Paper-made mat and method for manufacturing paper-made mat

Abstract

Provided is a papermaking mat which has a high initial surface pressure and can maintain a surface pressure even when subjected to repeated compression.　This papermaking mat is composed of inorganic fibers, and characterized in that the inorganic fibers include alumina fibers (AF) and refractory ceramic fibers (RCF), and in that when 100 of the inorganic fibers are randomly extracted and it is determined whether the inorganic fibers are alumina fibers or refractory ceramic fibers, the number of alumina fibers is 30% or more and the number of refractory ceramic fibers is less than 70%.

Description

[Technical Field]

[0001] The present invention relates to a paper-made mat and a method for manufacturing the same. [Background technology]

[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. In addition, 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, each of which is composed of an exhaust gas treatment body made of porous ceramics such as silicon carbide or cordierite, a casing that houses the exhaust gas treatment body, and a holding seal material (mat material) disposed between the exhaust gas treatment body and the casing. This holding seal material (mat material) is disposed mainly for the purposes of preventing the exhaust gas treatment body from coming into contact with the casing that covers its outer periphery and being damaged by 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 casing.

[0004] As such a mat material, Patent Document 1 discloses a non-expanding mat containing high-temperature resistant amorphous inorganic fibers for providing a support for a brittle structure in a low-temperature exhaust gas treatment device, the mat containing alumina / silica fibers having about 50% Al2O3 and about 50% SiO2. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2002-531720 Summary of the Invention [Problem to be solved by the invention]

[0006] The alumina / silica fibers containing approximately 50% Al2O3 and approximately 50% SiO2 as described in Patent Document 1 are called refractory ceramic fibers. Mats made of such refractory ceramic fibers have a low surface pressure, and the exhaust gas treatment body has a problem of being easily detached due to the pressure of the exhaust gas.

[0007] The present invention has been made to solve the above problems, and the object of the present invention is to provide a paper-made mat that has a high initial surface pressure and can maintain the surface pressure even when subjected to repeated compression. [Means for solving the problem]

[0008] That is, the papermaking mat of the present invention is a papermaking mat composed of inorganic fibers, the inorganic fibers including alumina fibers (AF) and refractory ceramic fibers (RCF), and is characterized in that when 100 of the inorganic fibers are randomly selected and determined to be alumina fibers or refractory ceramic fibers, the number of the alumina fibers is 30% or more and the number of the refractory ceramic fibers is less than 70%.

[0009] Alumina fibers are hard, and when a mat material is made of alumina fibers, the initial surface pressure of the mat material is high. On the other hand, alumina fibers are easily broken, and when a mat material made of alumina fibers is repeatedly compressed, the alumina fibers break and the surface pressure decreases. On the other hand, refractory ceramic fibers are soft, and when a mat material is made of refractory ceramic fibers, the initial surface pressure of the mat material is low. On the other hand, refractory ceramic fibers are not easily broken, and even if a mat material made of refractory ceramic fibers is repeatedly compressed, the surface pressure is not likely to decrease. Since the papermaking mat of the present invention contains alumina fiber and refractory ceramic fiber in the above-mentioned ratio, it has a balanced effect of improving the initial surface pressure of the mat material by the alumina fiber and maintaining the surface pressure when the mat material is repeatedly compressed by the refractory ceramic fiber. Therefore, the papermaking mat of the present invention has a high initial surface pressure and can maintain the surface pressure even when repeatedly compressed.

[0010] In the papermaking mat of the present invention, it is preferable that the weight ratio of the alumina fibers is 50 parts by weight or more but less than 100 parts by weight per 100 parts by weight of the inorganic fibers, and the weight ratio of the refractory ceramic fibers is more than 0 parts by weight but less than 50 parts by weight. When the weight ratio of the alumina fiber and the refractory ceramic fiber is within the above range, the two are balanced, the initial surface pressure is high, and the surface pressure can be maintained even when subjected to repeated compression, and the effect of this being able to be favorably exhibited.

[0011] The papermaking mat of the present invention preferably contains 0.1 to 20 parts by weight of an organic binder and 0.1 to 10 parts by weight of an inorganic binder per 100 parts by weight of inorganic fibers. The organic binder and the inorganic binder bond the inorganic fibers together and maintain the shape of the paper-made mat. When the contents of the organic binder and inorganic binder are within the above ranges, the inorganic fibers are bonded to each other appropriately, and the mat can have both flexibility and shape retention. In addition, it is possible to prevent inorganic fibers from falling off from the paper mat and scattering.

[0012] In the papermaking mat of the present invention, the glass transition temperature Tg of the organic binder is preferably 5° C. or lower. When the glass transition temperature Tg of the organic binder is 5° C. or less, the strength of the organic binder film formed by the organic binder is increased, and the resulting papermaking mat has high film elongation and excellent flexibility.

