JPH08169005A - Honeycomb molding mouthpiece and manufacture of honeycomb molding - Google Patents

Abstract

PURPOSE: To provide a honeycomb mouthpiece, which can relax the stress concentration at drying and baking and prevent a honeycomb molding from cracking. CONSTITUTION: In the honeycomb molding mouthpiece, which is equipped with discharge flow paths made of lattice-like groove 2 and feed flow paths 1 provided for feeding paste at the intersecting part of the grooves so as to form fed paste continuously into a latticelike body, the apex at the outlet end of each of a plurality of pins 3 partitioned with the latticelike grooves 2 is bevelled with a curved or flat surface under the condition that the depth Lc of the bevelled part 5 is set to be not more than 1/3 of the depth L of the groove and, at the same time, the tangent relief angle (α) of the bevelled part to a discharge molding is set to be not less than 20 deg..

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a honeycomb forming die and a method for manufacturing a honeycomb formed body, and more particularly, to a die for extruding ceramics and a catalyst into a honeycomb shape and a method for producing a honeycomb formed body using the die. The present invention also relates to a die for forming a honeycomb suitable for preventing dry firing cracking and a method for manufacturing a honeycomb formed body using the die.

[0002]

2. Description of the Related Art A main method for producing honeycomb-shaped ceramics and catalysts is to extrude a raw material paste from a die. A general base is shown in FIG. Reference numeral 1 denotes a cylindrical feed passage in a die (extrusion die) 7, and 2 a discharge passage (forming groove) formed in a honeycomb shape, which is connected to the feed passage 1. Incidentally, 6 is an intersection of the molding grooves 2. Further, 3 is a pin-shaped body formed by the molding groove 2 (hereinafter,
It is a pin). As shown in FIGS. 3 and 4, the paste flow path in the die is composed of a plurality of flow paths, and is divided into two layers of flow paths 1 and 2 in the flow direction. That is, the two-layer flow passage occupies the upstream side of the die and is a feed flow passage 1 for dividing and feeding the paste supplied from the extruder to the individual flow passages.
And a discharge channel (lattice-shaped molding groove) 2 that is connected to the feed channel and occupies a downstream portion of the die and that is used to shape the paste fed from the feed channel into a grid shape.

During extrusion molding, the paste supplied to the upstream end of the die is once divided and flows into the individual feed passages 1 and passes through the parallel portions thereof. The paste that has passed through the feed channel spreads to the discharge channel 2 that is connected to the adjacent channel and has a lattice-shaped groove, in which the basic channel connected to the downstream end of the feed channel has a cross section. While flowing in. FIG. 4 shows a pin structure defined by the grid-shaped forming grooves 2. The pastes are pressed against each other at the merging surface of the cross molded body while passing through the cross slit portion of the discharge flow path (molding groove) 2, and honeycomb cells are continuously molded and discharged at the downstream end of the die.

The obtained honeycomb molded body has a water content of 20 to 20.
Since it contains 50%, it needs to be dried. In the drying process, the device is devised to evenly evaporate the water so as not to generate cracks, which is disclosed in JP-A-56-95342.
The drying method disclosed in JP-A-60-226451.
Ambient air conditions etc. correspond to this. Next, heat treatment (baking) is performed for the purpose of improving the strength of the molded body, improving the water resistance, removing the molding aid, and the like. Also in this case, various ideas have been devised so that the firing is performed while suppressing the thermal stress (for example, JP-A-57-119843 and JP-A-63-2105).
This is the atmospheric condition and the like shown in Japanese Patent Publication No. 93).

[0005]

The molded body obtained by the conventional honeycomb molding die having the above structure has a large stress concentration due to the drying and firing at the intersection of the ribs forming the groove peripheral wall. , Structurally disadvantageous. For this reason, the proper range of operating conditions in the drying and firing process is narrowed, and the yield is reduced.

