WO2002026353A1

WO2002026353A1 - Multi-layer structure honeycomb filter and method of manufacturing the filter

Info

Publication number: WO2002026353A1
Application number: PCT/JP2001/008283
Authority: WO
Inventors: Atsushi Sakon; Hiroyuki Manabe
Original assignee: Ngk Insulators,Ltd.
Priority date: 2000-09-26
Filing date: 2001-09-25
Publication date: 2002-04-04
Also published as: AU2001288112A1; JP2002172304A

Abstract

A multi-layer structure honeycomb filter for dust collection, comprising one or more filter layers formed on the surface of a porous base material having a honeycomb structure, wherein the pressure loss of the base material is 150 to 700 Pa when the filtration flow velocity of the filter is 1 m/min, and the pressure loss of the filter layers of at least one layer is 50 to 300 Pa, whereby a capture efficiency can be increased and the pressure loss can also be reduced.

Description

Description Multilayer honeycomb filter and manufacturing method

The present invention relates to a multi-layered honeycomb filter for collecting dust that captures dust in a gas to be treated and a method for producing the same. Background art

In the past, dust collectors mainly used bag filters made of paper, fiber, or polymer resin.However, in recent years, environmental protection measures such as pollution prevention, product recovery from high-temperature gas, and clean high-temperature energy recovery have been required. Markets that require dust collection in temperatures above 250 ° C, where molecular materials cannot be used, have increased.

Under these circumstances, ceramics have excellent heat resistance and corrosion resistance, and have favorable characteristics as a filter material in a high-temperature, corrosive gas atmosphere. Examples of the ceramic filter made of this ceramic include a tubular filter and a candle-like filter having a closed tubular shape on one side. At present, the honeycomb filter for dust collection is It is used in a wide variety of fields, such as the chemical, electric power, steel, and industrial waste treatment industries, for the purpose of collecting products from high-temperature gas and removing dust from exhaust gas for environmental measures.

As shown in Fig. 2, such a honeycomb fill has a structure in which the ends of a large number of through holes 9 of the honeycomb are sealed on a square basis for the upstream side B and the downstream side C in reverse. The high-temperature gas that has entered passes through the porous partition 8 and passes through the hole on the downstream side C, and at that time, dust in the high-temperature gas is captured by the filter layer of the partition.

For conventional ceramic filters such as candle filters, the filtering area of the filter is smaller than that of the bag filter, and it is necessary to use a honeycomb filter to secure the same filtering area as a dust collector incorporating a bag filter. However, as the number of ceramic filters used increases, the size of the dust collector itself increases. However, there is a problem when the equipment cost is significantly increased. There are also other problems, such as a large pressure loss at the Philippines.

In order to solve these problems, it is advantageous to increase the thickness of the partition wall and reduce the pore diameter of the partition wall from the viewpoint of increasing the trapping efficiency, but this disadvantageously causes an increase in pressure loss. On the other hand, from the viewpoint of reducing the pressure loss, it is advantageous to make the partition wall thinner and increase the pore diameter of the partition wall. It becomes a problem.

In order to solve the above problem, Japanese Utility Model Application Laid-Open No. 6-63415 discloses that a ceramic powder called a precoat material is sprayed and fixed on a filtration surface of a filter in advance to form a precoat layer. In addition, an exhaust gas purifying apparatus is disclosed in which a mechanism for trapping dust in a dust-containing gas on the pre-coated material and removing the dust together with the pre-coated material is introduced.

However, in the exhaust gas purifying apparatus described in the above-mentioned publication in which the above-described mechanism is introduced, since the precoat material is consumed during operation, it takes time to add the precoat material periodically. In addition, there is a problem that waste is increased because the pre-coated material is mixed with the captured dust.

For this reason, in the current general honeycomb filter, in order to increase the trapping efficiency and to realize a small pressure loss, the honeycomb structure having a relatively large average pore diameter is usually disposed on the surface of the honeycomb structure. Also, a filter layer having a small average pore diameter is provided. As a method for forming such a filter layer, there has been conventionally known a dynamic pressure vacuum method in which one end of a porous substrate having pores saturated with a liquid is decompressed and a slurry containing ceramic particles is supplied from the other end. An air flow coating method in which a powder composed of ceramic particles is adhered to the surface of a porous substrate in an air stream, and then moisture is imparted and adsorbed (Japanese Unexamined Patent Publication No. No. 0-24991 24), a slurry containing ceramic particles is brought into contact with and held on the surface of a porous substrate, and then discharged. A dipping method in which the slurry is made of ceramic particles is supplied to each cell of the porous honeycomb structure, and moisture in the slurry is removed by permeating the inside of the porous material. A slurry direct filtration method in which ceramic particles are attached to the surface of a honeycomb structure is known.

