JP3343087B2 - Method for manufacturing cordierite-based ceramic honeycomb structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a cordierite ceramic honeycomb structure by extrusion molding.

[0002]

2. Description of the Related Art A cordierite-based honeycomb structure used for a catalyst carrier for purifying an automobile exhaust gas has a high heat resistance that withstands thermal stress caused by a temperature difference generated in the honeycomb structure due to rapid heating / cooling at the time of engine start / stop. Impact resistance is required. Japanese Patent Publication No. 7-61892 discloses a cordierite-based honeycomb excellent in heat resistance and thermal shock resistance by using aluminum hydroxide and silica.

Further, in order to respond to the recent tightening of exhaust gas regulations, the cell density for the purpose of improving the exhaust gas purification characteristics of the cordierite-based honeycomb structure has to be reduced in thickness, the cell density has to be increased, or the cell density has to be reduced. There is a demand for a thinner wall while maintaining the conventional level.

In general, a cordierite-based ceramic honeycomb structure is extruded to improve mass productivity. To improve extrudability, water, a binder, a surfactant, and the like are contained in a cordierite-forming raw material batch. (JP-A-2-81606).

However, when a cordierite-forming raw material batch contains a powder having an isoelectric point of 8 or more, such as magnesium oxide or aluminum hydroxide, a cordierite ceramic honeycomb structure having a partition wall thickness of less than 100 μm is to be extruded. In this case, there is a problem that the extrudability is reduced due to a decrease in fluidity due to agglomeration of the clay. This is the p of the kneaded clay obtained by adding water to the cordierite-forming raw material batch.
H becomes about 7.5 to 8.5, and the powder surface becomes negatively charged with magnesium oxide or magnesium hydroxide (powder having an isoelectric point of 8 or more) whose powder surface is positively charged in the clay. Talc, kaolin, silica, etc. (powder having an isoelectric point of less than 8) hetero-aggregate with each other to form a larger aggregate, thereby decreasing the fluidity of the clay and forming a die having a narrow slit width. It is presumed that it is difficult to pass.

[0006]

Accordingly, the present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide moldability during extrusion molding (particularly,
The present invention provides a method for producing a cordierite ceramic honeycomb structure which is suitable for mass production and can obtain a thin honeycomb structure having a small partition wall by improving the fluidity).

[0007]

That is, according to the present invention, there is provided a method for producing a cordierite ceramic honeycomb structure having a partition wall thickness of less than 100 μm by extrusion, wherein an isoelectric point is 8 or more. A cordierite-based ceramic, comprising: adding 0.5 to 10% by weight of a polyimine-based dispersant to a cordierite-forming raw material batch for extrusion molding containing 5% by weight or more of a powder of A method for manufacturing a honeycomb structure is provided.

At this time, in the present invention, the average molecular weight of the polyimine-based dispersant is preferably 1000 or less, and the powder having an isoelectric point of 8 or more is aluminum hydroxide.
Preferably.

Further, in the present invention, the cordierite ceramic honeycomb structure has a coefficient of thermal expansion between 40 and 800 ° C. of 0.8 × 10 ⁻⁶ / ° C. or less in a flow direction and a porosity of 24 ° C. It is preferably about 38%.

Further, in the present invention, it is preferable to use an extrusion die having a slit width of 100 μm or less during extrusion molding.

[0011]

Method for producing a cordierite ceramic honeycomb structure of the embodiment of the present invention is, septum by extrusion
In the method for manufacturing a cordierite-based ceramic honeycomb structure having a wall thickness of less than 100 μm , an isoelectric point of 8 or more is used.
In a cordierite-forming raw material batch for extrusion molding containing 5% by weight or more of powder , a polyimine-based dispersant is added in an amount of 0.5 to 1 %.
It is characterized by adding 0% by weight.

As described above, in the method for producing a cordierite-based ceramic honeycomb structure of the present invention, a cordierite-forming raw material batch is added to a cordierite-forming raw material batch for extrusion molding by adding a polyimine-based dispersant. In a clay (pH: about 7.5 to 8.5) to which water is added, a polyimine-based dispersant generates a strong cation charge, adsorbs to negatively charged particles, and takes on an apparently strong positive charge. As a result, all the powder surfaces can be in a positively charged state, so that hetero-aggregation can be prevented. Thereby, even when the powder having an isoelectric point of 8 or more such as aluminum hydroxide is contained in the cordierite forming raw material batch in an amount of 5% by weight or more, the fluidity of the clay can be improved. It is possible to smoothly extrude a cordierite ceramic honeycomb structure having a thin wall of 80 μm level.

The reason why the amount of the polyimine-based dispersant added is limited to 0.5 to 10% by weight is as follows.
If the amount is less than 10% by weight, the amount of the polyimine-based dispersant is not sufficient, so that some negatively charged particles are present, so that the fluidity during extrusion cannot be improved and the amount exceeds 10% by weight. In this case, since the amount of the polyimine-based dispersant added is excessive, dilatancy is caused and kneading becomes difficult.

Further, the average molecular weight of the polyimine-based dispersant is preferably 1,000 or less because of high fluidity and low viscosity, and more preferably 500 to 1,000.

The raw material powder to be blended in the cordierite-forming raw material batch used in the present invention is preferably a material that has been classified to a thickness less than the partition wall thickness.

