JP2022122669A - Mat material, exhaust gas purification device and manufacturing method for mat material - Google Patents

Abstract

To provide a mat material capable of improving a friction coefficient of a surface.SOLUTION: A mat material made of inorganic fibers, has a first main surface and a second main surface located on the opposite side of the first main surface, where at least one of the first main surface and the second main surface is subjected to surface processing to change its surface state.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a mat material, an exhaust gas purifier, and a method for manufacturing the mat material.

Exhaust gas emitted from internal combustion engines such as diesel engines contains particulate matter (hereinafter also referred to as PM), and in recent years, it has become a problem that this PM harms the environment and the human body. . Moreover, since the exhaust gas contains harmful gas components such as CO, HC, and NOx, there are concerns about the effects of these harmful gas components on the environment and the human body.

Therefore, as an exhaust gas purifying device for capturing PM in exhaust gas and purifying harmful gas components, an exhaust gas treating body made of porous ceramic such as silicon carbide or cordierite and a metal housing the exhaust gas treating body Various exhaust gas purifiers have been proposed which are composed of a casing and a holding sealing material (mat material) disposed between the exhaust gas treating body and the metal casing. This holding sealing material (mat material) prevents the exhaust gas treating body from coming into contact with the metal casing covering its outer periphery and being damaged due to vibrations and impacts caused by the running of the vehicle, and prevents the exhaust gas treating body and the metal casing from being damaged. It is installed mainly for the purpose of preventing exhaust gas from leaking from between.

When high-pressure exhaust gas flows into such an exhaust gas purifier, there is a problem that the exhaust gas treating body is pushed by the exhaust gas and falls off from the metal casing.

Patent Literature 1 describes that in order to improve the holding performance of the holding seal material, inorganic particles are attached to the surface of inorganic fibers that constitute the holding seal material to improve the coefficient of friction of the holding seal material. .

Further, in Patent Document 2, in order to improve the holding performance of the holding seal material, inorganic fibers constituting the holding seal material are compressed and fixed with an organic binder to form grooves on the surface of the holding seal material. It is said to improve the coefficient of friction.

JP 2013-213463 A JP-A-2017-31870

The present inventors measured the friction coefficient between the holding seal material and the metal casing of the holding seal material described in Patent Document 1, and found that the friction coefficient was smaller than expected.
The inventors presumed the reason for this as follows.

A holding sealing material such as that described in Patent Document 1 is used so that its main surface is in contact with the metal casing. Then, it is considered that a frictional force is generated between the surface of the metal casing and the surface of the holding seal material in contact with the metal casing.
However, when the surface of the holding seal material is viewed microscopically, the inorganic fibers forming the holding seal material are entangled with each other, so the surface of the holding seal material does not form a uniform surface.
When the surface of the holding sealing material is viewed microscopically, the area occupied by the inorganic fibers on the surface of the holding sealing material is smaller than the area of the mat material. Therefore, it is considered that the inorganic fibers are actually in point contact with the surface of the metal casing.

Further, in Patent Document 1, inorganic particles are arranged on the surfaces of inorganic fibers. Since the particles are in point contact with the surface, even if the inorganic particles are arranged on the surface of the inorganic fiber, the holding sealing material is considered to be in point contact with the surface of the metal casing.

When the holding seal material is in point contact with the surface of the metal casing, the area of actual contact between the holding seal material and the surface of the metal casing becomes small. In this case, the friction coefficient between the holding seal material and the metal casing is smaller than the friction coefficient when it is assumed that the holding seal material and the metal casing are in surface contact.

That is, for the reasons described above, when the holding seal material described in Patent Document 1 is used, the coefficient of friction between the holding seal material and the metal casing is considered to be smaller than expected.

In addition, attaching inorganic particles to inorganic fibers complicates the manufacturing process and increases the manufacturing cost.

In addition, the present inventors measured the coefficient of friction between the holding seal material and the metal casing of the holding seal material described in Patent Document 2. As a result, the effect of improving the friction coefficient could not be confirmed.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a mat material capable of improving the friction coefficient of the surface.

That is, the mat material of the present invention is a mat material made of inorganic fibers, the mat material has a first main surface and a second main surface located opposite to the first main surface, At least one of the first main surface and the second main surface is subjected to surface processing to change the surface state.

In the mat material of the present invention, at least one of the first main surface and the second main surface is subjected to surface processing to change the surface state. It is possible to improve the coefficient of friction of the surface to be machined among the surfaces.
In addition, since additional materials such as inorganic particles are not required and the manufacturing process is simple, manufacturing costs can be reduced.

In the mat material of the present invention, it is preferable that the first principal surface and the second principal surface are subjected to the surface treatment to change the surface state.
Since each main surface is a surface to be processed that has undergone surface processing, the mat member can have a high coefficient of friction on each main surface.

