Mat material and holding seal material

Abstract

This mat material includes a laminated mat including at least one layer of an alignment layer made of inorganic fibers and having the alignment directions of the inorganic fibers aligned, and at least one layer of a random layer made of inorganic fibers and having random orientation directions of the inorganic fibers. The laminated mat includes a binder.

Description

Mat material and holding seal material

[0001] The present invention relates to a mat material and a holding sealing material.

[0002] Particulate matter (hereinafter referred to as PM) is contained in exhaust gases emitted from internal combustion engines such as diesel engines, and in recent years, the harm that this PM poses to the environment and human health has become a problem. Furthermore, because exhaust gases also contain harmful gas components such as CO, HC, and NOx, there are concerns about the impact that these harmful gas components have on the environment and human health.

[0003] Therefore, various exhaust gas purification devices have been proposed that capture PM in exhaust gas and purify harmful gas components, and are composed of an exhaust gas treatment body made of porous ceramics such as silicon carbide or cordierite, a metal casing that houses the exhaust gas treatment body, and a holding seal material (mat material) disposed between the exhaust gas treatment body and the metal casing. This holding seal material (mat material) is disposed mainly for the purposes of preventing damage to the exhaust gas treatment body due to contact with the metal casing that surrounds it due to vibrations and impacts caused by the running of the automobile, and preventing exhaust gas from leaking from between the exhaust gas treatment body and the metal casing.

[0004] As a mat material used for such purposes, Patent Document 1 discloses a holding and sealing material consisting of a mat of a predetermined thickness containing inorganic fibers whose surface is covered with a binder layer, wherein the binder layer contains an organic binder and an inorganic binder, and when the mat is divided into three equal parts in the thickness direction into a first surface portion, a central portion, and a second surface portion, the amount of organic binder attached to the first surface portion is greater than the amount of organic binder attached to the central portion and is also greater than the amount of organic binder attached to the second surface portion.

[0005] JP 2015-63925 A

[0006] When wrapping the mat material around the exhaust gas treatment body, the wrapping operation may be performed while applying a tensile load to the mat material. If the tensile strength of the mat material is low during this operation, the tensile load may cause the mat material to break, which has been a problem. The mat material described in Patent Document 1 also has insufficient tensile strength, and it has been desired to improve the tensile strength of the mat material.

[0007] The present invention has been made in view of the above-mentioned problems, and has an object to provide a mat material having high tensile strength.

[0008] The mat material of the present invention comprises a laminated mat including at least one oriented layer made of inorganic fibers in which the orientation direction of the inorganic fibers is uniform, and at least one random layer made of inorganic fibers in which the orientation direction of the inorganic fibers is random, and the laminated mat includes a binder.

[0009] The laminated mat constituting the mat material of the present invention comprises an oriented layer and a random layer. The presence of the oriented layer makes the mat material less likely to stretch and has high tensile strength. In addition, the random layer is easily impregnated with a binder. By incorporating a binder into the mat material, the frictional force of the surface of the mat material can be increased.

[0010] In the mat material of the present invention, the orientation layers and the random layers are alternately laminated in the thickness direction, and it is preferable that the random layers are disposed on both of the two outermost layers of the laminated mat.

[0011] When the binder is impregnated into the laminated mat, the binder is placed on the outermost layer of the laminated mat and penetrates through the random layer in the thickness direction of the laminated mat. Because the binder easily penetrates the random layer and difficultly penetrates the oriented layer, the binder is blocked by the oriented layer in the thickness direction of the laminated mat. As a result, the binder content is high in the outermost layer of the laminated mat that comes into contact with the binder liquid for binder impregnation. Since a high binder content increases frictional force, if the outermost layer with a high binder content is used as the surface that comes into contact with the exhaust gas treatment body, which requires frictional force during winding, slippage between the exhaust gas treatment body and the mat material is prevented, making it preferable for use.

[0012] In the mat material of the present invention, the laminated mat preferably contains at least one binder selected from the group consisting of an organic binder and an inorganic binder.

[0013] In the mat material of the present invention, when the laminated mat is divided into three equal parts in the thickness direction into a first surface portion, a central portion, and a second surface portion, the random layer is arranged in the outermost layer of the first surface portion, and it is preferable that the binder content in the first surface portion is greater than the binder content in the central portion and greater than the binder content in the second surface portion.

[0014] In the above-mentioned mat material, since the binder content in the first surface portion is high, when the first surface portion is used as the portion that contacts the exhaust gas treatment body, misalignment between the exhaust gas treatment body and the mat material is prevented, making it suitable for use. Furthermore, the mat material is used in an exhaust gas purification device, but the environment in which the exhaust gas purification device is used is a high-temperature environment, which can cause the binder (especially an organic binder) to volatilize. Therefore, mat materials intended for use in exhaust gas purification devices are required to have a low binder content. In the above-mentioned mat material, the binder content is high in the first surface portion, but the content of the mat material throughout the entire mat material is not high. Therefore, the binder content requirement for the entire mat material can be met.

