Cordierite honeycomb structure body, method of producing the cordierite honeycomb structure body, and talc for use in the method

Abstract

In a method of producing a cordierite honeycomb structure body, talc, kaolin, and alumina as prepared raw materials are mixed. The mixed raw materials are extruded and molded in an extrusion molding step. The obtained green body is cut into plural green bodies of a specified length. In a following drying step, the green body is dried and then fired in order to make the cordierite honeycomb structure body. In particular, the talc for use in the mixing step has IgLoss (Ignition Loss) within a range of 5.7 to 6.5 wt % which is obtained by firing at 1,000° C. for two hours.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred, non-limiting embodiment of the present invention will be described by way of example with reference to the accompanying drawings, in which:

FIG. 1 is a perspective view showing an entire configuration of a cordierite honeycomb structure body according to a first embodiment of the present invention;

FIG. 2 shows a relationship between an average pore diameter and a talc particle diameter per ignition loss (IgLoss) in cordierite honeycomb structure bodies of the first embodiment and comparative examples;

FIG. 3 shows a relationship between a thermal expansion coefficient and a talc particle diameter per ignition loss (IgLoss) in cordierite honeycomb structure bodies of the first embodiment and comparative examples;

FIG. 4 shows a relationship between an average pore diameter and a talc particle diameter per wire abrasion in cordierite honeycomb structure bodies of the first embodiment and comparative examples;

FIG. 5 shows a relationship between a thermal expansion coefficient and a talc particle diameter per wire abrasion in cordierite honeycomb structure bodies of the first embodiment and comparative examples; and

FIG. 6 is a flow chart of steps in the method of producing the cordierite honeycomb structure body according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, various embodiments of the present invention will be described with reference to the accompanying drawings. In the following description of the various embodiments, like reference characters or numerals designate like or equivalent component parts throughout the several diagrams.

First Embodiment

In the first embodiment, various types of cordierite honeycomb structure bodies were produced using talc of different Ignition Loss (IgLoss) in order to quantitatively measure and estimate the average pore diameter and thermal expansion of the cordierite honeycomb structure bodies of the present invention and comparison examples.

That is, four cordierite honeycomb structure bodies were prepared as samples E1 and E2 correspond to the present invention and as comparison samples C1 and C2 that do not correspond to the present invention.

The samples E1 and E2 were made of the talc of IgLoss of 6.0 percentages by weight and 6.5 percentages by weight of the entire composition, respectively (6.0 wt % and 6.5 wt %, hereinafter, the term “percentages by weight” will be referred to as “wt %” for short). The comparison samples C1 and C2 according to the related art were made of the talc of IgLoss of 5.0 wt % and 5.5 wt %, respectively.

Further, in the first embodiment, the cordierite honeycomb structure bodies of different particle diameters of: 10, 15, 20, 25, 30, and 35 μm were prepared per talc (namely, per above sample). All of the talc described above have CaO of 0.3 wt % or less as impurity.

The talc was dressed or selected from talc raw ore of a mine in order to have the above specified IgLoss and then ground up into a desired particle diameter. In the first embodiment, the raw ore was produced from Hai Cheng in China in order to obtain the specified IgLoss described above.

In the experiment, the IgLoss (wt %) of each talc was determined by the following manner. A desired amount of the talc was prepared and a weight (=A) before heating was measured. The talc powder of a desired amount was then heated at 1,000° C. for two hours. A weight (=B) of the talc after heating was measured. The IgLoss (wt %) of the talc was prepared based on the equation {(A−B)/A}×100. The particle diameter of the talc was measured by using a laser-type particle size analyzer.

(Basic Configuration)

The basic configuration of the cordierite honeycomb structure body for use in the measurement of the first embodiment will now be explained.