In the mat member of the present invention, it is preferable that the surface to be processed of the first main surface and the second main surface has raised inorganic fibers.
As a result, the effect of improving the coefficient of friction is exhibited more favorably.
More specifically, when the surface to be processed has raised inorganic fibers, the fiber orientation is forcibly changed to random orientation at the interface where friction occurs. Therefore, it becomes difficult for the inorganic fibers to move against an external force, thereby suppressing step deviation and improving the holding force. As a result, the coefficient of friction is effectively improved.
As a result of measurements by the present inventors, it was found that a matting material having raised inorganic fibers on its main surface has a frictional force equal to or greater than that of a matting material to which inorganic particles are attached as described in Patent Document 1. is confirmed.

Here, the term "stepwise shift" means that the frictional resistance of the mat material as a whole is reduced by the gradual shift (movement) of each inorganic fiber at the friction-generating interface.

In the mat material of the present invention, it is preferable that the raised inorganic fibers form fiber clumps, and the fiber clumps are partially separated from the surface to be processed.

In the mat material of the present invention, it is preferable that the surface to be processed has a plurality of the fiber lumps, and the ends of the plurality of fiber lumps in the same direction are separated from the surface to be processed.
Since such a mat material can be produced using a processing apparatus such as a raising apparatus, it can be made into a mat material excellent in mass productivity.

In the mat material of the present invention, the coefficient of friction of the surface to be processed, of the first main surface and the second main surface, is 25 when the bulk density of the mat material is 0.3 g/cm ³ . It is preferably 0.21 to 0.45 in °C.

In the mat material of the present invention, the bulk density in the vicinity of the surface-processed surface of the first principal surface and the second principal surface is higher than the bulk density in the vicinity of the center in the thickness direction of the mat material. Small is preferred.

In the mat material of the present invention, the bulk density in the vicinity of the surface to be processed of the first principal surface and the second principal surface that has undergone the surface processing is 0.05 to 0.18 g/cm ³ , The bulk density of the mat material near the center in the thickness direction is preferably 0.11 to 0.20 g/cm ³ .

In the mat material of the present invention, the bulk density in the vicinity of the surface to be processed of the first principal surface and the second principal surface that has undergone the surface treatment is equal to the bulk density in the vicinity of the center in the thickness direction of the mat material. On the other hand, it is preferably 45 to 95%.

An exhaust gas purifying apparatus of the present invention comprises an exhaust gas treating body, a metal casing housing the exhaust gas treating body, a mat material disposed between the exhaust gas treating body and the metal casing and holding the exhaust gas treating body, , wherein the mat material is the mat material of the present invention.

As described above, the mat material of the present invention has the effect of improving the friction coefficient of the surface. Therefore, it is possible to provide an exhaust gas purifying apparatus in which the exhaust gas treating body is held with a high holding force.

A method for producing a mat material according to the present invention comprises a mat preparation step of preparing a mat made of inorganic fibers, a first main surface of the mat, and a second main surface of the mat opposite to the first main surface. and at least one of and a surface processing step of applying surface processing to change the surface state.

In the method for manufacturing a mat material of the present invention, it is preferable that at least one of the first main surface and the second main surface is raised in the surface processing step.

In the method for producing a mat material of the present invention, the mat is preferably produced by a needling method in the mat preparation step.

FIG. 1 is a perspective view schematically showing an example of the mat material of the present invention. FIG. 2 is a perspective view schematically showing a state of the mat member shown in FIG. 1 before surface processing. FIG. 3 is a schematic diagram showing a contact mechanism in a state in which a load W is applied to a flat surface with roughness and a force F is applied in the lateral direction. 4 is a perspective view schematically showing an enlarged part of the surface to be processed of the mat member shown in FIG. 1. FIG. FIG. 5 is a cross-sectional view schematically showing an example of a non-surface-treated needle mat. FIG. 6 is a cross-sectional view schematically showing an example of the mat member of the present invention. FIG. 7 is a cross-sectional view schematically showing an example of the exhaust gas purifier of the present invention. FIG. 8 is a plan view schematically showing the processed surface of the mat material of Example 2. FIG. FIG. 9 is a schematic diagram showing a friction coefficient measuring device for a mat material. FIG. 10 is a schematic diagram showing a friction coefficient measuring device for a mat material. FIG. 11 is a graph showing measurement results of friction coefficients of mat materials in Examples and Comparative Examples. FIG. 12 is a photograph of the processed surface of the mat material of Example 2 observed with a microscope.

(Detailed description of the invention)
The mat material of the present invention will be described in detail below.
The mat material of the present invention is a mat material made of inorganic fibers, the mat material has a first main surface and a second main surface located on the opposite side of the first main surface. At least one of the first main surface and the second main surface is subjected to surface processing to change the surface state.