[0015] In the mat member of the present invention, it is preferable that the content of the binder satisfies the following relationships: 0.4≦(center portion / first surface portion) 0.2≦(second surface portion / first surface portion) (second surface portion / center portion)≦0.5 Furthermore, it is preferable that the content of the binder further satisfies the following relationship: 0<(second surface portion / center portion)

[0016] If the binder contents in the first surface portion, the central portion, and the second surface portion satisfy the above relationship, when the first surface portion is brought into contact with and wrapped around the exhaust gas treatment body, the frictional force between the mat material and the exhaust gas treatment body is improved, and interfacial slippage between the mat material and the exhaust gas treatment body is less likely to occur when the mat material is assembled into the casing.

[0017] In the mat material of the present invention, the inorganic fibers in the orientation layer preferably contain 70% or more of inorganic fibers having an inclination of 60 to 90 degrees with respect to the width direction of the mat material.

[0018] The mat material of the present invention preferably has a tensile strength at break of 200 kPa or more as measured by a tensile test, and an elongation at break of 3.5 mm or less as measured by a tensile test.

[0019] When the tensile strength at break and the elongation at break measured by the tensile test are within the above ranges, breakage of the mat material can be more reliably prevented when it is wrapped around an exhaust gas treatment body, etc. Furthermore, when the tensile strength at break is high and the elongation at break is small, variation in workability during wrapping is reduced.

[0020] The holding seal material of the present invention is made of the mat material of the present invention and is used to hold an exhaust gas treatment body in an exhaust gas purification apparatus.

[0021] The mat material of the present invention is a mat material that is resistant to stretching and has high tensile strength, and therefore is resistant to breakage when wrapped around an exhaust gas treatment body, making it suitable for use as a holding and sealing material.

[0022] FIG. 1 is a perspective view schematically showing an example of a mat material. FIG. 2 is a cross-sectional view of the mat material shown in FIG. 1 taken along line A-A. FIG. 3 is a perspective view schematically showing an example of an orientation layer. FIG. 4 is an example of a micrograph including inorganic fibers. FIG. 5 is a perspective view schematically showing an example of a random layer. FIG. 6 is a cross-sectional view schematically showing a needle mat including a rivet portion. FIG. 7 is a cross-sectional view schematically showing an example of an exhaust gas purification device. FIG. 8 is a perspective view schematically showing an example of an exhaust gas treatment body constituting the exhaust gas purification device. FIG. 9 is a perspective view schematically showing an example of a method for manufacturing an exhaust gas purification device.

[0023] An example of the mat material and holding sealing material of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a perspective view schematically showing an example of the mat material. FIG. 2 is a cross-sectional view of the mat material shown in FIG. 1 taken along line A-A. The mat material 10 shown in FIG. 1 is a laminated mat 20 including an orientation layer 30 and a random layer 40. Three layers, namely, a random layer 40a, an orientation layer 30, and a random layer 40b, are laminated along the thickness direction of the laminated mat 20 (the direction indicated by the double-headed arrow T in FIGS. 1 and 2). The random layer 40a and the random layer 40b are layers with the same specifications.

[0024] The laminate mat 20 is a mat that is long in its longitudinal direction (the direction indicated by the double-headed arrow L in FIG. 1 ). The laminate mat 20 has two main surfaces, a first main surface 23 and a second main surface 24. The first main surface 23 is the surface of the random layer 40 a, and the second main surface 24 is the surface of the random layer 40 b.

[0025] The laminate mat 20 has four side surfaces, and the side surfaces along the longitudinal direction of the laminate mat 20 are a first long side surface 25 and a second long side surface 26. The side surfaces along the width direction of the laminate mat 20 (the direction indicated by the double-headed arrow W in FIG. 1 ) are a first short side surface 27 and a second short side surface 28. The top view of the laminate mat 20 is generally rectangular, with a recessed portion formed on the first short side surface 27 and a protruding portion formed on the second short side surface 28. The recessed portion and the protruding portion are shaped to fit together when the mat material is wrapped around an exhaust gas purification device, an exhaust gas treatment body, or an exhaust pipe having a cylindrical outer periphery. In the mat material of this embodiment, the fitting portions are shaped as a recessed portion and a protruding portion, but the fitting portions may also be shaped as an L-shaped combination.

