Paper-made mat and method for producing same

Abstract

To provide a paper-made mat which has a high initial surface pressure and can maintain the surface pressure even if it is repeatedly compressed. [Solution] A papermaking mat composed of two or more different types of inorganic fibers, an organic material, and an inorganic material, characterized in that the inorganic fibers include alumina fibers (AF) and refractory ceramic fibers (RCF).

Description

[Technical field]

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

[0002] Exhaust gas emitted from internal combustion engines such as diesel engines contains particulate matter (hereinafter referred to as PM), and in recent years, the harm that this PM poses to the environment and human body has become a problem. In addition, exhaust gas also contains harmful gas components such as CO, HC, and NOx, and there are concerns about the impact that these harmful gas components have on the environment and human body.

[0003] In response to this, 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 and 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. The main purpose of this holding seal material (mat material) is to prevent 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 to prevent 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 fiber having about 50% Al2O3 and about 50% SiO2 as described in Patent Document 1 is a fiber called a refractory ceramic fiber. A mat made of such a refractory ceramic fiber has a low surface pressure, and the exhaust gas treatment body is easily dropped off due to the exhaust gas pressure.

[0007] The present invention has been made to solve the above problems, and an object of the present invention is to provide a papermaking 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] In other words, the papermaking mat of the present invention is a papermaking mat composed of two or more different types of inorganic fibers, organic materials, and inorganic materials, and is characterized in that the inorganic fibers include alumina fibers (AF) and refractory ceramic fibers (RCF).

[0009] Alumina fibers are hard, and therefore when a mat material is made of alumina fibers, the initial surface pressure of the mat material is high. On the other hand, refractory ceramic fibers are easily broken, and when a mat material made of refractory ceramic fibers is repeatedly compressed, the refractory ceramic fibers break, and the surface pressure decreases. On the other hand, refractory ceramic fibers are soft, and when the mat material is made of refractory ceramic fibers, the initial surface pressure of the mat material is low. Since the papermaking mat of the present invention contains alumina fibers and refractory ceramic fibers, it has a balanced effect of improving the initial surface pressure of the mat material due to the alumina fibers, and of maintaining the surface pressure when the mat material is repeatedly compressed due to the refractory ceramic fibers. 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, the inorganic fibers preferably contain 5 wt % or more of the alumina fibers and less than 95 wt % of the refractory ceramic fibers. When the weight ratio of the alumina fiber and the refractory ceramic fiber is within the above range, the two are balanced, and the initial surface pressure is high and the surface pressure can be maintained even if the material is repeatedly compressed, thereby making it possible to preferably exert the effect of the above-mentioned.

[0011] In the papermaking mat of the present invention, when any of the inorganic fibers are randomly extracted and determined to be alumina fibers or refractory ceramic fibers, it is preferable that the number of the alumina fibers is 3% or more and the number of the refractory ceramic fibers is less than 97%. When the ratio of the number of alumina fibers and refractory ceramic fibers is within the above range, the two are balanced, the initial surface pressure is high, and the surface pressure can be maintained even when repeatedly compressed, making it possible to preferably exert the effect.

[0012] In the papermaking mat of the present invention, it is preferable that the organic matter is an organic binder, and the inorganic matter is an inorganic binder. The organic binder and the inorganic binder bond the inorganic fibers together and maintain the shape of the papermaking mat. In addition, it is possible to prevent the inorganic fibers from falling off the paper mat and scattering.

[0013] In the papermaking mat of the present invention, the organic binder preferably has a glass transition temperature Tg of 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.

[0014] 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-based latex, rubber-based 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.

[0015] The paper 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 paper mat. In the fiber-spreading step, a fiber bundle is formed by entangling a plurality of inorganic fibers. Such fiber bundles act as a core material, and can improve the surface pressure of the papermaking mat.

[0016] 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-formed mat, it can form a fiber bundle in the opening step. The first inorganic fiber molded body preferably contains the alumina fibers. The second inorganic fiber molded body preferably contains the refractory ceramic fiber.

[0017] 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 making.

