JP4699885B2 - Manufacturing method of honeycomb structure - Google Patents

Description

  The present invention relates to a method for manufacturing a honeycomb structure. More specifically, the present invention relates to a method for manufacturing a honeycomb structure capable of correcting a distortion of a honeycomb formed body and effectively preventing damage during firing.

  Honeycomb structures are widely used for filters, catalyst carriers, and the like, and in particular, are widely used as catalyst carriers and filters for exhaust gas purification or exhaust gas treatment of internal combustion engines such as gasoline engines and diesel engines and combustion devices. .

  As one of the methods for manufacturing a honeycomb structure used for such a purpose, for example, a forming raw material containing raw material powder, a binder, and water is used, and after mixing the forming raw material, for example, into a honeycomb shape Examples thereof include a method in which extrusion molding is performed, drying is further performed to obtain a honeycomb molded body, and the obtained honeycomb molded body is fired to be manufactured. The reason why the binder is included in the molding raw material is that the raw material powder and water alone do not provide sufficient plasticity and shape retention necessary for these moldings. Thus, a molding raw material containing a binder should be used. Thus, formability can be improved.

In the conventional method for manufacturing a honeycomb structure, the temperature at which the honeycomb formed body is fired, for example, the temperature rise rate of the firing atmosphere is strictly controlled so that there is no temperature difference between the inside and outside of the honeycomb formed body in the temperature rising process. Has been adopted. In the temperature range (about 180 to 300 ° C.) at which the organic binder burns, the present applicant also makes the burning of the organic binder as slow as possible in a firing atmosphere in which the rate of temperature rise is kept low (that is, the temperature is gradually raised). Have already been proposed, for example, a method for producing a porous ceramic structure in which the temperature is raised in a predetermined temperature range while the ambient temperature is substantially synchronized with the center temperature of the body to be fired (for example, (See Patent Documents 1 and 2). According to such a method for manufacturing a honeycomb structure, it is possible to suppress a rapid temperature increase during firing and prevent breakage due to the rapid temperature increase, for example, firing cracks.
Japanese Patent No. 2543565 JP 2003-212672 A

  However, even if the method for manufacturing a honeycomb structure described in Patent Documents 1 and 2 described above is used, the shape of the honeycomb molded body is distorted during forming, drying, transport before firing, and the like. There is a problem in that internal stress due to strain is generated, and the resulting honeycomb structure is damaged such as cell breakage.

  The present invention has been made in view of the above-described conventional problems, and can effectively prevent damage during firing of the honeycomb formed body, particularly damage during firing due to distortion of the honeycomb formed body. A method for manufacturing a honeycomb structure is provided.

  The inventor of the present invention has intensively studied to solve the above-mentioned problems of the prior art. As a result, when firing the honeycomb formed body, a temperature lower than the conventional firing temperature, specifically, 150 ° C. As described above, by heating for a predetermined time at a temperature at which the mass reduction rate of the honeycomb molded body is 10% / h or less, the distortion of the honeycomb molded body can be corrected by the internal stress generated in the honeycomb molded body. Even if the firing is continued at a higher temperature, no large internal stress will occur that will cause damage thereafter, and damage during firing due to distortion of the honeycomb molded body, especially damage such as cell breakage, is effective. Thus, the present invention has been completed. That is, according to the present invention, the following method for manufacturing a honeycomb structure is provided.

[1] A honeycomb structure in which a forming raw material including a raw material powder, a binder, and water is formed and further dried to obtain a honeycomb formed body, and the obtained honeycomb formed body is fired to produce a honeycomb structure. In the manufacturing method, the honeycomb formed body is primarily heated for at least 480 minutes at a temperature of 150 ° C. or more and a mass reduction rate of the honeycomb formed body is 10% / h or less, and then the honeycomb formed by the primary heating. A method for manufacturing a honeycomb structure, wherein the honeycomb structure is manufactured by further heating (secondary heating) and firing the body.