[0013] In the papermaking mat of the present invention, the organic binder is preferably at least one selected from the group consisting of acrylic resin, acrylate latex, rubber latex, carboxymethyl cellulose, and polyvinyl alcohol, which function as water-soluble organic polymers, styrene resin, which functions as a thermoplastic resin, and epoxy resin, which functions as a thermosetting resin. In the papermaking mat of the present invention, the inorganic binder preferably contains at least one of alumina, silica, silicon carbide, zirconia, boron nitride, diamond, and pumice. These organic binders and inorganic binders are suitable for bonding the inorganic fibers together and maintaining the shape of the papermaking mat.

[0014] The papermaking mat of the present invention is preferably produced through a fiber-opening step in which an inorganic fiber molding is opened in water to produce a slurry containing the opened inorganic fibers, and a papermaking step in which the slurry is paper-made into a papermaking mat. In the fiber-opening step, a fiber bundle is formed by twisting and entangling a plurality of inorganic fibers. Such fiber bundles act as a core material, and can improve the surface pressure of the papermaking mat.

[0015] In the papermaking mat of the present invention, the inorganic fiber molded body preferably includes a first inorganic fiber molded body derived from a needle mat and / or a second inorganic fiber molded body derived from a papermaking mat. Whether the inorganic fiber molded product is derived from a needle mat or a paper-made mat, a fiber bundle can be formed in the opening step. The inorganic fiber molded article preferably contains the alumina fiber. The second inorganic fiber molded body preferably contains the refractory ceramic fiber.

[0016] The papermaking mat of the present invention is preferably a papermaking mat obtained by carrying out papermaking by batch papermaking or continuous papermaking in the papermaking step. The sheet mat of the present invention can be easily obtained by batch or continuous sheet production.

[0017] The method for manufacturing a papermaking mat of the present invention includes a papermaking step of papermaking a slurry containing alumina fibers (AF) and refractory ceramic fibers (RCF) to form a papermaking mat, and is characterized in that when 100 inorganic fibers are randomly extracted from the slurry and determined to be alumina fibers or refractory ceramic fibers, the number of the alumina fibers is 30% or more and the number of the refractory ceramic fibers is less than 70%.

[0018] The above-described papermaking mat of the present invention can be produced by the method for producing a papermaking mat of the present invention.

[0019] The method for producing a papermaking mat of the present invention preferably includes a fiber-opening step of opening an inorganic fiber molded body containing the alumina fibers and the refractory ceramic fibers in water to prepare a slurry. By carrying out the fiber-opening step, a fiber bundle is formed in which a plurality of inorganic fibers are twisted and entangled. Such fiber bundles act as core materials, and can improve the surface pressure of the produced paper mat.

[0020] In the method for producing a papermaking mat of the present invention, the inorganic fiber molded body preferably includes a first inorganic fiber molded body derived from a needle mat and / or a second inorganic fiber molded body derived from a papermaking mat. Whether the inorganic fiber molded product is derived from a needle mat or a paper-made mat, a fiber bundle can be formed in the opening step. The inorganic fiber molded article preferably contains the alumina fiber. The second inorganic fiber molded body preferably contains the refractory ceramic fiber. [Effects of the Invention]

[0021] According to the present invention, it is possible to provide a paper-made mat that has a high initial surface pressure and can maintain the surface pressure even when subjected to repeated compression. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is a perspective view schematically showing an example of a paper-made mat of the present invention. [Figure 2A] FIG. 2A is a diagram schematically showing an example of the fiber-opening step in the method for producing a papermaking mat of the present invention. [Figure 2B] FIG. 2B is a schematic diagram of an example of a fiber bundle in a crimped state. [Figure 3] FIG. 3 is a cross-sectional view that schematically shows an example of an exhaust gas purification device of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0023] The papermaking mat of the present invention will be specifically described below. However, the present invention is not limited to the following configuration, and can be appropriately modified and applied within the scope that does not change the gist of the present invention. Note that a combination of two or more of the individual preferred configurations of the present invention described below also constitutes the present invention.

[0024] The papermaking mat according to the present invention will be described with reference to the drawings. FIG. 1 is a perspective view schematically showing an example of a paper-made mat of the present invention. As shown in FIG. 1, the papermaking mat 10 is a papermaking mat made of inorganic fibers and has a rectangular shape in a plan view. The papermaking mat 10 has a rectangular shape in plan view, with a protrusion 11a provided at one end 11 and a recess 12a provided at the other end 12.

[0025] As will be described in detail later, the papermaking mat 10 is wrapped around an exhaust gas treatment body and placed in the exhaust gas purification device. The convex portions 11a and the concave portions 12a are shaped so as to fit exactly together when the paper mat 10 is wrapped around the exhaust gas treatment body. The provision of such convex portions 11a and concave portions 12a improves the sealing performance when the papermaking mat 10 is placed in an exhaust gas purification device, which will be described later.

[0026] In the papermaking mat 10, the inorganic fibers include alumina fibers (AF) and refractory ceramic fibers (RCF). The inorganic fibers may also contain inorganic fibers other than alumina fibers and refractory ceramic fibers, such as silica fibers, glass wool, and rock wool.

