Molding and laminate including layer formed of molding

Abstract

To provide a molding including an alumina-based fiber and an inorganic binder, excellent in mechanical strength.SOLUTION: The molding includes an alumina-based fiber and an inorganic binder, with the ratio of the alumina-based fiber of an aspect ratio of 50 or lower among the alumina-based fibers, being 10% or higher. The molding includes an alumina-based fiber and an inorganic binder, with the ratio of the alumina-based fiber of a fiber length of 250 μm or less among the alumina fibers, being 5% or higher.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a molded article containing alumina-based fibers and an inorganic binder, and a laminate including a layer made of the molded article. [Background technology]

[0002] Nonwoven fabrics made of alumina-based fibers have high heat resistance and thermal insulation properties, and are therefore used, for example, as insulation materials for industrial furnaces and as gripping materials for catalytic converters that purify automobile exhaust gases. Furthermore, to increase mechanical strength, inorganic fiber molded bodies manufactured by combining alumina particles, mullite particles, or the like as fillers with alumina-based fibers are preferably used in places where hardness is required. However, there is a strong demand for the development of molded bodies with even higher mechanical strength. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2022-83005 [Patent Document 2] Patent Publication No. 2023-57657 Summary of the Invention [Problem to be solved by the invention]

[0004] The problem to be solved by the present invention is to provide a molded body containing alumina-based fibers and an inorganic binder, which has excellent mechanical strength. [Means for solving the problem]

[0005] Under these circumstances, the present inventors have conducted extensive trial and error to determine the raw materials for the molded body and the alumina-based fiber nonwoven fabric that constitutes it, and have found that mechanical strength can be improved by using a certain amount of alumina-based fibers with a certain aspect ratio and / or fiber length. Therefore, the present invention provides the following: Item 1. A molded body containing alumina-based fibers and an inorganic binder, wherein the proportion of alumina-based fibers having an aspect ratio of 50 or less is 10% or more. Item 2. The molded article according to Item 1, which satisfies at least one selected from the group consisting of the following requirements (i) to (iii): (i) The proportion of alumina-based fibers having an aspect ratio in the range of 10 to 30 is 10 to 50%. (ii) The proportion of alumina-based fibers having an aspect ratio in the range of 10 to 40 is 20 to 65%. (iii) The proportion of alumina-based fibers having an aspect ratio in the range of 10 to 50 is 25 to 75%. Item 3. A molded body containing alumina-based fibers and an inorganic binder, wherein the proportion of alumina-based fibers having a fiber length of 250 μm or less is 5% or more. Item 4. The molded article according to Item 3, which satisfies at least one selected from the group consisting of the following requirements (iv) to (vii): (iv) The proportion of alumina-based fibers having a fiber length in the range of 50 to 100 μm is 5 to 30%. (v) The proportion of alumina-based fibers having a fiber length in the range of 50 to 150 μm is 10 to 40%. (vi) The proportion of alumina-based fibers having a fiber length in the range of 50 to 200 μm is 15 to 60%. (vii) The proportion of alumina-based fibers having a fiber length in the range of 50 to 250 μm is 20 to 70%. Item 5. A molded body containing alumina-based fibers and an inorganic binder, wherein the alumina-based fibers include first alumina-based fibers pulverized by a first pulverization method and second alumina-based fibers pulverized by a second pulverization method that can pulverize the fibers more finely than the first pulverization method; The first alumina-based fiber has an FV value of 50 to 500 ml / 5 g, A molded body, wherein the second alumina-based fiber has an FV value of 5 to 20 ml / 5 g. Item 6. The molded article according to any one of Items 1 to 5, for use as a heat insulating material. Item 7. The molded article according to any one of Items 1 to 6, which has a three-point bending strength of 0.6 to 15.1 MPa. Item 8. A laminate comprising a layer made of the molded article according to any one of items 1 to 7 and a layer made of an inorganic fiber assembly. Item 9. The molded body has a compressive strength of 170 kg / m 3 ~1000kg / m 3 and having a bulk density of The inorganic fiber aggregate has a density of 90 kg / m 3 ~200kg / m 3 Item 9. The laminate according to item 8, having a bulk density of [Effects of the Invention]

[0006] According to the present invention, it is possible to provide a molded body containing alumina-based fibers and an inorganic binder, which has excellent mechanical strength. [Brief explanation of the drawings]

[0007] [Figure 1] The results of three-point bending tests conducted in the examples and comparative examples are shown. The vertical axis represents three-point bending strength. The horizontal axis represents bulk density. Black circles (labeled "pressed product") represent data for the molded body of the examples. White circles (labeled "alumina particles") represent data for the comparative examples. DETAILED DESCRIPTION OF THE INVENTION

[0008] Molded body The present invention provides a molded body containing alumina-based fibers and an inorganic binder. The molded body containing alumina-based fibers and an inorganic binder according to the present invention may also be referred to as an "alumina-based fiber-containing molded body."