[0018] The papermaking mat of the present invention includes a fiber bundle formed by twisting and intertwining 10 or more of the above-mentioned inorganic fibers, at least one of the fiber bundles being a fiber bundle in a crimped state, and it is preferable that the trace length of the above-mentioned crimped fiber bundle, as measured by the trace length measurement method described below, is at least 0.1 mm longer than the length of the above-mentioned crimped fiber bundle. How to measure trace length: The crimped fiber bundle is placed on a flat surface. The fiber bundle in the crimped state that has been left stationary is viewed from above, and a line is traced along the fiber bundle in the crimped state from one end of the fiber bundle in the crimped state to the other end, and the distance traced is defined as the "tracing length of the fiber bundle in the crimped state." The fiber bundles in a crimped state are elastic, and a papermaking mat containing such fiber bundles is subject to high surface pressure.

[0019] The papermaking mat of the present invention preferably further contains organic fibrils as the organic matter. The organic fibrils are preferably in the form of cellulose, acrylic, aramid, or PVA fibrillated to fluff the fine fibers at the ends or surfaces of the fibers.

[0020] The method for manufacturing a papermaking mat of the present invention is a method for manufacturing a papermaking mat composed of two or more different types of inorganic fibers, organic matter, and inorganic matter, wherein the inorganic fibers include alumina fibers (AF) and refractory ceramic fibers (RCF), and the method is characterized in that it includes a papermaking step of papermaking a slurry containing the alumina fibers (AF) and the refractory ceramic fibers (RCF) to form a papermaking mat.

[0021] The above-mentioned paper-made mat of the present invention can be produced by the method for producing a paper-made mat of the present invention.

[0022] In the method for producing a papermaking mat of the present invention, the inorganic fibers preferably contain 5 wt % or more of the alumina fibers and less than 95 wt % of the refractory ceramic fibers. When the weight ratio of the alumina fibers and the refractory ceramic fibers is within the above range, a balanced combination of the two can be achieved, making it possible to produce a papermaking mat that has a high initial surface pressure and can maintain that surface pressure even when subjected to repeated compression.

[0023] In the method for manufacturing a papermaking mat of the present invention, when any of the inorganic fibers are randomly extracted from the slurry and determined to be alumina fibers or refractory ceramic fibers, it is preferable that the number of the alumina fibers is 3% or more and the number of the refractory ceramic fibers is less than 97%. When the ratio of the number of alumina fibers and refractory ceramic fibers is within the above range, a balanced combination of the two can be achieved, resulting in a papermaking mat that has a high initial surface pressure and can maintain that surface pressure even when subjected to repeated compression.

[0024] 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 entangled. Such fiber bundles act as a core material, and can improve the surface pressure of the produced paper mat.

[0025] 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-formed mat, it can form a fiber bundle in the opening step. The first inorganic fiber molded body preferably contains the alumina fibers. The second inorganic fiber molded body preferably contains the refractory ceramic fiber.

[0026] In the method for producing a papermaking mat of the present invention, it is preferable that the slurry in the papermaking step contains organic fibrils as the organic matter. In the method for producing a paper mat of the present invention, it is preferable that in the opening step, the organic fibrils are opened in water to prepare the slurry. Effect of the Invention

[0027] According to the present invention, it is possible to provide a papermaking mat which has a high initial surface pressure and can maintain the surface pressure even when repeatedly compressed. [Brief description of the drawings]

[0028] [Figure 1] FIG. 1 is a perspective view showing a typical example of a papermaking mat of the present invention. [Diagram 2] FIG. 2 is an enlarged view that illustrates a schematic example of inorganic fibers of a papermaking mat when the papermaking mat of the present invention includes a papermaking mat. [Diagram 3] FIG. 3 is a schematic diagram of an example of a fiber bundle in a crimped state. [Figure 4] FIG. 4 is a cross-sectional view that illustrates an example of an exhaust gas purification device of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] 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. In addition, the present invention also includes a combination of two or more of the individual preferred configurations of the present invention described below.

[0030] 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 a papermaking 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 a plan view, with a protruding portion 11a provided at one end 11 and a recessed portion 12a provided at the other end 12.

[0031] 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 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.

[0032] The papermaking mat 10 contains an organic binder as an organic matter, and an inorganic binder as an inorganic matter. The organic binder and the inorganic binder bond the inorganic fibers together and maintain the shape of the papermaking mat 10 . In addition, the inorganic fibers can be prevented from falling off the paper mat 10 and scattering.