As shown in FIG. 1, the cordierite honeycomb structure body shown in the first embodiment is a honeycomb structure body made of cordierite ceramics for use in a catalyst carrier capable of purifying exhaust gas emitted by an internal combustion engine of a vehicle. In general, the honeycomb structure body 1 is composed of plural cells 3 of a square shape surrounded by cell walls (namely, porous partition walls) 2 and an outer peripheral wall 4 of a cylindrical shape surrounding the outer side wall of the honeycomb structure body 1. The outer diameter of the honeycomb structure body 1 is 50 mm, and the length thereof is 70 mm. The thickness of the honeycombs structure body 1 is 100 μm, and the thickness of the outer peripheral wall 4 is 500 μm.

(Manufacturing Method)

Next, a description will be given of the manufacturing method of the cordierite honeycomb structure body according to the first embodiment of the present invention.

FIG. 6 is a flow chart showing the manufacturing method according to the present invention.

The method of producing the honeycomb structure body includes a mixing step S10, an extrusion and molding step S11, a cutting step S12, a drying step S13, and a firing step S14.

In the mixing step S10, talc, kaolin, and alumina as ceramic raw materials of the cordierite honeycomb structure body are mixed. In the extrusion and molding (namely, shaping) step S11, the ceramic raw materials are extruded and molded in order to produce a honeycomb shaped green body. In the cutting step S12, the honeycomb shaped green body is cut into a plurality of bodies of a desired length. In the drying step S13, those green bodies divided from the honeycomb shaped green body are dried. Finally, in the firing step S14, the divided green bodies are fired so as to produce the honeycomb structure bodies.

Next, the manufacturing method of the above steps S10 to S14 for producing the cordierite honeycomb structure body according to the first embodiment of the present invention will be explained in detail.

In the mixing step (step S10), the ceramic raw material are firstly produced. As the ceramic raw material, the ceramic raw powder involves talc of 38 to 40 wt %, kaolin of 46 to 48 wt %, and alumina of 12 to 16 wt % so that the ceramic raw powders finally include ceramic cordierite 2MgO.2Al₂O₃.5 SiO₂. Further, the ceramic raw material is produced by adding binder of 5 to 6 wt %, water of 20 to 25 wt %, lubricant of 2 to 2.5 wt % per the above ceramic raw powder of 100 wt %, and mixing them for 20 to 30 minutes by a mixer (a kneader) of 5 liters in volume.

Next, in the extrusion and molding step (step S11), the ceramic raw material is extruded and molded by using an extrusion molding die in order to shape the honeycomb shaped green body while using an extrusion molding die having slit grooves corresponding to the shape of the cell walls in the honeycomb structure body finally produced.

In the cutting step (step S12), the honeycomb shaped green body is cut into plural green bodies of a specified length. In the drying step (step S13), the honeycomb shaped green bodies are dried by a microwave dryer. In the firing step (step S14), the honeycomb shaped green bodies of a specified length are fired at the temperature of 1,400° C. for a specified time. The cordierite honeycomb structure body 1 is thereby produced.

(Measurement Results)

Next, the average pore diameter and the thermal expansion coefficient were measured for samples E1 and E2 (present invention), C1 and C2 (comparison examples) of the cordierite honeycomb structure body obtained by the above manner.

The average pore diameter of the samples E1, E2, C1, and C2 were measured by using Mercury porosimeter and the thermal expansion coefficient thereof were measured in the temperature range of room temperature to 800° C. by using a thermal expansion coefficient measurement apparatus.

FIG. 2 and FIG. 3 show the measurement results of the average pore diameter and the thermal expansion coefficient per sample in the first embodiment. FIG. 2 shows the relationship between the average pore diameter and the talc particle diameter per IgLoss. In FIG. 2, the vertical line indicates the average pore diameter (μm), and the horizontal line indicates the talc particle size (μm).

As understood from FIG. 2, the average pore diameter of each of the samples E1 and E2 according to the present invention is greater than that of each of the comparison samples C1 and C2 of the related art. This means that the configuration of each of the samples E1 and E2 as the cordierite honeycomb structure body according to the present invention can enlarge the average pore diameter.

FIG. 3 shows the relationship between the thermal expansion coefficient and the talc particle diameter (or size) per IgLoss. In FIG. 2, the vertical line indicates the thermal expansion coefficient (×10⁻⁶/° C.), and the horizontal line indicates the talc particle size (μm).