[0009] <Alumina-based fiber> Alumina-based fibers are usually fibers made of alumina and silica. In the alumina-based fibers according to this embodiment, the alumina / silica composition ratio (mass ratio) of the alumina-based fibers is preferably in the range called a mullite composition or high alumina composition of 60 / 40 to 98 / 2, more preferably 70 / 30 to 95 / 5, and particularly preferably 70 / 30 to 76 / 24.

[0010] The average fiber diameter of the alumina-based fibers is preferably 3.0 μm to 10.0 μm, particularly preferably 4.0 μm to 8.0 μm, and may be 5.0 μm to 7.0 μm. When the average fiber diameter is within the above range, the proportion of stiff and easily broken fibers is reduced. Furthermore, the fiber length of the alumina-based fibers before pulverization, which will be described later, is not particularly limited, but is 0.1 mm to 1000 mm, preferably 1 mm to 800 mm. When the fiber length is within the above range, the entanglement of the fibers increases, and the strength of the alumina-based fiber aggregate increases.

[0011] The fiber diameter can be measured using a scanning electron microscope or the like, and the average fiber diameter can be obtained by, for example, measuring the fiber diameters of 300 randomly selected fibers and calculating the average value. The fiber length can be measured using a ruler, calipers, or the like from an image magnified by an optical microscope or, if necessary, a scanning electron microscope, and the fiber length can be obtained by, for example, individually measuring the fiber lengths of 300 randomly selected fibers.

[0012] In the present invention, it is preferable that the proportion of alumina-based fibers having a fiber length of 250 μm or less is 5% or more. In the present invention, "the proportion of alumina-based fibers having a fiber length of 250 μm or less" means the proportion of the number of alumina-based fibers having a fiber length of 250 μm or less among the total number of alumina-based fibers. More specifically, this proportion can be determined by measuring the fiber lengths of 300 fibers randomly selected from the alumina-based fibers and calculating the proportion of the number of fibers having a fiber length of 250 μm or less. Similarly to the above, in the present invention, "the proportion of alumina-based fibers having a fiber length of XX μm" means the proportion of the number of alumina-based fibers having a fiber length of YY μm among the total number of alumina-based fibers.

[0013] In one embodiment of the present invention, the proportion of alumina-based fibers having a fiber length in the range of 50 to 100 μm is preferably 4% or more, more preferably 5% or more, and even more preferably 6% or more. In one embodiment of the present invention, the proportion of alumina-based fibers having a fiber length in the range of 50 to 100 μm is preferably 35% or less, more preferably 30% or less, and even more preferably 25% or less. In one embodiment of the present invention, the proportion of alumina-based fibers having a fiber length in the range of 50 to 100 μm is preferably 4 to 35%, more preferably 5 to 30%, and even more preferably 6 to 25%.

[0014] In one embodiment of the present invention, the proportion of alumina-based fibers having a fiber length in the range of 50 to 150 μm is preferably 8% or more, more preferably 10% or more, and even more preferably 13% or more. In one embodiment of the present invention, the proportion of alumina-based fibers having a fiber length in the range of 50 to 150 μm is preferably 45% or less, more preferably 40% or less, and even more preferably 35% or less. In one embodiment of the present invention, the proportion of alumina-based fibers having a fiber length in the range of 50 to 150 μm is preferably 8 to 45%, more preferably 10 to 40%, and even more preferably 13 to 35%.

[0015] In one embodiment of the present invention, the proportion of alumina-based fibers having a fiber length in the range of 50 to 200 μm is preferably 10% or more, more preferably 15% or more, and even more preferably 20% or more. In one embodiment of the present invention, the proportion of alumina-based fibers having a fiber length in the range of 50 to 200 μm is preferably 65% ​​or less, more preferably 60% or less, and even more preferably 55% or less. In one embodiment of the present invention, the proportion of alumina-based fibers having a fiber length in the range of 50 to 200 μm is preferably 10 to 65%, more preferably 15 to 60%, and even more preferably 20 to 55%.