[2] The method for manufacturing a honeycomb structure according to [1], wherein a heating temperature in the primary heating is 150 to 190 ° C.

[ 3 ] The method for manufacturing a honeycomb structure according to [1] or [2] , wherein the primary heating is a heating step in which heating is performed at a heating rate of 10 ° C./h or less.

[ 4 ] The method for manufacturing a honeycomb structure according to any one of [1] to [ 3 ], wherein the binder of the forming raw material is an organic binder.

[ 5 ] The method according to any one of [1] to [ 4 ], wherein the primary heating is performed after disposing a plugging member in an opening of a part of cells on at least one end face of the honeycomb formed body. A method for manufacturing a honeycomb structure.

  The method for manufacturing a honeycomb structured body of the present invention can effectively prevent damage during firing of the honeycomb formed body, particularly damage during firing due to distortion of the honeycomb formed body.

  That is, in the method for manufacturing a honeycomb structure of the present invention, the primary heating is performed for at least 480 minutes at the above-described temperature at 150 ° C. or more and the mass reduction rate of the honeycomb formed body is 10% / h or less. It is possible to correct the distortion of the honeycomb formed body caused by conveyance before drying or firing, and then correct the distortion by heating (secondary heating) the primary heated honeycomb formed body at a predetermined temperature. In this state, firing of the honeycomb formed body is realized, and breakage due to distortion of the honeycomb formed body can be effectively prevented. In particular, in the method for manufacturing a honeycomb structure of the present invention, it is possible to effectively prevent the occurrence of cell breakage and improve the yield.

  In the primary heating, the binder is not rapidly burned out from the honeycomb formed body, and the heating is performed while maintaining a certain viscosity. Therefore, the internal stress generated in the honeycomb formed body is extremely small and increases very slowly, and the honeycomb formed body is plastically deformed so as to correct the distortion by itself.

  Since the distortion of the honeycomb molded body is corrected by such primary heating, the honeycomb molded body may be damaged even if secondary heating is performed at a temperature in the conventional method for manufacturing a honeycomb structure thereafter. No stress is generated, and the honeycomb structure can be manufactured satisfactorily.

  Hereinafter, an embodiment of a method for manufacturing a honeycomb structure of the present invention will be described in detail. Based on this knowledge, various changes, modifications, and improvements can be made.

  The method for manufacturing a honeycomb structure according to the present embodiment includes a honeycomb structure 1 having a plurality of through holes (cells 3) serving as a fluid flow path partitioned by a porous partition wall 2 as shown in FIG. It is a manufacturing method for manufacturing. Although illustration is omitted, the method for manufacturing a honeycomb structure according to the present embodiment can also manufacture a honeycomb structure in which the openings of some cells on at least one end face are plugged. .

  The method for manufacturing a honeycomb structure according to the present embodiment includes forming a forming raw material containing raw material powder, a binder, and water, further drying to obtain a honeycomb formed body, and firing the obtained honeycomb formed body to obtain a honeycomb. A method for manufacturing a honeycomb structure for manufacturing a structure, wherein the honeycomb formed body has a temperature of 150 ° C. or more and a mass reduction rate of the honeycomb formed body of 10% / h or less (that is, 0 to 10% / h). This is a method for manufacturing a honeycomb structure in which a honeycomb structure is manufactured by performing primary heating at a temperature of at least 480 minutes and then further heating (secondary heating) and firing the formed honeycomb molded body. By comprising in this way, the distortion of a honeycomb molded object can be corrected and the damage at the time of baking can be prevented effectively.

  The mass reduction rate (% / h) of the honeycomb formed body in the present specification is the total of the honeycomb formed body obtained by forming a forming raw material containing raw material powder, a binder, and water and further drying. It means the ratio of the mass (specifically, the mass decreased due to the volatilization or burning of the binder) changed by the primary heating of the honeycomb formed body with respect to the mass. This mass reduction rate (% / h) can be measured using a thermobalance (TGA).