However, it is difficult to apply the dynamic pressure vacuum method to a substrate having a complex shape such as a honeycomb structure, and if it is applied, complicated equipment is required, which is not preferable in terms of production efficiency and manufacturing cost. .

In addition, in the airflow coating method, since the ceramic particles adhere to the base material in an aggregated state, the average pore diameter of the coating layer becomes large, and it is difficult to achieve high trapping efficiency, and clogging is prevented. Due to the occurrence, there was a problem that the pressure loss rise rate was increased.

Furthermore, in the slurry injection / discharge method and the diving method, it is difficult to control the coat thickness, and therefore, there is a problem that the capture efficiency and the degree of pressure loss between filters vary.

Also, in the slurry direct filtration method, if it is attempted to form a filter layer using ceramic particles having a small average particle diameter, the ceramic particles penetrate into pores of the base material, and a dense structure is formed between the base material and the filter layer. However, there is a problem that a mixed layer of the two is formed and the pressure loss increases.

Japanese Patent No. 29266187 discloses a gas filter in which diatomaceous earth or rice husk ash is fixed on the surface of a base material so as to fill pores on the surface of the filter base material, and a filter layer is formed. The manufacturing method is disclosed.

However, regarding the gas filter described in the above-mentioned publication, when the material of the filter substrate and the material of the filter layer are different, the difference in thermal expansion coefficient between the two materials when used for a long time under a high temperature condition is considered. This may cause the filter layer to peel off or fall off.

Therefore, a honeycomb filter for dust collection that sufficiently satisfies both high trapping efficiency and small pressure loss has not yet been obtained, and development of such a honeycomb filter has been awaited.

On the other hand, if the fixing method of the 82-cam filter to the dust collector is a canning tie, the filtration fluid flows to the outside of the honeycomb filter through the outer wall of the 82-cam outer periphery. If there is a lot of leakage, there is a possibility that the original sealing performance of Canning may be reduced. In addition, the honeycomb filter is displaced by the stress generated during backwashing, and contacts with the casing metal used for cleaning the honeycomb filter, causing defects such as chipping or damage at the corner of the honeycomb filter. There is a risk of occurrence. Disclosure of the invention

The present invention has been made in view of the above-mentioned problems of the prior art, and aims to provide a high trapping efficiency, a small pressure loss, and a sufficient use in a dust collector. Multilayer honeycomb filter having high strength, and a multilayer structure capable of easily manufacturing such a multilayer honeycomb filter with a simple device and without causing a quality variation between filters. An object of the present invention is to provide a method for manufacturing a honeycomb filter.

That is, according to the present invention, there is provided a dust collecting multilayer filter having one or two or more filter layers on the surface of a porous substrate having an 82-cam structure, The pressure loss of the substrate is 150 to 700 Pa when the filtration flow rate of the filter is 1 mZmin, and the pressure loss of at least one filter layer is 50 to 300 Pa. Provided is a honeycomb filter having a multilayer structure, which is characterized by Pa.

In the present invention, the difference between the thinnest part and the thickest part of the filter layer is preferably within 35%, and the base material and the filter layer are preferably made of the same material.

Further, in the present invention, the thickness of the outer wall of the outer peripheral portion of the honeycomb is preferably 1.3 to 2.0 times the thickness of the partition wall of each honeycomb cell constituted by the base material. Is preferably cordierite.

On the other hand, according to the present invention, one or two or more filter layers are provided on the surface of a porous substrate having an 82-cam structure, and when the filtration flow rate of the filter is 1 mZmin, A method for producing a honeycomb filter having a multilayer structure in which the pressure loss of the base material is 150 to 700 Pa and the pressure loss of at least one or more of the filter layers is 50 to 300 Pa. Wherein each cell of a substrate having a honeycomb structure has the same material as the substrate. A slurry of porous ceramic particles, removing components in the slurry by permeating the pores of the substrate, attaching the ceramic particles to the surface of the substrate, and then firing. Forming a filter layer by using the method described above.