[0016] In one embodiment of the present invention, the proportion of alumina-based fibers having a fiber length in the range of 50 to 250 μm is preferably 15% or more, more preferably 20% or more, and even more preferably 25% or more. In one embodiment of the present invention, the proportion of alumina-based fibers having a fiber length in the range of 50 to 250 μm is preferably 75% or less, more preferably 70% or less, and even more preferably 65% ​​or less. In one embodiment of the present invention, the proportion of alumina-based fibers having a fiber length in the range of 50 to 250 μm is preferably 15 to 75%, more preferably 20 to 70%, and even more preferably 25 to 65%.

[0017] In the present invention, it is preferable that the proportion of alumina-based fibers having an aspect ratio of 50 or less is 10% or more. In the present invention, "the proportion of alumina-based fibers having an aspect ratio of 50 or less" means the proportion of the number of alumina-based fibers having an aspect ratio of 50 or less among the total number of alumina-based fibers. More specifically, this proportion can be determined by measuring the aspect ratios of 300 randomly selected alumina-based fibers and calculating the proportion of the number of fibers having an aspect ratio of 50 or less. In calculating the aspect ratio, the fiber diameters of 300 randomly selected alumina-based fibers were measured using the method described above, and the average fiber diameter of the 300 alumina-based fibers was calculated. Separately, the fiber lengths of 300 randomly selected alumina-based fibers were measured using the method described above. The aspect ratio can be calculated using the following formula. Aspect ratio = (individual fiber length / average fiber diameter) As described above, in the present invention, "the proportion of alumina-based fibers having an aspect ratio of YY" means the proportion of the number of alumina-based fibers having an aspect ratio of YY to the total number of alumina-based fibers.

[0018] In one embodiment of the present invention, the proportion of alumina-based fibers having an aspect ratio within the range of 10 to 30 is preferably 7% or more, more preferably 10% or more, and even more preferably 15% or more. In one embodiment of the present invention, the proportion of alumina-based fibers having an aspect ratio within the range of 10 to 30 is preferably 55% or less, more preferably 50% or less, and even more preferably 45% or less. In one embodiment of the present invention, the proportion of alumina-based fibers having an aspect ratio within the range of 10 to 30 is preferably 7 to 55%, more preferably 10 to 50%, and even more preferably 15 to 45%.

[0019] In one embodiment of the present invention, the proportion of alumina-based fibers having an aspect ratio within the range of 10 to 40 is preferably 15% or more, more preferably 20% or more, and even more preferably 25% or more. In one embodiment of the present invention, the proportion of alumina-based fibers having an aspect ratio within the range of 10 to 40 is preferably 70% or less, more preferably 65% ​​or less, and even more preferably 60% or less. In one embodiment of the present invention, the proportion of alumina-based fibers having an aspect ratio within the range of 10 to 40 is preferably 15 to 70%, more preferably 20 to 65%, and even more preferably 25 to 60%.

[0020] In one embodiment of the present invention, the proportion of alumina-based fibers having an aspect ratio within the range of 10 to 50 is preferably 20% or more, more preferably 25% or more, and even more preferably 30% or more. In one embodiment of the present invention, the proportion of alumina-based fibers having an aspect ratio within the range of 10 to 50 is preferably 80% or less, more preferably 75% or less, and even more preferably 70% or less. In one embodiment of the present invention, the proportion of alumina-based fibers having an aspect ratio within the range of 10 to 50 is preferably 20 to 80%, more preferably 25 to 75%, and even more preferably 30 to 70%.

[0021] The content of alumina-based fibers in the alumina-based fiber-containing molded article of the present invention is not limited, but is preferably in the range of, for example, 70 mass % or more, 80 mass % or more, 85 mass % or more, 88 mass % or more, etc. Furthermore, the upper limit of the content of alumina-based fibers in the alumina-based fiber-containing molded article of the present invention is also not limited, but is preferably in the range of, for example, 98 mass % or less, 95 mass % or less, 93 mass % or less, 91 mass % or less, etc.

[0022] <Inorganic binder> The inorganic binder functions as a binding agent for binding the alumina-based fibers. Examples of inorganic binders include, but are not limited to, colloidal silica and alumina sol. Examples of colloidal silica include alkaline colloidal silica, acidic colloidal silica, cationic colloidal silica, and anionic colloidal silica. Commercially available alumina sols, which function as inorganic binders, can be used, including stabilizers, with different particle shapes and crystal forms. The inorganic binder can also function as a fixing agent for the organic binder described below. These inorganic binders can be used alone or in combination. Furthermore, the inorganic binder can also be used as a binding agent in combination with the organic binder described below. The blending ratio of the inorganic binder is not limited, but is preferably, for example, 0.1 to 10 parts by mass, 0.5 to 8.0 parts by mass, or 0.8 to 5.0 parts by mass, calculated as solids, of the inorganic binder per 100 parts by mass of the alumina-based fibers.

