JP2002160976A - Method for manufacturing ceramic honeycomb structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a honeycomb structure composed of cordierite ceramics without generating slivers after sintering, in a drastically shortened sintering time at a lower manufacturing cost. SOLUTION: Methyl cellulose of 1-10 percent by mass, preferably 3-5 percent by mass as an auxiliary agent and hydroxypropyl methyl cellulose of 30-50 percent by mass of the methyl cellulose quantity are added to a raw argile. A molded form having a ceramic honeycomb construction is formed from this argile and sintered in a roller hearth kiln to produce a ceramic honeycomb structure. The sintering in the kiln is preferably carried out at a programming rate of 100-200 deg.C/h in the binder elimination phase, 60-100 deg.C/h in the dehydration of crystal water phase and 140-200 deg.C in the sintering phase.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art From the standpoint of preserving the local environment and the global environment, it is required to reduce harmful substances contained in exhaust gas discharged from engines of automobiles and the like. To meet this demand, catalytic converters for purifying exhaust gas have been used. ing. One of the catalytic converters is a ceramic honeycomb catalytic converter. A ceramic honeycomb catalytic converter is a ceramic honeycomb structure supporting a catalyst (hereinafter, referred to as a “honeycomb structure” for short, “ceramic honeycomb structure”).
Is heated by the thermal energy of the exhaust gas to activate the catalyst and purify the exhaust gas.

FIG. 2 is a perspective view of an example of a honeycomb structure. As shown in FIG. 2, the honeycomb structure 11 has a substantially cylindrical outer peripheral wall 11a and cell walls 11b orthogonal to each other in order to form an infinite number of ventilation holes 11c in the outer peripheral wall 11a.

Next, a general method for manufacturing a honeycomb structure will be described. First, in order to obtain a cordierite composition, a cordierite-forming raw material such as kaolin, talc, and alumina, a molding aid, or a pore-forming agent as necessary, are mixed and kneaded to form a ceramic clay. . Then, after the kneaded clay is degassed in vacuum, it is extruded through a special die with an extrusion screw to form a formed body 11 having a ceramic honeycomb structure in which an outer peripheral wall 11a and a cell wall 11b are formed. Further, in a firing furnace such as a tunnel furnace or a single furnace, binders such as forming aids, crystal water, and the like in the formed body 11 having the ceramic honeycomb structure are decomposed and removed, and fired under a predetermined atmosphere and a predetermined temperature. The reaction between the components is promoted to form cordierite, which is simultaneously shrunk and densified by sintering to form a honeycomb structure 11 having a predetermined shape and strength.

[0005] By the way, the kneaded material for obtaining the formed body 11 having the ceramic honeycomb structure is provided with the above-mentioned forming aid as
Organic binders such as methylcellulose, carboxymethylcellulose, polyvinyl alcohol, starch paste, and glycerin, surfactant wax, and the like are contained, or graphite, wheat flour, starch, and the like are contained as the pore-forming agent. However, the pore-forming agent and the forming aid contained in the molded body 11 having the ceramic honeycomb structure are hardly heated to the inside because they are vent holes 11c other than the outer peripheral wall 11a and the cell wall 11b, and are completely burned. In some cases, it takes a long time, and in some cases, heat is generated during combustion, in which case, a temperature difference occurs inside and cracks may occur.

On the other hand, in the molded body 11 having the ceramic honeycomb structure, if the pore-forming agent and the molding aid are not uniformly burned during firing, non-uniform shrinkage occurs between the outer side 11e and the central portion 11f in FIG. If the shrinkage becomes uneven, the cell walls of the honeycomb structure 11 after firing may be cut. FIG. 2 also schematically shows cuts 11 d generated in the honeycomb structure 11. When the cut 11d shown in FIG. 2 occurs, the cell walls 11b are not partially connected to each other, so that the exhaust gas vent 11c is not completely formed, and such a honeycomb structure 11 becomes unusable.

To solve this, Japanese Patent Publication No. 7-9358
Japanese Patent Application Laid-Open Publication No. H11-163873 discloses a method of firing a honeycomb structure under a predetermined atmosphere and a predetermined temperature, in which a firing atmosphere is forcibly forced at a speed of 1.0 to 5.0 m / s in parallel with the ventilation holes of the honeycomb structure. There is a description to pass. By uniformly heating the outside and the center of the honeycomb structure, the fired honeycomb structure can be prevented from being cut.

