JP2016067994A - Manufacturing method of honeycomb filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a honeycomb filter which can facilitate bonding of silicon carbide particles by converting a silicon compound as an impurity into other compound in a manufacturing process even when purity of the silicon carbide powder as a raw material is low and the silicon compound is contained, and which exhibits sufficient characteristics as a filter.SOLUTION: A manufacturing method of a honeycomb filter includes: a preparation process of raw material for a molding which prepares raw material for a molding by mixing silicon carbide powder containing 3 wt.% of impurity formed of a silicon compound, and an organic additive containing at least an organic binder; a molding manufacturing process of manufacturing a honeycomb molding by extruding the prepared raw material for a molding; a defatting process of defatting the manufactured honeycomb molding under a complete inert gas atmosphere; and a firing process of firing the defatted honeycomb molding.SELECTED DRAWING: Figure 2

Description

The present invention relates to a method for manufacturing a honeycomb filter.

Soot and other particulates (hereinafter sometimes referred to as PM) contained in exhaust gas discharged from internal combustion engines such as buses, trucks, etc. or construction machinery, etc., and other harmful components harm the environment and human body This has recently become a problem.

Therefore, as a honeycomb filter for purifying exhaust gas, there has been proposed a honeycomb filter composed of a ceramic block in which a plurality of honeycomb fired bodies in which a large number of cells are arranged in parallel in the longitudinal direction with a porous cell partition wall interposed therebetween. .

Patent Document 1 describes a method for manufacturing this honeycomb filter. After a raw material composition containing silicon carbide powder, an organic binder and the like is mixed to prepare a raw material for a molded body, extrusion forming of the raw material for the molded body is performed. To prepare a honeycomb formed body. Subsequently, the honeycomb formed body is degreased and fired to obtain a honeycomb fired body, and then a plurality of honeycomb fired bodies are bonded to produce a ceramic block, which is cut to form an outer peripheral coat layer. The manufacture of honeycomb filters is described.

JP 2007-230855 A

In order to manufacture a honeycomb filter having excellent characteristics as a filter, conventionally, a high-purity silicon carbide powder has been used as a main material as a raw material. Since energy and a purification process are required, there is a problem that the price of the raw material becomes expensive.

For this reason, the use of low-purity silicon carbide for refractories used in furnace materials such as bricks has been studied, but in the conventional method, silicon carbide particles as raw materials are bonded when the honeycomb formed body is fired. However, the silicon compound may interfere with the contact between the silicon carbide particles, and there is a problem that a porous silicon carbide sintered body having excellent mechanical properties is difficult to manufacture. In addition, since silicon compounds such as silica contained as impurities are easily detached from the filter during firing and adhere to the furnace wall of the firing furnace, in the firing process, the deposits obstruct the movement of the product. There is a problem that inconvenience is likely to occur.

The present invention has been made in order to solve the above-described problems. Even if the silicon carbide powder as a raw material has a low purity and contains a silicon compound, the silicon compound which is an impurity in the production process is replaced with another compound. An object of the present invention is to provide a method for manufacturing a honeycomb filter, which can promote bonding between silicon carbide particles by converting to, and can manufacture a honeycomb filter having sufficient characteristics as a filter.

In order to achieve the above object, a method for manufacturing a honeycomb filter of the present invention includes a silicon carbide powder containing 3% by weight or more of an impurity composed of a silicon compound, and an organic additive containing at least an organic binder. A raw material preparation process for forming a molded body for preparing a raw material, a molded body manufacturing process for manufacturing a honeycomb molded body by extruding the prepared raw material for a molded body, and the manufactured honeycomb molded body in a completely inert gas atmosphere And a degreasing step for degreasing and a firing step for firing the degreased honeycomb formed body.

In the method for manufacturing a honeycomb filter according to the present invention, the degreasing step is performed in a completely inert gas atmosphere, so that the organic additive such as an organic binder is hardly decomposed by oxidation and mainly thermally decomposed. Tends to remain as carbon. In the case of the present invention, silicon carbide powder contains 3% by weight or more of impurities composed of a silicon compound, and the honeycomb formed body after degreasing contains silicon compound and carbon. When this honeycomb formed body is fired, the silicon compound and carbon react to synthesize carbide. As a result, there is no thing inhibiting the bonding between the silicon carbide particles, the bonding between the silicon carbide particles can be promoted, and a honeycomb filter having sufficient characteristics as a filter can be manufactured.