Next, the cordierite-based ceramic honeycomb structure obtained by the present invention preferably has a coefficient of thermal expansion between 40 and 800 ° C. of 0.8 × 10 ⁻⁶ / ° C. or less in the flow direction. . This is because when the coefficient of thermal expansion in the flow channel direction exceeds 0.8 × 10 ⁻⁶ / ° C., the thermal shock resistance is 70%.
This is because the temperature is lower than 0 ° C. and cannot be used for an exhaust gas catalyst carrier for automobiles. The thermal expansion coefficient in the vertical direction of the flow path (between 40 and 800 ° C.) is preferably 1.0 × 10 ⁻⁵ / ° C. or less for the same reason as described above.

The porosity of the cordierite ceramic honeycomb structure obtained by the present invention is 24 to 3
Preferably, it is 8%. This is a wall thickness of 40-100
In manufacturing a thin-walled honeycomb structure of μm, the cell deformation after molding and the coefficient of thermal expansion after sintering are extremely small, the isostatic strength can be 10 kg / cm ² or more, and the porosity is 30%. In the above case, the catalyst carrying characteristics can be improved.

[0018]

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

(Examples 1 and 2, Comparative Examples 1 to 3) 44 μm
Each raw material powder passed through the m sieve was blended according to the blending ratio (%) shown in Table 1, and a dispersant was added to 100 wt% of the blend as shown in Table 2, and then water, methylcellulose, etc. An organic binder and a plasticizer were added and kneaded to obtain an extrudable kneaded clay.

[0020]

[Table 1]

Next, each kneaded material is slit into a slit width 75
A honeycomb formed body was prepared by extruding from a μm extrusion die at an extrusion pressure of 50 kg / cm ² . At this time, the kneaded mass passing amount (Kg / 10 sec) with respect to the kneaded mass passing amount (Kg) when the dispersant is added as shown in Table 2
FIG. 1 shows the relationship of c), and Table 2 shows the degree of decrease (sec ⁻¹ ) of the discharged clay amount represented by the slope of each straight line in FIG.

Finally, each of the formed honeycomb formed bodies is dried and fired at 1350 to 1440 ° C. to prepare a cordierite-based honeycomb structure, and the thermal expansion coefficient of the honeycomb structure at 40 to 800 ° C. ( The flow direction of the honeycomb structure) and the porosity were measured.
Table 2 shows the above results. The porosity is calculated from the total pore volume of the mercury porosimetry with the cordierite true specific gravity being 2.52.

[0023]

[Table 2]

(Consideration: Examples 1-2, Comparative Examples 1-3)
In Examples 1 and 2, no dispersant was added (Comparative Example 3)
Since the degree of decrease in the amount of the discharged clay can be reduced to about 1/3 as compared with the case of the above, the forming speed of the honeycomb structure can be significantly improved. On the other hand, when the nonionic dispersant is used (Comparative Example 2) and when the dispersant is not added (Comparative Example 3), the discharge speed, that is, the forming speed of the honeycomb structure is remarkably increased along with the degree of decrease in the discharge clay amount. Dropped.
In addition, it was found that when the amount of the dispersant added was too small (Comparative Example 1), the degree of reduction in the amount of the discharged clay was further increased as compared with the case where the dispersant was not added (Comparative Example 3). this is,
Because there are some powders that do not adsorb the dispersant,
This is because depletion aggregation is promoted.

[0025]

As described above, the method for producing a cordierite-based ceramic honeycomb structure of the present invention is suitable for mass production by improving formability (particularly, fluidity) at the time of extrusion molding, and is suitable for partition walls. A honeycomb structure having a small thickness can be obtained .

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the total amount of clay passing (Kg) and the amount of clay passing (Kg / 10 sec) when a dispersant is added to a cordierite raw material batch.

──────────────────────────────────────────────────続 き Continuation of front page (51) Int.Cl. ⁷ Identification code FI C04B 103: 40 C04B 35/00108 (56) References JP-A-2-81606 (JP, A) JP-A-6-329465 ( JP, A) JP-A-6-191924 (JP, A) JP-A-5-270884 (JP, A) JP-A-61-263627 (JP, A) JP-B-7-61892 (JP, B2) (58) ) Surveyed field (Int.Cl. ⁷ , DB name) C04B 35/195 C04B 35/632 B28B 3/26

Claims (5)

(57) [Claims] 1. The thickness of a partition wall by extrusion molding is 100 μm or less.
A method for producing a thin cordierite-based ceramic honeycomb structure, wherein a polyimine-based dispersant is added to a cordierite-forming raw material batch for extrusion molding containing 5% by weight or more of powder having an isoelectric point of 8 or more . A method for producing a cordierite-based ceramic honeycomb structure, comprising adding 5 to 10% by weight. 2. The polyimine-based dispersant has an average molecular weight of 1
The method for producing a cordierite-based ceramic honeycomb structure according to claim 1, which is not more than 000. 3. A powder having an isoelectric point of 8 or more is made of aluminum hydroxide.
The method for producing a cordierite-based ceramic honeycomb structure according to claim 1, wherein the cordierite-based ceramic honeycomb structure is made of nickel. 4. The extrusion has a slit width of 100 μm.
4. The method according to claim 1, wherein the following extrusion die is used.
The method for producing a cordierite-based ceramic honeycomb structure according to the above item. 5. The cordierite-based ceramic honeycomb structure has a coefficient of thermal expansion between 40 and 800 ° C. of 0.8 × 10 ⁻⁶ / ° C. or less in a flow direction and a porosity of 24.
The method for producing a cordierite-based ceramic honeycomb structure according to any one of claims 1 to 4, wherein the content is from about 38% to about 38%.