Method for producing inorganic fiber mat, and inorganic fiber mat

Abstract

The invention provides a method for manufacturing an inorganic fiber mat and an inorganic fiber mat. An inorganic fiber mat is produced by a method for producing an inorganic fiber mat, which uses a first inorganic fiber molded body derived from a needle-punched mat to which an organic binder has been added, and which is characterized by comprising: a splitting step for splitting the first inorganic fiber molded body to obtain inorganic fibers; and a papermaking and molding step for performing papermaking and molding of the inorganic fiber mat using the slurry containing the split inorganic fibers.

Description

[0001] This application is a divisional application of the Chinese invention patent application with application number 202380013806.1 (international application number PCT / JP2023 / 043608), Chinese national phase entry date March 27, 2024 (international application date December 6, 2023), and invention name “Manufacturing method of inorganic fiber mat and inorganic fiber mat”. Technical Field

[0002] The present invention relates to a method for manufacturing an inorganic fiber mat and the inorganic fiber mat. Background Art

[0003] Various proposals have been made for exhaust gas purification devices that capture particulate matter (PM) or purify harmful gas components in exhaust gas. These devices consist of an exhaust gas treatment body (composed of a porous ceramic such as silicon carbide or cordierite), a housing that houses the exhaust gas treatment body, and an inorganic fiber mat (retention sealant) positioned between the exhaust gas treatment body and the housing. This mat is primarily intended to prevent the exhaust gas treatment body from contacting the housing, which covers its outer circumference, and causing damage due to vibration or impact generated by vehicle movement, and to prevent exhaust gas from leaking out from between the exhaust gas treatment body and the housing.

[0004] In addition, such inorganic fiber mats are produced by punching or cutting out a large sheet of inorganic fiber mat into a predetermined shape, and the edges of the sheet are generated as scraps. In recent years, there has been a demand to reduce industrial waste and to reuse scraps generated during manufacturing without discarding them.

[0005] Patent Document 1 discloses a method for producing a thermal insulation molded body, characterized in that waste inorganic fibrous thermal insulation material is defibrated, new inorganic fibers are mixed with the defibrated thermal insulation material to form a cotton-like shape, and a binder is mixed and molded.

[0006] In addition, Patent Document 2 discloses a method for manufacturing a fiber molding, which is characterized in that ceramic fibers are mixed with ionic organic binder powder, and water containing a heat-resistant inorganic binder is further added and mixed so that the whole is roughly wet. Thereafter, the wet mixture is filled in a mold and pressurized for molding. In this manufacturing method, a part of the above-mentioned ceramic fibers is replaced with a crushed product obtained by finely crushing used fiber products.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Laid-Open No. 9-210289

[0010] Patent Document 2: Japanese Patent Application Laid-Open No. 2001-335379 Summary of the Invention

[0011] Problems to be solved by the invention

[0012] However, the methods disclosed in Patent Documents 1 and 2 have a problem in that the moldability of the product is insufficient.

[0013] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a method for producing an inorganic fiber mat that is easier to mold even when an inorganic fiber molded body is used as the inorganic fiber material.

[0014] Means for solving problems

[0015] The present inventors have conducted intensive studies and have found that the moldability of a newly produced inorganic fiber mat can be improved by using inorganic fibers derived from a needle-punched mat to which an organic binder is added as inorganic fibers.

[0016] That is, the method for manufacturing an inorganic fiber mat of the present invention (hereinafter also referred to as the manufacturing method of the present invention) is characterized in that it uses a first inorganic fiber molded body derived from a needle-punched mat to which an organic binder is added, and has the following steps: a fiber opening step, in which the above-mentioned first inorganic fiber molded body is fiberized to obtain inorganic fibers; and a papermaking and molding step, in which the inorganic fiber mat is papermade and molded using a slurry containing the above-mentioned inorganic fibers that have been fiberized.

[0017] The method for producing an inorganic fiber mat of the present invention uses inorganic fibers derived from a needle-punched mat to which an organic binder is added as inorganic fibers. Therefore, the inorganic fiber mat is not excessively opened, and has excellent moldability.

[0018] In the method for producing an inorganic fiber mat of the present invention, it is preferred to further use a second inorganic fiber molded body derived from a papermaking mat.

[0019] When the second inorganic fiber molded body derived from a papermaking mat is used, the produced inorganic fiber mat has both resilience and windability.

[0020] In the method for producing an inorganic fiber mat of the present invention, it is preferred that the first inorganic fiber molded body and the second inorganic fiber molded body contain an inorganic binder.

[0021] Since the first inorganic fiber molded body and the second inorganic fiber molded body contain an inorganic binder, the dispersibility of the inorganic binder in the produced inorganic fiber mat is high.

