Papermaking mat and method for manufacturing papermaking 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

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

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

[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 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 surrounds it 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, and the mat contains about 50% Al. ２ O ３ and about 50% SiO ２ A mat comprising alumina / silica fibers having the formula:

[0005] Special Publication No. 2002-531720

[0006] As described in US Pat. No. 5,649,999, approximately 50% Al ２ O ３ and about 50% SiO ２Alumina / silica fibers having the above structure are called refractory ceramic fibers. Mats made of such refractory ceramic fibers have a problem in that they have a low surface pressure, and the exhaust gas treatment body is 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.

[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 made of refractory ceramic fibers 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. The papermaking mat of the present invention contains alumina fibers and refractory ceramic fibers in the above ratio, so that the effect of improving the initial surface pressure of the mat material by the alumina fibers and the effect of maintaining the surface pressure when a mat material made of refractory ceramic fibers is repeatedly compressed are balanced. 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 preferred 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 part by weight but less than 50 parts by weight. When the weight ratios of the alumina fibers and the refractory ceramic fibers are within the above ranges, a good balance is achieved between the two, and the mat can preferably exhibit the effects of having a high initial surface pressure and being able to maintain the surface pressure even when repeatedly compressed.

[0011] The papermaking mat of the present invention preferably contains 0.1 to 20 parts by weight of organic binder and 0.1 to 10 parts by weight of inorganic binder per 100 parts by weight of inorganic fibers. The organic binder and inorganic binder bond the inorganic fibers together and maintain the shape of the papermaking mat. When the organic binder and inorganic binder contents are within the above ranges, the inorganic fibers are bonded together appropriately, allowing the papermaking mat to achieve both flexibility and shape retention. In addition, the inorganic fibers can be prevented from falling off the papermaking 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 lower, the strength of the organic binder film formed by the organic binder can be increased, and the papermaking mat can have 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 function as thermoplastic resins, and epoxy resin, which function as thermosetting resins. Furthermore, in the papermaking mat of the present invention, the inorganic binder preferably includes at least one selected from the group consisting of alumina, silica, silicon carbide, zirconia, boron nitride, diamond, and pumice. These organic and inorganic binders are suitable for bonding 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 prepare a slurry containing the opened inorganic fibers, and a papermaking step in which the slurry is paper-formed into a papermaking mat. In the fiber-opening step, a plurality of inorganic fibers are twisted and entangled to form fiber bundles. Such fiber bundles function as a core material, thereby improving 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 body is derived from a needle mat or a papermaking mat, a fiber bundle can be formed in the opening step. The first inorganic fiber molded body preferably includes the alumina fiber. The second inorganic fiber molded body preferably includes the refractory ceramic fiber.

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

[0017] The method for manufacturing a paper mat of the present invention includes a papermaking step of papermaking a slurry containing alumina fiber (AF) and refractory ceramic fiber (RCF) to form a paper mat, and is characterized in that when 100 inorganic fibers are randomly extracted from the slurry and determined to be alumina fiber or refractory ceramic fiber, 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 in which an inorganic fiber molding containing the alumina fiber and the refractory ceramic fiber is opened in water to produce a slurry. By performing the fiber-opening step, a fiber bundle is formed in which a plurality of inorganic fibers are twisted and entangled. Such fiber bundles function as a core material, thereby improving the surface pressure of the produced papermaking 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 body is derived from a needle mat or a papermaking mat, a fiber bundle can be formed in the opening step. The first inorganic fiber molded body preferably includes the alumina fiber. The second inorganic fiber molded body preferably includes the refractory ceramic fiber.

[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.

[0022] Fig. 1 is a perspective view schematically showing an example of a paper mat of the present invention. Fig. 2A is a view schematically showing an example of a fiber-opening step in a method for producing a paper mat of the present invention. Fig. 2B is a view schematically showing an example of a fiber bundle in a crimped state. Fig. 3 is a cross-sectional view schematically showing an example of an exhaust gas purification device of the present 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 showing a typical example of the papermaking mat according to 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 convex portion 11a at one end 11 and a concave portion 12a at the other end 12, and has a rectangular shape in a plan view.