[0027] In this specification, "alumina fiber" means a fiber in which the weight ratio of Al2O3 constituting the fiber exceeds 60% by weight. In this specification, the term "refractory ceramic fiber" refers to a fiber in which the weight percentage of Al2O3 constituting the fiber is 60% by weight or less.

[0028] The alumina fibers are preferably fibers containing Al2O3 and SiO2, and the weight ratio thereof is preferably Al2O3:SiO2=70:30 to 80:20. The refractory ceramic fibers are preferably fibers containing Al2O3 and SiO2, and the weight ratio thereof is preferably Al2O3:SiO2=40:60 to 60:40.

[0029] In the papermaking mat 10, when 100 inorganic fibers are randomly extracted and determined to be alumina fibers or refractory ceramic fibers, the number of the alumina fibers is 30% or more and the number of the refractory ceramic fibers is less than 70%.

[0030] Alumina fibers are hard, and when a mat material is made of alumina fibers, the initial surface pressure of the mat material is high. On the other hand, alumina fibers are easily broken, and when a mat material made of alumina fibers is repeatedly compressed, the alumina fibers break and the surface pressure decreases. Furthermore, since refractory ceramic fibers are soft, when a mat material is made of refractory ceramic fibers, the initial surface pressure of the mat material is low. On the other hand, since refractory ceramic fibers are not easily broken, even if a mat material made of refractory ceramic fibers is repeatedly compressed, the surface pressure is not likely to decrease. Since the papermaking mat 10 contains alumina fiber and refractory ceramic fiber in the above ratio, the effect of improving the initial surface pressure of the mat material by the alumina fiber and the effect of maintaining the surface pressure by the refractory ceramic fiber when the mat material is repeatedly compressed are balanced. Therefore, the papermaking mat 10 has a high initial surface pressure and can maintain the surface pressure even when repeatedly compressed.

[0031] When 100 inorganic fibers are randomly selected and judged to be alumina fibers or refractory ceramic fibers, the proportion of alumina fibers is preferably 30 to 90%, more preferably 50 to 80%, and the proportion of refractory ceramic fibers is preferably 10% or more and less than 70%, more preferably 20 to 60%.

[0032] In the papermaking mat 10, the weight ratio of the alumina fibers to 100 parts by weight of the inorganic fibers is preferably 50 parts by weight or more and less than 100 parts by weight, more preferably 50 to 90 parts by weight. Furthermore, in the papermaking mat 10, it is preferable that the weight ratio of the refractory ceramic fibers is greater than 0 parts by weight and less than 50 parts by weight per 100 parts by weight of the inorganic fibers, and it is more preferable that it is greater than 10 parts by weight and less than 50 parts by weight. When the weight ratio of the alumina fiber and the refractory ceramic fiber is within the above range, the two are balanced, the initial surface pressure is high, and the surface pressure can be maintained even when subjected to repeated compression, and the effect of this being able to be favorably exhibited.

[0033] The papermaking mat 10 preferably contains 0.1 to 20 parts by weight, and more preferably 0.5 to 10 parts by weight, of the organic binder per 100 parts by weight of the inorganic fibers. The inorganic binder is preferably contained in an amount of 0.1 to 10 parts by weight, more preferably 0.5 to 3.0 parts by weight, per 100 parts by weight of the inorganic fibers. The organic binder and the inorganic binder bond the inorganic fibers together and maintain the shape of the paper-made mat. When the contents of the organic binder and inorganic binder are within the above ranges, the inorganic fibers are bonded to each other appropriately, and the mat can have both flexibility and shape retention. In addition, it is possible to prevent inorganic fibers from falling off from the paper mat and scattering.

[0034] In the papermaking mat 10, the glass transition temperature Tg of the organic binder is preferably 5°C or lower, and more preferably -35 to 5°C. When the glass transition temperature Tg of the organic binder is 5° C. or lower, the strength of the organic binder film formed by the organic binder is increased, and the resulting papermaking mat has high film elongation and excellent flexibility. In addition, the mat is less likely to tear when it is wrapped around an exhaust gas treatment body, etc. Furthermore, because the organic binder film does not become too hard, it has the effect of binding the inorganic fibers together when the inorganic fibers break, and can prevent the inorganic fibers from scattering. Organic binders with a glass transition temperature Tg of less than -35°C are expensive, resulting in high production costs. If the glass transition temperature Tg of the organic binder exceeds 5°C, the flexibility of the papermaking mat may decrease, resulting in a decrease in breaking elongation.

[0035] In the papermaking mat of the present invention, the organic binder may be a water-soluble organic polymer, a thermoplastic resin, or a thermosetting resin. Examples of water-soluble organic polymers include acrylic resins, acrylate latexes, rubber latexes, carboxymethyl cellulose, and polyvinyl alcohol. Examples of thermoplastic resins include styrene resins. Examples of thermosetting resins include epoxy resins.