In the method for manufacturing a honeycomb filter of the present invention, the firing step is preferably performed in a completely inert gas atmosphere.
As described above, in the method for manufacturing a honeycomb filter of the present invention, the firing step can be performed in an inert gas atmosphere, and thus the degreasing step and the firing step can be performed without changing the type of the atmosphere gas. For this reason, the degreasing step and the firing step can be performed in one furnace, the required amount of heat can be greatly reduced, and the honeycomb filter can be manufactured at a lower cost. In addition, the degreased body is taken out from the degreasing furnace, once cooled, and then not carried into the firing furnace, the process can be simplified and the honeycomb filter can be efficiently manufactured without the possibility of breakage during transportation. can do.

In the method for manufacturing a honeycomb filter of the present invention, the silicon compound is preferably silica.
By using silica as the silicon compound, silicon carbide can be synthesized in the firing step, and almost no silica or carbon remains in the fired body. Therefore, a porous silicon carbide fired body having good characteristics can be produced, and the produced honeycomb filter can sufficiently exhibit performance as a honeycomb filter.

In the method for manufacturing a honeycomb filter of the present invention, the molar ratio of carbon to silica (carbon / silica) in the honeycomb formed body after the degreasing step is preferably 1 to 3.
When the molar ratio (carbon / silica) of silica and carbon in the honeycomb formed body after the degreasing process is 1 to 3, the silica and residual carbon in the honeycomb formed body react during the firing process to form silicon carbide. Thus, almost no silica or carbon remains in the fired body. Therefore, a porous silicon carbide fired body having good characteristics can be produced, and the produced honeycomb filter can sufficiently exhibit performance as a honeycomb filter.

In the honeycomb filter manufacturing method of the present invention, the degreasing step and the firing step are preferably performed in one batch furnace.
As described above, in the method for manufacturing a honeycomb filter of the present invention, the degreasing step and the firing step can be performed in an inert gas atmosphere. Therefore, the degreasing step and the firing step are continuously performed in one batch furnace. The honeycomb filter can be manufactured more inexpensively and more efficiently.

In the method for manufacturing a honeycomb filter of the present invention, the degreasing step and the firing step are preferably performed in one continuous furnace, and the continuous furnace preferably includes a degreasing area and a firing area.
As described above, in the method for manufacturing a honeycomb filter of the present invention, the degreasing step and the firing step can be performed in an inert gas atmosphere. Therefore, the degreasing step and the firing step include a degreasing area and a firing area. The degreasing step and the firing step can be performed while the honeycomb formed body is continuously supplied to and taken out from the continuous furnace, so that the honeycomb filter can be made cheaper and more efficient. Can be manufactured well.

Fig.1 (a) is a perspective view which shows typically the honeycomb molded object by which the one end part of the cell was plugged, FIG.1 (b) is A- of the honeycomb molded object shown to Fig.1 (a). It is A sectional view. FIG. 2 is a longitudinal sectional view schematically showing a case where the continuous heating furnace according to the present invention is cut in the vertical longitudinal direction along the longitudinal direction. FIG. 3 is a cross-sectional view schematically showing a case where the continuous heating furnace according to the present invention is cut in a cross section perpendicular to the longitudinal direction. FIG. 4 is a perspective view showing a honeycomb filter manufactured by the method for manufacturing a honeycomb filter of the present invention. Fig. 5 (a) is a perspective view of the honeycomb fired body constituting the honeycomb filter shown in Fig. 4, and Fig. 5 (b) is a cross-sectional view taken along line BB of the honeycomb fired body shown in Fig. 5 (a). FIG.

(Detailed description of the invention)
Hereinafter, the manufacturing method of the honeycomb filter of the present invention will be described.
A method for manufacturing a honeycomb filter according to the present invention includes forming a raw material for a molded body by mixing a silicon carbide powder containing 3% by weight or more of an impurity composed of a silicon compound and an organic additive containing at least an organic binder. A preparation process, a molded body production process for producing a honeycomb molded body by extruding the prepared raw material for the molded body, a degreasing process for degreasing the produced honeycomb molded body in a completely inert gas atmosphere, and degreasing And a firing step of firing the formed honeycomb formed body.

The manufacturing method of the honeycomb filter of the present invention includes a raw material preparation process for a molded body, a molded body manufacturing process, a degreasing process, and a firing process. Hereinafter, the manufacturing method of the honeycomb filter including the above steps will be described for each step.

