JP2008132752A - Extruder, extrusion molding method, and manufacturing process of honeycomb structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an extruder which has small abrasion of a blade part, etc. of a screw, a long life, and can manufacture a molding body having extremely low possibility of generating a defect, etc., an extrusion molding method using the extruder, and a manufacturing process of a honeycomb structure using the extruder and the extrusion molding method. <P>SOLUTION: In the extruder equipped with a screw disposed in a sealed space and having the blade part for extruding a molding material, and a die for molding the extruded molding material; wherein the space is held in a depressurized atmosphere, and a high-hardness covering layer is formed at least in the blade part. The extrusion molding method using the extruder is provided, and the manufacturing method of the honeycomb structure using the extruder and the extrusion molding method is provided. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to an extruder, an extrusion molding method, and a method for manufacturing a honeycomb structure.

Recently, it has become a problem that particulates such as soot contained in exhaust gas discharged from internal combustion engines such as vehicles such as buses and trucks and construction machinery cause harm to the environment and the human body.
Thus, various honeycomb filters using a honeycomb structure made of porous ceramics have been proposed as filters for collecting particulates in exhaust gas and purifying the exhaust gas.

Conventionally, when manufacturing a honeycomb structure, first, a ceramic powder, which is a raw material powder, and a binder are dry-mixed, and a dispersion medium is added and mixed to prepare a wet mixture. Then, the wet mixture is continuously extruded with a die, and the extruded molded body is cut into a predetermined length to produce a prismatic honeycomb molded body.

Next, the obtained honeycomb formed body is dried using microwave drying or hot air drying, and the dried honeycomb formed body is cut again to an accurate length, and then predetermined cells are sealed. Then, a honeycomb formed body in which any one end portion of the cell is sealed with the sealing material layer is manufactured. Thereafter, the honeycomb formed body is degreased, and then the degreased honeycomb formed body is placed on a firing jig and fired to produce a honeycomb fired body.

After this, after installing a void holding material on the side surface of the honeycomb fired body, a sealing material paste is applied, and the honeycomb fired bodies are bonded to each other through the gap holding material, and a sealing material layer (adhesive layer) An aggregate of honeycomb fired bodies in a state in which a large number of honeycomb fired bodies are bundled together is manufactured. Next, the obtained honeycomb fired body aggregate is cut into a predetermined shape such as a cylinder or an elliptical column using a cutting machine or the like to form a ceramic block, and finally, a seal is formed on the outer periphery of the ceramic block. The manufacturing of the honeycomb structure is completed by applying the material paste to form the sealing material layer (coat layer).

In the above manufacturing process, when a honeycomb formed body is manufactured, the formed formed body needs to have a uniform composition. For this reason, usually, as described above, after the ceramic powder and the binder are dry-mixed, the powder mixture and the liquid dispersion medium are mixed and mixed using a mixer, and then the extrusion provided with a screw again. Mixing is performed with a molding machine, and extrusion molding is performed with a die.

However, in a normal extruder, when a wet mixture containing ceramic powder is mixed with a screw, the blades constituting the screw are worn by the ceramic powder, and the screw must be replaced within a short period of time. .

Further, if the inside of the extrusion molding machine is at normal pressure, air may be easily taken into the wet mixture at the time of mixing with a screw, and a molded body having bubbles inside may be produced.

The present invention has been made to solve the above-mentioned problems, and is an extrusion that can produce a molded body that has little wear on the blades of the screw, has a long life, and has a very low possibility of occurrence of defects. It is an object of the present invention to provide a molding machine, an extrusion molding method using the extrusion molding machine, and a method for manufacturing a honeycomb structure using the extrusion molding machine and the extrusion molding method.

That is, the extrusion molding machine of the present invention is an extrusion molding machine that is disposed in a sealed space and includes a screw having a blade portion that extrudes a molding material and a die that molds the extruded molding material.
The inside of the space is maintained in a reduced pressure atmosphere, and a high hardness coating layer is formed at least on the blade portion.

In the extrusion molding machine, the main component of the high-hardness coating layer is preferably tungsten carbide, and the surface roughness Ra of the high-hardness coating layer is preferably 10 μm or less. The porosity of the high hardness coating layer is desirably 0.3% or less, and the maximum dimension of the concave portion on the surface of the high hardness coating layer is desirably 1 to 50 μm.
Further, as described above, when the main component of the high hardness coating layer is tungsten carbide, it is desirable that the binder for forming the high hardness coating layer is nickel.

Further, the extrusion molding machine includes a plurality of screws and the same number of dies as the plurality of screws, and after the molding material is extruded by one screw and the dies, it is extruded again by another screw and the dies. It is desirable that the extrusion molding machine is provided with a cutting member for cutting the molding material extruded through the one screw and the die.

The extrusion molding method of the present invention uses an extrusion molding machine that is disposed in a sealed space and has a screw having a blade portion that extrudes a molding material, and a die that molds the extruded molding material. In addition to mixing the wet mixture containing the mixture, and continuously extruding the wet mixture through the die provided at the outlet of the space, thereby continuously forming a columnar molded body. And
The inside of the space is maintained in a reduced pressure atmosphere, and a high hardness coating layer is formed at least on the blade portion.

In the extrusion molding method, the main component of the high hardness coating layer is preferably tungsten carbide, and the surface roughness Ra of the high hardness coating layer is preferably 10 μm or less. The porosity of the high hardness coating layer is desirably 0.3% or less, and the maximum dimension of the concave portion on the surface of the high hardness coating layer is desirably 1 to 50 μm.
Further, as described above, when the main component of the high hardness coating layer is tungsten carbide, it is desirable that the binder for forming the high hardness coating layer is nickel.
In the extrusion method, the pressure in the space is desirably 50 to 100 kPa lower than the atmospheric pressure, and the moisture content of the wet mixture is desirably 10 to 20% by weight.

Further, in the extrusion molding method, the extruder includes a plurality of screws and the same number of dies as the plurality of screws, and after being mixed by one screw, continuously extruded through the one die. It is desirable to mix the wet mixture again with another screw and continuously extrude through another die.
In the extrusion molding method, the extrusion molding machine preferably includes a cutting member that cuts the molding material extruded through the one screw and the die.

In the method for manufacturing a honeycomb structure of the present invention, a wet mixture containing an inorganic powder is obtained by wet mixing, and then an extrusion molding process for forming the wet mixture is performed, so that a large number of cells penetrating in the longitudinal direction are formed on the cell wall. A honeycomb structured body manufacturing method for manufacturing a columnar honeycomb formed body arranged side by side, and firing the honeycomb formed body to manufacture a honeycomb structured body made of a honeycomb fired body,
The extrusion molding step includes an extrusion molding machine that is disposed in a sealed space, has a blade portion that extrudes a molding material, and includes a screw having at least a high-hardness coating layer formed on the blade portion, and a die. use,
The wet mixture is mixed while keeping the inside of the space in a reduced pressure atmosphere, and the wet mixture is continuously extruded through the die provided at the outlet of the space.