[0036] In the papermaking mat 10, the inorganic binder preferably contains at least one of alumina, silica, silicon carbide, zirconia, boron nitride, diamond, and pumice.

[0037] These organic binders and inorganic binders are suitable for bonding the inorganic fibers together and maintaining the shape of the papermaking mat.

[0038] Next, an example of the method for producing the paper-made mat of the present invention will be described. An example of the method for producing a paper-made mat of the present invention, which will be described below, includes (1) a fiber-opening step and (2) a paper-making step. Each step will be described below.

[0039] (1) Opening process FIG. 2A is a diagram schematically showing an example of the fiber-opening step in the method for producing a papermaking mat of the present invention. In this step, an inorganic fiber molded body containing alumina fibers and refractory ceramic fibers is opened in water to prepare a slurry. In the method for manufacturing a papermaking mat of the present invention, when 100 inorganic fibers are randomly extracted from the slurry and determined to be alumina fibers or refractory ceramic fibers, the number of the alumina fibers is 30% or more and the number of the refractory ceramic fibers is less than 70%.

[0040] When the ratio of alumina fiber to refractory ceramic fiber in the slurry is within the above range, the mat material produced through subsequent processes will have a balanced effect between the alumina fiber improving the initial surface pressure of the mat material and the refractory ceramic fiber maintaining the surface pressure when the mat material is repeatedly compressed. Therefore, the produced paper mat has a high initial surface pressure and can maintain the surface pressure even when repeatedly compressed.

[0041] When 100 inorganic fibers are randomly selected from the slurry and determined to be alumina fibers or refractory ceramic fibers, the proportion of alumina fibers is preferably 30 to 90%, more preferably 50 to 80%, and the proportion of refractory ceramic fibers is preferably 10% or more and less than 70%, more preferably 20 to 60%.

[0042] Furthermore, when the inorganic fiber molded body is opened, the inorganic fibers 20 are not completely opened, and fiber bundles 21 are formed in which a plurality of inorganic fibers 20 are twisted and entangled, as shown in FIG. 2A. Such fiber bundles act as core materials, and can improve the surface pressure of the produced paper mat.

[0043] As shown in FIG. 2A, the fiber bundle 21 may include a straight state (denoted by reference symbol "21a" in FIG. 2A) and a crimped state (denoted by reference symbol "21b" in FIG. 2A).

[0044] In this specification, the term "straight state" means that the direction of the fiber bundle (the direction indicated by the arrow D1 in FIG. 2A) is linear. In addition, in this specification, the term "crimped state" means that the direction of the fiber bundle (the direction indicated by the arrow D2 in FIG. 2A) is curved at least once.

[0045] The fiber bundle 21 is formed by twisting and intertwining 10 or more inorganic fibers, and preferably has an average length (average length indicated by symbol L in FIG. 2A) of 5 to 15 mm and an average width (average length indicated by symbol W in FIG. 2A) of 0.2 to 1.0 mm. As shown in FIG. 2A, when the fiber bundle 21 is a straight fiber bundle 21a and when it is a crimped fiber bundle 21b, the maximum width (the lengths indicated by the symbols Wa and Wb, respectively, in FIG. 2A) is the width of the fiber bundle 21.

[0046] The crimped fiber bundle 21b will be described in detail below with reference to the drawings. FIG. 2B is a schematic diagram of an example of a fiber bundle in a crimped state. The fiber bundle 21b in the crimped state shown in FIG. 2B has a traced length L of the fiber bundle 21b in the crimped state measured by the following traced length measurement method. t is preferably longer than the length L of the fiber bundle 21b in the crimped state, more preferably by 0.1 mm or more, and even more preferably by 0.2 to 0.6 mm.

[0047] (Method for measuring tracing length) The crimped fiber bundle 21b is placed on a flat surface. Next, the fiber bundle 21b in the crimped state that has been left standing is viewed from above, and the fiber bundle 21b in the crimped state is traced from one end P1 of the fiber bundle 21b in the crimped state to the other end P2, and the tracing distance L t is defined as the "tracing length of the fiber bundle in a crimped state."

[0048] The tracing length L of the crimped fiber bundle 21b t If the length L of the fiber bundles 21b in the crimped state is longer than the length L of the fiber bundles 21b in the crimped state, the elasticity of the fiber bundles 21b in the crimped state increases, and the surface pressure of the papermaking mat 10 increases.

[0049] It is preferable that the papermaking mat 10 includes fiber bundles 21b in a crimped state such that when measuring the "tracing length of the fiber bundle in a crimped state" as shown in Figure 2B, the fiber bundles 21b in a crimped state can be traced so as to cross the line segment S connecting end P1 and end P2 two or more times. The fiber bundles 21b in such a crimped state have an appropriate degree of crimping, and the elasticity of the fiber bundles 21b in the crimped state is increased, thereby improving the surface pressure of the papermaking mat 10.