(1) Molded body raw material preparation step In this molded body raw material preparation step, a silicon carbide powder containing 3% by weight or more of an impurity composed of a silicon compound and an organic additive containing at least an organic binder are mixed to form a molded body. Prepare raw materials.

The particle size and the like of the silicon carbide powder are not particularly limited, but it is preferable to use two types of silicon carbide powders having different average particle sizes. As two types of silicon carbide powders having different average particle diameters, for example, a combination of silicon carbide powder having an average particle diameter of 0.3 to 50 μm and silicon carbide having an average particle diameter of about 0.1 to 1.0 μm Is mentioned. This is because it is easy to produce a porous silicon carbide fired body.

There are various types of silicon carbide powder that can be used as a raw material. Low-purity silicon carbide for refractories contains 3% by weight or more of a silicon compound or the like as an impurity. In addition, content of the silica in silicon carbide can be measured by the neutralization titration method.
Even when such low-purity silicon carbide powder is used, in the method for manufacturing a honeycomb filter of the present invention, carbon is left in the honeycomb formed body in the course of the manufacturing process, and the carbon and silicon compound and By reacting with the above, a honeycomb filter with a small silicon compound content can be produced without performing a purification treatment or the like for removing the silicon compound in the raw material stage. The silicon compound is not particularly limited, but silica is preferable.

As said organic additive, an organic binder is mentioned, A dispersion medium liquid, a plasticizer, a lubricant, etc. are mentioned. These organic additives are carbonized by thermal decomposition during the production.
Examples of the organic binder include methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, polyethylene glycol, phenol resin, and epoxy resin. Of these, methylcellulose is preferred.

Examples of the dispersion medium liquid include alcohols such as methanol, organic solvents such as benzene, and water.
It does not specifically limit as said plasticizer, For example, glycerol etc. are mentioned.

The lubricant is not particularly limited, and examples thereof include polyoxyalkylene compounds such as polyoxyethylene alkyl ether and polyoxypropylene alkyl ether. Specific examples of the lubricant include polyoxyethylene monobutyl ether and polyoxypropylene monobutyl ether.

Another organic additive includes an organic pore forming agent for increasing the porosity of the honeycomb fired body constituting the honeycomb filter to be manufactured. Part of the organic pore-forming agent also becomes carbon in the degreasing step described later, and SiC is generated by reacting with the silicon compound. Further, when carbon reacts with silica, a part of the carbon is separated from the honeycomb formed body as CO, so that pores are formed. Examples of the organic pore former include spherical acrylic particles and graphite.

When preparing the raw material for the molded body, the raw material for the molded body is prepared by mixing the low-purity silicon carbide powder, the organic binder, and the water that is the dispersion medium liquid using a wet mixer. . In that case, you may add the said plasticizer, the said lubricant, the said organic pore making agent, etc. as needed.

(2) Molded body manufacturing process In this molded body manufacturing process, a honeycomb molded body is manufactured by extruding the prepared raw material for a molded body.
In this step, the raw material for the obtained molded body is put into an extrusion molding machine, and extrusion molding is performed to produce a prismatic continuous body. A honeycomb formed body having through holes arranged in parallel is manufactured. This honeycomb formed body is dried by a dryer to obtain a dried body of the honeycomb formed body.

Next, a predetermined amount of a plug material paste is filled in any one of the end portions of the through holes constituting the dried body of the honeycomb formed body, and the cells are plugged. When plugging the cells, for example, a cell sealing mask is applied to the end face of the honeycomb formed body (that is, the cut face after cutting both ends), and the sealing material is applied only to the cells that need to be sealed. Fill the paste and dry the encapsulant paste. Through such a process, a honeycomb formed body in which one end of the cell is plugged is manufactured.

Fig.1 (a) is a perspective view which shows typically the honeycomb molded object by which the one end part of the cell was plugged, FIG.1 (b) is A- of the honeycomb molded object shown to Fig.1 (a). It is A sectional view.
As shown in FIGS. 1A and 1B, the manufactured honeycomb molded body 200 is provided with a large number of cells 210 having one end plugged with a sealing material 220 in the longitudinal direction. A wall 230 is formed between the cells 210.