  Hereinafter, the manufacturing method of the honeycomb structure of the present embodiment will be specifically described for each step.

(Preparation of molding raw materials)
In the method for manufacturing a honeycomb structure of the present embodiment, first, a raw material powder, a binder, and water are mixed and kneaded to prepare a forming raw material.

  As the raw material powder contained in the forming raw material, the raw material powder used in the conventional method for manufacturing a honeycomb structure can be suitably used. For example, it consists of cordierite raw material powder excellent in heat resistance and low thermal expansion, alumina, mullite, spinel, aluminum titanate, titania, zirconia, silicon nitride, aluminum nitride, silicon carbide, and LAS (lithium aluminum silicate). One kind selected from the group or a composite thereof, or an adsorbent material such as stainless steel, aluminum alloy, activated carbon, silica gel, and zeolite can be suitably used.

  The binder contained in the forming raw material is an auxiliary agent for improving the formability of the forming raw material and maintaining the viscosity of the honeycomb formed body constant in order to correct distortion in the primary heating. In the method for manufacturing a honeycomb structure of the present embodiment, this binder is preferably an organic binder, and specific examples include methylcellulose, hydroxypropylmethylcellulose, polyvinyl alcohol, acrylic resin, and the like. By forming using such a forming raw material containing a binder and performing primary heating on the formed honeycomb formed body, the distortion of the honeycomb formed body can be corrected more easily.

(Formation of honeycomb molded body)
Next, the obtained forming raw material is formed into a honeycomb shape and further dried to obtain a honeycomb formed body. About the method of shaping | molding and drying, it can carry out according to the manufacturing method of a conventionally well-known honeycomb structure.

  In the method for manufacturing a honeycomb structure of the present embodiment, plugging members are disposed in the openings of some cells on at least one end face of the honeycomb formed body, and the openings of some cells are formed. A honeycomb formed body in which is plugged may be produced. In addition, there is no restriction | limiting in particular about the method of plugging the opening part of a cell, It can carry out according to a conventionally well-known method. Note that the above-described plugging of the opening of the cell can be performed after the secondary heating is completed.

(Primary heating)
Next, the obtained honeycomb formed body is primarily heated for at least 480 minutes at a temperature of 150 ° C. or higher and a mass reduction rate of the honeycomb formed body of 10% / h or less. This primary heating corrects the distortion of the honeycomb formed body.

  As described above, the minimum temperature at the time of primary heating is 150 ° C. Even if heating is performed at a temperature lower than this temperature, it takes too much time to relieve internal stress due to distortion of the honeycomb formed body. The distortion of the molded body cannot be corrected.

  Further, as described above, the primary heating needs to be performed for at least 480 minutes. If the primary heating time is shorter than this, the distortion of the honeycomb formed body cannot be sufficiently corrected. In addition, although it does not specifically limit, When performing primary heating, it is preferable to set it as 6000 minutes at maximum.

  Further, the maximum temperature at the time of primary heating is a temperature at which the mass reduction rate of the honeycomb formed body is 10% / h or less, and if it is higher than this temperature, the binder is rapidly burned out from the honeycomb formed body. In addition, since the firing proceeds before the distortion of the honeycomb formed body is corrected, internal stress due to the distortion of the honeycomb formed body cannot be relieved, and the resulting honeycomb structure is damaged such as cell breakage. It will occur. The maximum temperature during the primary heating is preferably a temperature at which the mass reduction rate of the honeycomb formed body is 2% / h or less (that is, 0 to 2% / h), preferably 1% / h or less. More preferably, the temperature is 0 to 1% / h.

  The maximum temperature at the time of primary heating is specified by the mass reduction rate of the honeycomb formed body, and varies depending on the configuration of the forming raw material, specifically, the kind of the binder. In addition, although it does not specifically limit, 150-190 degreeC can be mentioned as a heating temperature in primary heating, for example.

  The primary heating may be performed while maintaining a constant temperature within the above-described temperature range, and may be within a range of 10 ° C./h or less (ie, 0 to 10 ° C./h). It may be a temperature raising step of heating at a temperature raising rate.