[0033] The paper mat 10 may also contain organic fibrils made of cellulose, acrylic, aramid, PVA, or the like as an organic matter. The organic fibrils are fibrillated with fine fibers (fibrils) at the ends and surface, and the fine fibers are entangled with the inorganic fibers to improve adhesion. The organic fibrils are preferably in the form of fine fibers fluffed at the ends or surfaces of fibers made of the above organic matter.

[0034] In the papermaking mat 10, the inorganic fibers include alumina fibers (AF) and refractory ceramic fibers (RCF). The inorganic fibers may contain inorganic fibers other than the alumina fibers and the refractory ceramic fibers, such as silica fibers, glass wool, and rock wool.

[0035] 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 ratio of Al2O3 constituting the fiber is 60% by weight or less.

[0036] 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.

[0037] Alumina fibers are hard, and therefore when a mat material is made of alumina fibers, the initial surface pressure of the mat material is high. On the other hand, refractory ceramic fibers are easily broken, and when a mat material made of refractory ceramic fibers is repeatedly compressed, the refractory ceramic fibers break, and the surface pressure decreases. On the other hand, refractory ceramic fibers are soft, and when the mat material is made of refractory ceramic fibers, the initial surface pressure of the mat material is low. Since the papermaking mat 10 contains alumina fibers and refractory ceramic fibers, it has a balanced effect of improving the initial surface pressure of the mat material due to the alumina fibers, and of maintaining the surface pressure when the mat material is repeatedly compressed due to the refractory ceramic fibers. Therefore, the papermaking mat 10 has a high initial surface pressure and can maintain the surface pressure even when repeatedly compressed.

[0038] In the papermaking mat 10, the inorganic fibers are preferably composed of alumina fibers at a weight ratio of 5 wt% or more and refractory ceramic fibers at a weight ratio of less than 95 wt%, and more preferably composed of alumina fibers at a weight ratio of 10 to 30 wt% and refractory ceramic fibers at a weight ratio of 70 to 90 wt%. When the weight ratio of the alumina fiber and the refractory ceramic fiber is within the above range, the two are balanced, and the initial surface pressure is high and the surface pressure can be maintained even if the material is repeatedly compressed, thereby making it possible to preferably exert the effect of the above-mentioned.

[0039] Furthermore, if you want to improve the flexibility of the papermaking mat 10, it is preferable to make the weight percentage of the alumina fibers less than 30 wt%, and if you want to make the papermaking mat 10 harder, it is preferable to make the weight percentage of the alumina fibers 30 wt% or more.

[0040] In the papermaking mat 10, when any of the inorganic fibers are randomly extracted and determined to be alumina fibers or refractory ceramic fibers, it is preferable that the number of alumina fibers is 3% or more and the number of refractory ceramic fibers is less than 97%, and it is more preferable that the number of alumina fibers is 20-50% and the number of refractory ceramic fibers is 50-80%. When the ratio of the number of alumina fibers and refractory ceramic fibers is within the above range, the two are balanced, the initial surface pressure is high, and the surface pressure can be maintained even when repeatedly compressed, making it possible to preferably exert the effect.

[0041] 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 papermaking mat. When the contents of the organic binder and the inorganic binder are within the above ranges, the inorganic fibers are appropriately bonded to each other, and the paper mat can have both flexibility and shape retention.

[0042] 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, 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 the exhaust gas treatment body, etc. Furthermore, since the organic binder film does not become too hard, when the inorganic fibers are broken, it has the effect of binding the inorganic fibers together, and it is possible to suppress scattering of the inorganic fibers. Organic binders with a glass transition temperature Tg of less than −50° 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 decreases, and the breaking elongation may decrease.

[0043] 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-based latexes, rubber-based latexes, carboxymethyl cellulose, and polyvinyl alcohol. Examples of thermoplastic resins include styrene resins. Examples of epoxy resins function as thermosetting resins.

[0044] In the papermaking mat 10, the inorganic binder preferably contains at least one of alumina, silica, silicon carbide, zirconia, boron nitride, diamond, and pumice.

[0045] These organic binders and inorganic binders are suitable for bonding the inorganic fibers together and maintaining the shape of the papermaking mat.

[0046] The papermaking mat 10 may include a fiber bundle formed by twisting and entangling 10 or more of the inorganic fibers described above. A paper mat containing such fiber bundles will be described with reference to the drawings.