In the present invention, the difference between the thinnest part and the thickest part of the thickness of the filler layer is preferably within 35%.

Further, in the present invention, the base material and the filler layer are preferably made of the same material, and the thickness of the outer wall of the outer periphery of the 82 cam is determined by the thickness of the partition wall of each honeycomb cell constituted by the base material. It is preferably 1.3 to 2.0 times.

Further, in the present invention, the material is preferably cordierite. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic view illustrating an example of a method for manufacturing a multilayer honeycomb filter of the present invention.

FIG. 2 is a perspective view showing a general configuration of a honeycomb filter. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described. However, the present invention is not limited to the following embodiments, and based on ordinary knowledge of a person skilled in the art without departing from the spirit of the present invention. It should be understood that design changes, improvements, etc. are made as appropriate.

The multilayer honeycomb filter of the present invention is mainly used as a dust-collecting filter, and is provided with one or two or more filter layers on the surface of a porous substrate having a honeycomb structure. The pressure loss of the substrate at a filtration flow rate of lm / min is preferably 150 to 700 Pa, more preferably 300 to 500 Pa, and 350 to 450 Pa. At the same time, the pressure loss of at least one or more filter layers is preferably from 50 to 300 Pa, more preferably from 70 to 250 Pa, and 100 It is particularly preferred that it is ~ 200 Pa. The details will be described below.

By setting the values of the pressure loss of the base material and the filter layer in the above-mentioned range, it is possible to obtain a multilayer filter having a characteristic such as a high trapping rate. When the pressure loss of the substrate under the above conditions is less than 150 Pa, the strength of the honeycomb filter itself is likely to be reduced, and when the pressure loss exceeds 700 Pa, the bag filter It is not preferable because it cannot use the same suction blower as the standard suction blower. Similarly, if the pressure loss of at least one or more filter layers is less than 50 Pa, the filter layer cannot be partially secured, and if it exceeds 300 Pa, it is the same as the base material. It is not preferable because a blower equivalent to the standard suction blower used in the filter cannot be used.

The strength of the honeycomb filter required for use as a filter for dust collection is sufficient if the cell bending strength of the honeycomb structure is about 4 MPa, which is 6 MPa. preferable.

In order to satisfy that the pressure loss of the base material is 150 to 700 Pa when the filtration flow rate of the filter is 1 mZm in, the average pore diameter of the base material is set to 10 to 50 m, The porosity must be within the range of 40 to 60%.

In addition, in order to satisfy that the pressure loss of at least one filter layer is 50 to 300 Pa when the filtration flow rate at the filter is 1 mZmin, the average pore diameter of the filter layer is required. Must be within a range of 2 to 10 m, a porosity of 30 to 50%, and a layer thickness of 20 to 50 m.

Furthermore, in order to obtain a performance equal to or higher than that of a bag filter which is also used as a filter for a dust collector, the pressure loss of the entire honeycomb filter is 10 when the filtration flow rate of the filter is 1 mZmin. It is preferably at most 000 Pa, more preferably at most 800 Pa. If it exceeds 10 O OPa, it is not preferable because a standard suction blower cannot be used.

On the other hand, in order to ensure the minimum strength of the honeycomb filter, the pressure loss of the entire honeycomb filter is limited to about 200 Pa. In the multilayer honeycomb filter of the present invention, the difference between the thinnest portion and the thickest portion of the filter layer is preferably within 35%, more preferably within 27%, and more preferably 20%. % Is particularly preferable. If the difference between the thinnest part and the thickest part of the filter layer is more than 35%, the trapping efficiency of the multilayer honeycomb filter is not sufficient, and the pressure loss also increases. Therefore, the multilayered honeycomb filter according to the present invention, which is specified within the above numerical values, has characteristics such that sufficient trapping efficiency is secured and pressure loss is reduced.

The above-described 82-cam filter having a multilayer structure in which the difference between the thinnest portion and the thickest portion of the filter layer described above is 35% or less can be specifically manufactured as follows. That is, the ceramic particles having a predetermined average particle diameter to be a filter layer are adjusted to a slurry liquid having a predetermined concentration, and the slurry liquid is injected from below the previously dried substrate, and the surface of the substrate is subjected to a direct filtration method. The thickness of the filler layer is adjusted by attaching ceramic particles to the substrate, and then turning the substrate upside down, thereby making it possible to produce a multilayer honeycomb filter.