[0026] FIG. 3 is a perspective view schematically showing an example of an alignment layer. FIG. 3 shows an alignment layer 30, and schematically shows inorganic fibers 31 constituting the alignment layer 30 together with their orientation direction. The alignment layer 30 is a layer made of inorganic fibers in which the orientation direction of the inorganic fibers is uniform. In the alignment layer, it is preferable that the orientation direction of the inorganic fibers is uniform in the direction along the main surface of the mat material (the LW plane direction in FIG. 3). It is also preferable that the inorganic fibers are oriented in the longitudinal direction (the L direction in FIG. 3) or width direction (the W direction in FIG. 3) of the mat material. In the alignment layer shown in FIG. 3, the inorganic fibers are oriented in the direction along the longitudinal direction of the mat material.

[0027] In this specification, "the orientation direction of inorganic fibers is uniform" means that, when the angle of the inorganic fibers is measured in one direction of the photographed area (usually the horizontal direction of the photographed area) in a micrograph containing inorganic fibers, 50% or more of the fibers are present in a range of 75 to 90 degrees.

[0028] Figure 4 is an example of a micrograph containing inorganic fibers. The photograph shown in Figure 4 shows inorganic fibers 31. In Figure 4, it can be visually seen that many of the inorganic fibers are oriented in the vertical direction (90° direction) of the photographed area. 52% of the inorganic fibers have an angle θ of 75 to 90 degrees, measured with respect to the horizontal direction (0° direction) of the photographed area. In other words, the layer from which the photograph shown in Figure 4 was taken is an oriented layer.

[0029] Furthermore, it is preferable that the inorganic fibers in the orientation layer contain 70% or more inorganic fibers inclined at 60 to 90 degrees relative to the width direction of the mat material. When the orientation layer satisfies the above conditions, the orientation of the inorganic fibers is aligned with the direction in which tensile stress is applied when the mat material is wrapped, which is preferable because it tends to increase the tensile strength of the mat material. The horizontal direction of the photograph shown in Figure 4 is the width direction of the mat material, and 78% of the inorganic fibers have an angle θ of 60 to 90 degrees. That is, in the orientation layer from which the photograph shown in Figure 4 was taken, the inorganic fibers contain 70% or more inorganic fibers inclined at 60 to 90 degrees relative to the width direction of the mat material. Since the direction inclined at 60 to 90 degrees relative to the width direction of the mat material can be said to be along the longitudinal direction of the mat material, it can be said that the inorganic fibers in the orientation layer are oriented along the longitudinal direction of the mat material.

[0030] In the orientation layer, the proportion of inorganic fibers whose angle θ measured with respect to the horizontal direction (0° direction) of the imaging area is in the range of 75 to 90 degrees may be 60% or more, or may be 70% or more, and the proportion of inorganic fibers whose angle θ is in the range of 75 to 90 degrees may be 90% or less, or may be 80% or less.

[0031] The orientation layer may contain 75% or more, or 85% or more, of inorganic fibers inclined at 60 to 90 degrees relative to the width direction of the mat material, and may contain 95% or less, or 90% or less, of inorganic fibers inclined at 60 to 90 degrees relative to the width direction of the mat material.

[0032] Fig. 5 is a perspective view schematically showing an example of a random layer. Fig. 5 shows a random layer 40, and schematically shows inorganic fibers 41 that make up the random layer 40. The random layer 40 is a layer made of inorganic fibers, the orientation direction of the inorganic fibers being random.

[0033] In this specification, "the orientation direction of inorganic fibers is random" means that in a micrograph containing inorganic fibers, it is visible that the inorganic fibers are not oriented in a specific direction in the photographed area. A layer in which the orientation of inorganic fibers does not fit the definition of an oriented layer described above may also be called a random layer.

[0034] It is preferable that the orientation layer and the random layer in the laminated mat are arranged alternately in the thickness direction. In Figures 1 and 2, they are arranged alternately in the order of random layer 40a / orientation layer 30 / random layer 40b, and the two outermost layers of the laminated mat are both random layers. The number of mats stacked in the laminated mat is not particularly limited as long as it includes at least one orientation layer and one random layer. Since it is preferable that the random layer is arranged as the outermost layer and the random layers and orientation layers are arranged alternately, three or five mats are preferable. Examples include three layers of random layer / orientation layer / random layer, and five layers of random layer / orientation layer / random layer / orientation layer / random layer.

[0035] The mats constituting the laminated mat contain inorganic fibers. The inorganic fibers are not particularly limited and may be alumina fibers, silica fibers, etc. They may also be glass fibers or biosoluble fibers. The inorganic fibers may be changed depending on the properties required of the mat material, such as heat resistance and wind erosion resistance, and it is preferable to use fibers with a large diameter and fiber length that comply with the environmental regulations of each country.

[0036] Among these, inorganic fibers of low crystalline alumina are preferred, inorganic fibers of low crystalline alumina having a mullite composition are more preferred, and inorganic fibers containing a spinel compound are even more preferred.

[0037] In the mat material of the present invention, the laminated mat contains a binder. By including a binder in the mat material, the frictional force of the surface of the mat material can be increased. Since the random layer is easily impregnated with the binder, it is preferable to impregnate the random layer with the binder.

