JPH08336819A - Molding method for fiber-containing honeycomb molding and mouthpiece for molding - Google Patents

Abstract

PURPOSE: To provide a molding mouthpiece of a fiber-containing honeycomb molding which can prevent damage of cells caused by clogging of a passage in the mouthpiece. CONSTITUTION: In a honeycomb molding mouthpiece equipped with a latticed discharge passage 2 and a plurality of supply passages 3 which are connected to an intersection 2a of the discharge passage 2 and supply a fiber-containing honeycomb molding material, an overlapping passage 4 of the two passages is provided at the connected part of the discharge passage and the supply passages. A length L3 in the extruding direction of the overlapping passage is set to be five or above times as long as a groove width W of the discharge passage 2. A part or the whole area in between the entrance ends of the supply passages and the downstream end of the overlapping passage is made to have a taper structure which tapers in the extruding direction. A taper angle a of the taper structure is set to 2 deg.<=α<=20 deg. and preferably to 5 deg.<=α<=10 deg. so as to orient the fibers in the honeycomb material toward the extruding direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a die for forming a fiber-containing honeycomb formed body, and more particularly to a method and a die for extruding fiber-containing ceramics or a catalyst into a honeycomb shape. TECHNICAL FIELD The present invention relates to a method for forming a honeycomb formed body and a die for forming the die, which are suitable for preventing damage at the time.

[0002]

2. Description of the Related Art In order to remove nitrogen oxides used for thermal power generation and from various factories, a method of detoxifying with a reducing agent such as ammonia and a denitration catalyst that promotes the reduction reaction is generally adopted. This catalyst has a plate shape, a granular shape, or a honeycomb shape, and is used depending on the exhaust gas property. Above all, the honeycomb shape capable of increasing the surface area per unit volume is effective for clean exhaust gas containing no dust.

To form a honeycomb, as shown in FIG. 5, it is efficient to extrude a paste 10 containing inorganic particles as a main component, a die 1 having a plurality of flow paths, and an extruder 11 for the production process. It is the mainstream. However, in the case of a non-sintered body such as a denitration catalyst honeycomb, it is necessary to devise a device for developing strength as compared with a general sintered honeycomb. Inorganic fibers (for example, various glass fibers and rock wool) are added to this as a catalyst strength enhancing member at the time of preparation of the catalyst paste, and the mixture is subjected to extrusion molding.

[0004]

The length of the inorganic fibers in the above-mentioned catalyst paste is several mm at the time of charging, but most of the fibers break during the kneading process, and the average length is several tens to several hundreds of μm. It has been confirmed by the inventor that the aspect ratio is about 10 to 20, but some of the paste adhered to the wall surface of the kneading machine and the fibers remain for a length of about 1000 μm without breaking for some reason. There are also things. On the other hand, in some cases, the catalyst paste is partially dried and solidified and exists as a dust lump larger than the groove width of the honeycomb die.

When forming a narrow-pitch thin rib honeycomb by using such a paste with a honeycomb die having a conventional structure, cell loss becomes a serious problem. For cell loss, the following 2
There are two forms. It is empirically known that one is that when the flow path is completely blocked and the cell penetrates and escapes, the other is that intermittent or sporadic defects occur and the position of the defect changes apparently. ing.

The former cause is considered to be caused by coarse dust mixed in the paste or extremely long fibers blocking the flow path, as disclosed in JP-A-53-137260.
As disclosed in JP-A-56-127411, it is possible to avoid the occurrence of defects by removing dust in the paste with a strainer. On the other hand, it is estimated that the latter defect causes a temporary defect due to a slight change in the molding speed depending on the orientation state of the fibers in the channel of the honeycomb die.

The present invention has been made in order to solve the problem of cell defects frequently occurring in the molding of narrow-pitch thin rib denitration honeycombs, and in particular, a molding die having a flow channel shape suitable for reducing cell defects. The present invention also relates to a method of forming a fiber-formed honeycomb formed body using the same.

[0008]

In order to achieve the above object, the invention claimed in the present application is as follows. (1) A honeycomb forming raw material containing fibers is pushed toward an extruding side through a plurality of independent feed passages that are perforated in parallel from the raw material inlet side of the honeycomb forming die toward the raw material outlet side, Next, in the overlapping flow passages in which a part of each of the feed passages is made to communicate with each other near the end of each of the feed passages and is open-connected to the lattice-shaped discharge passage provided on the molding raw material outlet side of the molding die. And the molding raw materials supplied from the supply channel in the overlapping flow channel are brought into close contact with each other, and the orientation of the fibers in the molding raw material in the feeding flow channel and / or the overlapping flow channel is oriented in the extrusion direction. A forming method of the honeycomb formed body containing fibers, wherein the forming raw material is pushed into the discharge flow path and extruded as a sufficiently formed honeycomb formed body.

