JP4959998B2 - Manufacturing method of particulate filter - Google Patents

Description

The present invention relates to a manufacturing method of the particulate filter for removing fine particles contained in the gas.

There is an increasing demand for removing fine particles and harmful substances in exhaust gas from internal combustion engines, boilers and the like from the exhaust gas in consideration of environmental impact.
In particular, there is a growing interest in the removal of particulate matter (PM) and nitrogen oxides (NOx) discharged from diesel engines, and a polygonal filter (called a particulate filter) for removing these PM and NOx. Attention has been paid.

As shown in FIG. 12A, such a particulate filter has a structure in which a plurality of fluid passages partitioned by porous partition walls are arranged vertically. As shown in the end face of FIG. 12 (b), the open ends on the inflow side of about half of the passages are closed, and the open ends on the outflow side of the remaining passages are closed. Therefore, the porous partition wall becomes the filtration surface.
When using this particulate filter, the end face of the particulate filter is installed perpendicularly to the exhaust gas flow path in the exhaust gas pipe. The exhaust gas enters from the opening end on the inflow side of the fluid passage on the end face of the particulate filter, passes through the partition wall, and is discharged from the opening end on the outflow side. Innumerable fine through holes are formed in the partition wall, so that the fine particles in the exhaust gas are collected by the fine particles.
JP 2004-896 A Japanese Patent Laid-Open No. 5-168881 JP 2001-334114 A

In the particulate filter disclosed in the conventional patent document, each fluid passage has a prismatic shape, and has the same cross-sectional area (diameter) from the inlet to the outlet.
When a particulate filter is used in a diesel engine muffler, etc., particulates discharged from the diesel engine (a lot of oil easily adheres) tend to stick to the vicinity of the inlet of the particulate filter and accumulate easily.

In this structure, since the open ends of about half of the fluid passages are closed at the inlet, the area ratio of the openings is small, and the gas collection efficiency is low. In this structure, the pressure loss is large because the area of the opening is small.
Therefore, an object of the present invention is to provide a method for manufacturing a particulate filter having a small pressure loss and a high collection efficiency.

In the particulate filter manufacturing method of the present invention, the filter portion is formed by a fluid passage partitioned by a porous partition wall , and the sectional area of the opening of the fluid passage at the inlet of the fluid to be processed is a manufacturing method of the particulate filter has a size than the cross-sectional area at the outlet side of the processing fluid, a ceramic powder, a step of fabricating a ceramic slurry containing a photocurable resin and a surfactant, supported in the ceramic slurry A step of immersing a plate, irradiating the ceramic slurry on the support plate with light to cure and lowering the support plate, and repeating the steps a plurality of times, thereby forming a ceramic molded body to be the filter part. And a step of sintering the ceramic molded body .
Due to the structure of this particulate filter, even if a large amount of fine particles discharged from a diesel engine stick to the vicinity of the inlet of the particulate filter, the pressure loss is reduced because the area of the opening on the inlet side is relatively large. In addition, the collection efficiency of fine particles can be increased.

Cross-sectional shape of the fluid passageway, until a certain distance from the inlet of the fluid to be treated is the same shape as the inlet port may be one which is cross-sectional area becomes smaller toward therefrom outflow side, this In this case , the collection amount of the fine particles in the vicinity of the inlet on the inlet side increases, and the collection efficiency is increased.
The cross-sectional shape of the inlet of the fluid passage is preferably a polygonal shape. If the opening has a polygonal shape, the area of the partition existing between the inlet and the inlet can be reduced. For example, if the opening is a square or a hexagon, the partition wall has a lattice shape, and the area of the opening can be further increased.

Since the cross-sectional area of the opening portion of the inlet is 70 to 80% of the total cross-sectional area including the opening portion and the partition wall of the filter portion , gas collection efficiency can be increased and pressure loss can be reduced. preferable.
The partition wall is a partition wall shared with an adjacent inlet port in the vicinity of the inflow port, and when the partition wall is a partition wall for each fluid passage from there to the outflow side, the partition wall is adjacent to the inflow port. Since it is a partition shared with the entrance, it has high strength. Moreover, since it has a partition for every fluid passage from there to an outflow port, the permeation | transmission efficiency of gas can be improved.