(3) Degreasing step Next, as the degreasing step, the produced honeycomb formed body is degreased in a completely inert gas atmosphere.
Conventionally, in the degreasing step, the organic matter is completely decomposed and removed by heating to 300 to 650 ° C. in an oxygen-containing atmosphere. However, in the method for manufacturing a honeycomb filter of the present invention, degreasing is performed by heating the honeycomb formed body 200 to, for example, 300 to 650 ° C. in a completely inert gas atmosphere.

The completely inert gas atmosphere refers to an inert gas atmosphere that does not contain oxygen or hydrogen at all, and examples thereof include an argon atmosphere and a nitrogen atmosphere. The organic additive is thermally decomposed by heating in such a completely inert gas atmosphere.
For this reason, when the organic additive has hydrogen or oxygen in the compound, it is separated from the honeycomb formed body 200 in the form of hydrocarbon or oxide by thermal decomposition, but some of the organic additive is carbon and carbon. It remains in the honeycomb formed body 200 as a compound. As described above, when heated in a completely inert gas atmosphere, the organic additive is thermally decomposed, but a part of it tends to remain as carbon in the degreased honeycomb formed body.

(4) Firing step After the degreasing step, in the firing step, the degreased honeycomb formed body is fired in a completely inert gas atmosphere. The firing step is usually performed at 1400 to 2200 ° C., but is preferably performed in a completely inert gas atmosphere.
Since the degreasing step and the firing step are performed in a completely inert gas atmosphere, they can be performed using one batch furnace. Moreover, since the said degreasing process and the said baking process are performed in a completely inert gas atmosphere, they can be performed in one continuous furnace provided with the degreasing area and the baking area.

Then, the case where the said degreasing process and the said baking process are performed in one continuous furnace provided with the degreasing | defatting area and the baking area is demonstrated.
FIG. 2 is a longitudinal sectional view schematically showing a case where the continuous heating furnace according to the present invention is cut in the vertical vertical direction along the longitudinal direction, and FIG. 3 is a longitudinal sectional view of the continuous heating furnace according to the present invention in the longitudinal direction. It is sectional drawing which shows typically the case where it cut | disconnects by a vertical cross section.

As shown in FIG. 2, the continuous heating furnace 30 according to the present invention includes a deaeration area 41, a degreasing area 42, a firing area 43, a slow cooling area 44, a cooling area 45, and a deaeration area 46 sequentially from the inlet direction. Is provided.

The deaeration area 41 is provided in order to change the atmosphere inside and around the honeycomb molded body 200 to be carried in, and after the honeycomb molded body 200 is placed on the conveying member 39 or the like and carried in, the deaeration area 41 is temporarily removed. The atmosphere in and around the honeycomb formed body 200 is made an inert gas atmosphere by evacuating 41 and subsequently introducing an inert gas.

In the degreasing area 42, the heater is heated or the heat of the firing area is used to raise the temperature of the honeycomb formed body 200 to 300 to 650 ° C., thereby heating the organic additive in the honeycomb formed body 200. Disassemble. The heating process in the degreasing area 42 corresponds to a degreasing process.

Next, the temperature is further increased to 650 ° C. or more in the firing area 43 and firing is performed at 1400 to 2200 ° C. The heating process in the firing area corresponds to the firing process. In the slow cooling area 44, the fired honeycomb formed body 200 is gradually cooled, and further returned to a temperature close to room temperature in the cooling area 45. Then, after the honeycomb formed body 200 is carried into the deaeration area 46, a series of degreasing and firing processes are performed on the honeycomb formed body 200 by removing the inert gas and introducing air to carry out the honeycomb formed body 200. The flow is complete.

Next, an example of the configuration of the continuous heating furnace will be described.
As shown in FIGS. 2 and 3, in the continuous heating furnace 30, the degreasing area 42 and the firing area 43 for degreasing and firing the honeycomb formed body 200 are formed so as to secure a space for accommodating the honeycomb formed body 200. The cylindrical muffle 31 thus formed, the heater 32 disposed above and below the muffle 31 at predetermined intervals, and the heat insulating material 33 provided so as to include the muffle 31 and the heater 32 therein. And a furnace material 34 disposed outside the heat insulating material 33, and is isolated from the surrounding atmosphere by the furnace material 34.

As shown in FIG. 2, the heater 32 is disposed in the firing area 43 and, if necessary, the degreasing area 42.

The muffle 31 is configured such that the entire floor portion is supported by a support member (not shown) and the honeycomb formed body 200 can be moved. The muffle 31 is provided in the entire area excluding the deaeration areas 41 and 46. Transport means such as a conveyor may be provided inside the muffle 31, thereby enabling the honeycomb molded body 200 to be automatically transported.