[0025] As will be described in detail later, the papermaking mat 10 is wrapped around an exhaust gas treatment body and placed in an exhaust gas purification device. The convex portions 11a and concave portions 12a are shaped to fit exactly when the papermaking mat 10 is wrapped around the exhaust gas treatment body. The provision of such convex portions 11a and concave portions 12a improves sealing properties 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 include inorganic fibers other than alumina fibers and refractory ceramic fibers. Examples of other inorganic fibers include silica fibers, glass wool, and rock wool.

[0027] In this specification, "alumina fiber" refers to Al that constitutes the fiber. ２ O ３ In this specification, the term "refractory ceramic fiber" refers to a fiber in which the weight ratio of Al constituting the fiber is more than 60% by weight. ２ O ３ The weight ratio of the fibers is 60% by weight or less.

[0028] The alumina fiber is Al ２ O ３ and SiO ２ The fiber preferably contains Al ２ O ３ : SiO ２ The ratio is preferably 70:30 to 80:20. As the refractory ceramic fiber, Al ２ O ３ and SiO ２ The fiber preferably contains Al ２ O ３: SiO ２ It is preferable that the ratio is 40:60 to 60:40.

[0029] In the papermaking mat 10, when 100 inorganic fibers are randomly extracted and judged as to whether they are 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. Also, refractory ceramic fibers are soft, and when a mat material made of refractory ceramic fibers 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 10 contains alumina fibers and refractory ceramic fibers in the above ratio, a balance is achieved between the effect of alumina fibers in improving the initial surface pressure of the mat material and the effect of refractory ceramic fiber in maintaining the surface pressure when the mat material is repeatedly compressed. 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 as being 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 but less than 100 parts by weight, and more preferably 50 to 90 parts by weight. Furthermore, in the papermaking mat 10, the weight ratio of the refractory ceramic fibers to 100 parts by weight of the inorganic fibers is preferably more than 0 parts by weight but less than 50 parts by weight, and more preferably 10 parts by weight or more but less than 50 parts by weight. When the weight ratios of the alumina fibers and the refractory ceramic fibers are within the above ranges, a good balance is achieved between the two, and the effect of a high initial contact pressure and the ability to maintain the contact pressure even when repeatedly compressed can be favorably exhibited.

[0033] The papermaking mat 10 preferably contains 0.1 to 20 parts by weight, more preferably 0.5 to 10 parts by weight, of organic binder per 100 parts by weight of inorganic fibers. Furthermore, the papermaking mat 10 preferably contains 0.1 to 10 parts by weight, more preferably 0.5 to 3.0 parts by weight, of inorganic binder per 100 parts by weight of inorganic fibers. The organic binder and inorganic binder bond the inorganic fibers together and maintain the shape of the papermaking mat. When the organic binder and inorganic binder contents are within the above ranges, the inorganic fibers are bonded together appropriately, achieving both flexibility and shape retention of the papermaking mat. Furthermore, the papermaking mat can be prevented from shedding and scattering of inorganic fibers.

[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 can be increased, while the papermaking mat can have high film elongation and excellent flexibility. In addition, the papermaking mat 10 is less likely to tear when wrapped around an exhaust gas treatment body, for example. Furthermore, because the organic binder film does not become too hard, it has the effect of connecting the inorganic fibers together when the inorganic fibers break, thereby suppressing the scattering of the inorganic fibers. Organic binders with a glass transition temperature Tg of less than -35°C are expensive and increase manufacturing costs. When the glass transition temperature Tg of the organic binder exceeds 5°C, the flexibility of the papermaking mat decreases, and the breaking elongation may decrease.

[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 the water-soluble organic polymer include acrylic resin, acrylate latex, rubber latex, carboxymethyl cellulose, and polyvinyl alcohol. Examples of the thermoplastic resin include styrene resin. Examples of the epoxy resin function as a thermosetting resin include epoxy resin.

[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 a method for manufacturing a paper mat of the present invention will be described. The example of the method for manufacturing a paper mat of the present invention described below includes (1) a fiber-opening step and (2) a paper-making step. Each step will be described below.