  When the partition is at least one selected from the group consisting of cordierite, silicon carbide, silicon nitride, aluminum titanate, lithium aluminosilicate, alumina, mullite, and spinel, heat resistance, strength, and durability are high. In particular, aluminum titanate is preferable because it has a small thermal expansion coefficient and particularly high thermal shock resistance.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
In the following, “cross section” means a cross section perpendicular to the longitudinal direction of the filter portion ( Z direction in FIG. 1) unless otherwise specified.
FIG. 1 is a longitudinal sectional view of a particulate filter. 2 is a cross-sectional view at the gas inflow end surface, FIG. 3 is a cross-sectional view at the intermediate portion, and FIG. 4 is a cross-sectional view at the gas outflow end surface.

This particulate filter has a large number of filter portions 1 arranged vertically from the inflow end surface to the outflow end surface of the fluid to be treated. Each filter portion 1 is formed by a pyramidal porous partition wall 2. The gas G passage divided by the pyramidal porous partition wall 2 is referred to as a “fluid passage”. Each filter unit 1 is formed in a united manner together with the frame 3.
Instead of being integrated with the frame 3, for example, it may be fixed to a metal frame.

As shown in FIG. 2, the inflow end face of each filter unit 1 is partitioned in a lattice form by partition walls 2. That is, the partition walls 2 of the adjacent filter units 1 are shared partition walls 2, and these partition walls 2 form a lattice.
The partition wall 2 of each filter unit 1 is narrowed in a cross-sectional shape in a straight line from the inflow port to the outflow side (Z direction). Accordingly, the partition walls 2 of the adjacent filter units 1 are separated from each other and become the partition walls 2 for each filter unit 1.

  FIG. 3 is a cross-sectional view showing the partition wall 2 at the narrowed position. As a result of the filter unit 1 being narrowed in a pyramid shape, the cross-sectional area of the fluid passage is reduced and the adjacent partition walls 2 are separated from each other. It shows a state. In the intermediate portion, the filter portions 1 are in a free state and are not necessarily fixedly connected to each other (but are fixed at the tip of the partition wall 2 as will be described later).

As shown in FIG. 4, the partition wall 2 of each filter unit 1 has the most narrowed cross-sectional shape at the outflow end face to form a lattice point. That is, the intersection of the lattices 5 shown in FIG. 4 corresponds to the tip of each filter unit 1.
The lattice 5 is made of, for example, the same material as that of the partition wall 2 and is used for fixing the tip portion of each filter portion 1. As shown in FIG. 1, the tip end of each filter unit 1 is fixed in a lattice 5. Note that the lattice 5 may be formed of stainless steel or the like. In this case, it is good to seal the front-end | tip part of each filter part 1 with low melting glass, such as metal borosilicate glass.

The feature of this embodiment is that the cross-sectional area of the inflow port into which the processing fluid flows in the filter unit 1 partitioned by the porous partition wall 2 is larger than the cross-sectional area on the outflow side of the processing fluid.
With this structure, even if a large amount of fine particles discharged from a diesel engine or the like adhere to the vicinity of the inflow port of the particulate filter, the clogging of the inflow port is reduced because the area of the opening on the inflow port side is relatively large. Therefore, the pressure loss is reduced, and the collection efficiency of the fine particles can be increased.

  FIG. 5 is a cross-sectional view of one filter unit 1, and shows a cross section taken along the XZ plane or the YZ plane of FIGS. 2 to 4. The cross section of the filter part 1 is narrowed as it goes from the inflow end surface of the gas G to the outflow side of the fluid to be processed, and it shows that it gradually becomes thinner. Since the partition wall 2 is linear and has no steps, the resistance applied to the flowing gas G is reduced. Therefore, the pressure loss is reduced and the collection efficiency is increased.

  FIG. 6 is a cross-sectional view of the filter unit 1 according to a modification. The cross-sectional shape of the filter unit 1 is the same shape as the inflow port up to a certain distance L (substantially intermediate position) from the gas G inflow port, and is curved toward the outflow side from there, and the cross-sectional area becomes smaller. Yes. For this reason, the surface area of the partition wall 2 is not reduced from the inlet to the distance L, the amount of collected particulates is increased, and the collection efficiency is increased.