[0050] In the papermaking mat 10, the length L of the fiber bundle 21b in the crimped state is t The ratio of L t It is preferable that / L=1.1 to 1.6.

[0051] In the papermaking mat 10, the value of the following formula (1) is preferably 0.1 or more, and more preferably 0.2 to 0.6. (L t -L) / Wb (1)

[0052] In the papermaking mat 10, the fiber bundles 21b in a crimped state are placed on a flat surface, and the area of ​​the fiber bundles 21b in a crimped state as viewed from above is 2.6 to 8.3 mm 2 It is preferable that:

[0053] In the papermaking mat 10, the proportion of crimped fiber bundles 21b contained in the fiber bundles 21 is preferably 85% or less, more preferably 60% or less, even more preferably 30% or less, and even more preferably 10 to 30%.

[0054] The shape and size of the fiber bundle can be controlled by adjusting the fiber-spreading conditions.

[0055] In the method for producing a papermaking mat of the present invention, the inorganic fiber molded body preferably includes a first inorganic fiber molded body derived from a needle mat and / or a second inorganic fiber molded body derived from a papermaking mat. Whether the inorganic fiber molded body is derived from a needle mat or a paper-made mat, the fiber bundles 21 can be formed in the opening step. The inorganic fiber molded article preferably contains the alumina fiber. The second inorganic fiber molded body preferably contains the refractory ceramic fiber.

[0056] Examples of the fiber opening include the following methods. First, the first inorganic fiber molded body is fired at 700 to 1000°C for 1.0 to 8.0 hours. The firing temperature is preferably 800 to 950°C. This allows the organic binder contained in the inorganic fiber molded body to be thermally decomposed, making it easier to open the inorganic fiber molded body.

[0057] Next, the fired inorganic fiber molded body is left to stand until it reaches room temperature, and then the inorganic fiber molded body is loosened by hand.

[0058] Next, the inorganic fiber molded body is placed in water in an amount of 50 to 400 times by weight, and stirred to open the fibers, thereby preparing a slurry containing inorganic fibers. The weight ratio is preferably 100 to 200 times. For example, when preparing a 10 L slurry, it is preferable to use a mixer (product name: SMT-101, manufacturer: ASONE) at a rotation speed of 500 to 1000 rpm and a stirring time of 200 to 900 seconds. A rotation speed of 650 to 850 rpm and a stirring time of 500 to 700 seconds are preferred, and a rotation speed of 700 to 800 rpm and a stirring time of 500 to 650 seconds are more preferred.

[0059] Next, an organic binder and an inorganic binder are added to the slurry. The organic binder is preferably added in an amount of 0.1 to 20 parts by weight, more preferably 0.5 to 15.0 parts by weight, per 100 parts by weight of the inorganic fibers in the produced paper mat. The inorganic binder is preferably added in an amount of 0.1 to 15.0 parts by weight, more preferably 0.5 to 10 parts by weight, per 100 parts by weight of the inorganic fibers in the produced paper mat. The preferred types of organic binders and inorganic binders have already been described, and therefore, a description thereof will be omitted here.

[0060] (2) Papermaking process Next, the slurry is poured into a molding machine having a filtering mesh formed on the bottom surface, and the solvent in the slurry is removed to obtain an inorganic fiber aggregate, which is then dehydrated and dried.

[0061] In the papermaking process, the inorganic fiber aggregate may be dried by heating and pressurizing. During the heating and pressurizing, a heat treatment may be performed in which hot air is passed through the inorganic fiber aggregate to dry it, or the inorganic fiber aggregate may be left in a wet state without being subjected to a heat treatment. When heat treatment is performed, the heating temperature or hot air temperature is preferably 100 to 250°C to prevent thermal degradation of the organic binder. Within the 100 to 250°C range, moisture can be removed from the inorganic fiber aggregate while suppressing degradation of the organic binder. If the heating temperature or hot air temperature is less than 100°C, the heat does not reach the center of the inorganic fiber aggregate, resulting in a long drying time. Furthermore, if the temperature exceeds 250°C, the organic binder will be deteriorated and the binding force between the fibers will be reduced, making it difficult to control the thickness of the inorganic fiber aggregate.

[0062] Through the above steps, the papermaking mat of the present invention can be produced. In the method for producing a paper mat of the present invention, it is preferable to carry out batch papermaking or continuous papermaking in the papermaking step. The sheet mat of the present invention can be easily obtained by batch or continuous sheet production.

[0063] In the above-mentioned method for manufacturing a papermaking mat, the papermaking process is carried out after the fiber-opening process, but in the method for manufacturing a papermaking mat of the present invention, the fiber-opening process does not need to be carried out if a slurry having the following characteristics can be prepared and paper-made to produce a mat material. In other words, the slurry to be produced in the method for producing a paper mat of the present invention has the following characteristics: when 100 inorganic fibers are randomly extracted from the slurry and determined to be alumina fibers or refractory ceramic fibers, the number of alumina fibers is 30% or more and the number of refractory ceramic fibers is less than 70%.