In the method for manufacturing a honeycomb structured body, the main component of the high hardness coating layer is preferably tungsten carbide, and the surface roughness Ra of the high hardness coating layer is preferably 10 μm or less. The porosity of the high hardness coating layer is desirably 0.3% or less, and the maximum dimension of the concave portion on the surface of the high hardness coating layer is desirably 1 to 50 μm.
Further, as described above, when the main component of the high hardness coating layer is tungsten carbide, it is desirable that the binder for forming the high hardness coating layer is nickel.
In the method for manufacturing the honeycomb structure, the pressure in the space is preferably 50 to 100 kPa lower than the atmospheric pressure. The moisture content of the wet mixture is desirably 10 to 20% by weight.

In the method for manufacturing the honeycomb structure, the extrusion molding machine includes a plurality of screws and the same number of dies as the plurality of screws, and after being mixed by one screw, continuously extruded through the one die. It is desirable to mix the wet mixture again with another screw and continuously extrude through another die.
In the method for manufacturing a honeycomb structure, the extruder preferably includes a cutting member that cuts the molding material extruded through the one screw and the die.

According to the extruder of the present invention, since the sealed space is maintained in a reduced-pressure atmosphere, even when the wet mixture is kneaded with a screw, the pores are not caught inside, and the uniform composition is obtained. At the same time, it is physically uniform, and there is no deviation in shape and composition, and a molded body having a shape almost as set can be produced.

In addition, since at least the blade portion has a high-hardness coating layer, even when a wet mixture containing ceramic powder is kneaded, the blade portion is less worn and without replacing parts such as screws over a long period of time. Thus, it is possible to continue producing the molded body efficiently.

In addition, according to the extrusion molding method of the present invention, the column-shaped molded body is continuously molded using the above-described extrusion molding machine in which the sealed space is maintained in a reduced-pressure atmosphere, so that the wet mixture is kneaded with a screw. Even if it is performed, pores are not bitten inside, it becomes a uniform composition, it is physically uniform, there is no bias in shape and composition, and a molded body with a shape almost as set is produced Can do.

In addition, since at least the blade portion has a high-hardness coating layer, even when a wet mixture containing ceramic powder is kneaded, the blade portion is less worn and without replacing parts such as screws over a long period of time. Thus, it is possible to continue producing the molded body efficiently.

Furthermore, according to the method for manufacturing a honeycomb structure of the present invention, since the honeycomb molded body is manufactured using the above-described extrusion molding machine and extrusion molding method, even if the wet mixture is kneaded with a screw, the pores are formed inside. The honeycomb molded body can be made into a uniform composition, is physically uniform, has no bias in shape and composition, and has a shape almost as set. It is possible to manufacture a honeycomb structure having characteristics almost designed using

Further, since at least the blade part of the extruder is formed with a high hardness coating layer, even if a wet mixture containing a ceramic powder is kneaded, the blade part is less worn, and parts such as screws are used over a long period of time. Thus, it is possible to continue to produce a ceramic molded body efficiently without replacing.

The extrusion molding machine of the present invention is an extrusion molding machine including a screw having a blade portion that is disposed in a sealed space and extrudes molding material, and a die that molds the extruded molding material.
The inside of the space is maintained in a reduced pressure atmosphere, and a high hardness coating layer is formed at least on the blade portion.

Further, the extrusion molding method of the present invention uses an extrusion machine that is disposed in a sealed space and has a screw having a blade portion that extrudes the molding material, and a die that molds the extruded molding material. An extrusion method for continuously forming a columnar shaped body by mixing a wet mixture containing an inorganic powder and continuously extruding the wet mixture through the die provided at the outlet of the space. Because
The inside of the space is maintained in a reduced pressure atmosphere, and a high hardness coating layer is formed at least on the blade portion.

Hereinafter, the extrusion molding machine and the extrusion molding method of the present invention will be described.
The material of the inorganic powder contained in the wet mixture used in the present invention is not particularly limited, and examples thereof include nitride ceramics such as aluminum nitride, silicon nitride, boron nitride, and titanium nitride, silicon carbide, zirconium carbide, and titanium carbide. And carbide ceramics such as tantalum carbide and tungsten carbide, and oxide ceramics such as alumina, zirconia, cordierite, mullite, and aluminum titanate.

Of these, non-oxide ceramics are preferred, and silicon carbide is particularly preferred. It is because it is excellent in heat resistance, mechanical strength, thermal conductivity and the like.
In addition, a silicon-containing ceramic in which metallic silicon is blended with the above-described ceramic, a ceramic bonded with silicon or a silicate compound, and the like can be given. For example, a silicon carbide blended with metallic silicon is also preferably used. In this case, a ceramic molded body is produced using silicon carbide powder and metal silicon powder.

The wet mixture contains an organic binder, a dispersion medium liquid, and the like. Further, the wet mixture may contain a plasticizer and a lubricant.
The organic binder is not particularly limited, and examples thereof include methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, and polyethylene glycol. Of these, methylcellulose is desirable.
As for the compounding quantity of the said organic binder, 1-10 weight part is desirable with respect to 100 weight part of ceramic powder.

The dispersion medium liquid is not particularly limited, and examples thereof include water, an organic solvent such as benzene, and an alcohol such as methanol.
When water is used as the dispersion medium, the desirable lower limit of the amount of water in the wet mixture is 10% by weight, and the more desirable lower limit is 12% by weight. A desirable upper limit of the amount of water in the wet mixture is 20% by weight, and a more desirable upper limit is 15% by weight. If the water content is less than 10% by weight, cracks or the like are likely to occur in the molded body. On the other hand, if the water content exceeds 20% by weight, it is difficult to maintain a certain shape until the extruded molded body is dried. become.

Moreover, it is desirable that the water content of the molded body to be produced is also in the above range.
Therefore, it is desirable to prevent a change in the amount of water in the wet mixture by mixing the wet mixture while cooling the inside of the molding machine. This is because the viscosity of the wet mixture can be kept constant by keeping the water content constant.

It does not specifically limit as said plasticizer, For example, glycerol etc. are mentioned.
The lubricant is not particularly limited, and examples thereof include polyoxyalkylene compounds such as polyoxyethylene alkyl ether and polyoxypropylene alkyl ether.
Specific examples of the lubricant include polyoxyethylene monobutyl ether and polyoxypropylene monobutyl ether.

FIG. 1 is a cross-sectional view schematically showing an extrusion molding machine according to the present invention, and FIG. 2 (a) is a vertical cross-sectional view schematically showing the vicinity of a cutter constituting the extrusion molding machine. 2 (b) is a cross-sectional view taken along line AA.

FIG. 3 is a perspective view schematically showing a kneading push roller constituting an extrusion molding machine, FIG. 4 is a front view schematically showing an entanglement screw constituting an upper stage screw, and FIG. It is a front view which shows a W blade | wing screw.

The extruder 20 includes a two-stage screw mixer, an upper screw mixer 51 and a lower screw mixer 61, each having a screw shaft and a screw blade (blade portion). .

At one end of the upper screw mixer 51, a charging hopper 31 for receiving a wet mixture of raw materials mixed in advance is provided, and at the receiving port 59 below the charging hopper 31, the wet mixture is supplied to the upper screw mixer 51. A kneading push roller 52 is provided for pushing into the inside.

As shown in FIG. 3, the kneading push roller 52 is composed of a pair of kneading push rollers 52 a and 52 b having blades provided perpendicular to the rotation direction of the roller, and the wet mixture dropped through the charging hopper 31, After being pushed in between the pair of kneading push rollers 52 a and 52 b while kneading, it is rotated inward so as to push downward, and the wet mixture is supplied into the upper screw mixer 51.