[0038] The laminate mat preferably contains at least one of an organic binder and an inorganic binder, which can increase the frictional force of the mat material.

[0039] Examples of organic binders include rubber-based resins, styrene-based resins, silicone-based resins, acrylic-based resins, polyester-based resins, and polyurethane resins.

[0040] Examples of inorganic binders include inorganic sol dispersions (alumina sol, silica sol, zirconia sol, titania sol, etc.).

[0041] The content of the binder (total amount of organic binder and inorganic binder) contained in the laminate mat is preferably 0.2 wt % or more and 30 wt % or less of the weight of the laminate mat. Furthermore, when an organic binder is contained, the content of the organic binder is preferably 0.1 wt % or more and 20 wt % or less, and when an inorganic binder is contained, the content of the inorganic binder is preferably 0.1 wt % or more and 10 wt % or less.

[0042] When the laminate mat contains a binder, it is preferable that the outermost layer of the laminate mat is a random layer and that an orientation layer is disposed inside the random layer. When the binder is impregnated into the laminate mat, the binder is disposed on the outermost layer of the laminate mat and penetrates through the random layer in the thickness direction of the laminate mat. Because the binder easily penetrates the random layer and difficultly penetrates the orientation layer, the binder is blocked by the orientation layer in the thickness direction of the laminate mat. As a result, the binder content is high in the outermost layer of the laminate mat that comes into contact with the binder liquid for binder impregnation. Since a high binder content increases frictional force, if the outermost layer with a high binder content is used as the surface that comes into contact with the exhaust gas treatment body, which requires frictional force during winding, slippage between the exhaust gas treatment body and the mat material is prevented, and it can be used preferably.

[0043] As a specific example of a configuration in which the outermost layer of the laminated mat is a random layer and an orientation layer is arranged inside the random layer, it is preferable that the orientation layer and the random layer are alternately laminated in the thickness direction, and that both of the two outermost layers of the laminated mat are random layers.

[0044] Furthermore, when the laminated mat is divided into three equal parts in the thickness direction into a first surface portion, a central portion, and a second surface portion, it is preferable that a random layer is disposed on the outermost layer of the first surface portion, and that the binder content in the first surface portion is greater than the binder content in the central portion and greater than the binder content in the second surface portion.

[0045] 2, the random layer 40a, the orientation layer 30, and the random layer 40b are all the same thickness, so that the random layer 40a can be considered as the first surface portion, the orientation layer 30 as the central portion, and the random layer 40b as the second surface portion. In this case, it is preferable that the binder content in the random layer 40a is greater than the binder content in the orientation layer 30 and greater than the binder content in the random layer 40b.

[0046] In a mat material having a random layer disposed on the outermost layer of the first surface portion, the binder content in the first surface portion is high. Therefore, when the first surface portion is used as a portion that contacts the exhaust gas treatment body, the mat material is prevented from slipping from the exhaust gas treatment body, making it suitable for use. Furthermore, the mat material is used in an exhaust gas purification device, but the environment in which the exhaust gas purification device is used is a high-temperature environment, which can cause the binder (especially an organic binder) to volatilize. Therefore, mat materials intended for use in exhaust gas purification devices are required to have a low binder content. In the mat material having the above configuration, the binder content is high in the first surface portion, but the mat material content is not high throughout the entire mat material. Therefore, the binder content requirement for the entire mat material can be met.

[0047] Furthermore, it is preferable that the binder content satisfy the following relationships: 0.4≦(central portion / first surface portion) 0.2≦(second surface portion / first surface portion) (second surface portion / central portion)≦0.5 Furthermore, it is preferable that the binder content satisfy the following relationships: 0<(second surface portion / central portion)

[0048] If the binder contents in the first surface portion, the central portion, and the second surface portion satisfy the above relationship, when the first surface portion is brought into contact with and wrapped around the exhaust gas treatment body, the frictional force between the mat material and the exhaust gas treatment body is improved, and interfacial slippage between the mat material and the exhaust gas treatment body is less likely to occur when the mat material is assembled into the casing.

[0049] Furthermore, it is preferable that the binder content of the first surface portion is 0.1% by weight or more and 29.0% by weight or less, the binder content of the central portion is 0.2% by weight or more and 15.0% by weight or less, and the binder content of the second surface portion is 0.05% by weight or more and 5.0% by weight or less.

[0050] The mat material of the present invention preferably has a tensile strength at break of 200 kPa or more as measured by a tensile test, and an elongation at break of 3.5 mm or less as measured by a tensile test.

