JPH08112809A - Mold for extrusion molding - Google Patents

Abstract

PURPOSE: To improve effect for preventing cracks from being developed and to improve thermal shock resistance by suppressing orientation of ceramic fibers in a honeycomb structural body and making the ceramic fibers exist randomly. CONSTITUTION: In a mold wherein a plurality of body-feeding holes 1 opening on one end face and being independent each other and a body-discharging channels 2 opening on another end face and consisting of a continuous honeycomb-shaped channel are communicated with each other, the number of the body-feeding holes 1 is made smaller than the number of points of intersection of the body-discharging channels 2 to decrease the number of confluences of the body passing through the discharging channel 2. In addition, the area of the opening of the body-feeding holes per unit area of the mold is made smaller than the area of the opening of the body-discharging channels 2 per unit area of the mold to decrease the extrusion pressure of the waste soil.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of an extrusion mold suitable for extruding a ceramic honeycomb structure containing ceramic fibers.

[0002]

2. Description of the Related Art A ceramic honeycomb structure is usually made of a porous material such as cordierite and is used as a filter for purifying fine particles in exhaust gas discharged from an internal combustion engine such as a diesel engine. Various molds have been proposed as a mold for extruding such a ceramic honeycomb structure (see, for example, JP-A-51-7).
No. 3008, etc.) and its general structure is shown in FIGS. 4 and 5, the mold has a large number of independent kneaded material supply holes 1 on one end side.
Having a continuous honeycomb-shaped kneaded material discharge groove 2 on the other end side,
The kneaded material supply holes 1 are usually provided in the same number so as to be connected to the respective intersections 3 of the kneaded material discharge grooves 2. In FIG. 5, reference numeral 4 indicates the flow of the kneaded clay, and the kneaded clay that has passed through the kneaded clay supply hole 1 merges with the kneaded clay that has passed through the adjacent kneaded clay supply hole 1 while passing through the kneaded clay discharge groove 2. Then, a honeycomb structure having a predetermined shape is formed by bonding.

By the way, in the filter for purifying particles, the collected particles are combusted periodically to regenerate the filter, but cracks may occur due to thermal stress during regeneration, which may damage the filter. . To solve this,
A fiber-reinforced porous body has been proposed in which a SiC short fiber having a length longer than the average pore diameter in the matrix is dispersed in a matrix made of porous cordierite (Japanese Patent Laid-Open Publication No. Hei 5 (1993) -58).
No. 256269), it is expected to be used as a filter material. The SiC short fibers exert their effect when positioned in a direction perpendicular to the crack propagation direction, hinder the crack propagation, and greatly improve the thermal shock resistance.

[0004]

However, when the fiber-reinforced porous body is extrusion-molded by the above-mentioned conventional die, there is a problem that the SiC short fibers in the honeycomb structure are arranged in the extrusion direction. This is because the kneaded material that has passed through the adjacent kneaded material supply holes 1 is bonded in the kneaded material discharge groove 2 and the SiC short fibers are oriented by the pressure when being extruded, so that the development of cracks in the extrusion direction is suppressed. However, there is a problem that the thermal shock resistance in this direction cannot be improved.

Thus, according to the present invention, the ceramic fibers are randomly present in the honeycomb structure, and the honeycomb structure having a high thermal shock resistance in both the extrusion direction and the direction orthogonal to the extrusion direction can be formed. An object is to provide an extrusion mold.

[0006]

The extrusion molding die of the present invention (FIG. 1) has a plurality of kneaded material supply holes 1 which are open at one end surface thereof and are independent of each other, and are opened at the other end surface and are continuous. The kneaded material discharge groove 2 formed of a honeycomb-shaped groove is connected in the mold. The number of the kneaded material supply holes 1 is smaller than the number of intersections of the kneaded material discharge grooves 2, and the opening area of the kneaded material supply holes 1 per unit area of the mold is the above-mentioned kneader per unit area of the mold. It is smaller than the opening area of the soil discharge groove 2 (Claim 1). Specifically, the ratio of the number of intersections 3 of the kneaded material discharge groove 2 to the number of the kneaded material supply holes 1 is 1: 0.5 to 1: 0.
75 (claim 2), and the ratio of the opening area of the kneaded clay discharge groove 2 per unit area of the mold to the opening area of the kneaded clay supply hole 1 per unit area of the mold is 1: 0.5 to 1. : 0.8 is preferred (claim 3). Further, the kneaded material supply holes 1 are regularly arranged with respect to the intersections 3 of the kneaded material discharge grooves 2 (claim 4), and the depth of the kneaded material discharge grooves 2 is 5 mm or more. Is preferable (Claim 5).

