturing a honeycomb structure according to claim 1 or 2, which manufactures a honeycomb structure having a diameter of 100 mm or more and a length of 100 mm or more.

[4] the thermal expansion coefficient of the center portion and the peripheral portion 1. or less 0 X 10- ⁶ Z ° C ha - the honeycomb structure according to claim 1 one 3 to manufacture the cam structure Production method.

[5] The method for manufacturing a honeycomb structure according to any one of claims 14 to 14, which manufactures a honeycomb structure having an A-axis compressive strength of a central portion and an outer peripheral portion of 1.5 MPa or more.

[6] The method for manufacturing a honeycomb structure according to any one of claims 15 to 15, which manufactures a honeycomb structure having a static strength of 1. OMPa or more.

[7] The method for producing a honeycomb structure according to any one of [16] to [16], wherein the plugging slurry is pressed into a molded body and then fired.

[8] A cordierite honeycomb structure having a porosity of 50-70%, an average pore diameter of 15-30 / ζπι, and a difference in average pore diameter between the center and the outer periphery of 5 m or less , center thermal expansion coefficient of the outer peripheral portion 1. 0 X 10- ⁶ Z ° C or less, and the center portion and the peripheral portion Ha a-axis compressive strength 1. is 5MPa or more - cam structure.

[9] The honeycomb structure according to claim 8, which has a static strength of 1. OMPa or more.