[0047] FIG. 2 is an enlarged view that illustrates a schematic example of inorganic fibers of a papermaking mat when the papermaking mat of the present invention includes a papermaking mat. As shown in FIG. 2, the papermaking mat may include fiber bundles 21 formed by twisting and intertwining ten or more inorganic fibers 20, and inorganic fibers 22 that do not constitute the fiber bundles 21. The fiber bundle 21 may be in a straight state (indicated by reference symbol "21a" in FIG. 2) or in a crimped state (indicated by reference symbol "21b" in FIG. 2).

[0048] In this specification, the fiber bundle means a portion of the papermaking mat where inorganic fibers are concentrated and entangled, and where the density is higher than other portions.

[0049] The average length of the fiber bundles 21 (the average value of the lengths indicated by the symbol L in FIG. 2) is preferably 5 to 15 mm, more preferably 7 to 13 mm, and further preferably 8 to 10 mm. The average width of the fiber bundle 21 (the average value of the length indicated by the symbol W in FIG. 2) is preferably 0.2 to 1.0 mm, and more preferably 0.2 to 0.8 mm. As shown in FIG. 2, when the fiber bundle 21 is a straight fiber bundle 21a and when the fiber bundle 21 is a crimped fiber bundle 21b, the maximum width (the lengths indicated by the symbols Wa and Wb, respectively, in FIG. 2) is the width of the fiber bundle 21.

[0050] The fiber bundles 21 are formed by twisting and intertwining 10 or more inorganic fibers 20, and since they support each other, they are not easily deformed by pressure. Therefore, when pressure is applied to the papermaking mat, the fiber bundles 21 act as a core material and can reduce the pressure on the inorganic fibers 22 that do not constitute the fiber bundles 21. Therefore, it is possible to prevent the inorganic fibers 22 that do not constitute the fiber bundles 21 from breaking due to pressure. As a result, the surface pressure of the papermaking mat is high. In particular, when the fiber bundles 21 are crimped fiber bundles 21b, this effect is exhibited favorably, and the surface pressure of the papermaking mat becomes higher.

[0051] If the average length of the fiber bundles is less than 5 mm, the fiber bundles are too short, making it difficult for the fiber bundles to act as a core material and to relieve the pressure applied to the inorganic fibers that do not constitute the fiber bundles. If the average length of the fiber bundle exceeds 15 mm, the fiber bundle is too long and when pressure is applied to the sides of the fiber bundle, it becomes easy to bend and does not function well as a core material.

[0052] If the average width of the fiber bundle is less than 0.2 mm, the strength of the fiber bundle will be low, the fiber bundle will be easily bent, and it will be difficult for the fiber bundle to function as a core material. If the average width of the fiber bundle exceeds 1.0 mm, the strength of the fiber bundle becomes too high, and the flexibility of the entire papermaking mat decreases.

[0053] Here, the crimped fiber bundle 21b will be described in detail below with reference to the drawings. FIG. 3 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. 3 has a trace length L 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.

[0054] (Method of measuring tracing length) The fiber bundle 21b in a crimped state is placed on a flat surface. Next, the fiber bundle 21b in the crimped state that has been left stationary is viewed from above, and a line is traced along the fiber bundle 21b in the crimped state from one end P1 to the other end P2 of the fiber bundle 21b in the crimped state, and the distance L t is defined as the "tracing length of the fiber bundle in a crimped state."

[0055] The length L of the fiber bundle 21b in the crimped state t When 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.

[0056] It is preferable that the papermaking mat 10 includes fiber bundles 21b in a crimped state such that, when measuring the "trace length of the fiber bundle in a crimped state" in the fiber bundles 21b in a crimped state shown in Figure 3, 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, so that the surface pressure of the papermaking mat 10 is improved.

[0057] In the papermaking mat 10, the length L of the fiber bundle 21b in the crimped state is compared to the tracing length L of the fiber bundle 21b in the crimped state. t The ratio of L t It is preferable that / L=1.1 to 1.6.

[0058] 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) It should be noted that "Wb" refers to the width of the fiber bundle 21b in a crimped state.

[0059] 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:

[0060] 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%.