[0008]

SUMMARY OF THE INVENTION The aforementioned Japanese Patent Publication No. 7-935.
Japanese Patent Publication No. 8 (KOKAI) No. 8 discloses that as a condition for setting a cut generation rate in a honeycomb structure after firing to 0%, Table 1 of the specification of the same publication discloses:
In a honeycomb structure made of cordierite ceramic fired using the invention of the same publication and having a forming aid, a diameter of 100 mm x a length of 100 mm and a minimum firing time of 26 hours,
Table 2 shows that a honeycomb structure made of cordierite ceramic fired using the invention of the publication and having a pore-forming agent has a diameter of 230 mm x a length of 300 mm and requires a minimum of 65 hours for firing. . However, in the method for firing a honeycomb structure made of cordierite ceramic described in Japanese Patent Publication No. 7-9358, the occurrence of cuts after firing is reduced,
It takes as long as 65 hours, which increases the manufacturing cost. Further, the generation of cut after firing has not been controlled by controlling the amount of a pore-forming agent or a molding aid added.

It is an object of the present invention to provide a method for manufacturing a honeycomb structure made of cordierite ceramics, which does not cause breakage after firing and can further greatly shorten the firing time and reduce the manufacturing cost. is there.

[0010]

Means for Solving the Problems In view of the above-mentioned problems, the present inventors have proposed a molding aid added to a cordierite-forming raw material such as kaolin, talc, or alumina so that a cordierite composition can be obtained. The amount of addition and the firing furnace were variously changed, and intensive studies were made on the occurrence of breakage after firing and the firing time. As a result, methylcellulose as a molding aid, and hydroxypropyl methylcellulose were added to methylcellulose by adding an appropriate amount to methylcellulose to form a kneaded material, and a formed body having a ceramic honeycomb structure was formed from the kneaded material,
The formed body having the ceramic honeycomb structure is fired by appropriately controlling the temperature rising rate in the debinding region or the decrystallized water region and the firing region using a roller hearth kiln. The characteristics are exhibited to the maximum, and the honeycomb structure after firing does not break,
Further, the inventors have found that the firing time can be greatly reduced and the manufacturing cost can be reduced, and have reached the present invention.

More specifically, the method for producing a honeycomb structure according to the present invention comprises, as molding aids, methyl cellulose in a mass ratio of 1 to 10% and hydroxypropyl methyl cellulose in a mass ratio of 30 to 50% with respect to the methyl cellulose. The kneaded clay is added to form a molded body having a ceramic honeycomb structure from the kneaded clay, and the molded body having the ceramic honeycomb structure is fired using a roller hearth kiln to form a ceramic honeycomb structure. I do. At this time, the mass ratio of the methylcellulose was 3 to 5%.
Preferably, it is added.

The firing in the roller hearth kiln is performed by increasing the temperature of the binder removal region at a rate of 100 to 200 ° C. /
h, the temperature rising rate in the decrystallization water region is 60 to 100 ° C./h,
The sintering is characterized in that the sintering is performed at a heating rate of 140 to 200 ° C./h in the sintering region.

Next, the reason for the above configuration will be described. (Molding aid) Methylcellulose is added to and mixed with a cordierite-based ceramic raw material to give plasticity and also gives strength after drying and before firing. Also, hydroxypropyl methylcellulose is added to and mixed with the ceramic raw material in the same manner as methylcellulose to give plasticity to pass through a molding die. In order to obtain good plasticity, it is necessary to add 1% or more by mass of methylcellulose to the cordierite-forming raw material and 30% or more by mass of hydroxypropylmethylcellulose to methylcellulose. On the other hand, when methylcellulose is added in a mass ratio of more than 10% and hydroxypropylmethylcellulose is added in a mass ratio of more than 50% with respect to methylcellulose, when fired with a roller hearth kiln, the cell walls of the ceramic honeycomb structure become Cuts may occur,
Not preferred. Therefore, methyl cellulose is contained in a mass ratio of 1
And 10 to 10%, and hydroxypropyl methylcellulose is added in an amount of 30 to 50% by mass relative to methylcellulose. In addition, it is preferable that methylcellulose contains 3 to 5% by mass.

(Firing in Roller Hearth Kiln) In a roller hearth kiln, a product is placed on a carrier table and baked by moving on rollers rotating the carrier table. Unlike a continuous furnace in which the transfer table is pushed in at the entrance, the frontage is narrow, the heat circulation in the furnace is stable, and the heat transfer to the product is excellent. Therefore, the rate of temperature rise in the decrystallization water region and the firing region, the temperature of the debinding region and the decrystallization water region can be finely controlled, and the occurrence of cuts after firing the honeycomb structure made of cordierite ceramics is reduced. In addition, since the firing time is shortened by continuous firing, firing is performed using a roller hearth kiln.