[0022] In the method for producing an inorganic fiber mat of the present invention, it is preferred that the first inorganic fiber molded body and the second inorganic fiber molded body are scraps.

[0023] By using the scraps in the inorganic fiber material, the scraps can be effectively utilized without being discarded.

[0024] The average fiber length of the inorganic fibers constituting the needle-punched mat is preferably 3.0 to 100 mm.

[0025] When the average fiber length of the inorganic fibers constituting the needle punched mat is within the above range, the inorganic fiber mat obtained by the production method of the present invention has both higher resilience and higher windability.

[0026] The fiber opening is preferably performed only by wet fiber opening.

[0027] When the inorganic fibers are opened only by wet opening, the process becomes simple.

[0028] The needle punch mat is preferably formed by folding thin sheets of an inorganic fiber precursor a plurality of times at a predetermined width, stacking the sheets, and then firing the stacked sheets.

[0029] The scraps of such needle punched mats contain a high proportion of inorganic fibers having long fiber lengths. By using these scraps in the material, the inorganic fiber mat obtained by the production method of the present invention has a high surface pressure.

[0030] Prior to the fiber-opening step, the first inorganic fiber molded body and the second inorganic fiber molded body are preferably cut.

[0031] This is because when the inorganic fiber molded body is cut before the fiber-opening step, the fiber-opening step can be smoothly performed.

[0032] In the method for producing an inorganic fiber mat of the present invention, the slurry preferably further comprises new inorganic fibers, which have the same composition as the fiberized inorganic fibers and are alumina-silica fibers containing 60 to 80 wt% of Al2O3.

[0033] By adding virgin inorganic fibers to the slurry, the inorganic fiber mat produced by the present invention can be adjusted to desired physical properties. Furthermore, if the virgin inorganic fibers and the previously fiberized inorganic fibers have the same composition, their thermal expansion coefficients are the same, preventing displacement of the interfiber bond at high temperatures and maintaining surface pressure. Furthermore, by using alumina-silica fibers containing 60-80% by weight of Al₂O₃, the resulting inorganic fiber mat exhibits improved resilience and heat resistance.

[0034] It is preferable that a firing step of firing the first inorganic fiber molded body and the second inorganic fiber molded body be performed before the fiber-opening step.

[0035] This is because fiber opening can be smoothly performed when the organic binder added to the first inorganic fiber molded body and the second inorganic fiber molded body is removed by firing.

[0036] The firing is preferably performed at 700 to 1000° C. for 1 to 8 hours.

[0037] When firing is performed under the above conditions, the organic binder can be removed more reliably.

[0038] In the method for producing the inorganic fiber mat of the present invention, it is preferred that an inorganic binder and an organic binder be added to the slurry.

[0039] The addition of an inorganic binder further increases the surface pressure of the inorganic fiber mat obtained by the production method of the present invention. Furthermore, the addition of an organic binder further improves the moldability of the inorganic fiber mat obtained by the production method of the present invention.

[0040] The inorganic fiber mat formed in the above-mentioned forming step is preferably dried by heating at a temperature of 150 to 210° C. for 5 minutes to 1 hour.

[0041] The inorganic fiber mat of the present invention comprises inorganic fibers derived from a needle-punched mat, inorganic fibers derived from a papermaking mat, an inorganic binder and an organic binder.

[0042] Since the inorganic fiber mat of the present invention contains inorganic fibers derived from a needle-punched mat and inorganic fibers derived from a papermaking mat, it has both resilience and windability.

[0043] The inorganic fiber mat of the present invention may comprise fired particles of an inorganic binder, and a mixture of an unfired inorganic binder and an organic binder.

[0044] The inorganic fiber mat of the present invention comprises fired particles of the inorganic binder when a needle-punched mat containing an inorganic binder is fired to form an inorganic fiber material. Alternatively, the inorganic fiber mat of the present invention comprises a mixture of unfired inorganic and organic binders when an inorganic binder and an organic binder are added to the inorganic fibers. For example, when silica sol and / or alumina sol are used as the inorganic binder, the inorganic binder in the mixture is unfired amorphous silica and / or unfired amorphous alumina.

[0045] It is preferred that the major diameter of the fired particles of the inorganic binder is 0.01 to 4 μm, and the major diameter of the mixture is 5 to 20 μm.

[0046] The fired particles of the inorganic binder are preferably glass particles of the inorganic binder and / or particles containing crystals of the inorganic binder and glass.