[0064] Next, a method for using the papermaking mat of the present invention will be described. FIG. 3 is a cross-sectional view that schematically shows an example of an exhaust gas purification device of the present invention. As shown in Fig. 3, the exhaust gas purification device 100 includes a metal casing 30, an exhaust gas treatment body 40 housed in the metal casing 30, and a paper mat 10 disposed between the exhaust gas treatment body 40 and the metal casing 30. The paper mat 10 is the paper mat of the present invention. The exhaust gas treatment body 40 is a columnar structure in which a large number of cells 41 are arranged in parallel in the longitudinal direction, separated by cell walls 42. Note that, if necessary, an inlet pipe for introducing exhaust gas emitted from the internal combustion engine and an outlet pipe for discharging exhaust gas that has passed through the exhaust gas purification device to the outside are connected to the ends of the metal casing 30. In the exhaust gas purification device 100 shown in Figure 3, an exhaust gas filter (honeycomb filter) in which one of the cells is sealed with a plugging material 43 is used as the exhaust gas treatment body 40, but a catalyst carrier in which none of the end faces are sealed with a plugging material may also be used.

[0065] As shown in FIG. 3, exhaust gas emitted from an internal combustion engine and flowing into the exhaust gas purification device 100 (in FIG. 3, the exhaust gas is indicated by G and the flow of the exhaust gas is indicated by arrows) flows into one cell 41 opening at the exhaust gas inlet end face 40a of the exhaust gas treatment body (honeycomb filter) 40 and passes through a cell wall 42 separating the cells 41. At this time, PM in the exhaust gas is captured by the cell wall 42, and the exhaust gas is purified. The purified exhaust gas flows out from another cell 41 opening at the exhaust gas outlet end face 40b and is discharged to the outside.

[0066] As described above, the papermaking mat 10 has a high initial surface pressure and can maintain the surface pressure even when repeatedly compressed. Therefore, even if the exhaust gas treatment body 40 is subjected to high pressure from exhaust gas in the early stages of use of the exhaust gas purification device 100, the exhaust gas treatment body 40 can be prevented from falling off from the metal casing 30. Furthermore, this effect of preventing falling off can be maintained for a long period of time.

[0067] The exhaust gas treatment body 40 may be made of a non-oxidizing porous ceramic such as silicon carbide or silicon nitride, or may be made of an oxidizing porous ceramic such as sialon, alumina, cordierite, or mullite. Of these, silicon carbide is preferred.

[0068] When the exhaust gas treatment body 40 is made of porous ceramics of silicon carbide, the porosity of the porous ceramics is not particularly limited, but is preferably 35 to 60%. If the porosity is less than 35%, the exhaust gas treatment body may easily become clogged, whereas if the porosity is more than 60%, the strength of the exhaust gas treatment body may decrease and it may easily break.

[0069] The average pore diameter of the porous ceramic is preferably 5 to 30 μm. If the average pore size is less than 5 μm, PM may easily clog the pores. If the average pore diameter exceeds 30 μm, PM may pass through the pores, making it impossible to capture PM and preventing the filter from functioning properly. The porosity and pore diameter can be measured by a conventionally known method using a scanning electron microscope (SEM).

[0070] The cell density in the cross section of the exhaust gas treatment body 40 is not particularly limited, but the preferred lower limit is 31.0 cells / cm 2 (200 pieces / inch 2 ), the preferred upper limit is 93.0 particles / cm 2 (600 pieces / inch 2 ) A more preferable lower limit is 38.8 particles / cm 2 (250 pieces / inch 2 ), and a more preferable upper limit is 77.5 particles / cm 2 (500 pieces / inch 2 )

[0071] The exhaust gas treatment body 40 may be supported with a catalyst for purifying the exhaust gas. The supported catalyst is preferably a noble 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. When these catalysts are supported, PM can be easily burned and removed, and toxic exhaust gases can also be purified.

[0072] (metal casing) The metal casing 30 is generally cylindrical. The inner diameter of the metal casing 30 (the inner diameter of the portion that houses the exhaust gas treatment body) is preferably slightly smaller than the diameter of the exhaust gas treatment body 40 around which the papermaking mat 10 is wrapped.

[0073] The metal casing 30 is preferably made of stainless steel, although there is no particular limitation thereto.

[0074] The present specification discloses the following:

[0075] The present disclosure (1) is a papermaking mat made of inorganic fibers, the inorganic fibers including alumina fibers (AF) and refractory ceramic fibers (RCF), characterized in that when 100 of the inorganic fibers are randomly selected and determined to be alumina fibers or refractory ceramic fibers, the number of the alumina fibers is 30% or more and the number of the refractory ceramic fibers is less than 70%.

[0076] The present disclosure (2) is a papermaking mat described in the present disclosure (1), in which the weight ratio of the alumina fiber is 50 parts by weight or more but less than 100 parts by weight per 100 parts by weight of the inorganic fiber, and the weight ratio of the refractory ceramic fiber is more than 0 parts by weight but less than 50 parts by weight.