The upper screw mixer 51 includes a feed screw 530 having a role of moving the wet mixture as well as kneading, an entanglement screw 532 (see FIG. 4) for mainly kneading the wet mixture, and a tip of the feed screw 530. The upper stage screw 53 which consists of the W blade | wing screw 534 (refer FIG. 5) provided in is provided. In the feed screw 530, screw blades (blade portions) 530b are spirally wound around the screw shaft 530a. The blades are kneaded and the wet mixture is pushed forward.

In the entanglement screw 532, as shown in FIG. 4, a plurality of screw blades (blade portions) 532b are formed so as to form a ring in the circumferential direction of the screw shaft 532a, and a part thereof is cut in an oblique direction. There is a portion without the screw blade (blade portion) 532b. The kneading further proceeds as the wet mixture passes through this portion.
In addition, as shown in FIG. 5, the W blade screw 534 has a screw blade (blade portion) 534b having a double helix shape, and a screw shaft 534a at the tip which is sharply thinned. It can be extruded.

At the other end of the upper screw mixer 51, an upper die (base) 54 (see FIGS. 2 (a) and 2 (b)) in which a number of through holes are formed is installed, and the wet mixture is a W blade screw. After passing through 534, it is pushed into this upper die 54, and the wet mixture is pushed out in a bar-like or udon noodle-like state.

As shown in FIGS. 2A and 2B, a decompression chamber 56 is provided in a portion of the upper die 54 where the wet mixture is pushed out, and the inside thereof is in a decompressed state close to a vacuum. The decompression chamber 56 is a part of a sealed space.
The insides of the upper screw mixer 51 and the lower screw mixer 61 are also kept at a reduced pressure. This is to prevent bubbles (air) from getting caught in the wet mixture. If bubbles are bitten into the wet mixture, defects due to the bubbles are likely to occur in the partition walls and the like when the molded body is produced.

An upper cutter 55 as a cutting member is provided in the decompression chamber 56 and in the vicinity of the upper die 54. That is, the blade 55 a of the upper cutter 55 exists inside the decompression chamber 56, and the air cylinder 57 provided in the decompression chamber 56 causes the blade portion to reciprocate up and down in the vicinity of the upper die 54. The wet mixture extruded into a more udon noodle shape (rod shape) is cut into fine lumps.

A large number of the cut small lumps fall into the receiving port 69 of the lower screw mixer 61 immediately below and are pushed into the lower screw mixer 61 by the kneading push roller 62.
The lower screw mixer 61 includes a lower screw 63 including a feed screw 630 and a W blade screw 634 provided at the tip thereof, and is quantitatively pushed into the die 64 at the tip portion.
In this way, by repeating kneading, the mixing proceeds sufficiently, a uniform mixture with respect to moisture, composition, etc., is continuously extruded from the die 64, and a rectangular column shape in which a large number of cells are formed in the longitudinal direction. The formed body is continuously formed.

In the extrusion molding machine 20 shown in FIG. 1, two screw mixers are provided for kneading. In the present invention, the number of screw mixers is not particularly limited, but 2 to 4 are desirable. If one unit is used, it may be difficult to sufficiently knead. Even if five units or more are provided, the degree of kneading does not change greatly, which is economically disadvantageous.

Further, in the extrusion molding machine 20 shown in FIG. 1, the wet mixture is pushed into the screw mixer by the kneading push roller, but may be pushed into the screw mixer by other means, and a charging hopper is simply formed. You may only have. Moreover, the combination of the screw provided in the inside of a screw mixer is not limited to the combination mentioned above, For example, it may be comprised only from the field screw and the other combination may be sufficient.

In the extruder 20, a high hardness coating layer is formed on at least the screw blades (blade portions) of the upper screw 53 and the lower screw 63 to prevent wear. This is because the blades are most likely to come into contact with the wet mixture and wear easily.

Further, it is desirable that a high hardness coating layer is formed on the entire surface of both the upper screw 53 and the lower screw 63. This is because the entire wear of the screw can be prevented.
The desirable lower limit of the thickness of the high-hardness coating layer is 300 μm, and the more desirable lower limit is 500 μm. The desirable upper limit of the thickness of the high hardness coating layer is 1200 μm, and the more desirable upper limit is 1000 μm.
If the thickness is less than 300 μm, sufficient wear resistance may not be ensured. On the other hand, if the thickness exceeds 1000 μm, peeling or cracking may occur.
The material of the screw is, for example, stainless steel, and the high hardness coating layer has higher hardness than the material of the screw.

In the present invention, the high hardness coating layer means a layer having a Vickers hardness (HV) of 1000 or more measured according to JIS Z 2244.
The Vickers hardness of the high hardness coating layer may be 1000 (HV) or more, but more preferably 2000 (HV) or more. This is because the wear resistance is particularly excellent.

Examples of the main component of the high-hardness coating layer include ceramic coating materials, industrial diamond, and plating films. Specific examples of the materials include tungsten carbide (HV: 2500) and titanium carbide (HV: 3600). ), Titanium nitride (HV: 1800-2500), cubic boron nitride (HV: 2700), CVD diamond (HV: 2500-4000), DLC (diamond-like carbon / HV: 2000-4000), ZrN (HV: 2000) ~2200), CrN (HV: 1800~2200 ), TiCN (HV: 2300~3500), TiAlN (HV: 2300~3300), Al 2 O 3 (HV: 2200~2400), Ti 3 (HV: 2300) WC-12% CO (HV: 1200) etc. Those with and the like. Specific examples of the plating film include, for example, electroless nickel plating (treated at about 400 ° C.) (HV: 1000), CrC ₄ (hard chromium carbide 4%) plating (HV: 1200), nickel plating (containing SiC) 2-6% by weight: 400 ° C. treatment) (HV: 1300-1400), ultra-hard chromium plating (HV: 1200), and the like.
In the present specification, the Vickers hardness of each material indicated in parentheses is an approximate value.

Of these, tungsten carbide is desirable. This is because, when a high-hardness coating layer is formed by thermal spraying, it is possible to easily form a layer that is uniform and has excellent adhesion to the blade portion (screw blade) and is firmly bonded. Further, the high hardness coating layer made of tungsten carbide can be formed at a relatively low cost.

Moreover, when forming the high hardness coating layer which has a tungsten carbide as a main component, it is desirable that the said high hardness coating layer is comprised including the binder component. And as a binder which comprises the said high-hardness coating layer, nickel, cobalt, etc. are mentioned, for example.
Of these, nickel is desirable. This is because nickel is excellent in corrosion resistance. In particular, as a high-hardness coating layer, when a thermal spray layer mainly composed of tungsten carbide with nickel as a binder is formed, tungsten is compared with when a thermal spray layer mainly composed of tungsten carbide with cobalt as a binder is formed. This is because there is little dropout of particles mainly composed of carbide.