(Raising Temperature in Binder Removal Region) As a pretreatment for firing, the temperature of the honeycomb structure is raised to the binder removal region to remove water and volatile components from the formed body having the ceramic honeycomb structure. Completely disassemble the binder and the like. If the rate of temperature rise in the binder removal region is less than 100 ° C./h, removal of water and volatile components from the honeycomb structure and decomposition of the binder and the like are not sufficient. In addition, it takes a long time for firing, which increases the manufacturing cost. On the other hand, if the rate of temperature rise in the binder removal region exceeds 200 ° C./h, breakage tends to occur. Therefore, the temperature rise rate in the binder removal region is set to 100 to
200 ° C./h.

(Temperature rising rate in decrystallized water region) The temperature of the honeycomb structure is raised to the decrystallized water region following the debinding region of the roller hearth kiln to accelerate the dehydration decomposition reaction of the mineral in the honeycomb structure. To remove strongly bound water of crystallization. If the rate of temperature rise in the decrystallization water region is less than 60 ° C./h, it takes a long time for calcination, and the production cost increases.
On the other hand, if the rate of temperature rise in the decrystallization water region exceeds 100 ° C./h, the temperature rises before the water of crystallization is completely removed,
Cracks may occur. Therefore, the rate of temperature rise in the decrystallization water region is set to 60 to 100 ° C./h.

(Rise Rate in Firing Region) Approximately 630 to approximately thorough fusion and diffusion of cordierite-forming raw material powder such as kaolin, talc, alumina, etc. and complete reaction.
During 1405 ° C., baking is performed with the temperature rising rate being particularly slow. If the temperature rise rate in the firing region exceeds 200 ° C./h, cracks are likely to occur due to the temperature difference inside each of the honeycomb structures. On the other hand, if the rate of temperature rise in the firing region is less than 140 ° C./h, it takes a long time to fire and the manufacturing cost increases. Therefore, the heating rate in the firing region is set to 140 to 200 ° C.
/ H.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments. (Material preparation of powder) kaolin, talc, silica, aluminum hydroxide, to adjust the powder, such as alumina, a chemical composition by weight _{ratio, SiO 2: 48~52%, Al} 2 O 3: 33~3
7%, MgO: 12 to 15%, CaO: 0 to 0.05
_{%, Na 2 O: 0~0.05%} , K 2 O: 0~0.05
_{%, TiO 2: 0~1.0%,} Fe 2 O 3: 0~1.0
%, PbO: 0~0.1%, P 2 O 5: the cordierite ceramic raw material powder containing 0 to 0.2%.

(Addition of Molding Aid and Purification of Clay) The mass of methylcellulose as a molding aid and the mass of hydroxypropylmethylcellulose with respect to methylcellulose with respect to the raw material powder of the cordierite ceramic are shown in the mass ratio shown in Table 1. The mixture was added at different ratios, and thoroughly mixed in a dry system.
In Table 1, in Invention Examples 2 to 6, methyl cellulose is 3 to 5% in a preferable range among 1 to 10% by mass ratio,
Hydroxypropyl methylcellulose is obtained by adding a mass ratio of 30 to 50% to methylcellulose. On the other hand, in Comparative Examples 1 and 2, methyl cellulose was added at a mass ratio of less than 1%, and in Comparative Example 2, hydroxypropyl methyl cellulose was further added at a mass ratio of 50% to methyl cellulose.
%, And Comparative Examples 3 and 4 are those in which hydroxypropyl methylcellulose was added at a mass ratio of less than 30% with respect to methylcellulose, and Comparative Example 5 was used.
Is a compound in which hydroxypropyl methylcellulose is added in excess of 50% by mass relative to methylcellulose, and Comparative Example 6 is a product in which methylcellulose is added in excess of 10% by mass. In Comparative Examples 7 and 8, methyl cellulose was used in a weight ratio of 1 to 10%, and hydroxypropylmethyl cellulose was used in a weight ratio of 3 to methyl cellulose.
Although 0 to 50% was added, the firing furnace was changed for comparison. Next, a specified amount of water was injected into the inventive examples 1 to 9 and the comparative examples 1 to 8 to further sufficiently mix.