[0023] <Organic binder> The alumina-based fiber-containing molded article of the present invention may further contain an organic binder in addition to the alumina-based fibers and inorganic binder. The organic binder, like the inorganic binder, functions as a binder to bind the alumina-based fibers. It can also function as a fixing agent for the inorganic binder. Examples of organic binders include starch, acrylic resins, and latex emulsions. Examples of starch include, but are not limited to, cationic starch, anionic starch, and amphoteric starch. Examples of acrylic resins include, but are not limited to, cationic, anionic, and amphoteric polyacrylamide-based strength agents. The molded article may also contain a polyamide polyamine-based wet strength agent. Examples of latex emulsions include, but are not limited to, acrylate-based latex, acrylonitrile-butadiene-based latex, and styrene-butadiene-based latex. These organic binders can be used alone or in combination. When an organic binder is used, the blending ratio is not limited, but for example, the range of 0.1 to 15 parts by mass, 0.5 to 13 parts by mass, 0.8 to 10 parts by mass, etc. of the organic binder converted into solid content per 100 parts by mass of alumina-based fibers is preferred.

[0024] <Inorganic fixing agent> The alumina-based fiber-containing molded article of the present invention may further contain an inorganic fixing agent. The inorganic fixing agent is not particularly limited, but examples include aluminum sulfate, alumina sol, and aqueous ammonia, with aluminum sulfate being preferred. When an inorganic fixing agent is used, its blending ratio is not limited, but may be set to, for example, a range of 0.1 parts by mass or more, 1.0 parts by mass or more, or 5.0 parts by mass or more of the inorganic binder per 100 parts by mass of the alumina-based fibers. When an inorganic fixing agent is used, its blending ratio is also not limited, but may be set to, for example, a range of 20 parts by mass or less, 15 parts by mass or less, 10 parts by mass or less, or 5.0 parts by mass or less of the inorganic binder per 100 parts by mass of the alumina-based fibers, calculated as solids.

[0025] The alumina fiber-containing molded article of the present invention preferably has a three-point bending strength of 0.6 to 15.1 MPa. The three-point bending strength can be measured, for example, by the method described in the Examples below. In addition, the alumina fiber-containing molded article of the present invention preferably has a three-point bending strength of 170 kg / m 3 ~1000kg / m 3 Preferably, the bulk density is 0.01 to 0.15.

[0026] The alumina fiber-containing molded article of the present invention can be used for heat insulating materials, gripping materials, etc., but is preferably used as a heat insulating material.

[0027] The method for producing the alumina-based fiber molded body of the present invention is not limited, but may include, for example, a method comprising a step of preparing an alumina-based fiber aggregate and a step of producing a molded body.

[0028] (Step of Preparing Alumina-Based Fiber Aggregate)

[0029] In this embodiment, an alumina fiber aggregate is prepared by the following steps (1) to (4). (1) A spinning solution preparation step for obtaining a spinning solution containing an alumina source, a silica source, a spinning aid, and water. (2) A spinning step in which the spinning solution obtained in (1) above is extruded into the atmosphere through a fine hole and dried to obtain accumulated alumina-based fibers. (3) A needling process in which the alumina-based fibers obtained in (2) above are subjected to a needling process using a needle punch to obtain a needle blanket. (4) A firing step in which the needle blanket obtained in (3) above is fired to obtain an alumina-based fiber aggregate. As the alumina fiber aggregate, commercially available products can also be used.

[0030] <Needle Blanket> Needling treatment leaves needle marks on the needle blanket. When needling treatment is performed, the number of needle marks per unit area on the surface of the accumulated alumina fiber (needle mark density) is usually 1 / cm. 2More than 3 / cm, preferably 3 / cm 2 More than 4 / cm is particularly preferable. 2 More than 100 pieces / cm 2 Less than 70 / cm, preferably 2 Less than 50 particles / cm is particularly preferable. 2 By setting the needle mark density within the above range, the peel strength of the alumina fiber aggregate can be increased, which is preferable.

[0031] <Alumina-based fiber aggregate> The basis weight (mass per unit area) of the alumina fiber aggregate is not particularly limited, but is preferably 300 g / m 2 More preferably, 400 g / m 2 More preferably, 500 g / m 2 The basis weight of the alumina fiber aggregate is not particularly limited, but is preferably 5000 g / m 2 or less, more preferably 4500 g / m 2 or less, more preferably 4000 g / m 2 Particularly preferably 3500 g / m or less 2 The following is the result.