A heat insulating material 33 is installed in the degreasing area 42, the baking area 43, and the slow cooling area 44. In the baking area 43, the heat insulating material 33 is provided further outside the heater 32 and is appropriately fixed by a fixing member. It is fixed. And the furnace material 34 is provided in the outermost area over the whole area except the deaeration area 41. The furnace material 34 is provided with a gas introduction pipe 37 for filling the atmosphere inside the heating furnace with an inert gas atmosphere and a gas exhaust pipe 38 for discharging the inert gas.

The degreasing step and the firing step can be performed using one batch furnace.
The configuration when the heating furnace is a batch furnace is not significantly different from the configuration of the continuous furnace. For example, the furnace material 34 is configured so that the heating furnace becomes a box-type heating furnace, and the firing area 43 of the continuous heating furnace. A batch furnace can be configured by installing only a portion used as an inside, attaching a door that can be opened and closed as a slot, and surrounding the interior of the furnace material 34 with a heat insulating material or the like. .

Then, after the honeycomb formed body 200 is carried into the batch furnace, an inert gas is introduced into the furnace, the temperature is gradually raised and degreasing is performed, and then the temperature is further raised and firing is performed.
Although the said degreasing | defatting process and the said baking process were demonstrated about the case where it performs using one batch furnace or one continuous furnace, a batch furnace and a continuous furnace are not limited to an above-described structure, From other structures A batch furnace or a continuous furnace may be used.

In the degreasing step and the subsequent firing step with respect to the total weight of the organic matter, the ratio (%) of the weight of carbon remaining in the honeycomb formed body 200 before reacting with silica or the like is referred to as the residual carbon ratio. The remaining charcoal rate varies depending on the type of organic matter. Therefore, the amount of carbon remaining in the honeycomb formed body 200 can be adjusted by selecting the type and amount of the organic additive.

In the method for manufacturing a honeycomb filter of the present invention, carbon remains in the honeycomb formed body after the degreasing step, and the silicon compound contained in the silicon carbide powder remains. Actually, since most of the silicon compound is considered to be silica, the following description will be given assuming that the silicon compound is silica.

The molar ratio of carbon to silica (carbon / silica) in the honeycomb formed body is preferably 1 to 3.
As shown in the following reaction formula (1), 1 mol of silica and 3 mol of carbon react to synthesize 1 mol of SiC and generate 2 mol of CO gas.
SiO ₂ + 3C = SiC + 2CO (1)
Therefore, in order for carbon and silica not to remain in the manufactured honeycomb filter, as shown in the above reaction formula (1), when both react ideally, 60 g of silica is obtained for 36 g of carbon. Preferably it is present. Actually, when silica and carbon react to form SiO having a relatively low melting point once, and considering that this SiO reacts with carbon to produce SiC, the molar ratio of silica to carbon ( Carbon / silica) is preferably 1 to 3.
The carbon content in silicon carbide can be determined based on the total carbon content analysis method of JIS R 1616.

A porous honeycomb fired body can be manufactured through the degreasing step and the firing step. The structure of the honeycomb fired body is basically the same as that of the honeycomb formed body 200 shown in FIG.

When a honeycomb filter is manufactured using the obtained honeycomb fired body, a sealing material paste is applied to the side surface of the honeycomb fired body to form a sealing material paste layer, and sequentially through the sealing material paste layer. Another honeycomb fired body is laminated. This procedure is repeated to produce an aggregate of honeycomb fired bodies in which a predetermined number of honeycomb fired bodies are bundled. In addition, as a sealing material paste, what consists of an inorganic binder, an organic binder, an inorganic fiber, and / or an inorganic particle can be used, for example.

Next, this aggregate of honeycomb fired bodies is heated to dry and solidify the sealing material paste layer to form a sealing material layer (adhesive layer). Then, by cutting the aggregate of honeycomb fired bodies using a diamond cutter or the like to form a ceramic block, by forming a coating layer by applying a sealing material paste to the outer peripheral surface of the ceramic block and drying and solidifying, A honeycomb filter can be manufactured.