[0077] The present disclosure (3) is the papermaking mat according to the present disclosure (1) or (2), which contains 0.1 to 20 parts by weight of an organic binder and 0.1 to 10 parts by weight of an inorganic binder, based on 100 parts by weight of the inorganic fibers.

[0078] The present disclosure (4) is the papermaking mat according to the present disclosure (3), wherein the glass transition temperature Tg of the organic binder is 5° C. or lower.

[0079] The present disclosure (5) is a papermaking mat according to the present disclosure (3) or (4), wherein the organic binder is at least one selected from the group consisting of acrylic resin, acrylate latex, rubber latex, carboxymethyl cellulose, and polyvinyl alcohol, which function as water-soluble organic polymers, styrene resin, which functions as thermoplastic resin, and epoxy resin, which functions as thermosetting resin.

[0080] The present disclosure (6) is the papermaking mat according to any one of the present disclosures (3) to (5), wherein the inorganic binder contains at least one of alumina, silica, silicon carbide, zirconia, boron nitride, diamond, and pumice.

[0081] The present disclosure (7) is a papermaking mat according to any one of the present disclosures (1) to (6), which is produced through a fiber-opening process in which an inorganic fiber molding is opened in water to produce a slurry containing the opened inorganic fibers, and a papermaking process in which the slurry is paper-formed into a papermaking mat.

[0082] The present disclosure (8) is the papermaking mat according to the present disclosure (7), wherein the inorganic fiber molded body includes a first inorganic fiber molded body derived from a needle mat and / or a second inorganic fiber molded body derived from a papermaking mat.

[0083] The present disclosure (9) is the papermaking mat according to the present disclosure (8), wherein the inorganic fiber molded product contains the alumina fiber.

[0084] The present disclosure (10) is the papermaking mat according to the present disclosure (8) or (9), wherein the second inorganic fiber molded body contains the refractory ceramic fiber.

[0085] The present disclosure (11) is a paper-made mat according to any one of the present disclosures (7) to (10), wherein the paper-making step is carried out by batch paper-making or continuous paper-making.

[0086] The present disclosure (12) is a method for producing a paper mat, which includes a papermaking step of producing a paper mat from a slurry containing alumina fiber (AF) and refractory ceramic fiber (RCF), wherein 100 inorganic fibers are randomly extracted from the slurry and determined to be alumina fiber or refractory ceramic fiber, and the number of the alumina fibers is 30% or more and the number of the refractory ceramic fibers is less than 70%.

[0087] The present disclosure (13) is a method for producing a papermaking mat according to the present disclosure (12), further comprising a fiber-opening step of opening an inorganic fiber molding containing the alumina fiber and the refractory ceramic fiber in water to prepare a slurry.

[0088] The present disclosure (14) is the method for producing a papermaking mat according to the present disclosure (13), wherein the inorganic fiber molded body includes a first inorganic fiber molded body derived from a needle mat and / or a second inorganic fiber molded body derived from a papermaking mat.

[0089] The present disclosure (15) is a method for producing a papermaking mat according to the present disclosure (14), wherein the inorganic fiber molded product contains the alumina fiber.

[0090] The present disclosure (16) is the method for producing a papermaking mat according to the present disclosure (14) or (15), wherein the second inorganic fiber molded body contains the refractory ceramic fiber. [Example]

[0091] EXAMPLES Hereinafter, examples will be given that more specifically disclose the present invention, but the present invention is not limited to these examples.

[0092] Example 1 It is made of alumina fibers with a weight ratio of Al2O3:SiO2 = 72:28, and has a bulk density of 0.17 g / mm 3 The density of needle marks is 21 / cm 2 A first inorganic fiber molded body derived from a needle mat having a density of 1000 kJ / cm2 was prepared. It is made of refractory ceramic fibers with a weight ratio of Al2O3:SiO2 = 50:50, and has a bulk density of 1.2 g / mm 3 A second inorganic fiber molded body derived from a papermaking mat was prepared.

[0093] Next, the first inorganic fiber molded body was fired at 800° C. for 1 hour to thermally decompose the organic binder contained in the first inorganic fiber molded body and the second inorganic fiber molded body.

[0094] Next, the fired first inorganic fiber molded body was left to stand until it reached room temperature, and then the first inorganic fiber molded body and the second inorganic fiber molded body were loosened by hand.

[0095] Next, 5.0 g of the first inorganic fiber molded body and 5.0 g of the second inorganic fiber molded body were taken out and placed in 0.4 L of water. After that, the mixture was stirred at a rotation speed of 1000 rpm for 10 minutes using a mixer (product name: SMT-101, manufacturer: ASONE) to open the fibers, thereby producing an inorganic fiber slurry.