[0061] The fiber bundles 21 are formed by intertwining a plurality of inorganic fibers 20, which support each other and are therefore resistant to deformation under pressure. Therefore, when pressure is applied to the papermaking mat 10, the fiber bundles 21 act as a core material and can reduce the pressure on the inorganic fibers 22 that do not constitute the fiber bundles 21. This prevents the inorganic fibers 22 that do not constitute the fiber bundles 21 from breaking under pressure. As a result, the surface pressure of the papermaking mat 10 is high.

[0062] Next, an example of the method for producing a paper mat of the present invention will be described. An example of the method for producing a papermaking mat of the present invention described below includes (1) a fiber-spreading step and (2) a papermaking step. Each step will be described below.

[0063] (1) Opening process In this step, an inorganic fiber molded body containing alumina fibers and refractory ceramic fibers is opened in water to prepare a slurry.

[0064] Since the slurry contains alumina fibers and refractory ceramic fibers, in the mat material manufactured through subsequent processes, a balance is achieved between the effect of the alumina fibers in improving the initial surface pressure of the mat material and the effect of the refractory ceramic fibers in 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 if it is repeatedly compressed.

[0065] In the above slurry, the inorganic fibers are preferably composed of alumina fibers at a weight ratio of 5 wt% or more and refractory ceramic fibers at a weight ratio of less than 95 wt%, and more preferably composed of alumina fibers at a weight ratio of 10 to 30 wt% and refractory ceramic fibers at a weight ratio of 70 to 90 wt%. When the weight ratio of the alumina fiber and the refractory ceramic fiber is within the above range, the two are balanced, and the initial surface pressure is high and the surface pressure can be maintained even if the material is repeatedly compressed, thereby making it possible to preferably exert the effect of the above-mentioned.

[0066] Furthermore, when any of the inorganic fibers are randomly extracted from the slurry and determined to be alumina fibers or refractory ceramic fibers, it is preferable that the number of alumina fibers is 3% or more and the number of refractory ceramic fibers is less than 97%, and it is more preferable that the number of alumina fibers is 20 to 50% and the number of refractory ceramic fibers is 50 to 80%. When the ratio of the number of alumina fibers and refractory ceramic fibers is within the above range, a balanced combination of the two can be achieved, resulting in a papermaking mat that has a high initial surface pressure and can maintain that surface pressure even when subjected to repeated compression.

[0067] Furthermore, when the inorganic fiber molded body is opened, the inorganic fibers are not completely opened, and fiber bundles in which a plurality of inorganic fibers are entangled are formed. Such fiber bundles act as a core material, and can improve the surface pressure of the produced paper mat.

[0068] 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-formed mat, the fiber bundles 21 can be formed in the opening step. The first inorganic fiber molded body preferably contains the alumina fibers. The second inorganic fiber molded body preferably contains the refractory ceramic fiber.

[0069] Examples of the fiber opening include the following methods. First, the first inorganic fiber molded body and / or the second 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 up the inorganic fiber molded body.

[0070] 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.

[0071] 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 stirrer (product name: SMT-101, manufacturer: ASONE) and stir at a rotation speed of 500 to 1000 rpm for a stirring time of 200 to 900 seconds. Preferably, the rotation speed is 650 to 850 rpm, the stirring time is 500 to 700 seconds, and more preferably, the rotation speed is 700 to 800 rpm, and the stirring time is 500 to 650 seconds.

[0072] Next, the organic and inorganic binders are added to the slurry. The organic binder is added to the produced paper mat in an amount of preferably 0.1 to 20 parts by weight, and more preferably 0.5 to 15.0 parts by weight, per 100 parts by weight of the inorganic fibers. The inorganic binder is preferably added in an amount of 0.1 to 10 parts by weight, and more preferably 0.5 to 3.0 parts by weight, per 100 parts by weight of the inorganic fibers in the produced paper mat. Since the preferred types of organic binders and inorganic binders have already been described, the description thereof will be omitted here.

[0073] (2) Papermaking process Next, the slurry is poured into a molding machine having a filtering mesh formed on the bottom surface thereof, and the solvent in the slurry is removed to obtain an inorganic fiber aggregate, which is then dehydrated and dried.

[0074] 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 deterioration of the organic binder due to heat. In the range of 100 to 250°C, moisture can be removed from the inorganic fiber aggregate while suppressing deterioration 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, and the drying time becomes long. Furthermore, if it exceeds 250°C, the organic binder is deteriorated and the binding force between the fibers is reduced, making it difficult to control the thickness of the inorganic fiber aggregate.