[0051] The tensile strength at break and elongation at break are measured by cutting the mat material into samples measuring 200 mm in length along the longitudinal direction of the mat material and 50 mm in width along the width direction of the mat material. The thickness of the sample is measured at three points, and using a universal testing machine equipped with a chuck (gripping jig) for tensile tests, the chuck distance is set to 40 mm on each side, and the mat material is pulled along the longitudinal direction of the sample at a speed of 100 mm / min, and the load at break and pulling distance are determined. Tensile strength at break is calculated as follows: Load at break / (Sample thickness x width). The pulling distance at break is taken as the elongation at break.

[0052] When the tensile strength at break and the elongation at break measured by the tensile test are within the above ranges, breakage of the mat material can be more reliably prevented when it is wrapped around an exhaust gas treatment body, etc. Furthermore, when the tensile strength at break is high and the elongation at break is small, variation in workability during wrapping is reduced.

[0053] The orientation layer and random layer constituting the laminated mat may be a paper-made mat obtained by a paper-making method, or a needle mat obtained by a needling method.

[0054] In the papermaking method, for example, inorganic fibers such as alumina fibers or silica fibers, an inorganic binder, and water are mixed together so that the inorganic fiber content in the raw material liquid reaches a predetermined value, and the mixture is stirred with a stirrer to prepare a slurry containing the inorganic fibers. The slurry may optionally contain a colloidal solution of a polymer compound or resin. The mixed liquid is then poured into a molding machine with a filtration mesh on the bottom, and the water in the mixed liquid is dehydrated through the mesh to produce a raw material sheet. The raw material sheet is then heated and compressed under predetermined conditions to obtain a papermaking mat.

[0055] In the case of the needling method, for example, a spinning mixture made from a basic aluminum chloride aqueous solution, silica sol, or the like is spun by a blowing method to produce an inorganic fiber precursor having an average fiber diameter of 3 to 10 μm. Subsequently, the inorganic fiber precursor is compressed to produce a continuous sheet-like product of a predetermined size, which is subjected to a needling treatment (needle-punching treatment), and then subjected to a firing treatment to obtain a needle mat.

[0056] The methods for producing the orientation layer and random layer are not particularly limited, but examples include the following methods. When producing the orientation layer by a papermaking method, if a slurry containing inorganic fibers is papered and allowed to flow in one direction, the fibers will be oriented in the flow direction, resulting in an orientation layer. When producing a random layer by a papermaking method, the slurry containing inorganic fibers is poured into a mold from above. Since there is no flow of the slurry, the fibers will not be oriented in a specific direction, resulting in a random layer. The slurry containing inorganic fibers may contain at least one of an organic binder and an inorganic binder.

[0057] The laminated mat may also be a paper-made mat obtained by laminating an orientation layer and a random layer and then subjecting them to a needling treatment.

[0058] A binder may be applied to the laminate mat. When applying a binder to the laminate mat, a binder liquid containing the binder is allowed to penetrate into the laminate mat in the thickness direction from one main surface (referred to as the first main surface) of the laminate mat. The penetration of the binder liquid may be performed by a method such as curtain coating, in which the binder liquid is dropped onto the mat to apply the binder liquid to the inorganic fibers in the mat, or by spraying the binder liquid onto the mat, as in spray coating.

[0059] When a random layer is placed on the outermost layer of a laminate mat and an oriented layer is placed inside it, the binder easily penetrates the random layer and difficultly penetrates the oriented layer, so the binder is blocked by the oriented layer in the thickness direction of the laminate mat. As a result, the binder content is high in the outermost layer of the laminate mat that comes into contact with the binder liquid for binder impregnation. Since a high binder content increases frictional force, if the outermost layer with a high binder content is used as the surface that comes into contact with the exhaust gas treatment body, which requires frictional force during winding, slippage between the exhaust gas treatment body and the mat material is prevented, and it can be used preferably.

[0060] It is also preferable that the needle mat contains a binder and has a rivet portion that extends in the thickness direction along the needle marks from the first main surface of the laminated mat and has a higher binder concentration than other portions.

[0061] FIG. 6 is a cross-sectional view schematically illustrating a needled mat including a rivet portion. FIG. 6 shows a rivet portion 51 formed by impregnating a needle mark 50 formed by a needling process from the first main surface 23 of the laminated mat 20 with a binder. Having a rivet portion in a needled mat is preferable because the binder penetrates in the thickness direction of the mat material, creating constraints between the inorganic fibers and strengthening the structure of the mat material. The rivet portion is a portion of the laminated mat where the burnt binder (organic binder) appears as a rivet in the cross section when the mat material is heated and the binder is scorched. The depth of the rivet portion is not particularly limited. FIG. 6 also shows that a needle mark 50 is present on the second main surface 24 of the laminated mat 20, but no rivet portion is present because the binder has not penetrated from the second main surface 24.

[0062] The mat material of the present invention can be used as a holding seal material used to hold an exhaust gas treatment body in an exhaust gas purification apparatus. The holding seal material of the present invention comprises the mat material of the present invention and is used as a holding seal material used to hold an exhaust gas treatment body in an exhaust gas purification apparatus.