FIG. 1 is a perspective view schematically showing an example of the mat material of the present invention.
FIG. 1 shows a mat member 1 of the present invention which is rectangular in plan view.
The plan view shape of the mat material 1 is not limited to a rectangle, and may be other shapes according to the place of use.
One end 2 in the longitudinal direction of the mat material 1 is provided with a projection 2a so that the ends of the mat material 1 are fitted to each other when the mat material 1 is wrapped around an object. A concave portion 3a is provided at the other end portion 3 in the longitudinal direction.
When such convex portions 2a and concave portions 3a are provided, the sealing performance is improved when the mat member 1 is arranged in an exhaust gas purifying device to be described later.
It should be noted that the mat material of the present invention may not have projections and recesses at the ends of the mat material.
Further, the end portions of the mat material may be L-shaped, and the end portions may be fitted together when the mat material is wrapped around the object.

The mat material 1 is a mat material made of inorganic fibers.
The inorganic fibers are not particularly limited, and include alumina fibers, alumina-silica fibers, silica fibers, biosoluble fibers, glass wool, rock wool and the like. Among these, alumina-silica fibers are preferred.
These inorganic fibers have high heat resistance, and mat materials formed from such inorganic fibers are less likely to change shape due to temperature changes.

Furthermore, when the inorganic fibers are alumina-silica fibers, the composition ratio of alumina and silica is preferably alumina (Al ₂ O ₃ ):silica (SiO ₂ )=60:40 to 80:20 by weight. , alumina (Al ₂ O ₃ ):silica (SiO ₂ )=70:30 to 74:26.

The inorganic fibers preferably have an average fiber length of 1 to 150 mm, more preferably 10 to 80 mm.
When the average fiber length of the inorganic fibers is less than 1 mm, the fiber length of the inorganic fibers is too short, so that the entanglement of the inorganic fibers becomes insufficient, the strength of the mat material is difficult to obtain, and the shape retention of the mat material is poor. easy to decline.
On the other hand, when the average fiber length of the inorganic fibers exceeds 150 mm, the fiber length of the inorganic fibers is too long, so that the number of fibers constituting the mat member decreases and the denseness of the mat member decreases. As a result, the shear strength of the mat material is lowered.

The average fiber diameter of the inorganic fibers is preferably 1 to 20 μm, more preferably 2 to 15 μm, even more preferably 3 to 10 μm.
When the average fiber diameter of the inorganic fibers is less than 1 μm, the breaking load is low and the inorganic fibers are easily broken by impact or the like.
When the average fiber diameter of the inorganic fibers exceeds 20 μm, defects are likely to occur inside the fibers, the strength of the inorganic fibers decreases, and the surface pressure value as a mat material for holding the exhaust gas treating body decreases.

The average fiber length and average fiber diameter of the inorganic fibers are obtained by observing 100 arbitrary inorganic fibers within the field of view in SEM (scanning electron microscope) observation of the mat material.

As shown in FIG. 1, the mat member 1 has a first principal surface 4 and a second principal surface 5 located on the opposite side of the first principal surface 4. The first principal surface 4 and the second principal surface No. 5 is one in which the surface condition has changed due to surface processing.
As a result, the coefficient of friction of the processed surface 6, which is the surface of the mat member 1 subjected to surface processing, can be improved.
Moreover, the mat material 1 can be manufactured at low cost by a simple manufacturing process without using additional materials such as inorganic particles.

FIG. 2 is a perspective view schematically showing a state of the mat member shown in FIG. 1 before surface processing.
As shown in FIGS. 1 and 2, the first main surface 4 and the second main surface 5 of the mat member 1 are subjected to surface processing to change their surface conditions.

The mat material 1 may be a surface to be processed 6 in which only one of the first principal surface 4 and the second principal surface 5 is surface-processed. However, as shown in FIGS. It is preferable that the surface conditions of the first main surface 4 and the second main surface 5 of 1 are changed by surface processing.
That is, it is preferable that each of the main surfaces 4 and 5 is the surface 6 to be machined.
As a result, the mat member can have a high coefficient of friction on each of the main surfaces 4 and 5 .

In addition, when each of the main surfaces 4 and 5 is the surface to be processed 6, the first main surface 4 and the second main surface 5 may be subjected to different types of surface processing, but usually the same type of surface processing is performed. Processing (preferably raising) is applied.

As shown in FIG. 1, the processed surface 6 of the first main surface 4 and the second main surface 5 preferably has raised inorganic fibers 10 .
As a result, the effect of improving the coefficient of friction is exhibited more favorably.
Such a surface to be processed 6 can be effectively formed by performing a raising treatment as the above-described surface processing.