As can be understood from FIG. 3, each of the samples E1 and E2 of the present invention has a smaller thermal expansion coefficient rather than that of each of the comparison samples C1 and C2 of the related art. This means that the configuration of each of the samples E1 and E2 as the cordierite honeycomb structure body of the present invention has the reduced thermal expansion coefficient.

According to the measurement results described above, the cordierite honeycomb structure body of the present invention can achieve both of the features of enlarging the average pore diameter and of reducing the thermal expansion coefficient by using the talc having IgLoss within a range of 6.0 wt % to 6.5 wt %.

It is further possible to obtain both of the features described above by using the talc having IgLoss within a range of 5.7 wt % to 6.5 wt %.

It is still further possible to remarkably obtain both of the features described above by using the talc having IgLoss within a range of 6.0 wt % to 6.5 wt %.

Although it is possible to slightly obtain the above effect of enlarging the average pore diameter when the talc particle size is 10 μm, it is possible to markedly obtain the effect of enlarging the average pore diameter when the talc particle size is approximately 15 μm (more precisely 13 μm). Although it is possible to obtain the effect of reducing the thermal expansion coefficient when the talc particle diameter (or size) is 30 μm from the measurement results shown in FIG. 3, the thermal expansion coefficient is slightly increased when the talc particle diameter (or size) is approximately 35 μm (more concretely, 33 μm).

Accordingly, it is preferred to take the talc particle size within a range of 13 to 33 μm in order to obtain both of the effects of enlarging the average pore diameter and of reducing the thermal expansion coefficient.

When the cordierite honeycomb structure body according to the present invention is applied to the catalyst carrier of purifying the exhaust gas emitted from an internal combustion engine mounted on vehicles, it is preferred to take the pore diameter (or size) of 5 μm or more in order to support the catalyst on the cordierite honeycomb structure body. It is still further preferred to have the thermal expansion coefficient of 0.5×10⁻⁶/° C. or less in order to adequately ensure the thermal impact resistance.

Accordingly, as can be understood from the measurement results shown in FIG. 2 and FIG. 3, it is preferred to take the talc particle diameter (or size) of 28 μm to 33 μm in order to satisfy the above-described conditions.

Second Embodiment

In the second embodiment, like the manner for use in the first embodiment, various types of plural cordierite honeycomb structure bodies were produced using talc of different wire abrasions in order to quantitatively measure and estimate the average pore diameter and thermal expansion of the cordierite honeycomb structure bodies according to the present invention and related art.

In the second embodiment, two cordierite honeycomb structure bodies E3 and E4 were produced, as the present invention, by using the talc of different wire abrasions of 25 mg and 35 mg, and a cordierite honeycomb structure body C3 was also produced, as the related art, by using the talc of wire abrasions of 10 mg.

As described above, the talc used in the measurement according to the second embodiment have the wire abrasions of 10 mg, 25 mg, and 35 mg. The cordierite honeycomb structure bodies of different particle diameters 10, 15, 20, 25, 30, and 35 μm were further prepared per talc (or per above sample). All of the talc described above have CaO of 0.3 wt % or less as impurity.

Each talc was dressed or selected from raw ores of a mine in order to obtain the specified wire abrasions and then ground up into a desired particle diameter. In the second embodiment, like the first embodiment, the raw ores were produced from Hai Cheng in China in order to obtain the desired wire abrasions described above.

The talc was dressed or selected from raw ores of a mine in order to obtain such a desired wire abrasions and then ground up into a desired particle diameter. In the second embodiment, the raw ores were produced from Hai Cheng in China in order to obtain the desired wire abrasion described above.