FIG. 4 is a perspective view showing a honeycomb filter manufactured by the method for manufacturing a honeycomb filter of the present invention. FIG. 5 (a) is a perspective view of the honeycomb fired body constituting the honeycomb filter of the present invention shown in FIG. 4, and FIG. 5 (b) is a B− of the honeycomb fired body shown in FIG. 5 (a). It is B line sectional drawing.

As shown in FIG. 4, the honeycomb filter 10 of the present invention includes a plurality of porous honeycomb fired bodies 20 made of silicon carbide combined with an adhesive layer 11 to form a cylindrical ceramic block 15. A coat layer 12 is formed around the ceramic block 15.

In the honeycomb filter 10 shown in FIG. 4, the shape of the ceramic block is a columnar shape. However, in the present invention, the ceramic block is not limited to a columnar shape as long as it is a columnar shape. Any shape may be used.

The honeycomb fired body 20 is manufactured by degreasing and firing the honeycomb formed body 200 shown in FIGS. 1 (a) and 1 (b). A large number of cells 21 are arranged in parallel in the longitudinal direction. Since one of the end portions of 21 is plugged, the cell partition wall 23 that separates the cells 21 functions as a filter. That is, in the cells 21 formed in the honeycomb fired body 20, as shown in FIG. 5 (b), either the inlet side or the outlet side end of the exhaust gas is plugged with the sealing material 22, The exhaust gas flowing into the cell 21 always passes through the cell partition wall 23 separating the cells 21 and then flows out from the other cells 21.

In the honeycomb filter configured as described above, the exhaust gas can be purified by collecting PM such as soot contained in the exhaust gas discharged from the internal combustion engine.
In addition, carbon remaining by degreasing treatment in a completely inert gas atmosphere is converted to silicon carbide by reacting with silica in the firing step, and the synthesized silicon carbide is composed of silicon carbide particles. It is easy to gather in the neck part which couple | bonds, and it plays the role which improves the mechanical characteristic of the manufactured honeycomb fired body.

As described above, in the method for manufacturing a honeycomb filter of the present invention, the degreasing step and the firing step are performed in a completely inert gas atmosphere, so that the heating can be performed in one heating furnace, and an organic additive such as an organic binder is added. The product is hardly oxidatively decomposed and is mainly thermally decomposed, and the organic additive is likely to remain as carbon. In the case of the present invention, silicon carbide powder contains 3% by weight or more of impurities composed of a silicon compound, and the honeycomb formed body after degreasing contains silicon compound and carbon. When this honeycomb formed body is fired, the silicon compound and carbon react to synthesize carbide. As a result, there is no thing inhibiting the bonding between the silicon carbide particles, the bonding between the silicon carbide particles can be promoted, and a honeycomb filter having sufficient characteristics as a filter can be manufactured.

In the method for manufacturing a honeycomb filter of the present invention, the degreasing step and the firing step can be continuously performed by using one batch furnace and sequentially raising the temperature after carrying the formed body into the batch furnace. Therefore, degreasing and firing can be performed in a short time, the honeycomb formed body can be prevented from being damaged, energy loss can be reduced, and a honeycomb filter can be produced efficiently and inexpensively.

In the method for manufacturing a honeycomb filter of the present invention, degreasing and firing can be performed continuously while moving the honeycomb formed body in a continuous furnace having a degreasing area and a firing area, and degreasing and firing can be performed in a short time. The honeycomb filter can be manufactured efficiently and inexpensively without any risk of damage to the honeycomb formed body. In the continuous furnace, since the honeycomb molded body is continuously carried in and out, it can be used without resting the furnace, and the honeycomb filter can be manufactured more efficiently and at a low cost. .

(Example)
Examples that more specifically disclose the first embodiment of the present invention will be described below. In addition, this invention is not limited only to these Examples.

Example 1
(1) Manufacture of honeycomb fired body First, as a raw material preparation step for a molded body, 54.5% by weight of a coarse powder of silicon carbide having an average particle diameter of 22 μm and fine powder of silicon carbide having an average particle diameter of 0.5 μm 23. 4% by weight, and with respect to the resulting mixture, 4.3% by weight of organic binder (methyl cellulose), 2.6% by weight of lubricant (Unilube, NOF Corporation), 1.2% by weight of glycerin, and Then, 14.0% by weight of water was added and kneaded to obtain a molded body raw material. In addition, the silicon carbide coarse powder used in this example is a 95% pure product (SiC purity: 92.56 wt%, silica content: 3.48 wt%) of RM325F manufactured by Yakushima Electric Works, Ltd. The silicon fine powder was GC-15 (SiC purity: 95.25 wt%, silica content: 3.59 wt%) manufactured by Yakushima Electric Works. The silica content of the mixture of both is 3.51% by weight. In Examples 1 and 2 and Comparative Examples 1 and 2, the content of silica in silicon carbide was measured by a neutralization titration method.