The surface roughness Ra of the high hardness coating layer is desirably 10 μm or less.
This is because when the surface roughness Ra of the high hardness coating layer exceeds 10 μm, the extrusion efficiency is lowered.
In addition, in this specification, extrusion efficiency means the ratio with respect to the ideal value of the extrusion amount (volume) with respect to the rotation speed of a screw, and the said extrusion efficiency will become high, so that this extrusion amount is large.
The initial surface roughness Ra (when not used) of the high hardness coating layer is preferably 1 μm or less. This is because when used over a long period of time, it is suitable for securing the above-described surface roughness Ra.

Further, the lower limit of the surface roughness Ra is not particularly limited, and the smaller the better, from the viewpoint of extrusion efficiency. However, as will be described later, the surface roughness Ra of the high-hardness coating layer can be adjusted by polishing treatment, but the more the surface roughness Ra is reduced, the more time and cost are required for the treatment. Moreover, even if it is made too small, the effect of reducing the surface roughness Ra is not so improved. From such points, the lower limit of the surface roughness Ra is preferably 0.1 μm.
The surface roughness Ra is a center line average roughness according to JIS B 0601 (1994), and can be measured by, for example, a stylus type surface roughness measuring instrument.

Moreover, when forming the said high-hardness coating layer, in order to make surface roughness Ra into the said range, you may perform the grinding | polishing process etc. which used buff grinding | polishing, a grindstone, or a sheet | seat as needed.
Examples of the buff used in the buffing include an abrasive-containing buff such as a disk-type buff, a flap-type buff and a spiral buff, and an abrasive-free buff such as a polypropylene non-woven cloth. Examples of the abrasive grains used in the abrasive grain-containing buff include aluminum silicate, aluminum oxide, silicon carbide and the like.

The porosity of the high hardness coating layer is desirably 0.3% or less.
This is because if the porosity exceeds 0.3%, it may be difficult to reduce the surface roughness Ra of the high hardness coating layer.
Specifically, a high hardness coating layer formed by thermal spraying will be described as an example. In a high hardness coating layer formed by thermal spraying, if the porosity is large, secondary particles having a relatively large diameter exist in the thermal spraying layer. This is because when such secondary particles having a large diameter fall off, the surface roughness Ra increases.
In the present specification, the porosity means an area ratio of a portion occupied by pores in an image obtained by photographing a cross section of the high hardness coating layer.

As for the maximum dimension of the recessed part in the surface of the said high-hardness coating layer, it is desirable that it is 1-50 micrometers.
In particular, when a high-hardness coating layer is formed by thermal spraying, it is desirable that the maximum dimension of the concave portion on the surface be in the above range. Usually, the recesses on the surface of the high-hardness coating layer formed by thermal spraying are caused by dropout of particles (primary particles and secondary particles), but when the maximum dimension of the recesses is in the above range, the surface roughness This is because Ra is not so large. The maximum size of the concave portion is preferably as small as possible. However, since the particle size of the primary particles constituting the high hardness coating layer formed by thermal spraying is usually 1 μm, the desirable lower limit of the maximum size is set to 1 μm. .
In the present specification, the maximum dimension of the concave portion on the surface of the high-hardness coating layer refers to the length of the longest opening portion of the concave portion. In addition, primary particles refer to the smallest unit particles that exist without breaking bonds between molecules, and secondary particles refer to particles formed by aggregating a plurality of primary particles.

The internal pressure of the screw mixer or the decompression chamber (the pressure in the space) is 50 to 100 kPa lower than the atmospheric pressure (that is, (atmospheric pressure −100 pKa) to (atmospheric pressure −50 kPa)). Is desirable.
This is because if the pressure is higher than (atmospheric pressure-50 kPa), it is easy to entrap bubbles in the wet mixture and defects and the like are likely to occur inside the molded body. On the other hand, when the pressure is smaller than (atmospheric pressure−100 kPa), since the vacuum is high, the wet mixture is dried and hardened, so that the moldability is deteriorated.
The pressure in the space is more preferably 60 to 100 kPa lower than the atmospheric pressure.

In this extrusion molding machine 20, the time from when the raw material enters the extrusion molding machine 20 until it is extruded is preferably 50 to 90 minutes. This is because it is necessary to make the entire composition uniform including water and the like by mixing well.
Moreover, as for the speed | rate at which a molded object is extruded in the case of extrusion molding, 3500-4500 mm / min is desirable. If it is less than 3500 mm / min, the production efficiency is lowered, which is not desirable. On the other hand, if it exceeds 4500 mm / min, it becomes difficult to obtain a ceramic molded body having the designed dimensions, and the produced ceramic molded body has defects. It tends to occur.

When kneading raw material powder containing inorganic powder having high hardness such as silicon carbide powder, if a normal metal material is used for the screw, the screw must be frequently replaced due to wear of the screw.
However, in the present invention, since a high-hardness coating layer is formed at least on the blade portion of the screw, it is less likely to be worn, and it is possible to operate without replacing the screw for a long period of time, resulting in an increase in equipment costs. Can be prevented. Usually, production can be continued for about 3 months without changing the screw.

Further, since the inside of the screw mixer is under reduced pressure, the wet mixture is less likely to bite the bubbles, and it is possible to prevent the molded body from being defective due to the bubbles. In addition, kneading in a screw mixer and extruding from a die (die) in which a large number of through holes are formed, and the extruded noodle-like (rod-like) wet mixture is further finely cut into fine lumps and then mixed. Therefore, the mixture can be sufficiently mixed without causing unevenness of mixing, resulting in a wet mixture having a uniform composition, and a molded product having uniform characteristics can be produced.

In this extrusion molding machine, the air cylinder 57 is provided in the decompression chamber 56 as the driving force of the cutter, but it is not limited to the air cylinder 57 as long as it can reciprocate, and an oil cylinder may be used. It may be a device.

Next, the manufacturing method of the honeycomb structure of the present invention will be described.
In the method for manufacturing a honeycomb structure of the present invention, a wet mixture containing an inorganic powder is obtained by wet mixing, and then an extrusion molding process for forming the wet mixture is performed, so that a large number of cells penetrating in the longitudinal direction are formed on the cell wall. A honeycomb structured body manufacturing method for manufacturing a columnar honeycomb formed body arranged side by side, and firing the honeycomb formed body to manufacture a honeycomb structured body made of a honeycomb fired body,
The extrusion molding step includes an extrusion molding machine that is disposed in a sealed space, has a blade portion that extrudes a molding material, and includes a screw having at least a high-hardness coating layer formed on the blade portion, and a die. use,
The wet mixture is mixed while keeping the inside of the space in a reduced pressure atmosphere, and the wet mixture is continuously extruded through the die provided at the outlet of the space.

As described above, in the method for manufacturing a honeycomb structure of the present invention, an extrusion molding machine equipped with a screw and a die is used, and a wet mixture containing an inorganic powder is kneaded in the extrusion molding machine and then extrusion molded. A columnar honeycomb formed body in which a large number of cells penetrating the cell wall are arranged with a cell wall therebetween, and the honeycomb formed body is fired to produce a honeycomb fired body, and the plurality of honeycomb fired bodies are bonded to the adhesive layer. Are bonded to each other, processed into a predetermined shape, and a honeycomb structure is manufactured by providing a sealing material layer on the outer periphery.

Although it does not specifically limit as said extruder, The extruder of this invention mentioned above can be used suitably. Also, the extrusion molding method is not particularly limited, but the above-described extrusion molding method of the present invention can be suitably used.
Therefore, here, the extrusion molding process will be described very simply, and the processes other than the extrusion molding process will be described in detail.