Here, with reference to FIG. 3, the function and effects of the raised inorganic fibers 10 will be described in more detail.
First, in a general elastic body such as a mat material, the mechanism of holding force generation is as follows.
FIG. 3 is a schematic diagram showing a contact mechanism in a state in which a load W is applied to a flat surface with roughness and a force F is applied in the lateral direction.
F (holding force) is generally expressed by W (surface pressure) × μ (coefficient of friction). When each projection is pressed against a plane P with a load W, the tip of the projection deforms due to the contact pressure _pn , forming a contact surface with a contact area A _n . The total sum of the shear forces τ _n ×A _n generated at the true contact points (each protrusion) is F (holding force).
F=τ ₁ ×A ₁ +τ ₂ ×A ₂ +τ ₃ ×A ₃ + . . . =Στ _n ×A _n (1)
where τ _n denotes the average shear force of each projection and n denotes the number of each projection.
Therefore, when the projections deviate from each other, the stress of the projections is relaxed and the shearing force decreases or disappears, resulting in a decrease in F (holding force).

The coefficient of friction _μM of the elastic body is expressed by the following formula (2).
μ _M =μ _K +C(μ _S −μ _K )W ^−1/3 (2)
Here, _μK indicates a coefficient of dynamic friction, μS indicates a coefficient of static friction, W indicates load, and _C indicates stiffness.

On the other hand, if the surface to be processed of the mat material of the present invention has raised inorganic fibers, the fiber orientation is forcibly changed to random orientation at the interface where friction occurs. Therefore, it becomes difficult for the inorganic fibers to move with respect to the external force, so that the step deviation is suppressed and the holding force F can be improved. As a result, the coefficient of friction is effectively improved.

4 is a perspective view schematically showing an enlarged part of the surface to be processed of the mat member shown in FIG. 1. FIG.
As shown in FIG. 4, the raised inorganic fibers 10 form a fiber mass 11, and the fiber mass 11 is preferably partially separated from the surface 6 to be processed.

Here, the term "fiber mass" means a fiber assembly in which a plurality of inorganic fibers are collectively integrated.
The fiber mass 11 is formed by partially peeling off the inorganic fibers on the surface 6 to be processed by hooking them on needles.
Therefore, the fiber mass 11 and other inorganic fibers (for example, the inorganic fibers in the center of the mat member in the thickness direction) basically differ only in the direction of fiber orientation.
However, since the fiber clump 11 is formed by being hooked by a needle, as shown in FIG. 4, there is usually a low accumulation portion 12 of inorganic fibers in the center. That is, the central portion of the fiber mass 11 may have a lower inorganic fiber density than its surroundings.
Since the center of the fiber mass 11 is the low-accumulation portion 12, it is possible to improve the coefficient of friction more effectively. On the other hand, if the fiber lumps 11 do not have the low accumulation portion 12 in the center and the overall degree of accumulation (density) is uniform, the fiber lumps 11 become hard lumps, and the effect of improving the coefficient of friction is not effectively achieved. may not be obtained in the future.
In addition, due to the presence of the low accumulation portion 12, when the exhaust gas treating body and the mat material are assembled in the manufacturing process of the exhaust gas purifier, the fiber clumps 11 reduce the pressing shock and suppress the breakage of the mat material body. can do.
On the other hand, if the fiber mass 11 is a hard mass without the low-accumulation portion 12 in the center, the fiber mass 11 may press against the mat material main body and break the inorganic fibers of the mat material main body during assembly.

As shown in FIG. 4, the surface 6 to be processed of the mat material has a plurality of fiber clumps 11, and the ends 13 of the plurality of fiber clumps 11 in the same direction D are separated from the surface 6 to be processed. is preferred.
That is, one end 13 of the fiber mass 11 in a certain direction D is separated from the surface 6 to be processed, and the other end 14 of the fiber mass 11 in the direction D is integrated without being separated from the surface 6 to be processed. preferably.
Since such a mat material can be produced using a processing apparatus such as a raising apparatus, it can be made into a mat material excellent in mass productivity.

Note that FIG. 4 shows a case where the direction D in which the end portion 13 away from the surface 6 to be processed is oriented is the longitudinal direction of the mat material, but the direction D is not particularly limited and can be set as appropriate. is.

^In the mat material of the present invention, the coefficient of friction of the surface to be processed, of the first main surface and the second main surface, which has undergone the above-described surface treatment is , preferably 0.21 to 0.45, more preferably 0.23 to 0.45.

In addition, when each main surface is a surface to be processed, the coefficient of friction of the first main surface and the second main surface may be different from each other, but from the viewpoint of easy production using the same processing equipment, substantially preferably substantially the same.