5 and 6, the cross section taken along the XY plane of the filter unit 1 is a quadrangular shape on the inflow port side, but may be deformed into a circular shape or the like as the cross sectional area becomes narrower. . Further, even when the cross-sectional area becomes narrow, the square shape may be kept as it is.
Next, the manufacturing method of the particulate filter of this invention is demonstrated .
FIG. 7 is a schematic cross-sectional view showing a particulate filter manufacturing apparatus.

The manufacturing apparatus includes a container 11 for storing ceramic slurry and a support plate 12 that is movable in the ceramic slurry up and down (Z direction) and is set parallel to the XY plane.
Further, the upper space of the container 11 includes a laser device 13 as a light irradiation unit and an XY moving unit 14 for scanning the irradiation light of the laser device 13 in the horizontal direction (on the XY plane). .

Examples of the laser device 13 include a laser device 13 such as an ultraviolet laser, a semiconductor laser, an excimer laser, an Ar ion laser, or a He—Cd laser. Further, a mercury lamp or the like may be used as a light source, and light may be irradiated through a mask having a predetermined shape.
In addition to the XY moving unit 14, a scanning member for finely scanning the irradiation light of the light irradiation unit, for example, a rotatable galvanometer mirror (not shown) for reflecting the irradiation light of the laser device 13 is provided. It may be done. When the galvano mirror is provided, the direction of the irradiation light of the laser device 13 may be set to a predetermined direction (a direction that is not necessarily downward) so that the light reflected by the galvano mirror is directed downward (Z direction).

In order to manufacture the particulate filter with this manufacturing apparatus, a “stereolithography method” using a photocurable resin used in the plastics molding field can be employed.
In this stereolithography method, a ceramic slurry (hereinafter referred to as a slurry) is prepared by mixing ceramic powder, a photocurable resin and a surfactant, and the slurry is irradiated with light to cure the photocurable resin. After obtaining a ceramic molded body having a desired shape, the ceramic molded body is heated to degrease the photocurable resin and sinter the ceramic molded body.

In addition, the said photocuring is influenced by the translucency with respect to the irradiation wavelength of the ceramic particle in a slurry. For this reason, it is preferable that the ceramic particles to be used have a substantially light-transmitting property with respect to the irradiation wavelength used or a light source having an irradiation wavelength exhibiting the light-transmitting property is used.
As the ceramic powder used in the present invention, various ceramics such as oxides, carbides such as silicon carbide, boron carbide and titanium carbide, nitrides such as silicon nitride and aluminum nitride, or mixtures thereof can be used. Examples of the ceramic include cordierite, silicon carbide, silicon nitride, aluminum titanate, lithium aluminosilicate, alumina, mullite, spinel, zirconia, and yttria.

In particular, aluminum titanate is preferable. Aluminum titanate has a thermal expansion coefficient close to 0 and excellent thermal shock resistance.
The ceramic powder preferably has an average particle size of 0.5 to 10 μm and a particle size distribution of 0.1 to 30 μm because it can be cured in a short time after light irradiation.
In addition, the photocurable resin used in the present invention is a resin that is cured by light such as X-rays, ultraviolet rays, and visible light. For example, a urethane acrylate resin, an epoxy acrylate resin, a polyester acrylate resin, or the like may be used. More specifically, radical polymerization photocurable resins such as epoxy acrylate, polyether acrylate, polyester acrylate, and urethane acrylate resins, and cationic polymerization photocurable resins such as epoxy resins can be used.

Furthermore, it is preferable to contain 0.1-7 volume% of cationic surfactants, such as an amine salt type, a quaternary ammonium salt type, and a pyridium salt type, with respect to the slurry.
In addition, as a photopolymerization initiator for inducing curing of the photocurable resin, an initiator used for normal photopolymerization, for example, peroxide, onium salt, acetophenyl, benzoin ether, benzyl petal Initiators such as systems, ketones, amines, aromatic diazonium salts and aromatic sulfonium salts can be used. The photopolymerization initiator is preferably 1 to 20% by weight with respect to 100% by weight of the photocurable resin. In addition, when using the photocurable resin also provided with the function of the photoinitiator, it is not necessary to add a photoinitiator.