In the multilayer filter of the present invention, the base material and the filter layer are preferably made of the same material. By using the same material, no difference in thermal expansion occurs even under high temperature conditions. Therefore, in the multilayered honeycomb filter according to the present invention, for example, even under a high temperature condition of up to 900 ° C., the filter layer does not peel off or fall off due to a difference in thermal expansion between the layers. It has such excellent characteristics. In the honeycomb filter having a multilayer structure of the present invention, the thickness of the outer wall of the outer peripheral portion of the honeycomb is 1.3 to 2.0 times the thickness of the partition wall of each honeycomb cell constituted by the base material. More preferably, it is 1.4 to 2.0 times, and particularly preferably 1.5 to 2.0 times.

At this time, if the thickness of the outer wall of the outer peripheral portion of the honeycomb is less than 1.3 times the thickness of the partition wall of each honeycomb cell constituted by the base material, the necessary strength of the honeycomb structure itself can be secured. At the same time, the filtration resistance of the outer wall becomes the same level as the filtration resistance of the partition walls of each 82-cam cell. Therefore, the filtration fluid may leak from the outer wall, and the sealing performance of the canning may be impaired. On the other hand, if the thickness of the outer wall of the outer peripheral portion of the honeycomb is more than 2.0 times the thickness of the partition wall of each honeycomb cell composed of the base material, the extrudability is reduced, and the Would be difficult to do. Therefore, in the honeycomb filter having the multilayer structure according to the present invention, the thickness of the outer wall of the outer peripheral portion of the honeycomb is within the above numerical range with respect to the thickness of the partition wall of each honeycomb cell formed by the base material. Thus, sufficient strength as the honeycomb filter / evening is secured, and leakage of the filtered fluid to the outside of the honeycomb filter through the outer wall of the honeycomb outer peripheral portion can be reduced. It is preferable that the material of the multilayer honeycomb filter of the present invention is cordierite. Cordylite is a ceramic material that has a small coefficient of thermal expansion and excellent thermal shock resistance, and also has excellent mechanical strength. In other words, since the honeycomb filter having a multilayer structure of the present invention made of cordierite has these characteristics, since it has characteristics suitable as a ceramic material constituting the honeycomb filter, the characteristics can be utilized and the desired size can be obtained. · It can be manufactured into shapes.

The multilayered honeycomb filter according to the present invention described above supplies slurry of ceramic particles of the same material as the base material to each cell of the porous base material having the honeycomb structure. It is manufactured by removing the moisture therein by passing through the pores of the substrate, attaching the ceramic particles to the surface of the substrate, and then firing to form a filter layer.

The concentration (w / w) of the ceramic particles in the slurry used for forming the filter layer should be 0.5% or more and less than 2.0% if the precipitation property of the slurry and the particle Although it is preferable from the viewpoint of balance with adhesion, it is more preferably 0.8% or more and less than 1.5%.

The volume of the slurry is preferably at least three times and at most six times the total volume of the coated cell. If the thickness is less than three times, a difference in film thickness occurs between the upper and lower parts of the cell.If the thickness exceeds six times, a large amount of slurry is required to balance the thickness and concentration of the fill layer and to form the fill layer. The second and subsequent filter layers are formed after firing the first filter layer. Perform in the same manner as described above. (Examples) Hereinafter, specific implementation results of the present invention will be described.

An average filter made of ceramic particles with an average particle size of 10 im by a slurry direct filtration method on a substrate having a honeycomb structure with a length of 500 mm and a square shape with a side of 150 mm on each side. A 50 m thick single filter layer was provided to manufacture a honeycomb filter having a multilayer structure. 'The details of the embodiment will be described below.

(Examples 1 to 14)

1. Production of base material

Using cordierite as a raw material, a honeycomb structure having a predetermined cell pitch was manufactured by a general extrusion molding method. Next, as shown in FIG. 2, the ends of the many through holes 9 of the honeycomb are sealed on the upstream side B and the downstream side C with the same material for each square, and dried. The substrate was manufactured by firing at a predetermined firing temperature (Examples 1 to 14). Table 1 shows the cell pitch, cell thickness, outer wall thickness, ratio of outer wall thickness to cell thickness (outer wall thickness Z cell thickness), firing temperature, cell bending strength, and average pore diameter of the base material manufactured by such a process. Show. The porosity at this time was 47%

2. Manufacturing of filter layer

The production of the filter layer was performed by the processing apparatus 4 shown in FIG. The processing apparatus 4 is provided with a slurry tank 6 on a magnetizer 5, and supplies the slurry in the slurry tank 6 to the substrate 1 by the pressure of the air A.