[0007]

[Operation] The orientation of the ceramic fibers in the conventional mold is
When the kneaded clay that has passed through the adjacent kneaded clay supply holes 1 joins and is bonded in the kneaded clay discharge groove 2, the kneaded clay is subjected to pressure in the extrusion direction, and the fibers are arranged in the extrusion direction. In order to suppress the orientation, therefore, the number of places where the kneaded material joins should be reduced. In the present invention, since the number of the kneaded material supply holes 1 is smaller than the number of the intersection points 3, the number of the kneaded material joining points is reduced. The fiber orientation is suppressed. Further, as the amount of the kneaded material supplied from the kneaded material supply hole 1 increases, the extrusion pressure increases and the orientation is promoted. However, in the present invention, the opening area of the kneaded material supply hole 1 per unit area of the mold is set to the mold unit. Puddle discharge groove 2 per area
Since the opening area is smaller than the opening area, the amount of kneaded clay is relatively small. Therefore, the extrusion pressure of the kneaded material is reduced, and the fibers are prevented from being arranged in a certain direction. Furthermore, if the kneaded material supply holes 1 are regularly arranged with respect to the intersections 3 of the above-mentioned kneaded material discharge grooves 2, the kneaded material can be uniformly supplied to the entire mold, and the depth of the kneaded material discharge groove 2 can be increased. By setting the distance to 5 mm or more,
The kneaded clay that has passed through the adjacent kneaded clay supply holes 1 can be reliably bonded, and the formability is improved.

[0008]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a view of an extrusion molding die of the present invention as seen from above. The die has a plurality of independent kneaded material supply holes 1 which are opened at the upper end surface thereof and extend in the vertical direction of the drawing, and the kneaded material. It is composed of a soil supply hole 1 and a kneaded clay discharge groove 2 communicating with the inside of the mold and opening at the lower end surface. The kneaded material discharge groove 2 is formed as, for example, a continuous grid-shaped groove so that the kneaded material passing therethrough has a desired honeycomb shape.

The kneaded material supply hole 1 is formed so as to be connected to the intersection 3 of the kneaded material discharge groove 2, but in the present embodiment,
The kneaded material supply holes 1 are arranged at every other intersection 3. In this way, by making the number of kneaded material supply holes 1 smaller than the number of intersections 3 of the kneaded material discharge groove 2, the number of places where the kneaded material that has passed through each kneaded material supply hole 1 is reduced, The orientation of the ceramic fibers in the kneaded clay can be suppressed. Moreover, by arranging the kneaded clay supply holes 1 regularly,
The kneaded material can be uniformly supplied to the entire mold. More specifically, it is preferable that the ratio of the number of intersections 3 of the kneaded material discharge groove 2 and the number of the kneaded material supply holes 1 is 1: 0.5 to 1: 0.75. In this embodiment, this ratio is 1: 0.5. If the number of kneaded material supply holes 1 is smaller than this, sufficient kneaded material cannot be supplied to the kneaded material discharge groove 2, and if the number of kneaded material supply holes 1 is too large, the effect of suppressing the orientation of the ceramic fibers is obtained. Inadequate and not preferable.

The opening area of the kneaded material supply hole 1 per unit area of the mold is smaller than the opening area of the kneaded material discharge groove 2 per unit area of the mold, and the orientation of the ceramic fibers is It can be further suppressed. This is because the smaller the opening area on the kneaded clay supply side, the smaller the pressure when the kneaded clay passes through the kneaded clay discharge groove 2 and the smaller the force for orienting the ceramic fibers. Specifically, the ratio of the opening area of the kneaded clay discharge groove 2 per unit area of the mold to the opening area of the kneaded clay supply hole 1 per unit area of the mold is 1: 0.5.
It is good to set to 1: 0.8. If the ratio is smaller than this, sufficient kneaded clay cannot be supplied to the kneaded clay discharge groove 2, and if it is larger than this ratio, a sufficient effect of suppressing the orientation of the ceramic fibers cannot be obtained.

The kneaded clay discharge groove 2 preferably has a depth of 5 mm or more. If this depth is less than 5 mm,
The kneaded material that has passed through the adjacent kneaded material supply holes 1 cannot be properly merged in the kneaded material discharge groove 2, and it is difficult to form the desired honeycomb structure.