The viscosity of the slurry is preferably 1.5 Pa · s or less. By setting it to 1.5 Pa · s or less, the smoothness of the semi-cured slurry layer can be improved, so the smoothness of the ceramic sintered body can also be improved. Further, molding can be performed in a short time and efficiently, and mass productivity can be improved.
In order to make the viscosity of the slurry 1.5 Pa · s or less, for example, 38 to 44.9% by volume of a photocurable resin containing a photopolymerization initiator, 0.1 to 7% by volume of a cationic surfactant, and an average A ceramic powder of 55 to 101.9% by volume of 0.5 to 10 μm is put into a pot of 500 to 2000 cc, and is stirred and mixed for 24 hours at a rotational speed of 100 to 700 rpm using an alumina ball having a diameter of 5 to 20 mm. That's fine.

  Furthermore, the viscosity of the slurry is more preferably 1.0 Pa · s or less. In order to set the viscosity of the slurry to 1.0 Pa · s or less, for example, 38 to 44.9% by volume of a photocurable resin containing a photopolymerization initiator, 0.1 to 7% by volume of a cationic surfactant, and an average particle diameter. 27.5 to 30.95% by volume of ceramic powder of 5 to 10 μm is put into a pot of 500 to 2000 cc and stirred for 0.5 to 2 hours at a rotational speed of 100 to 700 rpm using an alumina ball having a diameter of 5 to 20 mm. After mixing, 27.5 to 30.95% by volume of the ceramic powder is further charged into the pot and mixed by stirring for 24 hours.

Here, a process of manufacturing a particulate filter using the slurry obtained as described above will be described with reference to FIGS.
First, a ceramic powder, a photocurable resin, etc. are mixed to prepare a slurry, and the container 11 is filled. As shown in FIG. 8, the support plate 12 is submerged from the surface of the slurry by one hardened layer. Alternatively, the support plate 12 may be installed first, and then the slurry may be stored in the container 11 such that the support plate 12 sinks into the slurry.

Next, from the upper surface side of the slurry, the light irradiation portion is scanned in the XY directions, and the portion where the partition wall 2 as the cross section of the particulate filter is formed is irradiated with light having a small diameter to cure the slurry. In this case, the ultraviolet irradiation region is designed by a computer.
What is necessary is just to select the irradiation light quantity of a laser beam suitably according to the hardening depth of photocurable resin, and the kind of ceramic powder. For example, the amount of laser beam irradiation is preferably 50 to 1000 mJ / cm ² . The amount of laser beam irradiation is defined by laser output (mW) / (scan interval (cm) × scan speed (cm / sec).

Next, as shown in FIG. 9, after the support plate 12 is moved in the Z direction so that the upper surface of the hardened partition wall 2 is submerged in the slurry again, a predetermined amount is applied on the layer first cured by light irradiation. Slurry is supplied so that it may become thickness, and the part of the filter part 1 is light-irradiated and hardened. The descending distance is about 0.05 to 0.2 mm.
Thus, the process of irradiating with light and curing is repeatedly laminated. In this way, a three-dimensional ceramic molded body is produced as shown in FIG. After forming the part used as the partition 2 with a hardened layer, the hollow filter part 1 can be manufactured by discharging | emitting internal slurry.

FIG. 11 shows a state where the filter portion 1 having a predetermined size is formed and then pulled up from the ceramic slurry.
Next, the photocurable resin contained in the ceramic molded body is degreased as necessary in a vacuum atmosphere, a nitrogen gas atmosphere, or an inert gas atmosphere such as argon gas. By degreasing in such an atmosphere, the photocurable resin does not generate excessive heat, and the generation of cracks can be completely prevented.

  Degreasing is performed in any one of a vacuum atmosphere, a nitrogen gas atmosphere, and an inert gas atmosphere at a rate of temperature increase of 1 to 50 ° C./hour and a temperature of 300 to 600 ° C. Is preferably set so as not to cause rapid decomposition. The temperature conditions and the like may be individually set according to the thickness and volume of the ceramic molded body. For example, it is better to raise the rate of temperature rise more slowly as the wall thickness is thicker, and the atmosphere may be a mixed gas atmosphere of nitrogen gas and inert gas.

Thereafter, the degreased ceramic molded body is sintered by a normal pressure sintering method or the like, which is a firing method of a normal ceramic molded body, to obtain a ceramic sintered body. In this way, the particulate filter of FIG. 1 is completed.
The ceramic sintered body obtained by this manufacturing method is resistant to corrosive gases and used for parts that are required to be dense, such as parts for liquid crystal manufacturing equipment and semiconductor manufacturing equipment. In particular, it is possible to easily obtain a hollow ceramic sintered body that is also applicable to parts that require weight reduction or heat insulation.