[0047] When the inorganic binder is silica sol, for example, under the firing conditions of the production method of the present invention (700-1000°C, 1-8 hours), no crystals are formed, and the fired particles are composed of silica glass. When the inorganic binder is alumina sol, crystals are formed by firing at 500°C or above, and therefore, under the firing conditions of the production method of the present invention, a portion of the fired particles is composed of alumina glass as γ-alumina crystals.

[0048] It is preferred that the fired particles of the inorganic binder adhere to the surface of the inorganic fibers, and the mixture covers the contact portions between the inorganic fibers and the surfaces of the inorganic fibers, or adheres to the surfaces of the inorganic fibers in a massed form. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 This is a plan view showing a holding sealing material for an exhaust gas purifying device and scraps cut out from an inorganic fiber mat.

[0050] Figure 2A This is a schematic diagram showing one example of manufacturing a folded laminated needle punched mat.

[0051] Figure 2B yes Figure 2A AA cross-section of the folded laminated needle punched mat manufactured in .

[0052] Figure 3 This is an example of an enlarged electron microscope image of the inorganic fiber mat of the present invention. DETAILED DESCRIPTION

[0053] The following describes embodiments of the present invention in detail. However, the present invention is not limited to the following embodiments, and can be applied with appropriate modifications within the scope of the present invention.

[0054] (Method for producing inorganic fiber mat)

[0055] In the method for producing an inorganic fiber mat of the present invention, a first inorganic fiber molded body derived from a needle-punched mat to which an organic binder is added is used as a material of the inorganic fiber mat.

[0056] A needle-punched mat is a mat made by needle-punching a mat containing inorganic fibers. Needling involves inserting and removing needles, or other fiber-interlacing means, from the mat. The needle-punched mat used as the first inorganic fiber molded body has multiple interlacing points formed by needle-punching on at least one of its front and back surfaces.

[0057] To achieve a crisscross structure, the inorganic fibers constituting the needle-punched mat must have a certain average fiber length, preferably 3.0 to 100 mm. When the average fiber length of the inorganic fibers constituting the needle-punched mat falls within this range, the inorganic fiber mat produced by the production method of the present invention exhibits both enhanced resilience and improved windability. Furthermore, the average fiber diameter of the inorganic fibers constituting the needle-punched mat is preferably 2 to 10 μm, more preferably 3 to 7 μm.

[0058] In this specification, the average fiber length and average fiber diameter of the inorganic fibers are determined by observing 100 arbitrary inorganic fibers within a field of view during SEM (scanning electron microscope) observation of the holding sealing material.

[0059] The inorganic fiber constituting the first inorganic fiber molded body is not particularly limited, but is preferably composed of at least one selected from the group consisting of alumina fiber, silica fiber, alumina-silica fiber, mullite fiber, biosoluble fiber, and glass fiber. When the inorganic fiber is at least one of alumina fiber, silica fiber, alumina-silica fiber, and mullite fiber, it has excellent heat resistance, so even when the exhaust gas treatment body is exposed to sufficiently high temperatures, it will not deteriorate, and its function as a mat material can be fully maintained. In addition, when the inorganic fiber is a biosoluble fiber, when the mat material is used to manufacture an exhaust gas purification device, even if the scattered inorganic fiber is inhaled, it will dissolve in the body, so there is no harm to the health of the operator.

[0060] Alumina fibers may contain additives such as calcium oxide, magnesium oxide, and zirconium oxide in addition to aluminum oxide.

[0061] The composition ratio of the alumina-silica fibers is preferably Al 2 O 3 :SiO 2 = 60:40 to 80:20, more preferably Al 2 O 3 :SiO 2 = 70:30 to 74:26, in terms of weight ratio.

[0062] Examples of alumina-silica fibers include fibers containing 60 to 80% by weight of Al 2 O 3 .

[0063] The first inorganic fiber molded body is added with an organic binder. Examples of the organic binder include acrylic latex and rubber latex.

[0064] In the production method of the present invention, a second inorganic fiber molded body derived from a papermaking mat can be used together with the first inorganic fiber molded body. A papermaking mat is a mat produced by subjecting a mat containing inorganic fibers to a papermaking process. The papermaking process herein refers to the process of fiberizing, slurrying, and molding the inorganic fibers.

[0065] The average fiber length of the inorganic fibers constituting the papermaking mat is preferably about 0.01 mm to 5.0 mm. The preferred average fiber diameter (diameter) of the inorganic fibers constituting the papermaking mat is the same as that of the inorganic fibers constituting the needle-punched mat.

[0066] When the second inorganic fiber molded body derived from a papermaking mat is used together with the first inorganic fiber molded body, the produced inorganic fiber mat has both resilience and windability.

[0067] The inorganic fibers of the first inorganic fiber molded body and the inorganic fibers of the second inorganic fiber molded body may have the same composition or different compositions.