Thereafter, as a formed body manufacturing step, extrusion molding was performed using the obtained raw material for a formed body to obtain a raw honeycomb formed body. Subsequently, the raw honeycomb formed body was dried using a microwave dryer, thereby manufacturing a dried body of the honeycomb formed body.

Thereafter, the plugging material paste was filled in predetermined cells of the dried honeycomb molded body to seal the cells, and the plugged honeycomb molded body shown in FIGS. 1A and 1B was obtained. . The wet mixture was used as a sealing material paste. After sealing the cells, the dried honeycomb molded body filled with the plug paste was again dried using a dryer.

Subsequently, a plurality of dried honeycomb molded bodies are placed on a conveying member, and are loaded into a batch furnace. Then, nitrogen is introduced, and the temperature is raised to 400 ° C. in a normal-pressure nitrogen atmosphere. The degreasing process was performed by stopping. Then, without moving the honeycomb formed body after the degreasing treatment, after introducing argon into the same batch furnace and replacing the nitrogen gas with the argon gas, conditions of 2200 ° C. for 3 hours in an argon atmosphere at normal pressure A honeycomb fired body was manufactured by performing a firing process.

The obtained honeycomb fired body is composed of a porous silicon carbide sintered body having a porosity of 42%, an average pore diameter of 9 μm, a size of 34.3 mm × 34.3 mm × 150 mm, and the number of cells (cell density). ) Was 31 cells / cm ² (200 cells / inch ² ), the cell partition wall thickness was 0.1016 mm, and the outer peripheral wall thickness was 0.3 mm.
Silica was not detected in the obtained honeycomb fired body.

(2) Production of honeycomb filter A honeycomb structure was produced using the honeycomb fired body obtained by the above-described process.
An adhesive paste is applied to a predetermined side surface of the honeycomb fired body, and 36 (6 vertical × 6 horizontal) honeycomb fired bodies are bonded through the adhesive paste, thereby forming an aggregate of the honeycomb fired bodies. Produced.
Furthermore, the aggregate of the honeycomb fired bodies was dried and solidified at 180 ° C. for 20 minutes to produce a prismatic ceramic block having an adhesive layer thickness of 1 mm.

Then, the cylindrical ceramic block of diameter 198mm was produced by grinding the outer periphery of a prismatic ceramic block using a diamond cutter.

Next, the outer periphery coating material paste is applied to the outer periphery of the cylindrical ceramic block, and the outer periphery coating material paste is heated and solidified at 120 ° C., thereby forming an outer periphery coating layer having a thickness of 1.0 mm on the outer periphery of the ceramic block. Formed. In addition, the said adhesive material paste was used as an outer periphery coating material paste.
Through the above process, a honeycomb filter having a diameter of 200 mm and a length of 150 mm was produced.

(Example 2)
A honeycomb was obtained in the same manner as in Example 1 except that the silicon carbide crude powder used was changed to a 90% pure product of RM325F (SiC purity: 87.1% by weight, silica content: 5.88% by weight). A fired body was manufactured, and a honeycomb filter was manufactured using the fired body. In addition, the silica content of the mixture of the coarse powder and the fine powder is 5.19% by weight.
However, when the silica concentration of the honeycomb fired body after the firing process was measured, no silica was detected.

(Comparative Example 1)
(1) Production of honeycomb fired body First, 54.5% by weight of silicon carbide coarse powder having an average particle size of 22 μm and 23.4% by weight of fine powder of silicon carbide having an average particle size of 0.5 μm were mixed, To the resulting mixture, 4.3% by weight of organic binder (methylcellulose), 2.6% by weight of lubricant (Unilube, NOF Corporation), 1.2% by weight of glycerin, and 14.0% by weight of water In addition, kneading was performed to obtain a molded body raw material. In this example, the same silicon carbide coarse powder and silicon carbide fine powder as in Example 1 were used.