Examples of the present invention will be specifically described below.
As the ceramic powder, an aluminum titanate powder having an average particle size of 0.7 μm was used, and a paste prepared by mixing 20% by weight of urethane acrylate as a photocurable resin containing a photopolymerization initiator in 100% by weight of the alumina powder was 30 mm × 30. The slurry was applied to a plastic substrate of mm , and 0.1 ml of a surfactant was added dropwise to the paste and mixed to obtain a slurry.

Each of the obtained mixtures was put into a container 11 of a particulate filter manufacturing apparatus, irradiated with an Ar ion laser, and laminated 500 times every 0.1 mm in thickness, to obtain a 50 mm long shape having the shape of FIG. A pyramid-shaped filter portion 1 was formed. Next, after discharging the slurry from the molded body, it was washed with ethanol to remove uncured portions.
Then, it heated up to 600 degreeC with the temperature increase rate of 1.5 degreeC / hour in atmosphere, and degreased | defatted. The both ends of the entrance-side and exit-side frames of the obtained degreased body were fixed using a tape-shaped SUS plate. A particulate filter was obtained by raising the temperature to 1700 ° C. at a rate of temperature increase of 200 ° C./hour in the air, holding for 2 hours and firing.

The sectional area of the opening of the manufactured particulate filter was 70 to 80% of the total sectional area including the opening of the filter unit 1 and the partition wall 2. In the conventional structure shown in FIG. 12, since the opening ends of about half of the fluid passages are closed at the inlet, the area ratio of the opening is about 50%, and the gas G collection efficiency is low. In the structure of this example, since the area ratio of the opening can be increased to 70 to 80%, the collection efficiency of the gas G is increased and the pressure loss can be reduced.

  Although the embodiments of the present invention have been described above, the embodiments of the present invention are not limited to the above-described embodiments. For example, the cross-sectional shape of the inlet of the fluid passage is a quadrangular shape, but is not limited to a square shape, and may be an n-square shape (n is an integer of 3 or more). For example, it may be hexagonal. In the case of a hexagonal shape, the inflow port has a honeycomb shape and can be called a “honeycomb filter”. In addition, various modifications can be made within the scope of the present invention.

It is a longitudinal sectional view showing a path tee filter. It is a cross-sectional view at the inlet side end of the particulate filter. It is a cross-sectional view in the middle part of the particulate filter. It is a cross-sectional view at the outlet side end of the particulate filter. It is a longitudinal cross-sectional view of the particulate filter squeezed linearly. It is a longitudinal cross-sectional view of the curved particulate filter. It is a schematic sectional view showing a manufacturing apparatus for manufacturing a path tee filter. It is a manufacturing-process figure of the particulate filter by an optical shaping method. It is a manufacturing-process figure of the particulate filter by an optical shaping method. It is a manufacturing-process figure of the particulate filter by an optical shaping method. It is a manufacturing-process figure of the particulate filter by an optical shaping method, and after forming the filter part 1 of a predetermined dimension, the state pulled up from the ceramic slurry is shown. It is a figure which shows the internal structure of the conventional particulate filter.

Explanation of symbols

2 Partition 1 Filter unit 3 Frame 5 Grid 11 Container 12 Support plate 13 Laser device 14 XY moving unit

Claims (2)

The filter section is formed by a fluid passage partitioned by a porous partition wall, and the cross-sectional area of the opening of the fluid passage of the filter section at the inlet of the fluid to be processed is the cross-sectional area on the outflow side of the fluid to be processed. A method for producing a larger particulate filter,
Producing a ceramic slurry containing a ceramic powder, a photocurable resin and a surfactant;
Dipping a support plate in the ceramic slurry, lowering the support plate by curing the ceramic slurry on the support plate by light irradiation;
By repeating the above steps a plurality of times, a step of producing a ceramic molded body that becomes the filter portion;
Sintering the ceramic molded body, and a method for producing a particulate filter. The end surface of the inlet side of the particulate filter, the flow cross-sectional area of the inlet, according to claim 1, wherein 70 to 80% of the total cross-sectional area including the opening and the partition wall of the front notated filter unit Manufacturing method of particulate filter.

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