There are the following two types of bases devised as stress concentration relaxing measures. One is the Japanese Examined Japanese Patent Publication 51-2
This is a method of removing the corners of a plurality of pins defined by honeycomb-shaped grooves described in Japanese Patent No. 0435. This is indicated by reference numeral 8 in FIG. It has been pointed out that this method has a high manufacturing cost for the base and has no industrial value (in Japanese Patent Publication No. 61-20403). The other is Japanese Patent Publication No. Sho 61-20403, which tried to realize the above method at low cost.
This is a method in which a corner portion of a pin formed by intersecting grooves is penetrated by a drill. This is indicated by reference numeral A in FIG. The present inventor has investigated the degree of the effect of this method, and although the drying and firing yield is improved, it takes time to obtain a stable molded body, and the paste flows in the lateral direction of the grid-like grooves. It also became difficult, and the adverse effect of weakening the pressure bonding between cells occurred.

In view of the above-mentioned problems of the prior art, an object of the present invention is to provide a mouthpiece flow channel structure suitable for obtaining a molded body which is hard to crack in a drying and firing process and has a large strength during use, and a die to be processed. An object of the present invention is to provide a die for forming a honeycomb having excellent properties and a method for producing a catalyst using the die.

[0008]

In order to achieve the above object, the invention claimed in the present application is as follows. (1) A discharge flow path including a grid-shaped groove corresponding to the cross-sectional shape of the honeycomb molded body to be extruded and a supply flow path for supplying paste (kneaded clay) to the intersection of the grooves are provided and supplied. In a honeycomb forming die for forming a paste into a continuous lattice-shaped body, a predetermined oblique angle with respect to the discharge-formed body is formed at the apex of the outlet ends (downstream ends) of the plurality of pins defined by the lattice-shaped grooves. A honeycomb forming die, wherein a chamfered portion having the same is formed.

(2) A honeycomb forming die according to (1), wherein the chamfered portion has a chamfered depth of 1/3 or less of a groove depth. (3) A honeycomb forming die according to (1) or (2), characterized in that a tangential clearance angle α of the chamfered portion with respect to the honeycomb formed body is 20 ° <α. (4) Paste supplied by a die provided with a discharge flow path consisting of grid-like grooves corresponding to the cross-sectional shape of the honeycomb molded body to be extruded and a supply flow path for supplying paste to the intersection of the grooves In a method for forming a continuous honeycomb formed body, a method for producing a honeycomb formed body, wherein the formed body is discharged and separated from the discharge flow passage at the intersection of the grooves earlier than other portions .

(5) The paste is supplied to the honeycomb spinneret having the discharge passages formed of lattice-shaped grooves corresponding to the cross-sectional shape of the honeycomb molded body to be extruded and the feed passages for supplying the paste to the intersections of the grooves. In the method of molding the paste into a continuous honeycomb molded body, the discharge side apex of the outlet ends of the plurality of pins defined by the lattice-shaped grooves has a predetermined oblique angle with respect to the discharged molded body. A chamfered chamfer is formed, and the honeycomb molding die having the chamfered chamfer is used to shift the time at which the molded body is discharged and separated from the discharge flow passage at the intersection of the lattice-shaped grooves earlier than other portions. A method for manufacturing a honeycomb molded body, which comprises molding.

[0011]

The operation of the present invention will be described with reference to FIGS. The basic paste flow is almost the same as in the past. The paste that has been dividedly fed into the feed passage 1 spreads and flows into the discharge groove passage that forms the lattice-shaped groove 2 that is connected to the downstream end (see FIG. 3). This paste is pressed against each other at the confluence surface of the cross-shaped body while passing through the cross slit portion, and honeycomb cells are continuously molded and discharged at the downstream end of the die. The point of the present invention lies in this discharge part. That is, in the conventional die, the molded body was discharged all at once from the downstream end of the die, whereas in the die of the present invention, the chamfered portion was formed at the apex of the outlet end of the pin, so that the rib intersection point portion was formed. Is separated from the flow channel upstream of the downstream end of the die, and the intersections form the free surface first (the side of the rib is separated from the flow channel at the downstream end of the die).