The wire abrasion test for each talc was performed by a slurry of water solution of 2 wt % of the talc, in which three wires were contacted to three points on a rolling ceramic roll (φ60 mm×60 mm) while dropping the slurry on each wire in order to measure the wire abrasion of the talc. The dropping amount of the slurry is 2 liters/minutes and the wire applied-pressure weight to the ceramic roll was 750 g. A plastic wire (COS60 of 40 mm×180 mm, approximately 1.7 g produced by NIPPON FILCON CO., LTD) was used as the wire. After the test, the average wire abrasion was measured based on the reduced amount (mg) of the weight of each of the three wires by measuring the weight of each wire before and after the test. The particle diameter was measured by using a laser-type particle size analyzer.

The basic configuration (see FIG. 1) and the method of producing the cordierite honeycomb structure body in the second embodiment are same of those in the first embodiment. That is, the method of the second embodiment is performed based on the steps shown in FIG. 6, like the method of the first embodiment. In particular, the mixing step of the second embodiment uses the talc having a wire abrasion of not less than 25 mg.

In the measurement of the second embodiment, the average pore diameter and the thermal expansion coefficient of each of the samples E3, E4, and C3 of the cordierite honeycomb structure bodies were measured. The second embodiment used the same manner of measuring the average pore diameter and the thermal expansion coefficient of each sample used in the first embodiment.

FIG. 4 and FIG. 5 show the measurement results of the average pore diameter and the thermal expansion coefficient per sample used in the second embodiment.

FIG. 4 shows the relationship between the average pore diameter and the talc particle diameter per wire abrasion. In FIG. 4, the vertical line indicates the average pore diameter (μm), and the horizontal line indicates the talc particle size (μm).

As can be understood from FIG. 4, the average pore diameter of each of the samples E3 and E4 according to the present invention is greater than that of the sample C3 according to the related art. This means that the configuration of each of the samples E3 and E4 as the cordierite honeycomb structure body according to the present invention can enlarge the average pore diameter.

FIG. 5 shows the relationship between the thermal expansion coefficient and the talc particle diameter (or size) per wire abrasion. In FIG. 5, the vertical line indicates the thermal expansion coefficient (×10⁻⁶/° C.), and the horizontal line indicates the talc particle size (μm).

As can be understood from FIG. 5, each of the samples E3 and E4 according to the present invention has a smaller thermal expansion coefficient rather than that of the comparison sample C3 of the related art. This means that the configuration of each of the samples E3 and E4 as the cordierite honeycomb structure body of the present invention can reduce the thermal expansion coefficient.

According to the measurement results described above, the cordierite honeycomb structure body of the present invention can achieve both of the features capable of enlarging the average pore diameter and reducing the thermal expansion coefficient by using the talc having wire abrasion of 25 mg and 35 mg.

It is further possible to obtain both of the features described above by using the talc having wire abrasion of not less than 25 mg.

It is still further possible to markedly obtain both of the features described above by using the talc having wire abrasion of not less than 35 mg.

Although it is possible to slightly obtain the above effect of enlarging the average pore diameter when the talc particle size is 10 μm, it is possible to markedly obtain the effect of enlarging the average pore diameter when the talc particle size is approximately 15 μm or more (more precisely 13 μm or more).

Although it is possible to obtain the effect of reducing the thermal expansion coefficient when the talc particle diameter (or size) is 30 μm from the measurement results shown in FIG. 5, the thermal expansion coefficient is slightly increased when the talc particle diameter (or size) is approximately 35 μm (more concretely, 33 μm).

Accordingly, it is preferred to take the talc particle size within the specified range of 13 to 33 μm in order to obtain both of the effects of enlarging the average pore diameter and reducing the thermal expansion coefficient.

When the cordierite honeycomb structure body according to the present invention is applied to the catalyst carrier capable of purifying the exhaust gas emitted by an internal combustion engine mounted on vehicles, it is preferred to take the pore diameter (or size) of 5 μm or more in order to support the catalyst on the cordierite honeycomb structure body. It is still further preferred to have the thermal expansion coefficient of 0.5×10⁻⁶/° C. or less in order to adequately ensure the thermal impact resistance.

Accordingly, as can be understood from the measurement results shown in FIG. 4 and FIG. 5, it is preferred to take the talc particle diameter (or size) of 28 μm to 33 μm in order to satisfy the above-described conditions.