[0075] Through the above steps, the papermaking mat of the present invention can be manufactured. 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 making.

[0076] In the above-mentioned method for manufacturing a paper-formed mat, the paper-forming process is carried out after the fiber-opening process, but in the method for manufacturing a paper-formed mat of the present invention, the fiber-opening process does not need to be carried out if a slurry containing alumina fibers and refractory ceramic fibers is prepared and paper-formed to produce a mat material.

[0077] Next, a method for using the papermaking mat of the present invention will be described. FIG. 4 is a cross-sectional view that illustrates an example of an exhaust gas purification device of the present invention. As shown in Fig. 4, 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 with cell walls 42 separating them. Note that, to the ends of the metal casing 30, an inlet pipe for introducing exhaust gas discharged 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 as necessary. In the exhaust gas purification device 100 shown in FIG. 4, 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.

[0078] As shown in Fig. 4, exhaust gas discharged from an internal combustion engine and flowing into the exhaust gas purification device 100 (in Fig. 4, 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 an 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 an exhaust gas outlet end face 40b, and is discharged to the outside.

[0079] 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 stage 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. Moreover, this effect of preventing falling off can be maintained for a long period of time.

[0080] 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, mullite, etc. Among these, silicon carbide is preferable.

[0081] When the exhaust gas treatment body 40 is made of porous ceramics made 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 the body may easily be destroyed.

[0082] The average pore size of the porous ceramic is preferably 5 to 30 μm. If the average pore size is less than 5 μm, PM may easily cause clogging. If the average pore diameter exceeds 30 μm, PM may pass through the pores, making it impossible to capture PM and thus unable to function as a filter. The porosity and pore size can be measured by a conventionally known method using a scanning electron microscope (SEM).

[0083] 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 ).

[0084] The exhaust gas treatment body 40 may support a catalyst for purifying the exhaust gas. The catalyst to be supported is preferably a precious metal such as platinum, palladium, or rhodium, and among these, platinum is more preferable. In addition, other catalysts such as alkali metals such as potassium or sodium, or alkaline earth metals such as barium may also be used. These catalysts may be used alone or in combination of two or more kinds. When these catalysts are supported, PM can be easily burned and removed, and toxic exhaust gas can also be purified.

[0085] (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 shorter than the diameter of the exhaust gas treatment body 40 around which the papermaking mat 10 is wrapped.

[0086] The metal casing 30 is preferably made of, but not limited to, stainless steel.

[0087] The present specification discloses the following:

[0088] The present disclosure (1) is a papermaking mat composed of two or more different types of inorganic fibers, an organic material, and an inorganic material, characterized in that the inorganic fibers include alumina fibers (AF) and refractory ceramic fibers (RCF).

[0089] The present disclosure (2) is the papermaking mat according to the present disclosure (1), wherein the inorganic fibers are composed of 5 wt% or more of the alumina fibers and less than 95 wt% of the refractory ceramic fibers.

[0090] The present disclosure (3) provides that, when any of the inorganic fibers is randomly extracted from the papermaking mat and judged to be alumina fiber or refractory ceramic fiber, The papermaking mat according to the present disclosure (1) or (2), wherein the number of the alumina fibers is 3% or more and the number of the refractory ceramic fibers is less than 97%.

[0091] The present disclosure (4) is the papermaking mat according to any one of the present disclosures (1) to (3), in which the organic matter is an organic binder and the inorganic matter is an inorganic binder.

[0092] The present disclosure (5) is the papermaking mat according to the present disclosure (4), in which the glass transition temperature Tg of the organic binder is 5° C. or lower.

[0093] The present disclosure (6) is a papermaking mat according to the present disclosure (4) or (5), in which the organic binder is at least one selected from the group consisting of acrylic resin, acrylate-based latex, rubber-based 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.

[0094] The present disclosure (7) is the papermaking mat according to any one of the present disclosures (4) to (6), wherein the inorganic binder contains at least one of alumina, silica, silicon carbide, zirconia, boron nitride, diamond, and pumice.

[0095] The present disclosure (8) is a papermaking mat according to any one of the present disclosures (1) to (7), 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.

[0096] The present disclosure (9) is the papermaking mat according to the present disclosure (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.