In the mat material of the present invention, the bulk density near the surface to be processed is preferably smaller than the bulk density near the center in the thickness direction of the mat material.

More specifically, the mat material of the present invention has a bulk density of 0.05 to 0.18 g/cm ³ near the surface to be processed, and a bulk density of 0.05 g/cm 3 near the center in the thickness direction of the mat material. It is preferably 11 to 0.20 g/cm ³ , the bulk density near the surface to be processed is 0.05 to 0.14 g/cm ³ , and the bulk density near the center in the thickness direction of the mat material is 0. 0.11 to 0.20 g/cm ³ is more preferred.
More specifically, in the mat material of the present invention, the bulk density near the processed surface is preferably 45 to 95%, preferably 60 to 90%, of the bulk density near the center in the thickness direction of the mat material. is more preferable.
Here, the bulk density in the vicinity of the surface to be processed is the bulk density of the portion to be processed (the portion including the surface to be processed) when the mat material is divided into three equal parts in the thickness direction, and is the center of the thickness direction of the mat material. The bulk density in the vicinity is the bulk density in the central portion (portion not including the surface to be processed) when the mat material is divided into three equal parts in the thickness direction.

When each main surface is a surface to be processed, the bulk density in the vicinity of the first main surface and the second main surface may be different from each other, but from the viewpoint of easy production using the same processing apparatus, Preferably they are substantially the same.

The mat material of the present invention may be a mat produced by a paper-making method (hereinafter referred to as a paper-made mat) subjected to surface treatment, but a mat produced by a needling method (hereinafter referred to as a needle mat) may be used. It is preferable to apply surface treatment.
When a needle mat is used, it is possible to obtain the effect of improving the coefficient of friction more effectively than when a paper-made mat is used.
The reason for this will be described in detail below with reference to FIGS. 5 and 6. FIG.
FIG. 5 is a cross-sectional view schematically showing an example of a non-surface-treated needle mat.
FIG. 6 is a cross-sectional view schematically showing an example of the mat member of the present invention.
5 and 6 show a cross section of a portion that has not undergone needle punching.
Further, the upper right portion of FIG. 6 shows a partially enlarged view of the surface to be processed of the mat member.

Since the needle mat is basically produced by laminating fibers with a cross layer, as shown in FIG. be.
Therefore, it is considered that each inorganic fiber 10 is likely to move, and step deviation is likely to occur at the interface where friction occurs, and the holding force is likely to decrease.

However, as shown in FIG. 6, in the mat material 1 manufactured by the needling method and having the surface 6 to be processed raised, the inorganic fibers 10 are not separated at the interface where friction occurs, as shown in the enlarged view of FIG. The orientation will be forced to change to random orientation. Therefore, the inorganic fibers are less likely to move with respect to external force, so that step deviation can be effectively suppressed, and the holding force F can be significantly improved.

On the other hand, since the paper-processed mat has less bias in fiber orientation than the needle mat, the inorganic fibers are difficult to move in the first place, and the step deviation is less likely to occur. Therefore, compared with the needle mat, the effect of improving the coefficient of friction by the raising treatment is smaller.

Next, a method for manufacturing the mat material of the present invention will be described.
A method for producing a mat material according to the present invention comprises a mat preparation step of preparing a mat made of inorganic fibers, a first main surface of the mat, and a second main surface of the mat opposite to the first main surface. and at least one of and a surface processing step of applying surface processing to change the surface state.

A mat made of inorganic fibers can be obtained by various methods, for example, it can be produced by a papermaking method or a needling method, but is preferably produced by a needling method. As a result, as described above, the effect of improving the coefficient of friction can be obtained more effectively than when the mat is produced by the papermaking method.
In the case of the papermaking method, for example, it can be produced by the following method.
Inorganic fibers are opened, and the opened inorganic fibers are dispersed in a solvent to form a mixed solution. An inorganic fiber assembly is obtained by pouring the liquid mixture into a molding device having a mesh for filtration formed on the bottom surface and removing the solvent in the liquid mixture. A mat can be obtained by drying the inorganic fiber aggregate.
In the case of the needling method, for example, it can be produced by the following method.
A spinning mixture made from a basic aqueous solution of aluminum chloride and silica sol or the like is spun by a blowing method to produce an inorganic fiber precursor. Subsequently, the inorganic fiber precursor is compressed to form a continuous sheet-like material having a predetermined size, and the sheet-like material is subjected to a sintering treatment to obtain a mat. Either before or after this baking treatment, needle punching treatment is performed to entangle the inorganic fibers.