FIG. 6 is a perspective view schematically showing an example of the honeycomb structure, and FIG. 7A is a perspective view schematically showing the honeycomb fired body constituting the honeycomb structure, and FIG. ) Is a cross-sectional view taken along line AA.

In the honeycomb structure 130, a plurality of honeycomb fired bodies 140 as shown in FIG. 7A are bundled through a sealing material layer (adhesive layer) 131 to form a ceramic block 133, and the ceramic block 133 is further formed. A sealing material layer (coat layer) 132 is formed on the outer periphery of the substrate.
In the honeycomb fired body 140, as shown in FIGS. 7A and 7B, a large number of cells 141 are arranged in the longitudinal direction, and the cell walls 143 separating the cells 141 function as a filter. ing.

That is, in the cell 141 formed in the honeycomb fired body 140, as shown in FIG. 7B, either the inlet side or the outlet side end of the exhaust gas is plugged by the sealing material layer 142, and one cell The exhaust gas that has flowed into 141 always passes through the cell wall 143 that separates the cell 141 and then flows out from the other cell 141. When the exhaust gas passes through the cell wall 143, the particulates are separated from the cell wall 143. Captured at the part, the exhaust gas is purified.

Here, a method for manufacturing a honeycomb structure will be described by taking as an example the case of manufacturing a honeycomb structure made of silicon carbide using silicon carbide powder as the inorganic powder.
The material of the honeycomb structure manufactured by the manufacturing method of the present invention is not limited to silicon carbide, and the type of ceramic described in the section of the extruder can be used.

(1) In the method for manufacturing a honeycomb structured body of the present invention, first, a silicon carbide powder and an organic binder (organic powder) having different average particle diameters are dry mixed to prepare a mixed powder.

The particle size of the silicon carbide powder is not particularly limited, but it is preferable to have less shrinkage in the subsequent firing step, for example, 100 parts by weight of powder having an average particle size of 0.3 to 50 μm and 0.1 to 1.0 μm. A combination of 5 to 65 parts by weight of a powder having an average particle diameter of 5 to 65 parts by weight is preferred.
In order to adjust the pore diameter and the like of the honeycomb fired body, a method of adjusting the firing temperature is effective, but the pore diameter can be adjusted within a certain range by adjusting the particle size of the inorganic powder. it can.

(2) Next, a liquid plasticizer, a lubricant and water are mixed to prepare a mixed liquid. Subsequently, the mixed powder prepared in the step (1) and the mixed liquid are mixed with a wet mixer. By using and mixing, a wet mixture for producing a molded body is prepared.

Since the kind and amount of the organic binder, the kind of plasticizer and lubricant, the amount of water, and the like have been described in the extrusion method, description thereof is omitted here.

If necessary, a pore-forming agent such as balloons that are fine hollow spheres containing oxide ceramics, spherical acrylic particles, and graphite may be added to the wet mixture.

(3) The above wet mixture is mixed and prepared, and then conveyed to an extrusion molding machine equipped with the screw and the die described above by a conveyance machine. After sufficiently kneaded inside the extrusion molding machine, the wet mixture is passed through the die. A columnar honeycomb formed body in which a large number of cells penetrating in the direction are arranged side by side across the cell wall is manufactured.
Next, the honeycomb molded body is dried using a microwave dryer, a hot air dryer, a dielectric dryer, a vacuum dryer, a vacuum dryer, a freeze dryer, or the like, and near both ends of the honeycomb molded body after drying. Is cut to a predetermined length.
Then, if necessary, the end side of the inlet side cell group and the end side of the outlet side cell group at the inlet side are filled with a predetermined amount of sealing material paste as a sealing material, and the cells are To seal.

Although it does not specifically limit as said sealing material paste, The thing from which the porosity of the sealing material manufactured through a post process becomes 30 to 75% is desirable, For example, the thing similar to the said wet mixture can be used. .

Filling the plug material paste may be performed as necessary. When the plug material paste is filled, for example, a honeycomb structure obtained through a subsequent process is preferably used as a ceramic filter. In the case where the sealing material paste is not filled, for example, a honeycomb structure obtained through a subsequent process can be suitably used as a catalyst carrier.

(4) Next, the honeycomb formed body filled with the sealing material paste is degreased (for example, 200 to 600 ° C.) and fired (for example, 1400 to 2300 ° C.) under a predetermined condition, so that the whole A fired honeycomb body having a plurality of cells penetrating in the longitudinal direction arranged side by side across the cell wall, and sealing one end of each of the cells (FIG. 7 (a), ( b) can be produced.

As the conditions for degreasing and firing the honeycomb formed body, the conditions conventionally used when manufacturing a filter made of a porous ceramic can be applied.

(5) Next, if necessary, a gap holding material serving as a spacer is adhered to the side surface of the honeycomb fired body, and a sealing material paste serving as a sealing material layer (adhesive layer) is applied with a uniform thickness. Then, a sealing material paste layer is formed, and the process of sequentially laminating other honeycomb fired bodies on this sealing material paste layer is repeated to produce an aggregate of honeycomb fired bodies of a predetermined size.
In the method for manufacturing a honeycomb structure of the present invention, after assembling a required number of honeycomb fired bodies through the gap holding material, the gaps between the honeycomb fired bodies may be collectively filled with the sealing material paste. .

As said sealing material paste, what consists of an inorganic binder, an organic binder, an inorganic fiber, and / or an inorganic particle etc. are mentioned, for example.
Examples of the inorganic binder include silica sol and alumina sol. These may be used alone or in combination of two or more. Among the inorganic binders, silica sol is desirable.

Examples of the organic binder include polyvinyl alcohol, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, and the like. These may be used alone or in combination of two or more. Among the organic binders, carboxymethyl cellulose is desirable.

Examples of the inorganic fibers include ceramic fibers such as silica-alumina, mullite, alumina, and silica. These may be used alone or in combination of two or more. Among the inorganic fibers, alumina fibers are desirable.

Examples of the inorganic particles include carbides and nitrides, and specific examples include inorganic powders made of silicon carbide, silicon nitride, and boron nitride. These may be used alone or in combination of two or more. Among the inorganic particles, silicon carbide having excellent thermal conductivity is desirable.

Furthermore, a pore-forming agent such as a balloon, which is a fine hollow sphere containing an oxide-based ceramic, spherical acrylic particles, or graphite, may be added to the sealing material paste as necessary.
The balloon is not particularly limited, and examples thereof include an alumina balloon, a glass micro balloon, a shirasu balloon, a fly ash balloon (FA balloon), and a mullite balloon. Of these, alumina balloons are desirable.

(6) Next, this aggregate of honeycomb fired bodies is heated to dry and solidify the sealing material paste layer to form a sealing material layer (adhesive layer).
Next, using a diamond cutter or the like, the aggregate of the honeycomb fired bodies in which a plurality of honeycomb fired bodies are bonded through the sealing material layer is cut to produce a cylindrical ceramic block.
In addition, the shape of the ceramic block manufactured by this manufacturing method is not limited to a cylindrical shape, and includes an arbitrary column shape such as an elliptical column shape or a polygonal column shape.