[0032] The bulk density of the alumina fiber aggregate is 50 kg / m 3 ~300kg / m 3 It is preferable that the 3 ~200kg / m 3 It is more preferable that the bulk density is in this range, since it allows stable pulverization in the molding production step described below.

[0033] (Molded body manufacturing process) In a typical embodiment, the process for producing a green body includes a fiber-opening process, a slurry-preparing process, a dehydration and molding process, a pressing process, a drying and firing process, and an impregnation process. 1.Defibration process The defibration step is a step in which the alumina-based fiber aggregate is subjected to the following pulverization method.

[0034] Dry methods include, for example, grinding methods using cutters such as rotary cutters, grinding mills such as pin mills and hammer mills, presses such as roller presses, and picker rolls. Methods that can be used either dry or wet include grinding methods using ball mills. Wet methods include grinding methods using pulpers and high-speed disintegrators. These methods may be used alone or in combination. Each method will be explained below.

[0035] A rotary cutter is a method of cutting and pulverizing the raw material, alumina fiber, making it easy to control the fiber length for cutting to a specified size. A pin mill is a method of crushing and pulverizing raw materials using pin discs, resulting in finer pulverization. A hammer mill is a method of crushing raw materials using impact and friction with a swing hammer or tip hammer, making it easy to coarsely crush. A press (flat plate) is a method of crushing raw materials by applying pressure, making it easy to control the degree of crushing. A roller press is a method of crushing raw materials by passing them between rollers and applying pressure, making it easy to adjust the degree of crushing by adjusting the clearance between the rollers. A picker roll is a method of defibrating and pulverizing raw materials, making it easy to maintain long fiber length. A ball mill is a method of crushing raw materials by rotating hard balls, such as ceramic balls, in a cylindrical container. A pulper is a method of crushing water and alumina fiber in a tub (container) using a powerful rotor and a vigorous vortex. A "high-speed disintegrator" is a machine that further crushes raw materials that have not been crushed sufficiently by processing with a pulper alone. It is a crushing method that uses hydrodynamic shock waves from a ring-shaped blade with fine slits that rotates at high speed.

[0036] In this embodiment, a first alumina-based fiber is used, which is obtained by pulverizing an alumina-based fiber aggregate with a hammer mill (first pulverization method), and a second alumina-based fiber is used, which is obtained by pulverizing an alumina-based fiber aggregate with a roller mill (second pulverization method). The average fiber length of the first alumina-based fiber is preferably 200 μm to 2000 μm, and more preferably 300 μm to 1000 μm. When the average fiber length is within this range, molding can be performed with a uniform density. The average fiber length of the second alumina-based fiber is preferably 30 μm to less than 300 μm, and more preferably 50 μm to 250 μm. The average fiber length may be 50 μm to 200 μm, 50 μm to 150 μm, or 50 μm to 1000 μm. When the fiber length is within this range, the bulk density of the molded product can be increased while improving the three-point bending strength.

[0037] In the present invention, it is preferable to use relatively short fibers as part of the alumina-based fibers, and the FV value of the alumina-based fibers can be used as an indicator of the length of the alumina-based fibers. In this embodiment, the FV value of the first alumina-based fibers is, for example, 50 to 500 ml / 5g. The FV value of the second alumina-based fibers is, for example, 5 to 20 ml / 5g, preferably 10 to 20 ml / 5g.

[0038] FV values ​​can be measured by the following methods: The defibrated alumina-based fiber was weighed to a mass of 5.0±0.5 g and placed in a 500 mL beaker along with 300 mL of ion-exchanged water at 23°C. After ultrasonic dispersion at a frequency of 38 kHz for 1 minute, the mixture was transferred to a 500 mL measuring cylinder. Ion-exchanged water was added until the measuring cylinder reached 500 mL, and the opening of the measuring cylinder was covered with a hand or other object, and the mixture was stirred by turning it upside down, taking care to prevent water leakage. This process was repeated 10 times. After stopping the stirring, the mixture was left to stand on a flat surface for 15 minutes, and the sedimentation volume of the alumina-based fiber was measured visually, which was used as the FV value.