Although the thickness of the mat is not particularly limited, it is preferably 2 to 40 mm, more preferably 5 to 20 mm.
When the thickness of the mat is less than 2 mm, the holding power of the mat material is insufficient, and the exhaust gas treating body tends to fall off.
If the thickness of the mat exceeds 40 mm, the flexibility of the mat is lost, making it difficult to handle when winding the mat material around the exhaust gas treating body. In addition, winding wrinkles and cracks are likely to occur in the mat material.

Subsequently, at least one of the first main surface of the mat and the second main surface of the mat opposite to the first main surface is subjected to surface treatment to change the surface condition. conduct.

In the method for manufacturing a mat material of the present invention, preferably, in the surface processing step, at least one of the first main surface and the second main surface is subjected to a raising treatment.
As a result, it is possible to generate raised inorganic fibers on the first main surface and/or the second main surface, so that the effect of improving the coefficient of friction is exhibited more favorably as described above.
A specific means for applying the raising treatment is not particularly limited, and examples thereof include a treatment device such as a raising device, sandpaper, and the like. Raising may be performed manually with a needle.
From the viewpoint of mass productivity, it is preferable to perform the raising treatment using a treatment device such as a raising device.
The raising device has, for example, one or more rollers wound with a card cloth having a large number of needles, and the inorganic fibers are scratched out from the main surface of the mat by running the mat over the rollers while rotating the rollers. .

The exhaust gas purifier of the present invention will be described below.
An exhaust gas purifying apparatus of the present invention comprises an exhaust gas treating body, a metal casing housing the exhaust gas treating body, a mat material disposed between the exhaust gas treating body and the metal casing and holding the exhaust gas treating body, , wherein the mat material is the mat material of the present invention.

As described above, the mat material of the present invention has the effect of improving the friction coefficient of the surface. Therefore, the exhaust gas treating apparatus of the present invention can be used as an exhaust gas purifying apparatus in which the exhaust gas treating body is held with a high holding force.

FIG. 7 is a cross-sectional view schematically showing an example of the exhaust gas purifier of the present invention.
As shown in FIG. 7, the exhaust gas purifier 100 of the present invention includes a metal casing 50, an exhaust gas treating body 40 housed in the metal casing 50, and disposed between the exhaust gas treating body 40 and the metal casing 50 to and a mat material 1 for holding the processing object 40 .

The exhaust gas treating body 40 has a columnar shape in which a large number of cells 41 are arranged side by side in the longitudinal direction with cell walls 42 interposed therebetween. One end of the cell is sealed with a sealing material 43 .
An introduction pipe for introducing exhaust gas discharged from the internal combustion engine and an exhaust pipe for discharging the exhaust gas that has passed through the exhaust gas purifying device are connected to the ends of the metal casing 50 as necessary. It will happen.

A case where exhaust gas passes through the exhaust gas purifier 100 having the above configuration will be described below with reference to FIG.
As shown in FIG. 7, the exhaust gas discharged from the internal combustion engine and flowing into the exhaust gas purifying device 100 (in FIG. 7, the exhaust gas is indicated by G and the flow of the exhaust gas is indicated by the arrow) is an exhaust gas treating body (honeycomb filter) 40 The exhaust gas flows into one cell 41 opened at the exhaust gas inflow side end face of the , and passes through the cell wall 42 separating the cells 41 . At this time, the PM in the exhaust gas is captured by the cell walls 42, and the exhaust gas is purified. The purified exhaust gas flows out from another cell 41 that is open on the end surface on the exhaust gas outflow side and is discharged to the outside.

In the exhaust gas purifier 100 shown in FIG. 7, the mat material 1 is the mat material of the present invention, and the first and second main surfaces of the mat material 1 are both surface-treated (preferably raised). It is preferable that the surface to be machined has a changed surface condition due to the polishing.

The material of the metal casing that constitutes the exhaust gas purifier of the present invention is not particularly limited as long as it is a heat-resistant metal, and specific examples include metals such as stainless steel, aluminum, and iron.

In addition, the shape of the casing may preferably be a substantially cylindrical shape, a clamshell shape, a substantially elliptical shape in cross section, a substantially polygonal shape, or the like.

The exhaust gas treating body 40 shown in FIG. 7 is a filter in which one end of the cells 41 is sealed with a sealing material 43, but the exhaust gas treating body constituting the exhaust gas purifying apparatus of the present invention is , the ends of the cell may not be sealed. Such an exhaust gas treating body can be suitably used as a catalyst carrier.

The exhaust gas treating body 40 may be made of a non-oxide porous ceramic such as silicon carbide or silicon nitride, or may be made of an oxide porous ceramic such as alumina, cordierite or mullite. Among these, silicon carbide is preferred.

The cell density in the cross section of the exhaust gas treating body 40 is not particularly limited, but a preferable lower limit is 31.0 cells/cm ² (200 cells/inch ² ), and a preferable upper limit is 93.0 cells/cm ² (600 cells/inch 2 ). inch ² ). A more preferable lower limit is 38.8/cm ² (250/inch ² ), and a more preferable upper limit is 77.5/cm ² (500/inch ² ).