[0097] The present disclosure (10) is the papermaking mat according to the present disclosure (9), wherein the first inorganic fiber molded body contains the alumina fibers.

[0098] The present disclosure (11) is the papermaking mat according to the present disclosure (9), wherein the second inorganic fiber molded body contains the refractory ceramic fiber.

[0099] The present disclosure (12) relates to the papermaking mat according to any one of the present disclosures (8) to (11), wherein the papermaking step is performed by batch papermaking or continuous papermaking.

[0100] The present disclosure (13) is a papermaking mat according to any one of the present disclosures (1) to (12), wherein the papermaking mat includes fiber bundles formed by twisting and intertwining 10 or more of the inorganic fibers, at least one of the fiber bundles is a fiber bundle in a crimped state, and the trace length of the crimped fiber bundle measured by the following trace length measurement method is 0.1 mm or more longer than the length of the crimped fiber bundle. How to measure trace length: The crimped fiber bundle is placed on a flat surface. The fiber bundle in the crimped state that has been left stationary is viewed from above, and a line is traced along the fiber bundle in the crimped state from one end of the fiber bundle in the crimped state to the other end, and the distance traced is defined as the "tracing length of the fiber bundle in the crimped state."

[0101] The present disclosure (14) is the papermaking mat according to any one of the present disclosures (1) to (13), further comprising organic fibrils as the organic matter.

[0102] The present disclosure (15) is a method for producing a paper mat composed of two or more different types of inorganic fibers, an organic material, and an inorganic material, wherein the inorganic fibers include alumina fibers (AF) and refractory ceramic fibers (RCF), and the method for producing a paper mat is characterized by including a papermaking step of papermaking a slurry containing the alumina fibers (AF) and the refractory ceramic fibers (RCF) to form a paper mat.

[0103] The present disclosure (16) is a method for producing a papermaking mat according to the present disclosure (15), wherein the inorganic fibers are composed of 5 wt% or more of the alumina fibers and less than 95 wt% of the refractory ceramic fibers.

[0104] The present disclosure (17) is a method for producing a papermaking mat according to the present disclosure (15) or (16), in which when any of the 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 3% or more and the number of the refractory ceramic fibers is less than 97%.

[0105] The present disclosure (18) is a method for producing a papermaking mat according to any one of the present disclosures (15) to (17), further comprising a fiber-opening step of opening an inorganic fiber molding containing the alumina fiber and the refractory ceramic fiber in water to produce the slurry.

[0106] The present disclosure (19) is a method for producing a paper mat according to the present disclosure (18), 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 paper mat.

[0107] The present disclosure (20) is the method for producing a papermaking mat according to the present disclosure (19), wherein the first inorganic fiber molded body contains the alumina fibers.

[0108] The present disclosure (21) is the method for producing a papermaking mat according to the present disclosure (19) or (20), wherein the second inorganic fiber molded body contains the refractory ceramic fiber.

[0109] The present disclosure (22) is the method for producing a papermaking mat according to any one of the present disclosures (15) to (21), wherein in the papermaking step, the slurry further contains organic fibrils as the organic matter. EXAMPLES

[0110] EXAMPLES Hereinafter, examples that more specifically disclose the present invention will be described, however, the present invention is not limited to these examples.

[0111] 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 molding derived from a needle mat having a density of 1000 g / m2 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.

[0112] 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.

[0113] 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.

[0114] 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 a stirring time of 10 minutes using a stirrer (product name: SMT-101, manufacturer: ASONE) to open the fibers, thereby producing an inorganic fiber slurry.

[0115] Furthermore, 100 inorganic fibers were randomly extracted from the slurry and determined whether they were alumina fibers or refractory ceramic fibers. The proportion of alumina fibers was 71%, and the proportion of refractory ceramic fibers was 29%. Well, 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 per 100 parts by weight of the inorganic fibers.

[0116] 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. Further, an inorganic binder was added to the slurry in an amount of 0.3 to 3.0 parts by weight per 100 parts by weight of the inorganic fibers.

[0117] 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. The inorganic fiber aggregate was then dehydrated and dried at 150 to 210°C for 5 minutes to 1 hour to produce a papermaking mat according to Example 1.