Then, a sealing material layer (coat layer) is formed on the outer periphery of the honeycomb block using the sealing material paste. Through such a process, a honeycomb in which a plurality of honeycomb fired bodies are bonded to each other through a sealing material layer (adhesive layer) and a sealing material layer (coat layer) is provided on the outer periphery of a cylindrical ceramic block A structure (see FIG. 6) can be manufactured.

Further, in the method for manufacturing a honeycomb structure of the present invention, after that, a catalyst may be supported on the honeycomb structure as necessary.
The catalyst may be supported on the honeycomb fired body before producing the aggregate.
When the catalyst is supported, it is desirable to form an alumina film having a high specific surface area on the surface of the honeycomb structure, and to apply a promoter such as platinum and a catalyst such as platinum to the surface of the alumina film.

As a method for forming an alumina film on the surface of the honeycomb structure, for example, a method in which a honeycomb structure is impregnated with a solution of a metal compound containing aluminum such as Al (NO ₃ ) ₃ and heated, an alumina powder is contained. For example, the honeycomb structure may be impregnated with a solution to be heated and heated.
Examples of a method for applying a promoter to the alumina film include a method in which a honeycomb structure is impregnated with a solution of a metal compound containing a rare earth element such as Ce (NO ₃ ) ₃ and heated. .

As a method for imparting a catalyst to the alumina membrane, for example, a dinitrodiammine platinum nitric acid solution ([Pt (NH ₃ ) ₂ (NO ₂ ) ₂ ] HNO ₃ , platinum concentration 4.53% by weight) or the like is applied to the honeycomb structure. Examples of the method include impregnation and heating.
Alternatively, the catalyst may be applied by a method in which a catalyst is applied to the alumina particles in advance, and the honeycomb structure is impregnated with a solution containing the alumina powder to which the catalyst is applied and heated.

Further, the method for manufacturing a honeycomb structure described so far has a structure in which a plurality of honeycomb fired bodies are bundled through a sealing material layer (adhesive layer) (hereinafter also referred to as a collective honeycomb structure). However, the honeycomb structure manufactured by the manufacturing method of the present invention is a honeycomb structure in which a cylindrical ceramic block is composed of one honeycomb fired body (hereinafter also referred to as an integral honeycomb structure). May be.

When manufacturing such an integral honeycomb structure, the aggregated honeycomb structure is manufactured except that the size of the honeycomb molded body formed by extrusion molding is larger than that when manufacturing the aggregated honeycomb structure. A honeycomb formed body is manufactured by using the same method as that in the case of performing.
Here, the method of mixing the raw material powder and the like are the same as the method of manufacturing the aggregated honeycomb structure, and the description thereof is omitted here.

Next, similarly to the production of the aggregated honeycomb structure, the honeycomb formed body is dried using a microwave dryer, a hot air dryer, a dielectric dryer, a vacuum dryer, a vacuum dryer, a freeze dryer, or the like. . Next, a predetermined amount of a sealing material paste serving as a sealing material is filled in the outlet side end portion of the inlet side cell group and the inlet side end portion of the outlet side cell group, and the cells are sealed.
Thereafter, as in the production of the aggregated honeycomb structure, a ceramic block is manufactured by performing degreasing, firing, and deposit removal treatment, and if necessary, by forming a sealing material layer (coat layer), An integral honeycomb structure can be manufactured. By performing the deposit removal process, the sealing material layer can be satisfactorily formed.
Further, the above-mentioned integral honeycomb structure may be loaded with a catalyst by the method described above.

In the case where the honeycomb structure is manufactured by the manufacturing method as described above, when the aggregated honeycomb structure is manufactured, the main component of the material may be silicon carbide, metal silicon, and silicon carbide. Desirably, cordierite or aluminum titanate is desirable when producing an integral honeycomb structure.

Further, here, the honeycomb structure has been mainly described as a honeycomb filter (ceramic filter) used for the purpose of collecting particulates in exhaust gas. However, the honeycomb structure is a catalyst carrier (honeycomb catalyst) for purifying exhaust gas. Can also be used suitably.

The present invention will be described in more detail with reference to examples below, but the present invention is not limited to these examples.

(Example 1)
250 kg of α-type silicon carbide powder having an average particle size of 10 μm, 100 kg of α-type silicon carbide powder having an average particle size of 0.5 μm, and 20 kg of an organic binder (methyl cellulose) were mixed to prepare a mixed powder.
Next, separately, 12 kg of lubricant (Unilube manufactured by NOF Corporation), 5.6 kg of plasticizer (glycerin), and 64 kg of water are mixed to prepare a liquid mixture, and this liquid mixture and the mixed powder are wet-mixed. A wet mixture was prepared by mixing using a machine. At this time, the moisture content of the wet mixture is 14% by weight.

Next, using the extrusion molding machine equipped with the two-stage screw mixer shown in FIG. 1, the wet mixture is continuously fed from the feeding hopper 31 to perform extrusion molding to produce a long honeycomb molded body. Then, this was cut into a length of 25 cm, and then a drying process was performed to remove almost all moisture (reducing moisture content by almost 100%) using a dryer that used both microwaves and hot air, and a honeycomb formed body Was made.
In this extrusion molding machine 20, the vane portions constituting the upper screw 53 and the lower screw 63 have a thickness of 800 μm and a tungsten carbide having an initial surface roughness Ra of 0.6 μm as a main component. A high hardness coating layer (tungsten carbide film) was used.
The surface roughness Ra was adjusted by buffing. The surface roughness Ra was measured with a contact-type surface roughness measuring machine (manufactured by Tokyo Seimitsu Co., Ltd., Surfcom 804A).
Moreover, the pressure inside the extrusion molding machine was 65 kPa lower than the atmospheric pressure.
The tungsten carbide film was formed by forming a film by self-fluxing alloy spraying and then performing buffing so as to have the surface roughness. That is, Ni (nickel) was used as a binder, tungsten carbide and nickel were mixed and thermally sprayed, and then heat-welded to form a tungsten carbide film, and then buffed.

(Evaluation of shape of honeycomb molded body)
About the produced honeycomb molded body, the cell shape is mainly observed visually, and it is evaluated whether or not the cell has a desired shape without being partially cut. The amount of warpage was measured. And the thing with no cell cutting | disconnection and the curvature amount of less than 0.5 mm was evaluated as a good product. The results are shown in Table 1.

Note that the amount of warpage was measured using a warpage amount measuring jig.
As a jig for measuring the amount of warpage, in a straight square member having almost the same length as the entire length of the molded body, contact members having the same thickness are disposed at both ends of the square member, and the center of the square member is also provided. A scale slidable perpendicularly to the longitudinal direction of the square bar was used. Further, at the time of measurement, the contact member is brought into contact with the vicinity of both ends of the molded body, and then the warp amount measuring scale is moved to the molded body side, and the amount of movement of the scale when the molded body and the scale come into contact is read. The amount of warpage was measured.

(Measurement of wear amount of high hardness coating layer)
The operation by the extruder was continuously performed for 4000 hours and then decomposed, and the wear condition of the tungsten carbide film was visually observed.

(Examples 2 and 3 Reference Example 1)
A honeycomb molded body was produced in the same manner as in Example 1 except that the thickness of the high hardness coating layer of the molding machine was changed as shown in Table 1.
In the same manner as in Example 1, the shape evaluation of the honeycomb formed body and the wear amount of the high hardness coating layer were measured. The results are shown in Table 1.