As the kneaded material used for extrusion molding of the honeycomb structure, for example, a material obtained by adding a ceramic fiber such as SiC fiber to a raw material of cordierite is preferably used. In addition, a pore former, a binder and the like which are usually used may be added. Here, the addition amount of the ceramic fiber contained in the kneaded clay is preferably 50% or less. If the amount added exceeds 50%, the pressure during extrusion molding may become too high and extrusion molding may not be possible. Also,
It is desirable that the average length of the ceramic fibers be smaller than the diameter of the kneaded clay supply hole 1. If the average length of the ceramic fiber is larger than the diameter of the kneaded clay supply hole 1, the ceramic fiber will be
There is a risk of disconnection when passing through.

FIG. 2 shows another embodiment of the present invention. In the above embodiment, the kneaded clay supply holes 1 are provided every other intersection 3 of the kneaded clay discharge groove 2, but in the present embodiment, the kneaded clay supply holes 1 are arranged every other row. And columns connected to all intersections 3 are provided alternately. At this time, the above-mentioned clay discharge groove 2
The ratio of the number of intersections 3 and the number of the kneaded material supply holes 1 is 1: 0.
It becomes 75. Even with such a configuration, the same effect can be obtained by making the opening areas (per unit area) of the kneaded material supply hole 1 and the kneaded material discharge groove 2 satisfy the above-mentioned relationship.

In each of the above-mentioned embodiments, the kneaded material supply hole 1 is connected to the intersection 3 of the kneaded material discharge groove 2. However, this is not always necessary, and if it is connected to the kneaded material discharge groove 2. It may be connected to a place other than the intersection 3.

Next, in order to confirm the effect of the present invention, an extrusion molding die having the structure shown in FIG. 1 was produced. At this time, the diameter of the kneaded material supply hole 1 is 1.6 mm, and the cell pitch is 2.42 m.
m, the width of the kneaded clay discharge groove 2 is 0.45 mm, the depth of the kneaded clay discharge groove 2 is 6 mm, and the kneaded clay supply holes 1 are arranged at every other intersection with respect to the intersection of the kneaded clay discharge groove 2. (The ratio of the number of intersections of the kneaded material discharge grooves 2 to the number of the kneaded material supply holes 1 is 1: 0.5).
The ratio of the opening area of the kneaded material discharge groove 2 to the opening area of the kneaded material supply hole 1 was 1: 0.51 (per unit area of mold).

A honeycomb structure was extruded using the mold having the above structure. The kneaded clay was produced by the conventionally known method as follows. First, 18% by weight of fused silica, which is a raw material of cordierite, 36% by weight of talc, and 46% by weight of aluminum hydroxide, SiC fibers having an average length of about 0.5 mm and a diameter of 15 μm as ceramic fibers (Nippon Carbon Co., Ltd.). Manufactured by Nikoron Co., Ltd.) in an amount of 10% by weight based on the above cordierite raw material, and carbon as a pore-forming material for use as a fine particle purification filter.
0 wt% was added. To this, add water to make a slurry,
After sufficiently stirring with a mixer, it was dried. Further, 10% by weight of methyl cellulose and 30% by weight of water were added as a binder and kneaded with a kneader to obtain a kneaded clay.

Using this kneaded material, extrusion molding was performed with the above-mentioned mold, and firing was carried out to manufacture a honeycomb structure. When the cross section of the obtained honeycomb structure was observed, it was found that the ceramic fibers 5 were randomly present in the honeycomb structure 6 as shown in FIG. In order to quantitatively evaluate the arrangement of the ceramic fibers 5, the ratio (orientation degree) of the component in the extrusion direction of the ceramic fiber and the component in the direction orthogonal to this per unit area was measured. The results are shown in Table 1 as Example 1. Further, a fine particle purification filter was manufactured using the obtained honeycomb structure, and the maximum temperature inside the filter when the filter was subjected to a combustion regeneration test and no destruction occurred was also shown in Table 1 as thermal shock resistance. In addition,
The definition of the orientation degree T is as follows. Orientation degree T = Σ (L * cos θ) / Σ (L * sin θ) Here, L represents the length of the ceramic fiber 5, θ represents the angle formed by the ceramic fiber 5 with respect to the extrusion direction, and the orientation degree T is close to 1. This means that the ceramic fibers 5 are more random. As the degree of orientation T exceeds 1 and increases, the number of rows in the extrusion direction increases, and conversely, as the degree of orientation T decreases below 1, the number of rows in the direction orthogonal to the extrusion direction increases.