[0063] Fig. 7 is a cross-sectional view schematically illustrating an example of an exhaust gas purification apparatus. As shown in Fig. 7, the exhaust gas purification apparatus 100 includes a metal casing 130, an exhaust gas treatment body 120 housed in the metal casing 130, and a mat material 10 serving as a holding seal material disposed between the exhaust gas treatment body 120 and the metal casing 130. The exhaust gas treatment body 120 is columnar, with a large number of cells 125 arranged in parallel in the longitudinal direction, separated by cell walls 126. Note that, as necessary, an inlet pipe for introducing exhaust gas emitted from an internal combustion engine and an outlet pipe for discharging exhaust gas that has passed through the exhaust gas purification apparatus to the outside are connected to the ends of the metal casing 130.

[0064] The case where exhaust gas passes through the exhaust gas purification device 100 having the above-described configuration will be described below with reference to FIG. 7 . As shown in FIG. 7 , exhaust gas emitted from an internal combustion engine and flowing into the exhaust gas purification device 100 (in FIG. 7 , the exhaust gas is indicated by G, and the flow of the exhaust gas is indicated by arrows) flows into one cell 125 opening at the exhaust gas inlet end face 120 a of the exhaust gas treatment body (honeycomb filter) 120 and passes through a cell wall 126 separating the cells 125. At this time, PM in the exhaust gas is captured by the cell wall 126, resulting in the purification of the exhaust gas. The purified exhaust gas flows out of another cell 125 opening at the exhaust gas outlet end face 120 b and is discharged to the outside.

[0065] In the exhaust gas purification device 100 shown in Figure 7, the retaining sealing material is the mat material 10 of the present invention, and the first main surface 23 of the laminated mat that constitutes the mat material 10 is arranged on the side of the exhaust gas treatment body 120, and the second main surface 24 is arranged on the side of the metal casing 130.

[0066] The material of the metal casing constituting the exhaust gas purification device 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.

[0067] The casing may be of a generally cylindrical shape, a clamshell shape, or a generally elliptical or polygonal shape in cross section.

[0068] FIG. 8 is a perspective view that schematically shows an example of an exhaust gas treatment body that constitutes an exhaust gas purification device.

[0069] The exhaust gas treatment body 120 shown in Fig. 8 is a honeycomb structure made of a columnar ceramic material in which a large number of cells 125 are arranged in parallel in the longitudinal direction, separated by cell walls 126. Either end of the cells 125 is sealed with a plugging material 128. An outer periphery coating layer 127 is provided on the outer periphery of the honeycomb structure for the purposes of reinforcing the outer periphery of the honeycomb structure, shaping the honeycomb structure, and improving the heat insulating properties of the honeycomb structure.

[0070] When either end of the cell 125 is sealed, it is preferable that, when viewed from one end of the exhaust gas treatment body 120, cells with sealed ends and cells without sealing ends are arranged alternately.

[0071] The cross-sectional shape of the exhaust gas treatment body 120 cut in a direction perpendicular to the longitudinal direction is not particularly limited, and may be approximately circular, approximately elliptical, or approximately polygonal, such as approximately triangular, approximately rectangular, approximately pentagonal, or approximately hexagonal.

[0072] The cross-sectional shape of the cells 125 constituting the exhaust gas treatment body 120 may be a substantially polygonal shape such as a substantially triangular, substantially rectangular, substantially pentagonal, or substantially hexagonal, or may also be a substantially circular or substantially elliptical shape. The exhaust gas treatment body 120 may also be a combination of cells with a plurality of cross-sectional shapes.

[0073] The material constituting the exhaust gas treatment body 120 is not particularly limited, but non-oxides such as silicon carbide and silicon nitride, and oxides such as cordierite and aluminum titanate can be used. Of these, non-oxide porous sintered bodies such as silicon carbide or silicon nitride are particularly desirable. These porous sintered bodies are brittle materials and are therefore easily broken by mechanical impacts, etc. However, if a mat material 10 (holding seal material) is interposed around the side surface of the exhaust gas treatment body 120, it absorbs the impact, thereby preventing cracks, etc. from occurring in the exhaust gas treatment body 120 due to mechanical impacts or thermal shocks.

[0074] The exhaust gas treatment body may be supported with a catalyst for purifying exhaust gas. The supported catalyst is preferably a precious metal such as platinum, palladium, or rhodium, with platinum being more preferred. Other catalysts may also be used, such as alkali metals such as potassium or sodium, or alkaline earth metals such as barium. These catalysts may be used alone or in combination of two or more. Supporting these catalysts facilitates the combustion and removal of PM, making it possible to purify toxic exhaust gases.