[0039] Of the first alumina-based fibers, the proportion of fibers having an individual aspect ratio within the range of 50 to 250 is preferably 60% or more, and more preferably 50% or more within the range of 80 to 200. Setting the aspect ratio within this range allows molding with a uniform density. Of the second alumina-based fibers, the proportion of fibers having an individual aspect ratio within the range of 5 to 50 is preferably 75% or more, more preferably 60% or more within the range of 10 to 40, even more preferably 70% or more within the range of 10 to 50, and preferably 40% or more within the range of 10 to 30. Setting the aspect ratio within this range allows for increased density of the molded product while improving three-point bending strength. In calculating the aspect ratio, the fiber diameters of 300 randomly selected first alumina-based fibers and 300 randomly selected second alumina-based fibers were measured using the method described above, and the average fiber diameters of the 300 randomly selected first alumina-based fibers and 300 randomly selected second alumina-based fibers were calculated. Separately, the fiber lengths of the 300 randomly selected first alumina-based fibers and 300 randomly selected second alumina-based fibers were measured individually using the method described above. The aspect ratio can be calculated using the following formula. Aspect ratio = (individual fiber length / average fiber diameter) The method for measuring the average fiber diameter and individual fiber length is as described above in the section on <Alumina-based fibers>.

[0040] 2. Slurry preparation process The slurry preparation process includes a mixing process and a concentration adjustment process. In a preferred embodiment, the mixing step involves dispersing and mixing raw materials (hereinafter simply referred to as "raw materials") consisting of 70 to 99.5% by mass of alumina-based fibers, 0.5 to 15% by mass of an inorganic binder, and optionally 0 to 15% by mass of an organic binder and polymer flocculant, as well as, but not limited to, microfibrous cellulose and inorganic fixing agents, in water. Specifically, a predetermined amount of water is stored in a pulper (mixer), and the raw materials are added and stirred and mixed. Examples of the water include, but are not limited to, distilled water, tap water, groundwater, and industrial water. The concentration of the raw materials is not particularly limited, but is preferably 1 to 5% by mass, and more preferably 2 to 4% by mass, of the raw material solids, where the total of the raw material solids and water is 100% by mass.

[0041] The concentration adjustment process is a process in which water is further added to the mixture obtained by mixing the raw materials to adjust the concentration and obtain a slurry of a predetermined concentration. Specifically, the raw materials are agitated with a pulper and then pumped into a chest tank, and water is also added, thereby obtaining a slurry of a predetermined concentration. The obtained slurry is then fed to a slurry storage tank. In this case, additional water may be added to further lower the concentration and the slurry is then fed to the slurry storage tank. There are no particular limitations on the water, and the above-mentioned water can be used. The concentration of the slurry is not particularly limited, but when the entire slurry is taken as 100% by mass, the raw material solid content is 0.1 to 5% by mass, more preferably 0.1 to 4% by mass, and particularly preferably 0.1 to 3% by mass. If the slurry concentration is less than 0.1% by mass, the amount of water removed in the dehydration molding process becomes too large, resulting in poor work efficiency. If the concentration exceeds 5% by mass, it becomes difficult to uniformly disperse the solid content in the slurry.

[0042] 3.Dehydration molding process In a typical embodiment, in the dehydration molding step, the slurry obtained in the slurry preparation step is first dehydrated and molded using a papermaking machine or a mold. For dehydration molding using a papermaking machine, for example, the slurry is passed through a mesh in a slurry storage tank, and most of the water passes through the mesh, resulting in a paper product deposited on the mesh. For dehydration molding using a mold, for example, the slurry is poured into a molding die equipped with a mesh in a slurry storage tank, and water is sucked from the mesh surface using a vacuum pump or the like to form a dehydrated product in the molding die. The paper product or dehydrated product obtained as described above is usually subjected to a drying step. The drying temperature is not particularly limited, but is preferably 50 to 150°C, more preferably 70 to 130°C, and particularly preferably 80 to 120°C.

[0043] 4. Pressing process Before drying in the dehydration molding step, a pressing step can be performed in which the resulting paper molded body or dehydrated body is pressed. By pressing, the bulk density of the alumina-based fiber molded body can be increased. The pressing method and apparatus are not particularly limited, and examples include a flat plate press and a roller press. Alternatively, if the bulk density can be increased, manual pressing using a flat plate or hand roller can be used.

[0044] 5. Drying and baking process After drying in the dehydration molding step or after drying after the pressing step, a heat treatment step can be performed at 600°C or higher. Heat treatment can evaporate and remove organic components contained in the alumina-based fiber molded body. It can also improve the dimensional stability of the alumina-based fiber molded body at high temperatures. The heat treatment method and device are not particularly limited, and can be performed by firing in an electric furnace or gas furnace, for example. The firing temperature is also not particularly limited, and can be, for example, 800°C, 1200°C, or 1600°C.