(Extrusion molding) Extrusion molding is performed using an extrusion molding die, and further cut, and the outer peripheral wall and the cell wall are integrally formed. The major axis is 150 mm, the minor axis is 100 and the length is 160 mm.
A molded article having a honeycomb structure of

(Firing) Each formed body having a honeycomb structure of Invention Examples 1 to 9 and Comparative Examples 1 to 6 was fired using a roller hearth kiln. That is, each formed body having a ceramic honeycomb structure was placed on a carrier, and the carrier was moved in a roller hearth kiln and fired. As means for heating each formed body having a ceramic honeycomb structure, combustion burners were arranged in a staggered manner on the roller hearth kiln on both side walls of a carrier table and above and below the rollers. In addition, the roller hearth kiln has a binder region of 150 to 275 ° C., a decrystallization water region of 430 to 630 ° C., and a firing region of 630 from the inlet to the outlet.
Partitioned including 〜1405 ° C. FIG. 1 shows a firing time-temperature diagram of a honeycomb structure in a roller hearth kiln. Further, Table 1 shows the respective temperature rise rates (° C./h) in the binder removal region, the decrystallization water region, and the firing region. In addition, the compact having the honeycomb structure of Comparative Example 7 was fired at each of the heating rates shown in Table 2, using a batch-type gas furnace, and the compact having the honeycomb structure of Comparative Example 8 using a continuous tunnel furnace. Was.

[0022]

[Table 1]Addition amount of molding aid (% by mass) Heating rate of each temperature range (℃ / h)  Methylcellulose Human hydroxypropyl H / M Deintermediate Decrystallization water Firing(M) Methyl cellulose (H) (%) region region region  Invention Example 1 2.5 1.2 48 130 66 196 Invention Example 2 3.5 1.6 46 146 78 170 Invention Example 3 3.7 1.8 49 159 70 164 Invention Example 4 4.0 1.3 33 160 83 152 Invention Example 5 4.5 1.9 42 174 65 167 Invention Example 6 5.0 2.2 44 189 92 149 Invention example 7 7.5 2.4 32 191 77 143 Invention example 8 9.3 3.5 38 182 83 166 Invention example 9 3.5 1.4 40 214 66 196 Comparative example 1 0.8 0.3 43 60 60 60 Comparative example 2 0.8 0.5 58 176 87 149 Compare Example 3 3.5 0.5 14 226 79 147 Comparative Example 4 3.5 1.0 29 160 93 167 Comparative Example 5 5.0 3.0 60 286 88 93 Comparative Example 6 12.0 4.6 38 208 140 198 Comparative Example 7 3.5 1.4 40 130 64 171 Comparative Example 8 3.7 1.8 49 214 56 186

Each of the formed bodies having the honeycomb structure is gradually heated in the debinding region at a temperature rising rate shown in Table 1 to remove the binder and the like, and then moved to the decrystallization water region to remove the crystallization water. Then, it was moved to a firing region and fired, and then cooled gradually in a cooling region. Then, after firing, the major axis 150 mm x the minor axis 100 mm x the length 1
60 mm, cell wall thickness 0.15 mm, cell pitch 1.27
mm honeycomb structure.

(Evaluation of Firing Time and Occurrence of Cut) Next, for the above-mentioned invention examples 1 to 9 and comparative examples 1 to 8, the firing time,
The relationship between the cuts generated in each honeycomb structure after firing was determined. Table 2 shows the firing time and the evaluation of the occurrence of breakage after firing each honeycomb structure. In addition, the evaluation of the occurrence of cut was evaluated as follows: a case where no cut occurred (○), a case where there was slight cut but no problem in actual use (△), and a case where cut occurred (×) And

[0025]

[Table 2]Firing time (h) Cutting occursTemperature rising Retention Cooling Total Evaluation of  Invention Example 1 12.86 2.30 3.50 18.66 △ Invention Example 2 11.44 4.22 3.20 18.86 ○ Invention Example 3 10.46 3.20 3.00 16.66 ○ Invention Example 4 10.46 3.20 8.02 21.68 ○ Invention Example 5 12.16 2.22 5.61 19.99 ○ Invention Example 6 12.16 2.26 5.61 19.99 ○ Invention Example 7 12 .16 2.22 5.61 19.99 Δ Inventive Example 8 12.16 2.22 5.61 19.99 Δ Inventive Example 9 11.44 4.22 3.20 18.86 Δ Comparative Example 1 12.16 2.22 5.61 19.99 × Comparative Example 2 12.16 2.94 4.89 19.99 × Comparative Example 3 12.16 2.94 2.90 18.00 × Comparative Example 4 12.16 22 5.61 19.99 × Comparative Example 5 12.16 2.94 2.90 18.00 × Comparative Example 7 10.50 4.64 2.86 18.00 × Comparative Example 8 9.54 2.53 2.67 14.74 ×