As described above, when the timing of release from the flow path differs depending on the location of the cross section of the molded product, stress distribution in the extrusion direction and strain distribution in the cross sectional direction occur in the cross sectional direction of the obtained molded product. This is due to the viscoelastic property of the paste.Compressive stress occurs at the rib intersections and tensile stress occurs at the rib edges, and when the yield stress, which is the limit stress for deformation, is exceeded, buckling occurs at the compressed part and tensile stress occurs at the tensile part. Elongation will occur. The intersection of the buckled ribs (corner of the cell) bulges slightly in the cross-sectional direction compared to the corner formed along the ridge of the pin, and has a roundness, and in this state the yield stress of the paste is present as residual stress. However, since the compressive stress remains at the rib intersection point, the tensile stress generated during the dry firing is relaxed, and the generation of cracks from the cell corners is suppressed (see FIG. 5).

The inventor searched for conditions under which these effects are maximized. As a result, it is preferable that the rib intersection point of the molded body is separated from the downstream end by 1/3 or less of the groove depth. If it is deeper than this, the molded body is isolated and then adheres to the chamfered portion again, or cell strain occurs. It has been found that there is a possibility that dimensional accuracy will be increased due to too large.
Further, in order to smoothly separate the molded product from the flow channel, it is necessary to optimize the tangent angle formed by the extension line of the flow channel and the relief surface (chamfer), that is, the clearance angle α.
In this case, it was found that if the clearance angle α was 20 ° <α, peeling occurred, and if the clearance angle α was shallower than this, the molded body was molded while being attached to the flow path.

In order to process the die, first, stop holes are formed at a predetermined pitch from one direction of the steel plate to form a flow path for the paste, and then a grid-like groove is cut on the opposite surface to form a generally known honeycomb. Obtain the prototype of the base. At the intersection of the grid-shaped grooves of this prototype, die-cutting electric discharge machining using electrodes with a conical or quadrangular pyramidal cross section, cutting with a drill, pressing a steel ball corresponding to the chamfer dimension R to a predetermined depth ,
Can be chamfered by burnishing. As a processing procedure, a method of forming a chamfered portion at the top first and then making a groove or a hole may be used. Further, a method of combining a plurality of the above processing methods may be used. The mold thus obtained may be subjected to molding as it is, but may be subjected to a plating treatment in order to further smooth the flow path surface.

[0015]

【Example】

Example 1 A die having the following dimensions and shape was prototyped with the structure shown in FIG. 1 or 2. Cell pitch: 3.5 mm Rib thickness: 0.5 mm Supply passage hole diameter: 2.8 mm Parallel depth of supply passage: 14.5 mm Discharge passage depth: 5.0 mm Downstream end chamfer edge length: 1.0 mm Chamfer depth: 1.5 mm Die thickness: 19.0 mm Depth of intersection of parallel flow passage and discharge flow passage downstream of the feed flow passage: 0.5 mm Number of cells: 44 x 44 cells (outer shape 155.0 mm) × 155.
0mm) Here, the supply flow path is parallel to the drill and the reamer, and the discharge flow path is BN
Processed with a whetstone. At the intersection of the grid-like grooves, the pin apex was chamfered by die-sinking electric discharge machining using a conical electrode.