[0075] The exhaust gas treatment body constituting the exhaust gas purification device may be an integrally formed monolithic honeycomb structure made of cordierite or the like, or an aggregated honeycomb structure made of silicon carbide or the like, which is formed by bundling together a plurality of columnar honeycomb fired bodies having numerous through holes arranged in parallel in the longitudinal direction separated by partition walls, via a paste mainly containing ceramic.

[0076] The exhaust gas treatment body constituting the exhaust gas purification device may not have a sealing material provided in the cells, and the ends of the cells may not be sealed. In this case, the exhaust gas treatment body supports a catalyst such as platinum, and functions as a catalyst carrier that purifies harmful gas components such as CO, HC, and NOx contained in the exhaust gas.

[0077] The holding sealing material of the present invention made of the mat material of the present invention is used by being wrapped around an exhaust gas treating body. An example in which a wrapped body in which the holding sealing material is wrapped around an exhaust gas treating body is placed in an exhaust gas purification device will be described.

[0078] 9 is a perspective view schematically showing an example of a method for manufacturing an exhaust gas purification device. As shown in FIG. 9, a holding sealing material made of a mat material 10 is wrapped around the periphery of an exhaust gas treatment body 120 to form a wound body 140. Next, the wound body 140 is housed in a metal casing 130 to manufacture the exhaust gas purification device.

[0079] When preparing the wound body 140, the first main surface 23 of the laminated mat 20 constituting the mat material 10 is wound toward the exhaust gas treatment body 120. As a result, the first main surface 23 becomes the surface on the exhaust gas treatment body 120 side, and the second main surface 24 becomes the surface on the metal casing 130 side.

[0080] Next, examples of methods for accommodating the wound body 140 in the metal casing 130 include a stuffing method in which the exhaust gas treatment body 120 (wound body 140) is press-fitted to a predetermined position inside the metal casing 130, around which a holding seal material made of the mat material 10 is disposed; a swaging method in which the metal casing 130 is compressed from the outer periphery to reduce its inner diameter; and a clamshell method in which the metal casing is formed into a shape that can be separated into a first casing and a second casing, the wound body 140 is placed on the first casing, and then the second casing is placed over and sealed. When accommodating the wound body in the metal casing using the stuffing method, it is desirable that the inner diameter of the metal casing (the inner diameter of the portion that accommodates the exhaust gas treatment body) is slightly smaller than the outer diameter of the wound body. Through these processes, the wound body with the holding seal material wrapped around the exhaust gas treatment body can be placed in the exhaust gas purification device.

[0081] The present specification discloses the following:

[0082] The present disclosure (1) is a mat material comprising a laminated mat including at least one oriented layer made of inorganic fibers in which the orientation direction of the inorganic fibers is aligned, and at least one random layer made of inorganic fibers in which the orientation direction of the inorganic fibers is random, and the laminated mat includes a binder.

[0083] The present disclosure (2) is a mat material described in the present disclosure (1), in which the orientation layers and the random layers are alternately stacked in the thickness direction, and the random layers are arranged on both of the two outermost layers of the laminated mat.

[0084] The present disclosure (3) is the mat material according to the present disclosure (1) or (2), wherein the laminated mat contains at least one binder selected from the group consisting of an organic binder and an inorganic binder.

[0085] The present disclosure (4) is a mat material according to any one of the present disclosures (1) to (3), in which, when the laminated mat is divided into three equal parts in the thickness direction into a first surface portion, a central portion, and a second surface portion, the random layer is arranged in the outermost layer of the first surface portion, and the binder content in the first surface portion is greater than the binder content in the central portion and is also greater than the binder content in the second surface portion.

[0086] The present disclosure (5) is the mat material according to the present disclosure (4), wherein the content of the binder satisfies the following relationships: 0.4≦(center portion / first surface portion) 0.2≦(second surface portion / first surface portion) (second surface portion / center portion)≦0.5

[0087] The present disclosure (6) is the mat material according to the present disclosure (5), wherein the content of the binder further satisfies the following relationship: 0<(second surface portion / center portion)

[0088] The present disclosure (7) is the mat material according to any one of the present disclosures (1) to (6), wherein the inorganic fibers of the orientation layer contain 70% or more inorganic fibers having an inclination of 60 to 90 degrees with respect to the width direction of the mat material.

[0089] The present disclosure (8) is the mat material according to any one of the present disclosures (1) to (7), which has a tensile strength at break measured by a tensile test of 200 kPa or more.

[0090] The present disclosure (9) is the mat material according to any one of the present disclosures (1) to (8), in which the elongation at break measured by a tensile test is 3.5 mm or less.

[0091] The present disclosure (10) is a holding and sealing material made of the mat material according to any one of the present disclosures (1) to (9), and used to hold an exhaust gas treatment body in an exhaust gas purification device.

[0092] (Example 1) A papermaking mat made of inorganic fibers and consisting of an oriented layer and a random layer was produced using a papermaking method, and the mats were stacked in the order of random layer / oriented layer / random layer / oriented layer / random layer, and then subjected to a needling process to produce a laminated mat.