According to Tables 1 and 2, the methyl celluloses of Examples 1 to 9 of the present invention are added in a weight ratio of 1 to 10%, preferably methyl cellulose in a weight ratio of 3 to 5%, and hydroxypropyl methyl cellulose is added in a weight ratio of 3 to 5 in the methyl cellulose.
A molded body having a ceramic honeycomb structure is formed from the kneaded clay to which 0 to 50% is added, and the heating rate of the binder removal region is set to 100 to 200 ° C. using a roller hearth kiln for firing.
h, the temperature rising rate in the decrystallization water region is 60 to 100 ° C./h,
When the honeycomb structure is fired at a heating rate of 140 to 200 ° C./h in the firing region, the firing time is greatly reduced to 20 hours or less, and the characteristics of the forming aid are sufficiently exhibited, thereby causing the occurrence of cuts. It can be seen that a small number of honeycomb structures can be obtained.

On the other hand, in Comparative Example 1, methyl cellulose was added at a mass ratio of less than 1%, and calcination was carried out at a rate of temperature rise of less than 100 ° C./h between the binder removal region and the calcination region.
Are those in which methylcellulose is added at a mass ratio of less than 1%, and hydroxypropyl methylcellulose is added at a mass ratio of more than 50% to methylcellulose, Comparative Example 3
Was obtained by adding hydroxypropyl methylcellulose to methylcellulose in a mass ratio of less than 30% and calcining at a rate of temperature rise in the binder removal region exceeding 200 ° C./h. In Comparative Example 5, hydroxypropyl methylcellulose was added in excess of 30% by mass relative to methylcellulose, the rate of temperature rise in the binder removal region exceeded 200 ° C./h, and the temperature in the firing region was increased. In the case of calcining at a rate of less than 140 ° C./h, Comparative Example 6 added methyl cellulose in a mass ratio of more than 10%, and the rate of temperature rise in the binder removal region exceeded 200 ° C./h,
It was fired at a rate of temperature rise in the decrystallization water region exceeding 100 ° C./h. In each case, the firing was performed for a firing time of 20 hours or less, but all of them were cut. Furthermore, in Comparative Examples 7 and 8 in which methylcellulose was added at a mass ratio of 1 to 10% and hydroxypropylmethylcellulose was added at a mass ratio of 30 to 50% based on methylcellulose, a furnace other than a roller hearth kiln was used. , All of them had cuts.

As described above, the embodiment of the present invention will be described by referring to Invention Examples 1 to 4.
Although described based on No. 9, the present invention is not limited to the above example of the invention, and can be applied within the scope of the technical idea.

[0029]

As described above in detail, according to the method for manufacturing a honeycomb structure of the present invention, the firing time can be greatly reduced and the manufacturing cost can be reduced without occurrence of breakage after firing.

[Brief description of the drawings]

FIG. 1 is a firing time-temperature diagram of a honeycomb structure.

FIG. 2 is a perspective view of an example of a honeycomb structure.

[Description of Signs] 11 Honeycomb structure 11a Outer peripheral wall 11b Cell wall 11c Vent hole 11d Cut 11e Outside 11f Central part

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C04B 35/64 B01D 53/36 C 35/638 C04B 35/64 C F01N 3/28 301 301 F term (reference ) 3G091 AA02 AB01 BA39 GA06 GA07 GB01X GB10X GB17X GB19X 4D048 AA21 BA10X BA10Y BB02 CA08 4G030 AA36 AA37 CA10 GA15 GA21 GA23 GA27 HA05 4G054 AA05 AB09 BD00 4G069 AA01 AA08 AA09 BA13B ABA BAB BAB BAB BAB

Claims (4)

[Claims] 1. A molding aid comprising a mass of 1 to 10% by mass of methylcellulose and a mass of 30 to 50% by mass of hydroxypropylmethylcellulose relative to the methylcellulose to form a kneaded material, and a ceramic honeycomb structure formed by the kneaded material. A method for producing a ceramic honeycomb structure, comprising: forming a formed body having a ceramic honeycomb structure; and firing the formed body having the ceramic honeycomb structure with a roller hearth kiln to obtain a ceramic honeycomb structure. 2. A mass ratio of 3 to 5% of the methyl cellulose.
The method for producing a ceramic honeycomb structure according to claim 1, wherein the ceramic honeycomb structure is added. 3. The method for manufacturing a ceramic honeycomb structure according to claim 1, wherein the roller hearth kiln has a rate of temperature rise in a binder removal region of 100 to 200 ° C./h. 4. The roller hearth kiln has a heating rate in a decrystallization water region of 60 to 100 ° C./h and a heating rate in a firing region of 140 to 200 ° C./h. The method for producing a ceramic honeycomb structure according to any one of claims 1 to 3.