The slurry tank 6 is for preparing a slurry of ceramic particles having a predetermined concentration, and a slurry having a uniform concentration is prepared by the stirring action of the magnetic stirrer 15, and the prepared slurry is attached to the slurry injection tool 3. It is supplied to one end side of the base material 1 connected via the metal fitting 2, and is introduced into the inside of one of the cells through the opening. The supply amount of the slurry is monitored by a liquid level gauge 7 provided in the slurry tank 6, and the supply of the slurry is stopped when the supply amount reaches a predetermined value. Then, the substrate 1 is inverted, and the filtered water in the substrate is discharged. The water in the introduced slurry gradually permeates through the partition walls of each cell and flows out to the outside. During this time, the particles in the slurry gradually adhere to one side surface of the partition walls to form a layer of particles. The slurry was prepared by adding an organic binder in advance and stirring and mixing with a homomixer in a plastic container.

After forming the layer composed of the ceramic particles in this way, the base material on which the layer was provided was dried and fired at a predetermined firing temperature for 2 hours to produce a filter layer (Examples 1 to 10). Table 1 shows the slurry concentration, the average particle diameter, and the firing temperature of the ceramic particles used in the above step, and the thickness of the filter layer produced by such a step. In Table 1, “substantial strength” refers to the breaking load when a three-point bending stress is applied to a 150 × 150 × 500 mm entity, and the case where the safety factor for the design strength is 8 or more is “large”. A safety factor of 4 to 7 was judged as “medium”, and a safety factor of 1 to 3 was judged as “small”.

(Comparative Examples 1 to 5)

1. Production of base material

Substrates were manufactured in the same manner as in Examples 1 to 14 described above (Comparative Examples 1 to 5). Table 1 shows the cell pitch, cell thickness, outer wall thickness, ratio of outer wall thickness to cell thickness (outer wall thickness Z cell thickness), firing temperature, and average pore diameter of the base material manufactured by such a process. The porosity was 47%.

2. Production of filter layer

Filter layers were manufactured in the same manner as in Examples 1 to 10 described above (Comparative Examples 1 to 5).

(Measurement of pressure loss (aeration differential pressure))

With respect to the base material, filter layer, and the whole (base material + filter layer) of Examples 1 to 14 and Comparative Examples 1 to 5 manufactured by the above steps, the flow rate was lm / min '(in terms of flow rate, lm / min. (6 m ² = 2.6 m ³ / min), the pressure at the inlet and outlet when air at normal temperature was permeated was measured, and the difference was calculated. Table 1 shows the results. [Table]-] Base material (support layer) Filter layer Whole cell bitch Cell thickness Outer wall thickness ratio Firing temperature Cell bending strength Average pore size Vent fell: Slurry-concentration Average particle size Layer thickness Firing temperature Ventilation differential pressure 5ί¾ Soil body strength nm (mm) (mm; (° C) (MPa) (μm) (Pa) (%) (m) (μm) (° C) (Pa) (Pa)

Example 1 10 1.3 1.95 1.5 1413 9.8 15 400 1 10 50 1350 300 700 Large Example 2 6 0.65 1.3 2.0 1 13 7.7 14 350 0.9 10 30 1350 130 480 Medium Example 3 6 0.65 1.3 2.0 413 413 7 7 14 350 0,6 10 20 ■ j 350 120 470 Medium Example 4 6 0.65 1.3 2.0 1 13 F.7 14 350 0.3 10 10 1350 50 400 Medium Example 5 6 0.9 1.7 1.9 1420 8 16 5 380 0.6 10 20 1350 100 480 Large Example 6 6 0.9 1.7 1.9 1410 10 15 430 1.5 10 50 1350 300 730 Large Example 7 6 0.9 1.7 1.9 1410 10 15 430 0.9 10 30 1350 150 580 Large Example 8 6 0.9 1.7 1.9 1410 10 15 430 0.9 10 30 1410 135 565 Large example 9 6 0.9 1.7 1.9 1410 10 15 430 0.6 10 20 1350 100 530 Large example 10 6 0.9 1.7 1.9 1390 '11.6 11.5 690 0.9 10 30 1350 140 830 Large example 1 1 10 1.3 1.95 1.5 1420 7.8 15 400 Large Example 1 2 10 1.3 1.95 1.5 1400 9.5 14 500 Large Example 1 3 10 1.3 1.95 1.5 1413 7.5 30 200 Medium Example 14 6 0.65 1.3 2.0 1420 7.3 15 365 Medium Comparative Example 1 10 1.3 1.95 1.5 1370 10.1 6.5 1450 Large Comparative Example 2 10 1.3 1.95 1.5 1430 6.7 17 300 Small Comparative Examples 3 6 0.65 0.8 1.2 1410 10 15 400 Small Comparative Example 4 6 0.65 0.8 1.2 1400 10.9 13 450 Small Comparative Example 5 6 0.65 0.8 1.2 1390 1 1.2 1 1 490 Small