[0118] (Example 2), (Example 3) and (Comparative Example 1) The papermaking mats of Examples 2, 3 and Comparative Example 1 were produced in the same manner as in Example 1, except that the first inorganic fiber molded body and the second inorganic fiber molded body used were adjusted and the ratio (weight ratio) of alumina fiber and refractory ceramic fiber was changed as shown in Table 1.

[0119] [Table 1]

[0120] (Measurement of surface pressure) The papermaking mats according to Examples 1 to 3 and Comparative Example 1 were set in a testing machine (product name: SMT-101, manufacturer: ASONE) and the void bulk density (GBD) was 0.40 mm 3 The material was compressed at a rate of 25.4 mm / min until the void bulk density (GBD) was 0.40 mm 3 The mat was then held at 0.05 mm / g for 10 min, after which it was 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.

[0121] As shown in Table 1, the papermaking mats according to Examples 1 to 3 exhibited high surface pressure even after repeated compression and release. [Explanation of symbols]

[0122] 10 Paper mat 11 One end 11a Convex part 12 The other end 12a Recess 20, 22 Inorganic fibers 21, 21a, 21b Fiber bundle 30 Metal Casing 40 Exhaust gas treatment body 40a Exhaust gas inlet end 40b Exhaust gas exhaust side end 41 Cell 42 Cell Wall 43 Encapsulating materials 100 Exhaust gas purification equipment

Claims

1. A paper mat composed of two or more different types of inorganic fibers, an organic material, and an inorganic material, The inorganic fibers include alumina fibers (AF) and refractory ceramic fibers (RCF); The inorganic fibers are composed of 10 to 30 wt % alumina fibers and 70 to 90 wt % refractory ceramic fibers.

2. When any of the inorganic fibers is randomly extracted from the papermaking mat and judged to be alumina fibers or refractory ceramic fibers, 2. The papermaking mat according to claim 1, wherein the number of said alumina fibers is 3% or more and the number of said refractory ceramic fibers is less than 97%.

3. 3. The papermaking mat according to claim 1, wherein the organic matter is an organic binder, and the inorganic matter is an inorganic binder.

4. The papermaking mat according to claim 3 , wherein the organic binder has a glass transition temperature Tg of 5° 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-based latex, rubber-based 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. The paper mat includes a fiber bundle formed by twisting and entangling 10 or more of the inorganic fibers, At least one of the fiber bundles is a crimped fiber bundle, 3. The paper mat according to claim 1 or 2, wherein the trace length of the fiber bundle in the crimped state, as measured by the following trace length measuring method, is at least 0.1 mm longer than the length of the fiber bundle in the crimped state. How to measure trace length: The crimped fiber bundle is placed on a flat surface. The fiber bundle in a crimped state that has been placed still is viewed from above, and a line is traced along the fiber bundle in a crimped state from one end of the fiber bundle to the other end, and the distance traced is defined as the "tracing length of the fiber bundle in a crimped state."

8. The papermaking mat according to claim 1 or 2, further comprising organic fibrils as the organic matter.

9. A method for producing a paper mat composed of two or more different types of inorganic fibers, an organic material, and an inorganic material, comprising: The inorganic fibers include alumina fibers (AF) and refractory ceramic fibers (RCF); A papermaking process is included in which a slurry containing the alumina fiber (AF) and the refractory ceramic fiber (RCF) is paper-formed into a paper mat, The method for producing a paper mat is characterized in that the inorganic fibers are composed of 10 to 30 wt % alumina fibers and 70 to 90 wt % refractory ceramic fibers.

10. When the inorganic fibers are randomly extracted from the slurry and judged to be alumina fibers or refractory ceramic fibers, The method for producing a paper mat according to claim 9, wherein the number of the alumina fibers is 3% or more, and the number of the refractory ceramic fibers is less than 97%.

11. The method for producing a paper mat according to claim 9 or 10, 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 the slurry.

12. The method for producing a paper mat according to claim 11, 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 paper mat.

13. The method for producing a papermaking mat according to claim 12 , wherein the first inorganic fiber molded body contains the alumina fibers.

14. The method for producing a papermaking mat according to claim 12 , wherein the second inorganic fiber molded body contains the refractory ceramic fiber.

15. The method for producing a papermaking mat according to claim 9 or 10, wherein in the papermaking step, the slurry further contains organic fibrils as the organic matter.

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