[0096] Furthermore, 100 inorganic fibers were randomly extracted from the slurry and determined to be alumina fibers or refractory ceramic fibers. The proportion of alumina fibers was 71%, and the proportion of refractory ceramic fibers was 29%. Further, the weight ratio of the alumina fibers was 70 parts by weight and the weight ratio of the refractory ceramic fibers was 30 parts by weight relative to 100 parts by weight of the inorganic fibers.

[0097] Next, an organic binder was added to the slurry in an amount of 0.5 to 10 parts by weight relative to 100 parts by weight of the inorganic fibers. Furthermore, an inorganic binder was added to the slurry in an amount of 0.3 to 3.0 parts by weight relative to 100 parts by weight of the inorganic fibers.

[0098] Next, the slurry was poured into a molding machine with a filtering mesh formed on the bottom surface, and the solvent in the slurry was removed to obtain an inorganic fiber aggregate. Thereafter, the inorganic fiber aggregate was dehydrated and dried at 150 to 210°C for 5 minutes to 1 hour to produce a papermaking mat according to Example 1.

[0099] (Example 2) and (Comparative Example 1) The papermaking mats of Example 2 and Comparative Example 1 were produced in the same manner as Example 1, except that the first inorganic fiber molded body and second inorganic fiber molded body used were adjusted and the ratio (number, weight ratio) of alumina fiber and refractory ceramic fiber was changed as shown in Table 1.

[0100] [Table 1]

[0101] (Measurement of surface pressure) The papermaking mats according to Examples 1, 2 and Comparative Example 1 were set in a testing machine (product name: SMT-101, manufacturer: ASONE) and tested to see if the void bulk density (GBD) was 0.40 mm 3 The void bulk density (GBD) was 0.40 mm / g. 3 The mat was held at this temperature for 10 minutes, and then released at a speed of 25.4 mm / min. This compression and release cycle was repeated 1000 times, after which the surface pressure of each mat was measured. The results are shown in Table 1.

[0102] As shown in Table 1, the papermaking mats according to Examples 1 and 2 were shown to have a high surface pressure even after repeated compression and release. [Explanation of symbols]

[0103] 10 Paper mat 11 One end 11a Convex part 12 Other end 12a Recess 20 Inorganic Fibers 21 Fiber bundle 30 Metal Casing 40 Exhaust gas treatment body 40a Exhaust gas inlet end 40b Exhaust gas discharge end 41 cells 42 Cell Wall 43 Encapsulating material 100 Exhaust gas purification device

Claims

1. A papermaking mat made of inorganic fibers, The inorganic fibers include alumina fibers (AF) and refractory ceramic fibers (RCF), 100 of the inorganic fibers were randomly selected and judged to be alumina fibers or refractory ceramic fibers. A papermaking mat characterized in that the number of the alumina fibers is 30% or more and the number of the refractory ceramic fibers is less than 70%.

2. A papermaking mat as described in claim 1, wherein the weight ratio of the alumina fibers is 50 parts by weight or more but less than 100 parts by weight per 100 parts by weight of the inorganic fibers, and the weight ratio of the refractory ceramic fibers is more than 0 parts by weight but less than 50 parts by weight.

3. 3. The paper mat according to claim 1, wherein the inorganic fibers contain 0.1 to 20 parts by weight of an organic binder and 0.1 to 10 parts by weight of an inorganic binder, based on 100 parts by weight of the inorganic fibers.

4. 4. The papermaking mat according to claim 3, wherein the organic binder has a glass transition temperature Tg of 5[deg.] C. or lower.

5. The papermaking mat according to claim 3, wherein the organic binder is at least one selected from the group consisting of acrylic resin, acrylate latex, rubber latex, carboxymethyl cellulose, and polyvinyl alcohol, which function as water-soluble organic polymers, styrene resin, which functions as a thermoplastic resin, and epoxy resin, which functions as a thermosetting resin.

6. 4. The papermaking mat according to claim 3, wherein the inorganic binder contains at least one of alumina, silica, silicon carbide, zirconia, boron nitride, diamond, and pumice.

7. A method for producing a paper mat, comprising a papermaking step of producing a paper mat from a slurry containing alumina fiber (AF) and refractory ceramic fiber (RCF), 100 inorganic fibers were randomly extracted from the slurry and judged to be alumina fibers or refractory ceramic fibers. A method for producing a paper mat, characterized in that the number of alumina fibers is 30% or more and the number of refractory ceramic fibers is less than 70%.

8. The method for producing a paper mat according to claim 7, further comprising a fiber-opening step of opening an inorganic fiber molded body containing the alumina fibers and the refractory ceramic fibers in water to prepare a slurry.

9. The method for producing a papermaking mat according to claim 8 , wherein the inorganic fiber molded body includes a first inorganic fiber molded body derived from a needle mat and / or a second inorganic fiber molded body derived from a papermaking mat.

10. The method for producing a papermaking mat according to claim 9 , wherein the first inorganic fiber molded body contains the alumina fiber.

11. The method for producing a papermaking mat according to claim 9 , wherein the second inorganic fiber molded body contains the refractory ceramic fiber.

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