While specific embodiments of the present invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limited to the scope of the present invention which is to be given the full breadth of the following claims and all equivalent thereof.

Claims

1. A method of producing a cordierite honeycomb structure body composed of a plurality of cells surrounded by cell walls arranged in a honeycomb structure, comprising steps of: mixing talc, kaolin, and alumina for producing a ceramic raw material as a cordierite, in which the talc has Ignition Loss (IgLoss) within a range of 5.7 wt % to 6.5 wt % obtained by firing at a temperature of 1,000° C. for two hours;extruding and molding the ceramic raw material so as to produce a honeycomb shaped green body;cutting the honeycomb shaped green body to plural bodies of a specified length;drying the honeycomb shaped green body of the specified length; andfiring the dried honeycomb shaped green body in order to produce a honeycomb structure body.

2. The method of producing a cordierite honeycomb structure body according to claim 1, wherein the talc has IgLoss within a range of 6.0 wt % to 6.5 wt %.

3. The method of producing a cordierite honeycomb structure body according to claim 1, wherein the talc has an average particle diameter within a range of 13 μm to 33 μm.

4. The method of producing a cordierite honeycomb structure body according to claim 1, wherein the talc has an average particle diameter within a range of 28 μm to 33 μm.

5. A method of producing a cordierite honeycomb structure body composed of a plurality of cells surrounded by cell walls arranged in honeycomb structure, comprising steps of: mixing talc, kaolin, and alumina for producing a ceramic raw material as a cordierite, in which the talc has a wire abrasion of not less than 25 mg;extruding and molding the ceramic raw material so as to produce a honeycomb shaped green body;cutting the honeycomb shaped green body to plural parts of a specified length;drying the honeycomb shaped green body of the specified length; andfiring the dried honeycomb shaped green body in order to produce a honeycomb structure body.

6. The method of producing a cordierite honeycomb structure body according to claim 5, wherein the talc has the wire abrasion of not less than 35 mg.

7. The method of producing a cordierite honeycomb structure body according to claim 1, wherein the talc involves CaO of not more than 0.3 wt % as an impurity.

8. A talc as a cordierite raw material to be used in a manufacture of a cordierite honeycomb structure body composed of plural cells surrounded by cell walls arranged in a honeycomb structure, wherein the talc has Ignition Loss (IgLoss) within a range of 5.7 to 6.5 wt % obtained by firing at 1,000° C. for two hours.

9. The talc according to claim 8, wherein the talc has IgLoss of within a range of 6.0 wt % to 6.5 wt %.

10. The talc according to claim 8, wherein the talc has an average particle diameter within a range of 13 μm to 33 μm.

11. The talc according to claim 8, wherein the talc has an average particle diameter within a range of 28 μL m to 33 μm.

12. A talc as a cordierite raw material to be used in a manufacture of a cordierite honeycomb structure body composed of plural cells surrounded by cell walls arranged in a honeycomb structure, wherein the talc has a wire abrasion of not less than 25 mg.

13. The talc according to claim 12, wherein the talc has the wire abrasion of not less than 35 mg.

14. The talc according to claim 8, wherein the talc involves CaO of not more than 0.3 wt % as an impurity.

15. A cordierite honeycomb structure body manufactured by the method according to claim 1.

16. The cordierite honeycomb structure body according to claim 15, wherein the cordierite honeycomb structure body has an average pore diameter of not less than 5 μm.

17. The cordierite honeycomb structure body according to claim 15, wherein the cordierite honeycomb structure body has a thermal expansion coefficient of not more than 0.5×10−6/° C.

18. A cordierite honeycomb structure body manufactured by the method according to claim 5.

19. The cordierite honeycomb structure body according to claim 18, wherein the cordierite honeycomb structure body has an average pore diameter of not less than 5 μm.

20. The cordierite honeycomb structure body according to claim 18, wherein the cordierite honeycomb structure body has a thermal expansion coefficient of not more than 0.5×10−6/° C.