[0068] When the second inorganic fiber formed body is used, the ratio of the first inorganic fiber formed body to the second inorganic fiber formed body is not particularly limited. However, in order for the inorganic fiber mat obtained by the production method of the present invention to have both resilience and windability, the ratio of the first inorganic fiber formed body to the total weight of the first and second inorganic fiber formed bodies is preferably 5 to 95% by weight, and more preferably 70 to 90% by weight.

[0069] The second inorganic fiber molded body may be added with an organic binder. The composition of the organic binder may be the same as that of the first inorganic fiber molded body.

[0070] The first and second inorganic fiber molded bodies preferably contain an inorganic binder. This is because the dispersibility of the inorganic binder in the inorganic fiber mat newly produced by the method of the present invention is improved by including the inorganic binder in the first and second inorganic fiber molded bodies.

[0071] The inorganic binder may be contained in either the first inorganic fiber molded body or the second inorganic fiber molded body, or in both the first inorganic fiber molded body and the second inorganic fiber molded body, but is preferably contained in both the first inorganic fiber molded body and the second inorganic fiber molded body.

[0072] Examples of the inorganic binder include any appropriate hard ceramic material such as at least one of alumina, silica, silicon carbide, zirconia, boron nitride, diamond, and pumice, or a combination thereof, preferably alumina sol or silica sol.

[0073] The first inorganic fiber molded body and the second inorganic fiber molded body are preferably scraps. Scraps refer to the remaining portion after taking the required portion from the material. In the case of manufacturing a retaining sealing material for an exhaust gas purification device, etc., it is made by punching out a predetermined shape or cutting out a large sheet of inorganic fiber mat material, so the corners of the sheet are generated as scraps. By using scraps in the inorganic fiber material, it can be effectively utilized without being discarded, so it is preferred.

[0074] Figure 1 This is a top view showing the holding seal material and scraps cut out of an inorganic fiber mat for an exhaust gas purification device. At the manufacturing site of the holding seal material, in order to cut out multiple holding seal materials from a large inorganic fiber mat, as shown in FIG. Figure 1 As shown, the inorganic fiber mat 31 is first divided into a holding sealant forming portion 32 and scraps 33. The outer peripheral end 31a of the inorganic fiber mat shows the outer shape of the inorganic fiber mat 31 before cutting. Next, the holding sealant forming portion 32 is divided into individual holding sealants 34.

[0075] When cutting out the holding sealing material forming portion 32, the pattern is considered in such a way as to increase the number of straight portions for efficient cutting and to minimize the generation of scrap 33. When the holding sealing material 34 has a concave-convex shape, the scrap 33 may have a concave-convex shape.

[0076] In the production method of the present invention, it is more preferable to use such irregular scraps having an uneven shape as the material of the inorganic fibers.

[0077] When the holding sealing material forming portion 32 is cut from the central portion of the inorganic fiber mat 31, the scrap 33 becomes a frame shape. The scrap 33 can also be used directly in the manufacturing method of the present invention in the frame shape, but if it is cut in the longitudinal and transverse directions, for example, scraps 33 of various shapes can be obtained.

[0078] In the production method of the present invention, the needle punched mat is preferably formed by folding thin sheets of an inorganic fiber precursor multiple times at a predetermined width, stacking them, and then firing them. Such a needle punched mat is also called a folded and laminated needle punched mat. Figure 2A This is a schematic diagram showing one example of manufacturing a folded laminated needle punched mat. Figure 2B yes Figure 2A AA cross-section of the folded laminated needle punched mat manufactured in . Figure 2A 、 Figure 2B As shown, the pre-fired needle punch mat 31A is formed by folding and laminating a thin layer 35 of an inorganic fiber precursor multiple times with a predetermined width. Figure 2A As shown, the thin layer 35 of the inorganic fiber precursor is folded while continuously moving in a direction perpendicular to the folding direction. The width and number of folds are not particularly limited; for example, the width can be 1000 mm or greater and the number of folds can be five or more. Before firing, the folded portion 36 of the needle-punched mat 31A has a high proportion of long inorganic fibers.

[0079] By using scraps including such folded-back portions as the material of the inorganic fiber mat, the inorganic fiber mat obtained by the production method of the present invention has a high surface pressure.

[0080] The folded laminated needle punch mat can be produced by the method described in, for example, Japanese Patent Application Laid-Open No. 2008-7933.

[0081] The method for producing an inorganic fiber mat of the present invention comprises the following steps: a fibrillating step of fibrillating the first inorganic fiber molded body to obtain inorganic fibers; and a sheet forming step of sheet forming the inorganic fiber mat using a slurry containing the fibrillated inorganic fibers. When a second inorganic fiber molded body is used, the inorganic fibers can be obtained by fibrillating the second inorganic fiber molded body together with the first inorganic fiber molded body or separately from the first inorganic fiber molded body.