Next, the mold having the structure shown in FIG. 2 was prepared in the same manner, and the degree of orientation T and the thermal shock resistance were measured. The ratio of the number of intersections 3 of the kneaded material discharge groove 2 and the number of the kneaded material supply holes 1 is 1: 0.
The ratio of the opening area of the kneaded material discharge groove 2 to the opening area of the kneaded material supply hole 1 was 1: 0.76 (per unit area of mold). The results are also shown in Table 1 as Example 2. Further, as shown in Table 1, the ratio of the number of kneaded material supply holes 1 to the intersection point 3,
And various molds were produced by changing the ratio of the opening area, and the same measurement was performed (Examples 3 to 5). For comparison, the mold of the structure shown in FIG. 4 in which the number of kneaded material supply holes 1 and the number of intersections 3 are the same (comparative example 1) and the arrangement of the kneaded material supply holes 1 are the same as those in the first embodiment. A mold (Comparative Example 2) having a structure shown in FIG. 6 in which the diameter of the kneaded clay supply hole 1 was increased was manufactured, and the same measurement was performed.
The results are also shown in Table 1.

As is clear from Table 1, in Example 1, the degree of orientation T is 1.5, indicating that the ceramic fibers 5 are present in the honeycomb structure 6 substantially randomly. On the other hand, in Comparative Example 1, the degree of orientation is 4.5,
Further, when the cross section was observed, it was found that the ceramic fibers 5 were arranged in the extrusion direction in the honeycomb structure 6 as shown in FIG. 3 (b). Each of Examples 2 to 5 also exhibits an orientation degree of 2 or less, which is far smaller than that of Comparative Examples 1 and 2 in which the orientation degree is around 4. Also, thermal shock resistance,
In each of the examples, it is 1000 ° C., which is higher than that of the comparative example by 60 ° C. or more.

[0020]

[Table 1]

[0021]

As described above, by using the extrusion molding die of the present invention, the orientation of the ceramic fibers in the honeycomb structure can be suppressed. That is, since the ceramic fibers can be present at random in the obtained honeycomb structure, it has an action of suppressing the progress of cracks in both the extrusion direction and the direction orthogonal thereto, and has a large thermal shock resistance. Can be improved.

[Brief description of drawings]

FIG. 1 is a front view of an extrusion molding die according to an embodiment of the present invention.

FIG. 2 is a front view of an extrusion molding die showing another embodiment of the present invention.

[Fig. 3] Fig. 3 is a diagram for explaining the effect of the present invention, (a) is a schematic view showing the structure of a honeycomb structure by the extrusion molding die of the present invention, and (b) is a conventional extrusion molding die. FIG. 3 is a schematic view showing a structure of a honeycomb structure according to the present invention.

FIG. 4 is a front view of a conventional extrusion molding die.

5 is a partial cross-sectional view of a conventional extrusion molding die, which is a cross-sectional view taken along line VV of FIG.

FIG. 6 is a front view of a conventional extrusion molding die.

[Explanation of reference symbols] 1 kneaded clay supply hole 2 kneaded clay discharge groove 3 intersection 4 flow of kneaded clay 5 ceramic fiber 6 honeycomb structure

Claims (5)

[Claims] 1. A plurality of kneaded material supply holes, which are opened at one end surface of the mold and are independent from each other, and a kneaded material discharge groove, which is a continuous honeycomb-shaped groove and is opened at the other end surface, in the mold. It is an extrusion molding die that is communicated, the number of the kneaded material supply holes is less than the number of intersections of the kneaded material discharge grooves, and the opening area of the kneaded material supply holes per unit area of the mold is a mold unit. An extrusion molding die characterized by being smaller than the opening area of the kneaded clay discharge groove per area. 2. The extrusion molding die according to claim 1, wherein the ratio of the number of intersections of the kneaded material discharge grooves and the number of the kneaded material supply holes is 1: 0.5 to 1: 0.75. 3. The ratio of the opening area of the kneaded material discharge groove per unit area of the mold to the opening area of the kneaded material supply hole per unit area of the mold is 1: 0.5 to 1: 0.8. The extrusion mold according to claim 1 or 2. 4. The extrusion molding die according to claim 1, wherein the kneaded material supply holes are regularly arranged at intersections of the kneaded material discharge grooves. 5. The extrusion molding die according to claim 1, wherein the kneaded clay discharge groove has a depth of 5 mm or more.