The exhaust gas treating body 40 may carry a catalyst for purifying the exhaust gas, and the catalyst to be carried is preferably a noble metal such as platinum, palladium, rhodium, etc. Among them, platinum is more preferable. As other catalysts, for example, alkali metals such as potassium and sodium, and alkaline earth metals such as barium can also be used. These catalysts may be used alone or in combination of two or more.
When these catalysts are carried, it becomes easier to burn and remove PM, and it becomes possible to purify toxic exhaust gas.

(Example)
Examples that more specifically disclose the present invention are shown below. In addition, the present invention is not limited only to these examples.

(Example 1)
A mat made of inorganic fibers (mullite fibers) was produced by a needling method.
This mat was punched into a square having a side of 50 mm.
The thickness of the mat was 8.5 mm, and the inorganic fibers forming the mat had a fiber length of 1 to 150 mm, an average fiber length of 10 mm, and an average fiber diameter of 5.5 μm.

Subsequently, one main surface of the square-punched mat was uniformly processed with sandpaper (no. 150), and the raised treatment was repeated three times to prepare the mat member of Example 1.

(Example 2)
FIG. 8 is a plan view schematically showing the processed surface of the mat material of Example 2. FIG.
The mat used in Example 1 was punched into a square with a side of 50 mm.
Subsequently, one main surface of the square-punched mat was raised using a needle with a diameter of 1 mm to prepare the mat material of Example 2.
More specifically, a needle is inserted obliquely into the main surface by hand to a depth of about 2 mm and then pulled up to scrape out the inorganic fibers on the main surface. It was performed at a pitch interval of 3 mm.

(Comparative example 1)
The mat used in Example 1 was punched into a square with a side of 50 mm and used as it was.

(Measurement of friction coefficient)
The coefficient of friction of the mat materials of Examples and Comparative Examples was measured by the following method.
9 and 10 are schematic diagrams showing a friction coefficient measuring device for a mat material.
In the friction coefficient measuring device 200, stainless steel flat plates (left plate 210 and right plate 220) are arranged on the left and right sides of the device so as to face each other.

First, the two mat members 1a and 1b and the middle plate 230 were arranged in this order: the left plate 210, the mat member 1a, the stainless steel flat plate (middle plate 230), the mat member 1b, and the right plate 220. .
Projecting members 240 are provided on the surfaces of the left plate 210 and the right plate 220 to prevent slipping between the left plate 210 and the mat material 1a and between the right plate 220 and the mat material 1b (between the plate and the mat material). established.
In the mat material of the example, the raised surface was arranged on the intermediate plate 230 side.
The mat member 1a is sandwiched between the left plate 210 and the middle plate 230, and the mat member 1b is sandwiched between the middle plate 230 and the right plate 220. As shown in FIG.
In addition, the intermediate plate 230 is a load cell and can measure the load applied to the intermediate plate.

First, pressure was applied to the left plate 210 and the right plate 220 in the direction of the middle plate 230 to compress the mat material until the bulk density (GBD) thereof reached 0.3 g/cm ³ .
The compressed state was held (relaxed) for 10 minutes.

Next, the intermediate plate 230 is moved in the direction indicated by the arrow in FIG. , shear stress was applied to the main surface of the mat material.
FIG. 10 shows the state in which the middle plate has been moved.
The direction in which the intermediate plate is moved is the same as the direction in which the shear stress is applied to the main surface of the mat material on the side in contact with the intermediate plate.
The load value of the load cell during movement and the static frictional force applied to the intermediate plate were measured, and the coefficient of friction (static frictional coefficient) when the static frictional force reached its maximum was measured.

(Measurement of bulk density)
First, a mat member punched into a square having a side of 50 mm was cut equally into three pieces in the thickness direction.
Next, the weight and thickness of each of the mat members cut into three pieces were measured. The thickness was measured with a dial gauge (measurement terminal φ20 mm, load 4.9 kPa).
Then, as shown in the following formula, from the surface specific gravity (weight/area) calculated from the weight and the thickness, the bulk density in the vicinity of the surface to be processed (processed portion) and the vicinity of the center in the thickness direction of the mat material (central portion ) were calculated respectively.
(weight/area)/thickness = bulk density [g/cm ³ ]

FIG. 11 and Table 1 show the measurement results of the friction coefficients of the mat materials in Examples and Comparative Examples.
Table 2 shows the ratio of the coefficient of friction of the mat member of the example to the coefficient of friction of the mat member of the comparative example.