[0082] As described above, when the first and second inorganic fiber molded bodies contain an organic binder, it is preferable to perform a firing step prior to the fiber-opening step. This firing step is performed, for example, at 700-1000°C for 1-8 hours. Firing under these conditions allows for more reliable removal of the organic binder. A preferred firing temperature is 800-950°C.

[0083] The fiber opening in the fiber opening step can be performed by a single process of wet fiber opening alone or a two-stage process of dry fiber opening and wet fiber opening. In the production method of the present invention, it is preferred that only wet fiber opening be performed in the fiber opening step for the sake of process simplicity.

[0084] Wet fiber opening can be performed using a wet fiber opening device such as a beater or a mixer. Wet fiber opening can be performed by adding the first inorganic fiber molded body and the optional second inorganic fiber molded body into water and stirring. When the second inorganic fiber molded body is used, the order of adding the first inorganic fiber molded body and the second inorganic fiber molded body is not particularly limited. It is preferred that the first inorganic fiber molded body is first added into the water and stirred, and then the second inorganic fiber molded body is added and stirred; or the first inorganic fiber molded body and the second inorganic fiber molded body are simultaneously added into the water and stirred. In the production method of the present invention, in order to fully fiberize the first inorganic fiber molded body, it is preferred that the first inorganic fiber molded body is first added and stirred, and then the second inorganic fiber molded body is added and further stirred.

[0085] When dry fiber opening is performed, it is performed before wet fiber opening. Dry fiber opening can be performed using a device such as a screen-type crusher Feather Mill.

[0086] It should be noted that the first inorganic fiber molded body and the second inorganic fiber molded body may be pre-cut to the desired size before the fiber-opening step. This is because pre-cutting the inorganic fiber molded body before the fiber-opening step facilitates the fiber-opening step. When using scraps as the first inorganic fiber molded body and the second inorganic fiber molded body, the fiber-opening step may be performed directly without further cutting.

[0087] Here, the average fiber length of the resulting inorganic fibers can be adjusted by changing the processing conditions for wet fiber opening and dry fiber opening (e.g., stirring speed, stirring time, etc.). An example of the processing conditions for wet fiber opening includes a stirring speed of 500 to 1000 rpm and a stirring time of 200 to 900 seconds. Preferably, the stirring speed is 650 to 850 rpm and a stirring time of 500 to 700 seconds, and more preferably, the stirring speed is 700 to 800 rpm and a stirring time of 500 to 650 seconds.

[0088] Through such a fiber opening step, inorganic fibers having a desired fiber length distribution can be obtained. It should be noted that whether the inorganic fibers have a desired fiber length distribution can be confirmed by examining the bulk density.

[0089] Next, a sheet forming step is performed to form an inorganic fiber mat using a slurry containing the fiberized inorganic fibers.

[0090] The slurry can be prepared, for example, as follows.

[0091] First, prepare a liquid containing water and fiberized inorganic fibers so that the concentration of the inorganic fibers is about 0.5 to 2.0% by weight. When adding water or fiberized inorganic fibers to the liquid during the preparation of the slurry, stir it with a stirrer for about 20 to 120 seconds. Next, add an organic binder in an amount of about 0.5 to 10% by weight relative to the inorganic fibers to the liquid and stir it for about 1 to 5 minutes. Further, add an inorganic binder in an amount of about 0.5 to 3% by weight relative to the inorganic fibers to the liquid and stir it for about 1 to 5 minutes. Further, add a coagulant in an amount of about 0.01 to 1.0% by weight relative to the inorganic fibers to the liquid and stir it for about 2 minutes at most to prepare the slurry.

[0092] The slurry preferably further contains virgin inorganic fibers. By adding virgin inorganic fibers to the slurry, the inorganic fiber mat obtained by the production method of the present invention can be adjusted to desired physical properties. Virgin inorganic fibers herein refer to inorganic fibers that have been newly formed into inorganic fibers and have never been used as a product.

[0093] The average fiber length of the virgin inorganic fibers can be adjusted according to the desired physical properties and is preferably about 0.01 mm to 100 mm. The preferred average fiber diameter of the virgin inorganic fibers is the same as that of the inorganic fibers constituting the needle punched mat and the inorganic fibers constituting the papermaking mat.