Then, extrusion molding was performed using the obtained raw material for a molded body to obtain a raw honeycomb molded body. Subsequently, the raw honeycomb formed body was dried using a microwave dryer, thereby manufacturing a dried body of the honeycomb formed body. Thereafter, the plugging material paste was filled in predetermined cells of the dried honeycomb molded body to seal the cells, and the plugged honeycomb molded body shown in FIGS. 1A and 1B was obtained. . The wet mixture was used as a sealing material paste. After sealing the cells, the dried honeycomb molded body filled with the plug paste was again dried using a dryer.

Next, the honeycomb formed body was placed on a conveying member, carried into a degreasing furnace, and degreased by degreasing at 500 ° C. in air. After cooling the honeycomb formed body that has been degreased in a degreasing furnace, the honeycomb formed body is unloaded from the degreasing furnace, loaded into the firing furnace, and then fired in a normal pressure argon atmosphere at 2200 ° C. for 3 hours. Thus, a honeycomb fired body was manufactured.
When the silica content of the obtained honeycomb fired body was measured, the silica content was 1.22% by weight.

The obtained honeycomb fired body is made of a porous silicon carbide sintered body, has a size of 34.3 mm × 34.3 mm × 150 mm, and the number of cells (cell density) is 31 cells / cm ² (200 cells). / Inch ² ), the cell partition wall thickness was 0.1015 mm, and the outer peripheral wall thickness was 0.3 mm.

(2) Production of Honeycomb Filter A honeycomb filter was produced in the same manner as in Example 1 using the honeycomb fired body obtained by the above process.

(Comparative Example 2)
A honeycomb fired body was manufactured in the same manner as in Comparative Example 1 except that the same silicon carbide coarse powder and silicon carbide fine powder as in Example 2 were used, and a honeycomb filter was manufactured using the obtained honeycomb fired body.
The obtained honeycomb fired body is made of a porous silicon carbide sintered body, has a size of 34.3 mm × 34.3 mm × 150 mm, and the number of cells (cell density) is 31 cells / cm ² (200 cells). / Inch ² ), the cell partition wall thickness was 0.1015 mm, and the outer peripheral wall thickness was 0.3 mm.
When the silica content of the honeycomb fired body after the firing step was measured, the silica content was 1.50% by weight.

(Evaluation)
In the degreasing furnaces in which Comparative Example 1 and Comparative Example 2 were performed, organic decomposition products and the like adhered to the furnace inner wall surface and were stained black. In the batch furnaces in which Example 1 and Example 2 were performed, the furnace inner wall surface was contaminated. Was minor. Thereby, the maintenance frequency in the batch furnace in which Example 1 and Example 2 were implemented was reduced to about 40% compared to Comparative Example 1 and Comparative Example 2.

DESCRIPTION OF SYMBOLS 10 Honeycomb filter 11 Adhesive layer 12 Coat layer 15 Ceramic block 20 Honeycomb fired body 21 Cell 22 Sealing material 23 Cell partition 30 Continuous heating furnace 31 Muffle 32 Heating heater 33 Heat insulating material 34 Furnace material 37 Gas introduction pipe 38 Gas exhaust pipe 39 Conveying members 41 and 46 Deaeration area 42 Degreasing area 43 Firing area 44 Slow cooling area 45 Cooling area 200 Honeycomb molded body 210 Cell 220 Sealing material 230 Wall part

Claims (6)

A molded body raw material preparation step of preparing a molded body raw material by mixing silicon carbide powder containing 3% by weight or more of an impurity composed of a silicon compound, and an organic additive containing at least an organic binder,
A molded body production step of producing a honeycomb molded body by extruding the prepared molded body raw material;
A degreasing step of degreasing the produced honeycomb formed body in a completely inert gas atmosphere;
A method for manufacturing a honeycomb filter, comprising: a firing step of firing the degreased honeycomb formed body. The method for manufacturing a honeycomb filter according to claim 1, wherein the firing step is performed in a completely inert gas atmosphere. The method for manufacturing a honeycomb filter according to claim 1 or 2, wherein the silicon compound is silica. The method for manufacturing a honeycomb filter according to claim 3, wherein a molar ratio of carbon to silica (carbon / silica) in the honeycomb formed body after the degreasing step is 1 to 3. The method for manufacturing a honeycomb filter according to any one of claims 1 to 4, wherein the degreasing step and the firing step are performed in one batch furnace. The method for manufacturing a honeycomb filter according to any one of claims 1 to 4, wherein the degreasing step and the firing step are performed in one continuous furnace, and the continuous furnace includes a degreasing area and a firing area. .

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