Using this die and screw extruder, Ti
A denitration catalyst paste (kneaded clay) obtained by kneading O ₂ (titanium oxide) -based denitration catalyst powder / glass fiber / methyl cellulose / water with a kneader was extruded and molded. As a result, the molding pressure P
= 45 to 50 kg / cm ² , flow velocity V = 200 to 250 mm / m
A molded body having a good in-cell crimping without bending was obtained, and the shape was such that the corner portion of the cell cross section was slightly padded. Next, the molded body was covered with a cardboard jig and dried at 85 ° C. under a condition of 70% to obtain a sound dry body without cracks. Further, this was heated at 40 ° C./h, kept at 550 ° C. for 6 hours, and then cooled to room temperature in about 10 hours. As a result, it was possible to obtain a fired body with almost no cracks during firing. These results were the same when the vertices were chamfered using a quadrangular pyramidal electrode. Comparative Example 1 A honeycomb was formed at the apex using a die without chamfering under the same conditions as in the example. As a result, the corners of the cell cross section became sharp and perpendicular, and the molding was sound, but cracks were found on the end faces from the cell edges in the drying process. Further, cracks extending in the molding direction near the cell edges were observed on the outermost peripheral side surface during firing. From these results, it was found that the yield of dry baking was lower than that of the examples. Example 2 After machining the outer shape of the die with a milling machine, a portion having a φ3 mm diameter (tip angle: 108 °) was used to form a grid-shaped groove intersection.
A hole having a depth of 5 mm was opened to form a chamfered portion, then a supply flow passage hole was opened, and finally, a groove of a lattice-shaped discharge flow passage was cut. As a finish, 50 μm plating was applied. Using this die, a honeycomb was formed under the same conditions as in Example 1. As a result, similarly to Example 1, a honeycomb molded body was obtained in which a curved surface due to compression was formed in the corner portion of the cell cross section and hardly cracked during dry firing.

[0017]

According to the die structure of the present invention, it is possible to provide a die for honeycomb forming which is excellent in workability of the die and is effective in improving the yield of molding and dry firing. Further, it was confirmed that the honeycomb formed body obtained by this was strong against temperature change and external force during use.

[Brief description of drawings]

FIG. 1 is a view showing a pin structure of a base according to the present invention.

FIG. 2 is a view showing another pin structure of the base according to the present invention.

FIG. 3 is a cross-sectional perspective view of a general conventional die.

FIG. 4 is a view showing a pin structure of a general conventional base.

FIG. 5 is a diagram showing a pressure distribution of a mouthpiece flow channel according to the present invention.

FIG. 6 is a view showing a pin structure of a base according to a conventional technique.

FIG. 7 is a view showing a pin structure of a base according to a conventional technique.

[Explanation of symbols]

1 ... Feeding channel, 2 ... Discharging channel (molding groove), 3 ... Pin, 4
... pin discharge end apex, 5 ... (pin apex) chamfer, 6
... intersection of discharge channels, 7 ... base, 8 ... conventional pin corner removing section.

Claims (5)

[Claims] 1. A discharge flow path comprising a grid-shaped groove corresponding to a cross-sectional shape of a honeycomb molded body to be extruded, and a supply flow path for supplying paste to an intersection of the grooves, and the supplied paste is provided. In a die for forming a honeycomb formed into a continuous lattice-like body, a chamfered portion having a predetermined oblique angle with respect to the discharge-formed body is formed at the apex of the outlet ends of the plurality of pins defined by the lattice-like grooves. A die for forming a honeycomb characterized by being formed. 2. The honeycomb forming die according to claim 1, wherein the chamfered portion has a chamfered depth of 1/3 or less of a groove depth. 3. The honeycomb forming die according to claim 1, wherein a tangential clearance angle α of the chamfered portion with respect to the honeycomb formed body is 20 ° <α. 4. A spinneret provided with a discharge channel formed of lattice-shaped grooves corresponding to a cross-sectional shape of an extruded honeycomb molded body, and a feed channel for supplying paste to an intersection of the grooves,
In the method of forming the supplied paste into a continuous honeycomb formed body, the formed body is formed by shifting the time when the formed body is discharged and separated from the discharge flow path at the intersection of the grooves earlier than other portions. Body manufacturing method. 5. A paste is supplied to a honeycomb die having a discharge flow path having a grid-shaped groove corresponding to a cross-sectional shape of an extruded honeycomb molded body and a feed flow path for supplying paste at an intersection of the grooves. In the method of molding the paste into a continuous honeycomb molded body, a surface having a predetermined oblique angle with respect to the discharged molded body at the discharge side vertex of the outlet ends of the plurality of pins defined by the grid-like grooves. Forming a chamfered chamfer and using the honeycomb forming die having the chamfered chamfer formed to shift the time when the molded body is discharged and separated from the discharge flow path at the intersection of the lattice-shaped grooves earlier than other parts A method for manufacturing a honeycomb formed body, comprising: