JPH05124021A - Extrusion molding method for honeycomb molded item - Google Patents

Abstract

PURPOSE:To provide an extrusion molding method of a honeycomb filter wherein, when a honeycomb molded item is manufactured by means of an extrusion molding machine, generation of deflection and strain in the molded item can be prevented beforehand and a large honeycomb filter and a honeycomb filter having thin cell wall can be manufactured surely. CONSTITUTION:A molded item F mainly comprising silicon carbide delivered from an extrusion molding machine 1 is introduced into a refrigerated tank 10 including refrigerant C to freeze the item immediately, so that the item F maintains a constant shape.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a honeycomb filter from a molding raw material mainly composed of silicon carbide, and more particularly to a method for molding a molded body for manufacturing the filter by an extruder. Is.

[0002]

2. Description of the Related Art Conventionally, the problems to be solved by the invention
As this type of method, for example, a method already disclosed by the present inventors in Japanese Patent Laid-Open No. 2-34333 is known. In this conventional method, a step (a) of preparing a plastic molding raw material by blending a silicon carbide powder, a binder and a dispersion solvent, and a step of manufacturing a honeycomb green body from the molding raw material using an extruder. (b) The step of freezing the green molded body in a state where the entire outer surface of the green molded body is covered with an airtight film, and maintaining the soft green molded body in a constant shape (c), drying the green molded body under reduced pressure The step (d) of removing the dispersion solvent has a plurality of cells by undergoing step (e) of sealing the end openings of the obtained green body in a checkerboard pattern and firing the molded body. A honeycomb filter is manufactured. In this manufacturing method, by providing the step (c) immediately before the drying step (d), the occurrence of cracks due to the difference in the drying speed inside and outside the molded body was prevented.

However, the green molded body immediately after extrusion molding is relatively soft, and it is difficult to maintain the green molded body in a constant shape. The diameter and the thickness of the inner wall of the cell are naturally subject to certain restrictions. For example, when the thickness of the cell wall of the honeycomb molded body is 0.3 mm or less and the outer diameter of the molded body is 140 mm or more, the molding itself is difficult because of deformation and distortion during molding.

Further, in the conventional method, as in the step (c), it is necessary to coat the outer surface of the formed body having low physical strength with an airtight film, which is not only troublesome, but also depending on how to handle it. The shape could be deformed or distorted.
Therefore, it is necessary to pay close attention to the handling of the green molded body, and there is a problem that the manufacturing is time-consuming.

The present invention has been made in view of the above circumstances, and an object thereof is to prevent deformation and distortion occurring in a green formed body when a honeycomb formed body is manufactured by an extrusion molding machine. It is an object of the present invention to provide an extrusion molding method of a honeycomb molded body which can reliably manufacture a honeycomb filter having a larger size and a cell wall having a thinner wall than the conventional one.

[0006]

Means and Actions for Solving the Problems In order to solve the above problems, the present invention provides a method of forming a forming raw material mainly made of silicon carbide into a honeycomb shape by an extrusion molding machine, wherein By introducing the discharged honeycomb molded body into a freezing tank containing a refrigerant,
It is frozen continuously.

According to the above method, the extruded green compact can be immediately frozen without directly contacting the soft honeycomb green compact, and the green compact can be held in a constant shape. Therefore, even in the case of a large-sized honeycomb molded body or a honeycomb molded body having thin cell walls, the molded body is not deformed or distorted.

The extrusion molding method of the honeycomb molded body of the present invention will be described in detail below with reference to the drawings. Silicon carbide powder is used as the main raw material for molding the filter. Further, a binder such as methyl cellulose, polyvinyl alcohol, lignin sulfonate and a phenol resin, and a dispersion solvent such as water, cyclohexane and benzene are blended with the main raw material.

The above mixture is sufficiently kneaded with a conventional stirrer such as a Henschel mixer to prepare a high-viscosity raw material B for molding. In the method of the present invention, it is preferable to use the vertical extruder 1 as a means for extrusion molding. As shown in FIG. 1, the extrusion molding machine 1 includes a vertical cylinder 2 for containing a molding raw material B.
And a molding material B is provided outside the cylinder 2.
A vacuum pump 3 is provided for degassing. Further, an extrusion die 4 is disposed at the molded body discharge port 2a of the cylinder 2, and the extrusion die 4 is formed with a hole for forming the forming raw material B into a honeycomb shape.

A plunger 5 for pushing the molding raw material B toward the discharge port 2a is housed in the cylinder 2 so as to be vertically movable, and a hydraulic unit 6 for driving is connected to the plunger 5. ing. And the vacuum pump 3
And the hydraulic unit 6 is electrically connected to the control device 7,
The drive amount and drive timing of the vacuum pump 3 and the hydraulic unit 6 are determined based on the output signal of the control device 7.

As shown in FIG. 1, a cutting device 8 is provided on the discharge port 2a side of the cylinder 2 in order to cut the molded body F continuously discharged from the extrusion die 4 into a cylindrical shape. There is. Further, inside the freezing tank 10, a gripping device 9 for gripping the outer peripheral surface of the molded body F when cutting the molded body F is provided.

As shown in FIG. 2, when a predetermined amount of the molding raw material B is supplied into the cylinder 2 and the plunger 5 is moved downward, the molding raw material B is pressure fed to the extrusion die 4 side.
The forming raw material B is extruded from the extrusion die 4. At this time, the forming raw material B is formed into a honeycomb-shaped formed body F having a large number of cells, and is continuously discharged from the discharge port 2a side. Further, the molded body F is gradually introduced into the freezing tank 10 and is continuously frozen by the refrigerant C filled in the freezing tank 10. As a result, the soft green molded body F immediately after molding is not deformed or distorted, and
Becomes a freeze-molded body F ′ having a predetermined physical strength by freezing.

It is desirable that a freezing tank 10 is arranged close to the molded body discharge port 2a side of the cylinder 2. The reason is that since the honeycomb-shaped forming raw material B discharged from the extrusion die 4 can be frozen in a short time, the possibility of deformation or distortion of the honeycomb-shaped green body F is extremely reduced. ..

The refrigerant C is preferably at least one of dry ice, CFC, liquid nitrogen and liquid oxygen. Liquid refrigerant C generally has a larger endothermic capacity than gaseous refrigerant, and is excellent in that when used as refrigerant C, the liquid temperature is unlikely to rise. Further, by immersing the green compact F in the refrigerant C, the entire compact F can be cooled uniformly and within a short time.

Further, as shown in FIGS. 3 and 4, it is desirable that the honeycomb formed body F be discharged into a predetermined amount, frozen, and then cut into a predetermined length. The green body F is obtained by extrusion-molding a plastic material, and plastic deformation easily occurs due to the pressing force during cutting. Further, in general, a portion that is deformed or distorted is cut and removed in a later step, but this is not preferable because the loss of expensive raw materials increases. Therefore, it is preferable that the freeze-molded body F ′ is gripped by the gripping device 9 (see FIG. 3), and in this state, the cutting device 8 is used to cut into a predetermined length (see FIG. 4).

It is preferable that the extrusion molding speed of the molded body F and the cutting speed of the frozen molded body F'be synchronized to carry out the extrusion molding work and the cutting work continuously. for that purpose,
For example, there is a method in which the cutting device 8 and the gripping device 9 are electrically connected to the control device 7, respectively, and the control portion is shared. Then, for example, if the freezing tank 10 is separated from the extruder 1, the frozen molded body F ′ can be taken out from the freezing tank 10. Further, productivity can be improved by continuously performing the above-mentioned work.

Each embodiment in which a honeycomb filter is manufactured by applying the honeycomb molded body extrusion molding method of the present invention will be described in detail below with reference to the drawings.

[0018]

EXAMPLE In this example, a silicon carbide fine powder 1 having an average particle size of 0.28 μm and 96.2% of which is β-type crystal.
8 parts by weight of methyl cellulose and 23 parts by weight of water were mixed with 00 parts by weight and uniformly mixed with a Henschel mixer to obtain a raw material B for molding.

Then, as shown in FIG. 1, after a predetermined amount of the molding raw material B is supplied into the cylinder 2 of the extrusion molding machine 1, the plunger 3 is degassed by the vacuum pump 3 while the plunger is being degassed. Moved 5 down. Thereafter, as shown in FIG. 2, a honeycomb-shaped molded body F having a large number of cells was formed into 5
It was continuously extruded through the holes of the extrusion die 4 at a speed of 0 mm / sec. In addition, in the freezing tank 10 provided in the vicinity of the molded body discharge port 2a, a liquid refrigerant (substance name Freon R113, temperature-3
(0 ° C.) C, and the molded body F is filled with the refrigerant C.
Was gradually introduced into a frozen molded body F ′. Then, after discharging a predetermined amount of the molded body F, the driving of the plunger 5 was stopped, and the gripping device 9 gripped the outer peripheral surface of the frozen molded body F ′ (see FIG. 3). In this state, drive the cutting device 8,
The freeze-molded body F ′ was cut so that the length in the axial direction was 170 mm (see FIG. 4). Then, the cut frozen molded body F ′ was taken out from the freezing tank 10. The above series of steps are continuously performed, and the axial length is 150 mm and the outer diameter is 230 mm.
mm, the cell pitch was 2 mm, the number of cells was 170 cells / square inch, and a honeycomb molded body F having a cell inner wall thickness of 0.2 mm was manufactured. When the external shape and the cell shape of the obtained molded body F were examined, no deformation or distortion was observed.
Therefore, according to the method of this example, it was found that even a molded body F having a large outer diameter and a small cell wall thickness can be reliably manufactured.

Next, the molded body F is charged into a vacuum dryer, and for 40 hours at 40 ° C. under a reduced pressure condition of 0.1 to 1 Torr.
Was dried. Then, the molded body F dried under reduced pressure
After sealing the openings at both ends in a checkerboard pattern with a sealing material, the mixture was placed in a Tammann-type firing furnace and fired at 2200 ° C. for 4 hours in an argon gas atmosphere to obtain a desired honeycomb. Got a filter. As a result, there was no peeling or variation in the sealed portion, which was extremely suitable.

[0021]

As described above in detail, according to the extrusion molding method for a honeycomb molded body of the present invention, when the honeycomb molded body is manufactured by the extrusion molding machine, the deformation or distortion occurring in the green molded body can be prevented. It is possible to prevent this, and thus it is possible to reliably manufacture a large-sized honeycomb filter having thin cell walls.

[Brief description of drawings]

FIG. 1 is a schematic view showing an extruder, a freezing tank, a gripping device, and a cutting device used in a method for manufacturing a honeycomb formed body of the present invention.

FIG. 2 is a schematic view showing a state where a molding raw material is extruded from an extrusion die.

FIG. 3 is a schematic view showing a state in which a freeze-molded body is gripped by a gripping device.

FIG. 4 is a schematic view showing a state in which a freeze-molded body is cut by a cutting device.

[Explanation of symbols]

B raw material for molding, 1 extrusion molding machine, F (honeycomb) molded body, C refrigerant, 10 freezing tank, 2a (molded body) discharge port.

Claims (4)

[Claims] 1. A method for forming a forming raw material (B) mainly made of silicon carbide into a honeycomb shape by an extrusion molding machine (M), wherein a honeycomb formed body (F) discharged from the extrusion molding machine (1) is A method for extrusion-molding a honeycomb formed body, characterized by continuously freezing by introducing the refrigerant (C) into a freezing tank (10). 2. The honeycomb formed body according to claim 1, wherein a freezing tank (10) is disposed in close proximity to the formed body discharge port (2a) side of the extruder (1). Extrusion method. 3. The extrusion molding method for a honeycomb molded body according to claim 1, wherein the refrigerant (C) is at least one of dry ice, freon, liquid nitrogen and liquid oxygen. 4. The extrusion molding method for a honeycomb formed body according to claim 1, wherein the honeycomb formed body (F) is discharged after being discharged by a predetermined amount, frozen, and then cut. ..