  Although not particularly limited, the primary heating is preferably performed in an atmosphere in which the combustion of the binder contained in the forming raw material does not proceed. For example, the primary heating is performed in an atmosphere including an inert atmosphere. Is effective.

(Secondary heating)
Next, the primary heated honeycomb formed body is subjected to secondary heating. This secondary heating step can be realized in accordance with a firing step in a conventionally known method for manufacturing a honeycomb structure.

  By manufacturing the honeycomb structure as described above, the distortion of the honeycomb formed body caused by forming, drying, conveyance before firing, or the like can be corrected by primary heating, and then, at a predetermined temperature, the distortion can be corrected. By subsequent heating, firing of the honeycomb formed body is realized in a state where the distortion is corrected, and breakage due to the distortion of the honeycomb formed body can be effectively prevented.

  For this reason, the method for manufacturing a honeycomb structure of the present embodiment has a large honeycomb structure that is likely to be damaged due to distortion of the honeycomb molded body, and more specifically, the diameter of the end face is 150 mm or more. This is a particularly effective manufacturing method for manufacturing the honeycomb structure. Of course, even when a honeycomb structure having an end face diameter of less than 150 mm is manufactured, breakage due to distortion of the honeycomb formed body can be effectively prevented.

  In the method for manufacturing a honeycomb structure of the present embodiment, primary heating and secondary heating are continuously performed, and the primary heating and the secondary heating may be performed as a series of firing steps. Heating may be regarded as a firing step, and primary heating may be performed as a pretreatment for the firing step.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

Example 1
100 parts by mass of the raw material powder, 8 parts by mass of methyl cellulose as a binder, and water were mixed to prepare a forming raw material. After extrusion of the forming raw material, drying was performed to prepare 20 honeycomb formed bodies.

The shape of the honeycomb formed body in Example 1 was a columnar shape with an end face diameter of 100 mm and an axial length of 100 mm, a partition wall thickness of 300 μm, and a cell density of 30 cells / cm ² . Drying is performed with microwaves and hot air, and in this example, the drying temperature is increased by 10 ° C. from the normal drying temperature so as to facilitate comparison with the conventional manufacturing method, and the honeycomb formed body is distorted. Was generated.

  The honeycomb molded body thus prepared was measured for mass with a thermobalance device (TGA), and 600 minutes (10 hours at 185 ° C., which is the temperature at which the mass reduction rate of the honeycomb molded body was 10% / h or less. After the primary heating, the honeycomb structure was manufactured by further heating (secondary heating) and firing the honeycomb formed body that was primarily heated. The temperature at which the mass reduction rate of the honeycomb formed body is 10% / h is 195 ° C.

  The appearance of the obtained 20 honeycomb structures was confirmed by visual observation to confirm the presence or absence of breakage such as cell breakage. The results are shown in Table 1.

(Actual examples 2 to 24)
Except for changing the shape of the honeycomb formed body to be formed as shown in Table 1, 20 honeycomb structures were manufactured in the same manner as in Example 1, and the presence or absence of each damage was confirmed. The results are shown in Table 1.

(Comparative Examples 1 to 24)
20 honeycomb structures were formed in the same manner as in Example 1 except that the shape of the honeycomb formed body to be formed was changed as shown in Table 2, and the heating time of primary heating was 300 minutes (5 hours). The body was manufactured and the presence or absence of each damage was confirmed. The results are shown in Table 2.

(Example 25 to 33)
The shape of the honeycomb formed body to be formed is changed as shown in Table 3, and the binder used for the forming raw material is methyl cellulose in Examples 25 to 27, hydroxypropyl methyl cellulose in Examples 28 to 30, and Examples 31 to 33. and polyvinyl alcohol in, except that a primary heating time as shown in Table 3, to produce 20 pieces of honeycomb structures each in the same manner as in example 1, confirming the existence of each failure did. Each result is shown in Table 3.

(Comparative Examples 25-36)
The shape of the honeycomb formed body to be formed is changed as shown in Table 4, and the binder used for the forming raw material is methyl cellulose in Comparative Examples 25 to 27, hydroxypropyl methyl cellulose in Comparative Examples 28 to 30, and Comparative Examples 31 to 33. In the comparative examples 34 to 36, water-soluble acrylic resin is used, and 20 honeycomb structures are formed in the same manner as in Example 1 except that primary heating is performed at the time and temperature as shown in Table 4. The body was manufactured and the presence or absence of each damage was confirmed. Each result is shown in Table 4.

(Examples 37 to 48)
While changing the shape of the honeycomb formed body to be formed as shown in Table 5, the primary heating temperature was 150 ° C. in Examples 37 to 39, 170 ° C. in Examples 40 to 42, and Examples 43 to 45. 20 honeycomb structures were manufactured in the same manner as in Example 1 except that the temperature was 180 ° C. and that in Examples 46 to 48 was 190 ° C., and the presence or absence of each damage was confirmed. The results are shown in Table 5.

(Comparative Examples 37-42)
The shape of the honeycomb formed body to be formed was changed as shown in Table 6, and the primary heating temperature was 140 ° C. in Comparative Examples 37 to 39 and 196 ° C. in Comparative Examples 40 to 42. 20 honeycomb structures were manufactured in the same manner as in No. 1, and the presence or absence of each breakage was confirmed. Each result is shown in Table 6.

In Examples 1 to 33 and 37 to 48, the number of occurrences of breakage such as cell breakage in the 20 manufactured honeycomb structures was at most one, and no breakage was confirmed under most conditions. On the other hand, in Comparative Examples 1 to 42, although the number of breakage differs depending on the size of the honeycomb structure, the time of temporary heating, the type of binder, and the like, the number of breakage generally increased as compared with the Examples. .

  The method for manufacturing a honeycomb structure of the present invention includes a catalyst carrier, a filter, and the like, in particular, an internal combustion engine such as a gasoline engine or a diesel engine, or a catalyst carrier or filter for exhaust gas purification or exhaust gas treatment of a combustion apparatus. It is a method of manufacturing. According to the method for manufacturing a honeycomb structured body of the present invention, it is possible to correct the distortion of the honeycomb formed body that has been formed and dried from the forming raw material, and to effectively prevent breakage during firing. In particular, the method for manufacturing a honeycomb structured body of the present invention is a particularly effective manufacturing method for manufacturing a large-sized honeycomb structured body that is likely to be damaged due to distortion of the honeycomb formed body.

It is a perspective view which shows typically an example of a honeycomb structure.

Explanation of symbols

1: honeycomb structure, 2: partition, 3: cell.

Claims (5)

A method for manufacturing a honeycomb structure, in which a forming raw material including a raw material powder, a binder, and water is formed, further dried to obtain a honeycomb formed body, and the obtained honeycomb formed body is fired to manufacture a honeycomb structure. There,
The honeycomb formed body is primarily heated for at least 480 minutes at a temperature of 150 ° C. or higher and the mass reduction rate of the honeycomb formed body is 10% / h or less, and then the primary heated honeycomb formed body is further heated (two A method for manufacturing a honeycomb structure, wherein the honeycomb structure is manufactured by performing subsequent heating and firing.   The method for manufacturing a honeycomb structured body according to claim 1, wherein a heating temperature in the primary heating is 150 to 190 ° C. The method for manufacturing a honeycomb structured body according to claim 1 or 2 , wherein the primary heating is a heating step of heating at a heating rate of 10 ° C / h or less. The method for manufacturing a honeycomb structure according to any one of claims 1 to 3 , wherein the binder of the forming raw material is an organic binder. The method for manufacturing a honeycomb structure according to any one of claims 1 to 4 , wherein the primary heating is performed after disposing a plugging member in an opening of a part of cells in at least one end face of the honeycomb formed body. .

Images