(2) A lattice-shaped discharge channel and a plurality of independent supply channels connected to the intersections of the discharge channels to supply the honeycomb-forming raw material containing fibers, and the supplied molding channels. In a die for honeycomb molding for extruding a raw material from a discharge flow channel as a continuous lattice-shaped honeycomb molded body, an overlapping flow channel portion of both flow channels is provided at a connecting portion between the discharge flow channel and the supply flow channel,
The length of this overlapping flow passage in the extrusion direction is set to 5 to 2 of the discharge flow passage groove thickness.
A forming die for a honeycomb formed article containing fibers, which has a taper structure in which a part or the whole area between the inlet end of the supply passage and the downstream end of the overlapping passage has a taper structure in the extrusion direction.

(3) A die for forming a honeycomb molded body containing fibers, characterized in that in (2), the taper angle α of the tapered taper structure portion is 2 ° ≦ α ≦ 20 °. (4) In the molding die for a honeycomb molded body containing fibers, according to (2) or (3), the taper angle α of the tapered tapered structure portion is 5 ° ≦ α ≦ 10 °.

(5) Equipped with a lattice-shaped discharge channel and a plurality of supply channels connected to the intersections of the discharge channels to supply the honeycomb-forming raw material containing fibers, and the supplied molding raw material is discharged from the discharge channel. In a honeycomb molding die extruded as a continuous lattice-shaped honeycomb molded body, an overlapping flow path portion of both flow paths is provided at a connecting portion between the discharge flow path and the supply flow path, and the depth of the overlapping flow path is set to the discharge flow path. Groove thickness of 5 to 10 times, and a part or the whole area between the inlet end of the supply flow passage and the downstream end of the overlapping flow passage is tapered in the extrusion direction, and the taper angle α is 2
A forming die for a honeycomb formed article containing fibers, which has a function of orienting fibers in a honeycomb raw material in an extrusion direction by setting ° ≦ α ≦ 20 °.

(6) A die for forming a honeycomb formed article containing fibers according to (5), wherein the taper angle α of the tapered taper structure portion is 5 ° ≦ α ≦ 10 °.

[0013]

The operation will be described with reference to FIG. 1, which is an embodiment of the present invention. The major features of this mouthpiece structure are that the overlapping portion of the discharge flow channel 2 and the supply flow channel 3, that is, the overlapping flow channel 4, is long, and that the supply flow channel 3 is formed with a tapered end portion 5. When the overlapping flow paths are long, the occurrence of defects due to spherical dust is suppressed. That is, even if dust is clogged in the hole bottom portion (downstream end of the overlapping flow passage) of the supply flow passage, the supply to the discharge flow passage is not closed, and the paste is continuously supplied from the upstream portion of the overlapping flow passage. It is possible. Therefore, even if the flow path is clogged with dust, it is difficult to cause cell loss in the molded body (FIG. 2). Regarding the length of the overlapping portion, the supply flow path can be secured even if dust having the same thickness as the groove is clogged. If the depth is 5 times the groove thickness or more, the effect is sufficiently exhibited. On the other hand, if the overlapping flow path becomes longer, the remaining pin that cuts the lattice groove on the downstream side of the die becomes longer,
Since the part where the corner is carved becomes long, there is a concern that it may be a negative factor for the pin strength of the base or the handling of the base.

The decrease in pin strength can be solved by tapering the supply passage. Generally, the rigidity of the pin is lowered by scooping off the four corners by the supply flow path (hole). Therefore, by tapering the holes,
The amount of wall thinning on the side surface of the pin is reduced, and the decrease in strength can be minimized. Further, as another effect, the taper toward the end makes it easier for the fibrous dust to be oriented and suppresses the occurrence of defects. The mechanism for preventing defects due to fiber orientation can be considered as follows. That is, by making the supply channel thin, it is possible to suppress the slip of the paste on the channel wall surface during extrusion molding and to shear the paste up to the vicinity of the center axis of the channel. Therefore, the fibers can be oriented in the flow direction throughout the flow path.
From this, the paste flows smoothly even in the throat where the flow passage cross-sectional area is the minimum value, and the probability of chipping is reduced (figure 3 and FIG. 4 compare the fiber orientation due to the difference in the shape of the supply flow passage). Is). As a result of considering and considering these, it was found that the depth of the overlapping flow path L ₃ was 5 to 20 times, preferably 5 to 10 times the groove thickness.

In order to suppress the occurrence of defects due to the fiber orientation control, the inventor repeated various experiments, and as a result, as shown in FIG.
The effect is recognized when the taper angle α shown in 2 is set to 2 ° ≦ α ≦ 20 °, and in order to maximize the suppressing effect, it is necessary to set α to 5 ° ≦ α ≦ 10 °. Reached That is, when the taper angle is set to a steep gradient of α> 20 °, the orientation of the fibers is promoted, but the paste adheres to the wall surface of the flow channel, and a peculiar paste having a reduced water content may be generated. Therefore, when the adhered paste blocks the flow path or peels off for some reason and flows out, it may cause cell loss due to clogging of the flow path. On the contrary, if the taper angle is a small angle of α <2 °, on the other hand, the effect of orienting the fibers in the entire region of the channel is reduced, and the molding state is the same as that of the conventional die.

Japanese Unexamined Patent Publication (Kokai) No. 49-74208 shows a taper at the end of the supply flow path (FIG. 6). However, it is not a necessary condition that the structure has a taper, and there is no void in the discharge groove. The point of the present invention is that the cross-sectional area of the outlet of the supply channel is 1.2 times or more the cross-sectional area of the discharge groove in order to supply the paste. On the other hand, the present invention promotes fiber orientation in order to prevent cell loss, and it is a necessary condition itself that the supply flow path has a taper at the end, and a taper angle of 2 ° ≦ α ≦ 20 ° is a sufficient condition. Is. Therefore, the present invention is essentially different from JP-A-49-74208. Further, the above-mentioned publicly known examples do not relate to honeycomb molding with fibers.

In the die (FIG. 7) disclosed in Japanese Patent Laid-Open No. 53-106711, the paste supply passage (parallel hole) 22 and the discharge passage (groove) 21 have an overlapping passage 24. The existing object is to reduce the flow resistance of the die and to strengthen the pressure bonding of the pastes in the lattice-shaped discharge passage. However, in the above-mentioned conventional flow path, the overlapping flow path is a parallel flow path, and compared with the flow path of the present invention, the orientation function of the fiber is not considered at all, and the flow path is surrounded by a discharge groove in a grid pattern. There is a problem that the strength of the pin and the rigidity of the base become small.

[0018]

EXAMPLES Next, the present invention will be described in more detail by way of examples. Example 1 A die having the structure shown in FIG. Cell pitch: 3.5 mm Rib thickness (W): 0.5 mm Supply channel inlet hole diameter: 2.9 mmφ Supply channel outlet hole diameter: 2.0 mmφ Supply channel depth: 20.0 mm (taper vertical angle 5 °, Discharge channel depth: 10.0 mm Overlap length: 5.0 mm Die thickness: 25.0 mm Number of cells: 9 x 9 cells (outer shape 32.5 mm x 32.5)
mm) Here, the supply flow path is a drill and taper reamer, and the discharge flow path is B
Processed with N whetstone.

Using this die and screw extruder, 11
The No. 02 powder catalyst / glass fiber / methyl cellulose / water was kneaded with a kneader for 20 minutes to form a denitration catalyst paste. Kneading of this paste is slightly insufficient, and the water retention of the paste and the occurrence of defects can be magnified and evaluated. As a result of molding experiment, molding pressure P = 50 to 55 kg / c
At m ² and flow velocity V = 200 to 250 mm / min, there was almost no defect, and even if it occurred, it was not a defect at the rib intersection, but a defect at the center of the side. The rare defects that occurred were not permanent, and there was a recovery phenomenon that returned to a healthy state. In addition, a molded body having no bending and good pressure bonding between cells was obtained.

Next, a molding experiment was conducted in the same manner as in Example 1 above, while changing the flow channel structure of the die. Example 2 Even when the taper angle was set to be small and α = 2 ° while the length L _t of the taper portion was made equal to that of Example 1, a compact having almost no defects was obtained as in Example 1. Example 3 Even when the taper angle was the same as in Example 2 and the length of the taper portion was doubled to L _t = 20.0 mm (the entire supply hole), a molded body with almost no defects was obtained as in Example 1. Was obtained. Example 4 Even when the die was thinned and the taper angle was increased to α = 10 °, there was almost no defect. Example 5 When the die was thinned and the taper angle was set to a large value of α = 20 °, some defects were more likely to occur in comparison with the above-mentioned examples with respect to the occurrence of defects, and there was a tendency that the defects would not recover once clogged. . From this, it is highly possible that water separation of the paste occurs at the taper portion and the flow path is blocked. Therefore, it is considered that the upper limit of the taper angle is 20 °. Comparative Example 1 According to a general mouthpiece (the parallel holes of the supply flow passages and the overlapping flow passages are extremely short), some defects were generated, and the recovery phenomenon of returning to a healthy state was small. Comparative Example 2 As compared with Comparative Example 1, when the supply flow path had a tapered structure, the number of defects was smaller than that of Comparative Example 1, but the phenomenon of recovery of defects was small as in Example 1. Comparative Example 3 When the overlapping flow paths are made longer than in Comparative Example 1 (taper angle 0
°), the frequency of occurrence of defects was slightly higher than that of Comparative Example 2, but recovery of defects was likely to be good.

Table 1 summarizes the structures of the die of Examples and Comparative Examples and the experimental results.

[0022]

[Table 1]

Note): Specifications common to all caps ・ Cell pitch: 3.5 mm ・ Rib thickness: 0.5 mm ・ Supply channel inlet hole diameter: 2.9 mmφ ・ Number of cells: 9 × 9 cells (outer shape 32.5 mm × 32) .5
mm) It should be noted that, as a result of examining variously changing the depth L ₃ of the overlapping flow passage for the die of the above-mentioned example and the comparative example, the depth L ₃ of the overlapping flow passage was found to be the groove thickness W (honeycomb forming) of the discharge flow passage. Rib thickness of the body)
It was found that 5 to 20 times is preferable, and 5 to 10 times is the most preferable in view of rigidity of the die and clogging of the flow channel.

[0024]

EFFECTS OF THE INVENTION According to the present invention, it has been clarified that it is effective for preventing defects during molding. As a result, not only is the quality stable, but the frequency of replacement and cleaning of the clogging die during molding is also reduced, leading to a reduction in man-hours. Further, the rigidity of the die and the strength of the pin surrounded by the grid-like grooves are improved, and the problem of chipping or deformation of the pin during washing of the die can be reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional perspective view of a flow path of a die according to the present invention.

FIG. 2 is a diagram showing a comparison of dust behavior when the overlapping flow passage according to the present invention is deep and when it is shallow (conventional).

FIG. 3 is a diagram showing fiber orientation in a case where general supply channels are parallel to each other.

FIG. 4 is a diagram showing fiber orientation when the supply channel is tapered.

FIG. 5 is a view showing a general honeycomb forming method.

[FIG. 6]

FIG. 7 is a view showing a conventional technique of a honeycomb forming die.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Base, 2 ... Discharge channel, 3 ... Supply channel, 4 ... Overlap channel, 5 ... Tapered taper section, 6 ... Pin section.

Claims (6)

[Claims] 1. A honeycomb forming raw material containing fibers is pushed toward an extruding side in a plurality of independent feed passages that are perforated in parallel from a raw material inlet side of a honeycomb forming die toward a raw material outlet side. Next, a part of each feed passage is made to communicate with each other near the end of each feed passage, and an overlapping flow is opened and connected to the lattice-like discharge passage provided on the molding raw material outlet side of the forming die. The extrusion raw material is extruded into the passage so that the forming raw materials supplied from the supply passage in the overlapping passage are brought into close contact with each other, and the direction of the fibers in the forming raw material is extruded in the feeding passage and / or the overlapping passage. A method for forming a honeycomb formed body containing fibers, which comprises orienting the formed raw material and pushing the forming raw material into the discharge flow channel to extrude a honeycomb formed body having a sufficient adhesion. 2. A molding material supplied, comprising a lattice-shaped discharge channel and a plurality of independent supply channels connected to the intersections of the discharge channels and supplying the honeycomb-formed raw material containing fibers. In a honeycomb forming die for extruding as a continuous lattice-shaped honeycomb molded body from the discharge flow channel, an overlapping flow channel portion of both flow channels is provided at a connecting portion of the discharge flow channel and the supply flow channel, and extrusion of the overlapping flow channel is performed. The length in the direction is 5 to 20 times the thickness of the discharge flow channel groove, and a part or the entire area between the inlet end of the supply flow channel and the downstream end of the overlapping flow channel has a tapered structure in the extrusion direction. A die for forming a honeycomb formed body containing fibers. 3. The die for forming a honeycomb molded body containing fibers according to claim 2, wherein the taper angle α of the tapered taper structure portion is 2 ° ≦ α ≦ 20 °. 4. The die for molding a honeycomb molded body containing fibers according to claim 2, wherein the taper angle α of the tapered taper structure portion is 5 ° ≦ α ≦ 10 °. 5. A lattice-shaped discharge channel and a plurality of supply channels connected to the intersections of the discharge channels to supply the honeycomb-forming raw material containing fibers, and the supplied molding raw material is continuously supplied from the discharge channel. In the honeycomb forming die extruded as a lattice-shaped honeycomb formed body, an overlapping flow path portion of both flow paths is provided at a connecting portion of the discharge flow path and the supply flow path, and the depth of the overlapping flow path is set to a value of the discharge flow path. The groove thickness is 5 to 10 times, and a part or the whole area between the inlet end of the supply flow path and the downstream end of the overlapping flow path has a taper structure in the extrusion direction, and the taper angle α is 2 ° ≦.
A die for forming a honeycomb formed article containing fibers, which has a function of orienting the fibers in the honeycomb raw material in the extrusion direction by setting α ≦ 20 °. 6. The die for molding a honeycomb molded body containing fibers according to claim 5, wherein the taper angle α of the tapered taper structure portion is 5 ° ≦ α ≦ 10 °.