[0039] (1) Fiber-Opening Step Figure 2A is a diagram showing a schematic diagram of an example of the fiber-opening step in the method for producing a paper mat of the present invention. In this step, an inorganic fiber molding containing alumina fibers and refractory ceramic fibers is opened in water to produce a slurry. In the method for producing a paper 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 can be balanced between the effect of the alumina fiber in improving the initial contact pressure of the mat material and the effect of the refractory ceramic fiber in maintaining the contact pressure when the mat material is repeatedly compressed. Therefore, the produced papermaking mat has a high initial contact pressure and can maintain the contact 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 molding 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. These 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 numeral "21a" in FIG. 2A) and a crimped state (denoted by reference numeral "21b" in FIG. 2A).

[0044] In this specification, the term "straight state" refers to the direction of the fiber bundle (arrow D in FIG. 2A).１ In this specification, the term "curly state" means that the direction of the fiber bundle (the direction indicated by the arrow D in FIG. 2A) is linear. ２ This means that the direction indicated by the arrow (the direction indicated by the arrow) is bent at least once.

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

[0046] The fiber bundle 21b in a crimped state 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 a crimped state shown in Fig. 2B has a traced length L of the fiber bundle 21b in a 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 of measuring the tracing length) The fiber bundle 21b in a crimped state is placed on a flat surface. Next, the fiber bundle 21b in a crimped state is viewed from above, and one end P １ to the other end P ２ The fiber bundle 21b is traced along the crimped fiber bundle 21b from the 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 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] When measuring the "tracing length of the crimped fiber bundle" in the fiber bundle 21b in the crimped state shown in FIG. 2B, the end P １ and end P ２ It is preferable that the fiber bundles 21b are in a crimped state so that the fiber bundles 21b can be traced so as to cross the line segment S connecting the line segments S and L two or more times. Such crimped fiber bundles 21b have an appropriate degree of crimp, and the elasticity of the crimped fiber bundles 21b 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 the number 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 papermaking mat, the fiber bundle 21 can be formed in the opening step. The first inorganic fiber molded body preferably includes the alumina fiber. The second inorganic fiber molded body preferably includes the refractory ceramic fiber.

[0056] The following method can be given as an example of the fiber-opening method: 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 50 to 400 times by weight, and the mixture is stirred to open the fibers, thereby producing a slurry containing inorganic fibers. The weight ratio is preferably 100 to 200 times. It is preferable to set the stirring conditions appropriately. For example, when producing a 10 L slurry, it is preferable to use a stirrer (product name: SMT-101, manufacturer: ASONE) and stir the mixture at a rotation speed of 500 to 1000 rpm for 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 paper mat to be produced. 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 paper mat to be produced. Preferred types of organic binders and inorganic binders have already been described, so further description will be omitted here.

[0060] (2) Papermaking Step 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. The inorganic fiber aggregate is then dehydrated and dried.

[0061] In the papermaking process, the inorganic fiber aggregate may be dried by heating and pressurizing. During 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 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 range of 100 to 250°C, 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 temperature 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] The paper mat of the present invention can be manufactured through the above steps. In the paper mat manufacturing method of the present invention, it is preferable to perform batch papermaking or continuous papermaking in the papermaking step. By performing batch papermaking or continuous papermaking, the paper mat of the present invention can be easily obtained.

[0063] In the above-mentioned methods for manufacturing a papermaking mat, the papermaking step is carried out after the fiber-opening step, but in the method for manufacturing a papermaking mat of the present invention, the fiber-opening step does not have to be carried out if a mat material can be manufactured by preparing a slurry having the following characteristics and papermaking it: In other words, the slurry to be made in the method for manufacturing a papermaking mat of the present invention only needs to be 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 alumina fibers is 30% or more and the number of refractory ceramic fibers is less than 70%.