[0093] A binder liquid containing an organic binder was applied to one main surface (random layer) of the laminated mat and dried to produce a mat material. The laminated mat was divided into three equal parts in the thickness direction, and the part containing the random layer on the side where the binder liquid was applied was designated as the first surface portion, and the part containing the random layer on the opposite side to the side where the binder liquid was applied was designated as the second surface portion. The part between the first surface portion and the second surface portion was designated as the center portion. The binder content was determined from the change in weight before and after applying the binder liquid. The binder content ratio, which is the ratio of the binder contents of two of the first surface portion, center portion, and second surface portion, is shown in Table 1.

[0094] The photograph of the oriented layer is shown in Figure 4, and 52% of the inorganic fibers had an angle θ of 75 to 90 degrees. Also, 78% of the inorganic fibers had an inclination of 60 to 90 degrees with respect to the width direction of the mat material. Regarding the random layer, which was photographed in the same manner as the photograph shown in Figure 4, 14% of the inorganic fibers had an angle θ of 75 to 90 degrees with respect to the width direction of the mat material. Also, 27% of the inorganic fibers had an inclination of 60 to 90 degrees with respect to the width direction of the mat material.

[0095] (Comparative Example 1) A mat material (holding sealing material) was prepared according to Example 1 of Patent Document 1. The mat material according to Example 1 of Patent Document 1 is not a laminated mat, and does not have both an oriented layer and a random layer therein.

[0096] (Tensile Test) A sample was prepared by cutting the mat material into a length of 200 mm along the longitudinal direction of the mat material and a width of 50 mm along the width direction of the mat material. The thickness of the sample was measured at three locations, and using a universal testing machine equipped with a chuck (gripping jig) for tensile tests, the chuck distance was set to 40 mm on each side, and the mat material was pulled along the longitudinal direction of the sample at a speed of 100 mm / min. The load at break and the pulling distance were determined. The tensile strength at break was calculated as follows: Load at break / (Sample thickness x width). The pulling distance at break was defined as the elongation at break. The results are shown in Table 1.

[0097]

[0098] The results shown in Table 1 reveal that the mat material of Example 1 has high tensile strength.

[0099] REFERENCE SIGNS LIST 10 Mat material 20 Laminated mat 23 First main surface of laminated mat 24 Second main surface of laminated mat 25 First long side of laminated mat 26 Second long side of laminated mat 27 First short side of laminated mat 28 Second short side of laminated mat 30 Orientation layer 31 Inorganic fibers constituting the orientation layer 40, 40a, 40b Random layer 41 Inorganic fibers constituting the random layer 50 Needle marks 51 Rivet portion 100 Exhaust gas purification device 120 Exhaust gas treatment body 120a, 120b Exhaust gas inlet side end surface 125 Cell 126 Cell wall 127 Outer peripheral coating layer 128 Sealing material 130 Metal casing 140 Wound body

Claims

1. A mat material comprising a laminated mat including at least one oriented layer made of inorganic fibers in which the orientation direction of the inorganic fibers is uniform, and at least one random layer made of inorganic fibers in which the orientation direction of the inorganic fibers is random, wherein the laminated mat includes a binder.

2. The mat material according to claim 1, wherein the orientation layers and the random layers are alternately laminated in the thickness direction, and the random layers are disposed on both of the two outermost layers of the laminated mat.

3. The mat material according to claim 1 or 2, wherein the binder is at least one of an organic binder and an inorganic binder.

4. A mat material according to any one of claims 1 to 3, wherein when the laminated mat is divided into three equal parts in the thickness direction into a first surface portion, a central portion, and a second surface portion, the random layer is disposed on the outermost layer of the first surface portion, and the binder content in the first surface portion is greater than the binder content in the central portion and is also greater than the binder content in the second surface portion.

5. The mat member according to claim 4, wherein the binder content satisfies the following relationships: 0.4≦(center portion / first surface portion), 0.2≦(second surface portion / first surface portion), (second surface portion / center portion)≦0.

5.

6. The mat member according to claim 5, wherein the content of the binder further satisfies the following relationship: 0<(second surface portion / center portion).

7. The mat material according to any one of claims 1 to 6, wherein the inorganic fibers in the orientation layer contain 70% or more inorganic fibers inclined at an angle of 60 to 90 degrees relative to the width direction of the mat material.

8. The mat material according to any one of claims 1 to 7, which has a tensile strength at break of 200 kPa or more as measured by a tensile test.

9. The mat material according to any one of claims 1 to 8, wherein the elongation at break measured by a tensile test is 3.5 mm or less.

10. A holding and sealing material made of the mat material according to any one of claims 1 to 9, which is used to hold an exhaust gas treatment body in an exhaust gas purification device.

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