As shown in FIG. 11 and Tables 1 and 2, the mat member of the example whose surface was raised has a higher coefficient of friction than the mat member of the comparative example, which is not surface-treated. % or more was confirmed.
Further, the mat members of the examples do not require additional materials and the manufacturing process is simple, so that they can be manufactured at low cost.

Table 3 shows the measurement results of the bulk density of the mat materials in Examples and Comparative Examples. Table 3 also shows the results of calculating the ratio of the bulk density of the processed portion (the upper portion in Comparative Example 1) to the bulk density of the central portion in each of the examples and comparative examples.

As shown in Table 3, the non-surface-treated comparative mat material has approximately the same bulk density in the upper portion and the central portion, and has a uniform bulk density throughout the mat material. It was confirmed that, in the mat material of the example having the raised surface, the processed portion had a lower bulk density than the central portion, and the bulk density decreased in the vicinity of the processed surface where the raised processing was performed.

(Surface observation)
FIG. 12 is a photograph of the processed surface of the mat material of Example 2 observed with a microscope. In FIG. 12, the left side shows the state before the surface treatment by the raising treatment, and the right side shows the state after the surface treatment by the raising treatment.
As shown in FIG. 12, the mat material of the embodiment having a raised surface has raised inorganic fibers 10 on the surface 6 to be processed, and these raised inorganic fibers 10 partially extend from the surface 6 to be processed. It was confirmed that the fiber clumps 11 spaced apart were formed.
Moreover, many of the fiber clumps 11 had a low accumulation portion 12 in the center where the density of the inorganic fibers was lower than that of the surrounding area.

1 mat material 1a mat material 1b mat material 2 one end portion 2a convex portion 3 other end portion 3a concave portion 4 first main surface 5 second main surface 6 surface to be processed 10 inorganic fiber 11 fiber mass 12 low accumulation portion 13 fiber One end of lump 14 The other end of fiber lump 40 Exhaust gas treating body 41 Cell 42 Cell wall 43 Sealing material 50 Metal casing 100 Exhaust gas purification device 200 Friction coefficient measuring device 210 Left plate 220 Right plate 230 Middle plate 240 Projection Member G Exhaust gas

Claims (13)

A mat material made of inorganic fibers,
The mat material has a first main surface and a second main surface located on the opposite side of the first main surface,
A mat member, wherein at least one of the first main surface and the second main surface is subjected to a surface treatment to change the surface state. 2. The mat material according to claim 1, wherein said first principal surface and said second principal surface are subjected to said surface processing to change the surface state thereof. 3. The mat material according to claim 1, wherein the surface to be processed of the first main surface and the second main surface has raised inorganic fibers. The raised inorganic fibers form a fiber mass,
4. The mat material according to claim 3, wherein said fiber mass is partially separated from said surface to be processed. The surface to be processed has a plurality of the fiber lumps,
5. The mat material according to claim 4, wherein the ends of the plurality of fiber clumps in the same direction are separated from the surface to be processed. The coefficient of friction of the surface to be processed, of the first main surface and the second main surface, to which the surface treatment has been applied is from 0.21 to 0.21 at 25° C. and the bulk density of the mat material is 0.3 g/cm ³ . 6. The mat material according to any one of claims 1 to 5, which is 0.45. 7. The method according to any one of claims 1 to 6, wherein the bulk density in the vicinity of the surface to be processed of the first principal surface and the second principal surface that has been surface-processed is smaller than the bulk density in the vicinity of the center in the thickness direction of the mat material. The matting material according to any one of the above. The bulk density in the vicinity of the surface to be processed of the first main surface and the second main surface that has been surface-treated is 0.05 to 0.18 g/cm ³ ,
The mat material according to any one of claims 1 to 7, wherein the bulk density near the center in the thickness direction of the mat material is 0.11 to 0.20 g/cm ³ . The bulk density near the processed surface of the first principal surface and the second principal surface is 45 to 95% of the bulk density near the center in the thickness direction of the mat material. A mat material according to any one of claims 1 to 8. an exhaust gas treating body;
a metal casing housing the exhaust gas treating body;
and a mat member disposed between the exhaust gas treating body and the metal casing and holding the exhaust gas treating body, the exhaust gas purifying apparatus comprising:
An exhaust gas purifier, wherein the mat material is the mat material according to any one of claims 1 to 9. a mat preparation step of preparing a mat made of inorganic fibers;
a surface processing step of subjecting at least one of a first principal surface of the mat and a second principal surface of the mat opposite to the first principal surface to surface processing to change the surface state;
A method for producing a mat material, comprising: 12. The method of manufacturing a mat material according to claim 11, wherein in the surface processing step, at least one of the first main surface and the second main surface is raised. 13. The method of manufacturing a mat material according to claim 11, wherein in the mat preparing step, the mat is manufactured by a needling method.

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