Table 1 shows that the honeycomb filters of the examples all had a ventilation differential pressure (pressure loss) of not more than a predetermined value, and the evaluation of the actual strength was all medium to large. On the other hand, when the firing temperature of the substrate was lower than the predetermined temperature (Comparative Example 1), the ventilation differential pressure (pressure loss) of the honeycomb filter of the comparative example was equal to or higher than the predetermined value. Also, in the comparative examples, even when the ventilation differential pressure (pressure loss) was equal to or less than a predetermined value, the evaluations of the body strength were all small, and the excellent effects of the present invention could be confirmed.

Industrial applicability

As described above, according to the honeycomb filter having a multilayer structure of the present invention, since the trapping efficiency is good and the pressure loss is small, the honeycomb filter is used in various fields such as the chemical, electric power, and industrial waste treatment industries. It can be suitably used as a dust collecting filter for capturing dust.

Further, according to the method for manufacturing a honeycomb filter having a multilayer structure of the present invention, a honeycomb filter having a multilayer structure having no variation in quality between filters can be easily manufactured with a simple apparatus. It is possible to provide a honeycomb filter for dust collection that contributes to improvement and reduction of production cost and has excellent performance.

Claims

The scope of the claims

1. A multi-layer honeycomb filter for dust collection, comprising one or more filter layers on the surface of a porous substrate having a honeycomb structure,

When the filtration flow rate of the filter is 1 m / min, the pressure loss of the substrate is 150 to 700 Pa, and the pressure loss of at least one filter layer is 50 to 300 Pa. A honeycomb filter having a multilayer structure, wherein the honeycomb filter is Pa.

2. The multilayer filter according to claim 1, wherein the difference between the thinnest portion and the thickest portion of the thickness of the filler layer is within 35%.

3. The honeycomb filter having a multilayer structure according to claim 1, wherein the base material and the filter layer are made of the same material.

4. The thickness of the outer wall of the outer peripheral portion of the honeycomb is 1.3 to 2.0 times the thickness of the partition wall of each honeycomb cell constituted by the base material, according to any one of claims 1 to 3. The multi-layered honeycomb filter described.

5. The multilayered honeycomb filter according to any one of claims 1 to 4, wherein the material is cordierite.

6. One or two or more filter layers are provided on the surface of a porous substrate having a honeycomb structure, and the pressure loss of the substrate is 15 when the filtration flow rate at the filter is 1 m / min. 0 to 700 Pa, and a pressure loss of at least one or more of the filter layers is 50 to 30 OPa.

A slurry of ceramic particles of the same material as the substrate is supplied to each cell of the substrate having the honeycomb structure,

Removing the components in the slurry by permeating the pores of the substrate, adhering the ceramic particles to the surface of the substrate,

Next, a filter layer is formed by baking, and a method for manufacturing a honeycomb filter having a multilayer structure.

7. The difference between the thinnest part and the thickest part of the filter layer thickness is within 35%. A method for manufacturing a honeycomb filter having a multilayer structure.

8. The method according to claim 6, wherein the base material and the filler layer are made of the same material.

9. The method according to any one of claims 6 to 8, wherein the thickness of the outer wall of the outer peripheral portion of the honeycomb is 1.3 to 2.0 times the thickness of the partition wall of each honeycomb cell constituted by the base material. The method of manufacturing the multilayer honeycomb fill described above.

10. The method for producing a multilayered honeycomb filter according to any one of claims 6 to 9, wherein the material is cordierite.