[0045] 6.Impregnation process The impregnation step is a step of impregnating an alumina-based fiber compact with an inorganic binder. In the impregnation step, the strength of the alumina-based fiber molding can be increased by impregnating the alumina-based fiber molding with colloidal silica and / or alumina sol. The impregnation method and apparatus are not particularly limited, and can be carried out by, for example, a method of infiltrating the alumina-based fiber molding from the surface thereof by dipping or showering, or a method of attaching the alumina-based fiber molding to the surface thereof by brush coating or roller coating.

[0046] The impregnation process can be carried out in the following stages: (a) During the dehydration molding step, during dehydration before drying and / or after drying (b) during dehydration before the pressing step and / or after drying after the pressing step (c) Before and / or after the heat treatment step In (a) to (c), if the impregnation step is the final step, redrying is further carried out. The temperature for redrying is not particularly limited, but is preferably 50 to 150°C, more preferably 70 to 130°C, and particularly preferably 80 to 120°C.

[0047] The shape of the alumina-based fiber-containing molded body of the present invention is not limited, and can be, for example, a substantially flat plate-like shape. The molded body of the present invention exhibits high mechanical strength (three-point bending strength) compared to molded bodies of the same bulk density. Generally, attempts to increase mechanical strength tend to increase bulk density as well. However, as bulk density increases, work efficiency such as installing the molded body decreases. As described above, the molded body of the present invention is useful because it combines high mechanical strength with a relatively low bulk density. The alumina-based fiber-containing molded body of the present invention can also be used to produce a laminate, which will be described later.

[0048] Laminate In one embodiment, the present invention provides a laminate including a layer of the molded article and a layer of an inorganic fiber aggregate. In this specification, the laminate of the present invention including a layer of the molded article and a layer of an inorganic fiber aggregate may be simply referred to as the "laminate of the present invention."

[0049] <Layer composed of the molded article of the present invention> The raw materials and manufacturing method of the alumina fiber-containing molded body constituting the layer made of the molded body of the present invention are as follows: Molded body In the embodiment of the laminate, the layer made of the molded body has a strength of 170 kg / m 3 ~1000kg / m 3 In the embodiment of the laminate, the layer made of the molded article preferably has a three-point bending strength of 0.6 to 15.1 MPa.

[0050] <Layer made of inorganic fiber aggregate> The inorganic fiber aggregate may have a substantially flat plate shape such as a blanket or a mat.

[0051] The inorganic fibers constituting the inorganic fiber aggregate are not particularly limited, and examples thereof include single or composite fibers of silica, alumina / silica, and zirconia, spinel, titania, and calcia containing these. Among these, fibers made of alumina and silica, particularly polycrystalline fibers, are particularly preferred in terms of heat resistance, fiber strength (toughness), and safety. In particular, alumina / silica fibers with an alumina ratio of 70 to 80 mass% and a silica ratio of 30 to 20 mass% are preferred.

[0052] As the inorganic fiber aggregate, a mat (needle blanket) in which a needling process is applied to an aggregate of inorganic fibers that does not substantially contain fibers with a diameter of 3 μm or less is preferred, for reasons of ensuring safety while improving heat resistance and durability.

[0053] The bulk density of the inorganic fiber aggregate is not particularly limited, but from the viewpoint of heat resistance and strength, it is preferably 85 kg / m 3 ~250kg / m 3 90kg / m 3 ~230kg / m 3 is preferred, and 90 kg / m 3 ~2200kg / m 3 More preferably, 90 kg / m 3 ~200kg / m3 is more preferable. The laminate of the present invention may have a two-layer structure consisting of a layer of the molded product of the present invention and a layer of an inorganic fiber aggregate, or may have a two-layer structure further laminated with a layer of the molded product of the present invention and a layer of an inorganic fiber aggregate. In the present invention, a two-layer structure consisting of a layer of the molded product of the present invention and a layer of an inorganic fiber aggregate is preferred.

[0054] In this embodiment, the bulk density of the layer made of the inorganic fiber aggregate is preferably lower than the bulk density of the layer made of the molded article of the present invention.

[0055] <Joining means> When producing an alumina-based fiber-containing compact, an inorganic fiber aggregate is used as a substrate, and the alumina-based fiber-containing compact is paper-formed onto the substrate, so that the starch in the slurry can bond the interface between the compact and the aggregate. Alternatively, an adhesive such as starch can be applied to one surface of the alumina-based fiber aggregate or the alumina-based fiber compact by roller coating or spray coating, and then dried under load to bond the interface between the aggregate and the laminate.