(Reference Example 2)
A honeycomb molded body was produced in the same manner as in Example 1 except that the pressure inside the molding machine was changed to (atmospheric pressure -40 kPa).
In the same manner as in Example 1, the shape evaluation of the honeycomb formed body and the wear amount of the high hardness coating layer were measured. The results are shown in Table 1.

(Reference Examples 3 and 4)
A honeycomb formed body was produced in the same manner as in Example 1 except that the amount of water in preparing the liquid mixture was changed as follows. That is, in Reference Example 3, the amount of water was 34 kg, and in Reference Example 4, the amount of water was 130 kg.
In the same manner as in Example 1, the shape evaluation of the honeycomb formed body and the wear amount of the high hardness coating layer were measured. The results are shown in Table 1.

(Reference Example 5)
A honeycomb formed body was prepared in the same manner as in Example 1 except that the thickness of the high hardness coating layer was changed as shown in Table 1. However, in this reference example, since a crack was generated in the high hardness coating layer when the high hardness coating layer was formed, the honeycomb formed body was not manufactured.

(Comparative Example 1)
A honeycomb formed body was produced in the same manner as in Example 1 except that the high hardness coating layer was not formed.
In the same manner as in Example 1, the shape evaluation of the honeycomb formed body and the wear amount of the high hardness coating layer were measured. The results are shown in Table 1.
In addition, surface roughness Ra as used in this comparative example is surface roughness Ra of a blade | wing part main body.

As is apparent from the results shown in Table 1, the honeycomb formed body produced in the example had a good shape, and the wear amount of the high-hardness coating layer was less than 400 μm and the wear amount was small.
On the other hand, in Reference Example 1 and Comparative Example 1, the wear amount of the high-hardness coating layer was large. This is presumably because the high hardness coating layer was thin or the high hardness coating layer was not formed.

In the honeycomb molded body manufactured in Reference Examples 2 and 3, cell cutout was observed in some cells.
In this regard, the honeycomb molded body of Reference Example 2 was formed by a molding machine having a high internal pressure (atmospheric pressure −40 kPa), so it is considered that bubbles were entrained in the wet mixture. It is thought that the body had a low moisture content in the wet mixture.
Further, in the honeycomb molded body manufactured in Reference Example 4, a large warp exceeding 0.5 mm occurred. This is presumably because the moisture content in the wet mixture was high.
In Reference Example 5, when the high hardness coating layer was formed, cracks occurred in the high hardness coating layer. This is presumably because the high-hardness coating layer was thick.

(Examples 4 to 9, Reference Example 6)
A honeycomb formed body was manufactured in the same manner as in Example 1 except that the initial surface roughness Ra of the high hardness coating layer formed on the surface of the screw was set to the size shown in Table 2.
Here, the extrusion efficiency in an extruder was evaluated by the following method, and the results are shown in Table 2.
First, assuming that the rotation speed of the lower screw 63 is 10 rotations / min, the extrusion speed of the molded body is measured per unit time, and the volume of the extruded molding material is calculated. Next, the ideal extrusion volume of the molding material is calculated based on the pitch (interval) of the blade portion of the screw, the diameter of the pitch circle (circle drawn by the tip of the blade portion), and the number of rotations according to the unit time. To do. Then, the extrusion efficiency (%) was obtained by dividing the actually measured extrusion volume by the ideal extrusion volume.
FIG. 8 shows the relationship (test results) between the initial surface roughness Ra (μm) and the extrusion efficiency (%) in Examples 4 to 9 and Reference Example 6.

As is apparent from the results shown in Table 2 and FIG. 8, when the surface roughness Ra of the high-hardness coating layer is 10 μm or less, an extrusion efficiency of about 11% or more can be ensured. When the surface roughness Ra of the hardness coating layer exceeds 10 μm, the extrusion efficiency is greatly reduced.
In particular, when the surface roughness Ra of the high-hardness coating layer is as small as 5 μm or less, it was revealed that an extrusion efficiency of about 21% or more can be secured, and the working efficiency is excellent.

(Examples 10 to 12, Reference Example 7)
A honeycomb formed body was manufactured in the same manner as in Example 1 except that the initial surface roughness Ra of the high hardness coating layer formed on the surface of the screw and the porosity of the high hardness coating layer were set to the sizes shown in Table 3. Produced. The porosity of the high hardness coating layer was adjusted by changing the fading conditions after spraying. Here, fading refers to a process of remelting the coating layer after thermal spraying.
Here, after the operation of the extruder was continuously performed for 4000 hours, the surface roughness Ra of the high-hardness coating layer was measured, and the maximum dimension of the recess formed on the surface of the high-hardness coating layer was measured. . The results are shown in Table 3.
Note that the maximum dimension of the recess was calculated based on an electron microscope image of the surface of the high hardness coating layer.

(Reference Example 8)
A honeycomb formed body was produced in the same manner as in Example 1 except that the tungsten carbide film was formed by the following method.
The tungsten carbide film was formed by using Co (cobalt) as a binder, mixing tungsten carbide and cobalt and spraying them to form a tungsten carbide film by heating and then buffing.
In this reference example, in the same manner as in Example 10, after the operation of the extruder was continuously performed for 4000 hours, the surface roughness Ra of the high hardness coating layer was measured, and the surface of the high hardness coating layer was measured. The maximum dimension of the formed recess was measured. The results are shown in Table 3.
In Examples 10 to 12 and Reference Examples 7 and 8, the relationship between the porosity (%) and the surface roughness Ra (μm) after continuous operation for 4000 hours is shown in FIG. 9A, the porosity (%) and the high hardness. FIG. 9B shows the relationship with the maximum dimension (μm) of the concave portion on the surface of the coating layer, and FIG. 9C shows the relationship between the porosity (%) and the extrusion efficiency (%).

As apparent from the results of Examples 10 to 12 and Reference Examples 7 and 8 shown in Table 3 and FIGS. 9A, 9B, and 9C, the porosity of the high-hardness coating layer is 0.3%. If it is less than 4,000 hours, it is possible to maintain a surface roughness Ra of 10 μm or less that can ensure a sufficient extrusion efficiency even after continuous operation for 4000 hours, and the concave portions formed on the surface of the high-hardness coating layer. The maximum dimension tends to be as small as 50 μm or less.
On the other hand, as in Reference Example 7, when the porosity of the high hardness coating layer is larger than 0.3%, the surface roughness Ra is increased. And when surface roughness Ra becomes larger than 10 micrometers, as already shown in the reference example 6, extrusion efficiency will fall large. When the porosity exceeds 0.3%, the surface roughness Ra increases because the particle size of the particles constituting the tungsten carbide film tends to be large. It is also clear from the fact that the maximum dimension of the recesses on the surface of the layer is larger than 50 μm.

Further, as is apparent from the results of Reference Example 8, when Co was used as the binder of the tungsten carbide film, the surface roughness Ra after 4000 hours of continuous operation was as large as 26 μm. This is presumably because the tungsten carbide film is made of Co, so the corrosion resistance of the tungsten carbide film is inferior, and the particles constituting the tungsten carbide film are more frequently dropped. In addition, when the electron micrograph image at the time of calculating the maximum dimension of the recessed part of the surface of a high-hardness coating layer was observed, the number of the recessed parts currently formed compared with Example 10 was large.