[0064] Next, a method of using the papermaking mat of the present invention will be described. FIG. 3 is a cross-sectional view schematically showing an example of an exhaust gas purification apparatus of the present invention. As shown in FIG. 3, the exhaust gas purification apparatus 100 includes a metal casing 30, an exhaust gas treatment body 40 housed in the metal casing 30, and a papermaking mat 10 disposed between the exhaust gas treatment body 40 and the metal casing 30. The papermaking mat 10 is the papermaking mat of the present invention. The exhaust gas treatment body 40 is columnar, with a large number of cells 41 arranged in parallel in the longitudinal direction, separated by cell walls 42. 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 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 Figure 3, exhaust gas emitted from an internal combustion engine and flowing into the exhaust gas purification device 100 (in Figure 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 the other 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 the exhaust gas in the initial stage of use of the exhaust gas purification device 100, the exhaust gas treatment body 40 can be prevented from falling off 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 a silicon carbide porous ceramic, the porosity of the porous ceramic 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, while if the porosity is more than 60%, the strength of the exhaust gas treatment body may decrease and the body may easily break.

[0069] The average pore diameter of the porous ceramic is preferably 5 to 30 μm. If the average pore diameter is less than 5 μm, PM may easily clog the pores. If the average pore diameter is more than 30 μm, PM may pass through the pores, making it impossible to capture PM and preventing the ceramic from functioning as a filter. 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 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.

[0072] (Metal Casing) The metal casing 30 is substantially 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 shorter 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 a 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 per 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 less.

[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-made 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 papermaking mat according to the present disclosures (7) to (10), in which the papermaking process is carried out by batch papermaking or continuous papermaking.

[0086] The present disclosure (12) is a method for manufacturing a paper mat, which includes a papermaking step of papermaking a slurry containing alumina fiber (AF) and refractory ceramic fiber (RCF) to form a paper mat, 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 a 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.

[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) Al ２ O ３ : SiO ２ = 72:28 (weight ratio), and the bulk density was 0.17 g / mm ３ and the density of needle marks is 21 marks / cm ２ A first inorganic fiber molded body derived from a needle mat having a density of Al ２ O ３ : SiO ２= 50:50 (weight ratio) of refractory ceramic fibers, and the bulk density was 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 allowed 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 using a mixer (product name: SMT-101, manufacturer: ASONE) at a rotation speed of 1000 rpm for a stirring time of 10 minutes to open the fibers, thereby producing an inorganic fiber slurry.

[0096] One hundred inorganic fibers were randomly extracted from the slurry and identified as alumina fibers or refractory ceramic fibers. The ratio of alumina fibers was 71% and the ratio of refractory ceramic fibers was 29%. Furthermore, the weight ratio of alumina fibers was 70 parts by weight and the weight ratio of refractory ceramic fibers was 30 parts by weight per 100 parts by weight of 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, and 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 having a filtering mesh formed on the bottom surface, and the solvent in the slurry was removed to obtain an inorganic fiber aggregate. The inorganic fiber aggregate was then dehydrated and dried at 150 to 210°C for 5 minutes to 1 hour to produce the papermaking mat according to Example 1.

[0099] (Example 2) and (Comparative Example 1) Papermaking mats for Example 2 and Comparative Example 1 were manufactured 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]

[0101] (Measurement of surface pressure) The paper-made mats according to Examples 1, 2 and Comparative Example 1 were set in a testing machine (product name: SMT-101, manufacturer: ASONE), and the void bulk density (GBD) was measured at 0.40 mm ３ The void bulk density (GBD) was 0.40 mm / g. ３ The mats were held in this state of 0.15 psi / g for 10 minutes. Then, the mats were released at a speed of 25.4 mm / min. This compression and release cycle was repeated 1,000 times. Then, the surface pressure of each mat was measured. The results are shown in Table 1.

[0102] As shown in Table 1, the mats according to Examples 1 and 2 exhibited high surface pressure even after repeated compression and release.

[0103] REFERENCE SIGNS LIST 10 Paper-made mat 11 One end 11a Convex portion 12 Other end 12a Concave portion 20 Inorganic fiber 21 Fiber bundle 30 Metal casing 40 Exhaust gas treatment body 40a Exhaust gas inlet end 40b Exhaust gas outlet end 41 Cell 42 Cell wall 43 Sealing 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 paper-made 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 the alumina fibers is 30% or more and the number of the refractory ceramic fibers is less than 70%.

8. 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.