[0094] The composition of the new inorganic fiber can be the same as that exemplified for the inorganic fibers constituting the first inorganic fiber molded body and the inorganic fibers constituting the second inorganic fiber molded body. The new inorganic fiber preferably has the same composition as that of the inorganic fibers constituting the first inorganic fiber molded body and the inorganic fibers constituting the second inorganic fiber molded body. This is because, if the inorganic fibers have the same composition, their thermal expansion coefficients are the same, thus preventing the inter-fiber contact from shifting at high temperatures and maintaining surface pressure.

[0095] The new inorganic fibers, the inorganic fibers constituting the first inorganic fiber molded body, and the inorganic fibers constituting the second inorganic fiber molded body are more preferably alumina-silica fibers containing 65 to 80% by weight of Al2O3. This is because the resulting inorganic fiber mat has improved resilience and heat resistance.

[0096] As the inorganic binder added in the preparation of the slurry, the same binder as that contained in the first inorganic fiber molded body and the second inorganic fiber molded body can be cited. In addition, latex can be used as the organic binder, and a conventionally known coagulant can be used as the coagulant.

[0097] In the manufacturing method of the present invention, an inorganic binder is preferably added during the slurry preparation. When the first inorganic fiber molded body and the second inorganic fiber molded body contain an inorganic binder, no new inorganic binder needs to be added during the papermaking molding process. Even when an inorganic binder is added, the amount added can be a small amount compared to the above-mentioned amount. Even when the first inorganic fiber molded body and the second inorganic fiber molded body contain an inorganic binder, the same amount of inorganic binder as described above can be added to the slurry. By adding an inorganic binder during the slurry preparation, the surface pressure of the inorganic fiber mat obtained by the manufacturing method of the present invention can be further increased.

[0098] When the first inorganic fiber molded body and the second inorganic fiber molded body contain an inorganic binder, the inorganic binder mixed in the papermaking molding process can be the same material as the inorganic binder contained in the first inorganic fiber molded body and the second inorganic fiber molded body, or an inorganic binder of a different material can be used.

[0099] In the production method of the present invention, it is preferred to add an organic binder during the slurry preparation. By adding the organic binder, the inorganic fiber mat obtained by the production method of the present invention has excellent moldability.

[0100] In the production method of the present invention, it is more preferable to add an inorganic binder and an organic binder during the preparation of the slurry.

[0101] The sheet-forming of the inorganic fiber mat using the slurry can be performed, for example, as follows.

[0102] The prepared slurry is added to a former of the desired shape to form a raw material sheet, which is then dehydrated. Typically, a filter mesh (mesh size: 30 mesh) is provided at the bottom of the former, through which the moisture in the slurry added to the former is drained. Therefore, by using such a former, the raw material sheet can be formed and dehydrated simultaneously. Alternatively, a suction pump, vacuum pump, or the like can be used to forcibly extract moisture from the lower side of the former via the filter mesh.

[0103] Next, the obtained raw material sheet is taken out from the molding machine and compressed using a press to a thickness of about 0.3 to 0.5 times, and at the same time, heated and dried at a temperature of, for example, 150 to 210°C for 5 minutes to 1 hour, thereby obtaining an inorganic fiber mat.

[0104] The inorganic fiber mat obtained by the production method of the present invention can be cut into a desired shape and used as a holding sealing material for an exhaust gas purification device or the like.

[0105] (Inorganic fiber mat)

[0106] The inorganic fiber mat of the present invention comprises inorganic fibers derived from a needle-punched mat, inorganic fibers derived from a paper-made mat, an inorganic binder, and an organic binder. The inorganic fiber mat of the present invention is a paper-made mat obtained by sheeting and forming a slurry comprising inorganic fibers derived from a needle-punched mat, inorganic fibers derived from a paper-made mat, an inorganic binder, and an organic binder.

[0107] Examples of the needle punched mat, papermaking mat, inorganic fiber, inorganic binder, and organic binder include the same materials as exemplified in the method for producing the inorganic fiber mat of the present invention.

[0108] The method for obtaining inorganic fibers derived from a needle punched mat and inorganic fibers derived from a papermaking mat is not particularly limited, and examples thereof include the same method as in the fiber opening step of the method for producing the inorganic fiber mat of the present invention.

[0109] In the inorganic fiber mat of the present invention, the inorganic binder preferably includes fired particles of an inorganic binder and an unfired inorganic binder (a mixture of a dried inorganic binder and an organic binder). Fired particles of an inorganic binder are particles formed by firing an inorganic binder. When at least one of the needle-punched mat and the paper-made mat contains an inorganic binder and an organic binder, and firing is performed to remove the organic binder from the inorganic fibers, the inorganic binder becomes glass particles or particles containing inorganic binder crystals and glass.

[0110] For example, when the inorganic binder is silica sol, under the firing conditions (eg, 700 to 1000° C., 1 to 8 hours) in the production method of the present invention, almost no crystals are formed but glass particles are formed.

[0111] On the other hand, when the inorganic binder is aluminum sol, crystals are generated by firing at 500°C or above, and under the firing conditions in the manufacturing method of the present invention (e.g., 700-1000°C, 1-8 hours), glass particles partially composed of crystalline γ-alumina are formed.

[0112] The major diameter of the fired particles of the inorganic binder is preferably 0.01 to 4 μm.

[0113] The inorganic fiber mat of the present invention preferably has an inorganic binder added separately from the inorganic binder derived from the needle punched mat and / or the inorganic binder derived from the papermaking mat. When the inorganic binder is added to the inorganic fiber mat material after the firing, the inorganic binder is an amorphous inorganic binder that has not undergone the firing step.

[0114] The inorganic fiber mat of the present invention contains an organic binder. In the inorganic fiber mat of the present invention, it is preferred that the unfired amorphous inorganic binder and the organic binder form a mixture. The mixture preferably has a major diameter of 5 to 20 μm.

[0115] Figure 3 This is an example of an enlarged electron microscope image of the inorganic fiber mat of the present invention. Figure 3 As shown, fired particles 42 of the inorganic binder are attached to the surface of the inorganic fibers 41. A mixture 43 of unfired amorphous inorganic binder and organic binder covers the contact areas between the inorganic fibers 41 and the surface of the inorganic fibers 41, or is attached to the surface of the inorganic fibers 41 in a mass form.

[0116] The inorganic fiber mat of the present invention contains inorganic fibers derived from a needle-punched mat and inorganic fibers derived from a papermaking mat, and therefore has both resilience and windability.

[0117] The inorganic fiber mat of the present invention can be produced, for example, by the method for producing an inorganic fiber mat of the present invention, but the production method is not particularly limited.

[0118] This specification discloses the following matters.

[0119] The present disclosure (1) relates to a method for manufacturing an inorganic fiber mat, characterized in that it uses a first inorganic fiber molded body derived from a needle-punched mat to which an organic binder is added, and has the following steps: a fiber opening step, in which the above-mentioned first inorganic fiber molded body is fiberized to obtain inorganic fibers; and a papermaking and molding step, in which the inorganic fiber mat is papermade and molded using a slurry containing the above-mentioned fiberized inorganic fibers.

[0120] The present disclosure (2) relates to the method for producing the inorganic fiber mat described in the present disclosure (1), wherein a second inorganic fiber molded body derived from a papermaking mat is further used.

[0121] The present disclosure (3) relates to the method for producing the inorganic fiber mat described in the present disclosure (2), wherein the first inorganic fiber molded body and the second inorganic fiber molded body contain an inorganic binder.

[0122] The present disclosure (4) relates to the method for producing the inorganic fiber mat described in the present disclosure (2) or (3), wherein the first inorganic fiber molded body and the second inorganic fiber molded body are scraps.

[0123] The present disclosure (5) relates to the method for producing the inorganic fiber mat according to any one of the present disclosures (1) to (4), wherein the average fiber length of the inorganic fibers constituting the needle-punched mat is 3.0 to 100 mm.

[0124] The present disclosure (6) relates to the method for producing the inorganic fiber mat according to any one of the present disclosures (1) to (5), wherein the fiber opening is performed only by wet fiber opening.

[0125] The present disclosure (7) relates to a method for producing an inorganic fiber mat according to any one of the present disclosures (1) to (6), wherein the needle-punched mat is formed by folding thin sheets of an inorganic fiber precursor a plurality of times in a predetermined width, stacking the sheets, and then firing the sheets.

[0126] The present disclosure (8) relates to the method for producing an inorganic fiber mat according to any one of the present disclosures (2) to (4), wherein the first inorganic fiber molded body and the second inorganic fiber molded body are cut before the fiber-opening step.

[0127] The present disclosure (9) relates to a method for manufacturing an inorganic fiber mat as described in any one of the present disclosures (1) to (8), wherein the slurry further comprises new inorganic fibers, the new inorganic fibers have the same composition as the fiberized inorganic fibers, and are alumina-silica fibers containing 60 to 80 weight percent of Al2O3.

[0128] The present disclosure (10) relates to the method for producing the inorganic fiber mat described in the present disclosure (3), wherein a firing step of firing the first inorganic fiber molded body and the second inorganic fiber molded body is performed before the fiber-opening step.

[0129] The present disclosure (11) relates to the method for producing the inorganic fiber mat described in the present disclosure (10), wherein the firing is performed at 700 to 1000°C for 1 to 8 hours.

[0130] The present disclosure (12) relates to the method for producing the inorganic fiber mat according to any one of the present disclosures (1) to (11), wherein an inorganic binder and an organic binder are added to the slurry.

[0131] The present disclosure (13) relates to a method for producing the inorganic fiber mat described in the present disclosure (12), wherein the inorganic fiber mat formed by the above-mentioned papermaking and molding step is heated and dried at a temperature of 150 to 210° C. for 5 minutes to 1 hour.

[0132] The present disclosure (14) relates to an inorganic fiber mat comprising inorganic fibers derived from a needle-punched mat, inorganic fibers derived from a papermaking mat, an inorganic binder, and an organic binder.

[0133] The present disclosure (15) relates to the inorganic fiber mat described in the present disclosure (14), which comprises fired particles of an inorganic binder and a mixture of an unfired inorganic binder and an organic binder.

[0134] The present disclosure (16) relates to the inorganic fiber mat described in the present disclosure (15), wherein the major diameter of the fired particles of the inorganic binder is 0.01 to 4 μm, and the major diameter of the mixture is 5 to 20 μm.

[0135] The present disclosure (17) relates to the inorganic fiber mat described in the present disclosure (15) or (16), wherein the fired particles of the inorganic binder are glass particles of the inorganic binder and / or particles containing crystals of the inorganic binder and glass.

[0136] The present disclosure (18) relates to the inorganic fiber mat described in any one of the present disclosures (15) to (17), wherein the fired particles of the inorganic binder are attached to the surface of the inorganic fibers, and the mixture covers the contact parts between the inorganic fibers and the surface of the inorganic fibers, or is attached to the surface of the inorganic fibers in the form of blocks.

[0137] Explanation of symbols

[0138] 31 Inorganic fiber mat

[0139] 31A Needle Punched Mat Before Firing

[0140] 31a outer peripheral end

[0141] 32 Maintaining the sealing material forming part

[0142] 33 scraps

[0143] 34 Maintain sealing material

[0144] 35 Thin sheets of inorganic fiber precursors

[0145] 36 Turnback

[0146] 41 Inorganic fiber

[0147] 42 fired particles of inorganic binder

[0148] 43 Amorphous mixture of inorganic binder and organic binder

Claims

1. An inorganic fiber mat produced by a method for producing an inorganic fiber mat having the following characteristics: This production method uses a first inorganic fiber molded body derived from a needle-punched mat to which an organic binder is added, and comprises the following steps: a fiber opening step of opening the first inorganic fiber molded body to obtain inorganic fibers; and In the papermaking and molding step, a papermaking and molding process is performed on an inorganic fiber mat using a slurry containing the fiberized inorganic fibers.

2. The inorganic fiber mat according to claim 1, wherein Furthermore, a second inorganic fiber molded body derived from a papermaking mat is used.

3. The inorganic fiber mat according to claim 2, wherein The first inorganic fiber molded body and the second inorganic fiber molded body contain an inorganic binder.

4. The inorganic fiber mat according to claim 2 or 3, wherein The first inorganic fiber molded body and the second inorganic fiber molded body are scraps.

5. The inorganic fiber mat according to claim 1 or 2, wherein The average fiber length of the inorganic fibers constituting the needle-punched mat is 3.0 mm to 100 mm.

6. The inorganic fiber mat according to claim 1 or 2, wherein: The fiber opening is performed only by wet fiber opening.

7. The inorganic fiber mat according to claim 1 or 2, wherein: The needle punch mat is formed by folding thin sheets of an inorganic fiber precursor multiple times at a predetermined width, stacking them, and then firing them.

8. The inorganic fiber mat according to claim 2 or 3, wherein Prior to the fiber-opening step, the first inorganic fiber molded body and the second inorganic fiber molded body are cut.

9. The inorganic fiber mat according to claim 1 or 2, wherein: The slurry further comprises new inorganic fibers, The new inorganic fiber has the same composition as the fiber-opened inorganic fiber and is an alumina-silica fiber containing 60 wt % to 80 wt % of Al 2 O 3 .

10. The inorganic fiber mat according to claim 3, wherein Before the fiber-opening step, a firing step of firing the first inorganic fiber molded body and the second inorganic fiber molded body is performed.

11. The inorganic fiber mat according to claim 10, wherein The firing is performed at 700° C. to 1000° C. for 1 to 8 hours.

12. The inorganic fiber mat according to claim 1 or 2, wherein: An inorganic binder and an organic binder are added to the slurry.

13. The inorganic fiber mat according to claim 12, wherein The inorganic fiber mat formed in the forming step is heated and dried at a temperature of 150° C. to 210° C. for 5 minutes to 1 hour.

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