It is sectional drawing which shows typically the extrusion molding machine which concerns on this invention. (A) is a longitudinal cross-sectional view which shows typically the cutter vicinity which comprises the said extrusion molding machine, (b) is the AA sectional view taken on the line. It is a perspective view which shows typically the kneading | mixing pushing roller which comprises the extrusion molding machine concerning this invention. It is a front view which shows typically the twine screw which comprises the upper stage screw of the extruder which concerns on this invention. It is a front view which shows the front-end | tip W blade | wing screw which comprises the middle stage screw of the extruder concerning this invention. It is a perspective view which shows typically an example of a honeycomb structure. (A) is a perspective view which shows typically the honeycomb calcination object which constitutes the above-mentioned honeycomb structure, and (b) is the AA line sectional view. It is a graph which shows the relationship between the initial stage surface roughness of Examples 4-9 and Reference Example 6, and extrusion efficiency. (A) is a graph which shows the relationship between the porosity of Examples 10-12 and Reference Examples 7 and 8, and the surface roughness Ra after 4000 hours continuous operation. (B) is a graph which shows the relationship between the porosity of Examples 10-12 and the reference examples 7 and 8, and the largest dimension of the recessed part of the surface of a high-hardness coating layer. (C) is a graph which shows the relationship between the porosity of Examples 10-12 and the reference examples 7 and 8, and extrusion efficiency.

Explanation of symbols

20 Extruder 31 Loading hopper 51 Upper screw mixer 52 (52a, 52b), 62 Kneading push roller 53 Upper screw (one screw)
54 Upper die (No. 1 die)
55 Upper cutter (cutting member)
56 Decompression chamber (part of sealed space)
57 Air cylinder 59, 69 Receiving port 61 Lower screw mixer 63 Lower screw (another screw)
530, 630 Feed screw 530a, 532a, 534a Screw shaft 530b, 532b, 534b Screw blade 532 Entangled screw 534, 634 W blade screw

Claims (28)

An extruder comprising a screw that is disposed in a sealed space and has a blade portion that extrudes a molding material, and a die that molds the extruded molding material,
An extrusion molding machine characterized in that the inside of the space is maintained in a reduced-pressure atmosphere, and a high-hardness coating layer is formed at least on the blade portion. The extrusion molding machine according to claim 1, wherein a main component of the high hardness coating layer is tungsten carbide. The extrusion molding machine according to claim 1 or 2, wherein the surface roughness Ra of the high-hardness coating layer is 10 µm or less. The extrusion molding machine according to any one of claims 1 to 3, wherein the porosity of the high hardness coating layer is 0.3% or less. The extrusion molding machine according to any one of claims 1 to 4, wherein the maximum dimension of the concave portion on the surface of the high-hardness coating layer is 1 to 50 µm. The extrusion molding machine according to any one of claims 1 to 5, wherein a binder for forming the high hardness coating layer is nickel. A plurality of screws, and the same number of dies as the plurality of screws,
The extrusion molding machine according to any one of claims 1 to 6, wherein the molding material is configured to be extruded again by another screw and die after being extruded by one screw and die. The extrusion molding machine according to any one of claims 1 to 7, further comprising a cutting member that cuts the molding material extruded through the one screw and the die. A wet mixture containing an inorganic powder as a molding material using an extrusion molding machine that is disposed in a sealed space and includes a screw having blades for extruding the molding material and a die for molding the extruded molding material And extruding the columnar shaped body continuously by extruding the wet mixture through the die provided at the outlet of the space,
An extrusion molding method characterized in that the inside of the space is maintained in a reduced-pressure atmosphere, and a high-hardness coating layer is formed at least on the blade portion. The extrusion molding method according to claim 9, wherein a main component of the high hardness coating layer is tungsten carbide. The extrusion molding method according to claim 9 or 10, wherein the surface roughness Ra of the high-hardness coating layer is 10 µm or less. The extrusion molding method according to any one of claims 9 to 11, wherein the porosity of the high hardness coating layer is 0.3% or less. The extrusion molding method according to any one of claims 9 to 12, wherein the maximum dimension of the concave portion on the surface of the high-hardness coating layer is 1 to 50 µm. The extrusion molding method according to claim 9, wherein the binder for forming the high-hardness coating layer is nickel. The extrusion method according to any one of claims 9 to 14, wherein the pressure in the space is 50 to 100 kPa lower than the atmospheric pressure. The extrusion molding method according to any one of claims 9 to 15, wherein the moisture content of the wet mixture is 10 to 20% by weight. The extruder includes a plurality of screws and the same number of dies as the plurality of screws.
17. A wet mixture continuously mixed through one die after being mixed by one screw is mixed again by another screw and continuously extruded through another die. An extrusion molding method according to claim 1. The extrusion molding method according to any one of claims 9 to 17, wherein the extrusion molding machine includes a cutting member that cuts the molding material extruded through the one screw and the die. After a wet mixture containing an inorganic powder is obtained by wet mixing, a columnar honeycomb molding in which a number of cells penetrating in the longitudinal direction are arranged side by side across the cell wall by performing an extrusion molding process for molding the wet mixture A honeycomb structure manufacturing method for manufacturing a honeycomb structure, and manufacturing the honeycomb structure including the honeycomb fired body by firing the honeycomb formed body,
The extrusion molding step includes an extrusion molding machine that is disposed in a sealed space, has a blade portion that extrudes a molding material, and has a screw having at least a high-hardness coating layer formed on the blade portion, and a die. use,
A honeycomb structure characterized by mixing the wet mixture while maintaining a reduced-pressure atmosphere in the space, and continuously extruding the wet mixture through the die provided at the exit of the space Body manufacturing method. The method for manufacturing a honeycomb structured body according to claim 19, wherein a main component of the high-hardness coating layer is tungsten carbide. 21. The method for manufacturing a honeycomb structured body according to claim 19, wherein a surface roughness Ra of the high hardness coating layer is 10 μm or less. The method for manufacturing a honeycomb structure according to any one of claims 19 to 21, wherein a porosity of the high hardness coating layer is 0.3% or less. The method for manufacturing a honeycomb structured body according to any one of claims 19 to 22, wherein the maximum dimension of the concave portion on the surface of the high-hardness coating layer is 1 to 50 µm. The method for manufacturing a honeycomb structured body according to any one of claims 19 to 23, wherein a binder for forming the high hardness coating layer is nickel. The method for manufacturing a honeycomb structured body according to any one of claims 19 to 24, wherein the pressure in the space is 50 to 100 kPa lower than the atmospheric pressure. The method for manufacturing a honeycomb structured body according to any one of claims 19 to 25, wherein the moisture content of the wet mixture is 10 to 20 wt%. The extruder includes a plurality of screws and the same number of dies as the plurality of screws.
27. Any one of claims 19 to 26, wherein after being mixed by one screw, the wet mixture continuously extruded through one die is mixed again by another screw and continuously extruded through another die. A method for manufacturing a honeycomb structure according to claim 1. The manufacturing method of the honeycomb structure according to any one of claims 19 to 27, wherein the extrusion molding machine includes a cutting member that cuts the molding material extruded through the one screw and the die.

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