[0056] The laminate of the present invention includes a layer made of the above-described molded article of the present invention. The molded article of the present invention exhibits high mechanical strength (three-point bending strength) compared to molded articles with comparable bulk densities. Therefore, a laminate including a layer made of the molded article is also useful because it has high mechanical strength and good workability. In a typical embodiment, the alumina-based fiber-containing molded article has low thermal conductivity at high temperatures and slightly high thermal conductivity at low temperatures. On the other hand, in a typical embodiment, the inorganic fiber aggregate has high thermal conductivity at high temperatures and low thermal conductivity at low temperatures. Therefore, when installing the laminate of the present invention, by arranging a layer made of the alumina-based fiber-containing molded article on the high-temperature side of the installation target, it is possible to suppress temperature drop compared to a molded article alone that does not have an inorganic fiber aggregate layer. On the other hand, inorganic fiber aggregates that are (substantially) binder-free are more flexible than alumina-based fiber-containing molded articles. Therefore, when installing the laminate of the present invention, by arranging a layer made of the aggregate on the high-temperature side of the installation target, the aggregate can follow the thermal expansion and / or contraction of the installation target, making it useful and less likely to produce gaps. In this way, the layer located on the high-temperature side can be selected depending on the conditions of the installation target. [Example]

[0057] Examples of alumina-based fiber molded articles of the present invention will be described below. However, the present invention is not limited to these examples. Examples 1 to 7 and Comparative Examples 1 to 4 shown below were produced by the methods described below.

[0058] [Table 1]

[0059] As the first main material, an alumina-based fiber aggregate (product name: MAFTEC (registered trademark) Blanket: product number MLS (manufactured by MAFTEC Co., Ltd.) with an average fiber diameter of 6.0 μm and an Al2O3:SiO2 = 72:28 (mass ratio) is crushed using a hammer mill to obtain a first alumina-based fiber with an FV value of 268 (ml / 5g) and an average fiber length of 618 μm.

[0060] An alumina-based fiber aggregate (product name: MAFTEC (registered trademark) Blanket: product number MLS2 (manufactured by MAFTEC Corporation) with an average fiber diameter of 5.7 μm and an Al2O3:SiO2 = 72:28 (mass ratio) was pulverized using a hammer mill to obtain a first alumina-based fiber with an FV value of 400 (ml / 5g) and an average fiber length of 654 μm, which was used as the second main material, and a second alumina-based fiber with an FV value of 78 (ml / 5g) and an average fiber length of 499 μm, which was used as the third main material.

[0061] An alumina-based fiber aggregate (trade name: MAFTEC (registered trademark) Blanket, product number MLS2 (manufactured by MAFTEC Corporation) having an average fiber diameter of 5.7 μm and an Al2O3:SiO2 = 72:28 (mass ratio)) was pulverized using a roller press to obtain a second alumina-based fiber with an FV value of 10 (ml / 5 g) and an average fiber length of 154 μm, which was used as the first filler.

[0062] Alumina particles (inorganic particles) [SA34] manufactured by Nippon Light Metal Co., Ltd. with an average particle size of 3.5 μm (Al 2 O 3 : 99.6%) and an FV value of 5 (ml / 5g) are used as the second filler.

[0063] As colloidal silica (inorganic binder), 30 mass % amorphous silica (trade name: Snowtex 30 (manufactured by Nissan Chemical Industries, Ltd.)) was used.

[0064] As the starch (organic binder), Ace Din HP-150 (trade name, manufactured by Yamato Chemical Industries Co., Ltd.) was used.

[0065] [Example 1] Using the raw materials listed in Table 1, an alumina fiber-containing compact of Example 1 was prepared by carrying out the following slurry preparation step and dehydration molding step: Slurry preparation process (1) 800 L of water was added to the pulper. (2) 15.0 kg of first alumina-based fibers were added while stirring. (3) 7.5 g of second alumina-based fiber was added while stirring. (4) While stirring, 1.125 kg (solids equivalent) of colloidal silica was added. (5) 1.125 kg (solids equivalent) of starch was added while stirring. (6) The mixture was pumped from the pulper to a chest tank, and 400 L of water was added and stirred. (7) The slurry obtained in (6) was fed to a slurry storage tank and stirred.

[0066] Dehydration molding process (1) A mold equipped with a stainless steel mesh was placed in the slurry obtained in (7) above. (2) Water was sucked from the mesh surface using a vacuum pump, and a flat dehydrated body was formed on the mesh surface of the mold. (3) The dehydrated body was transferred to a dryer and dried at 100°C for 12 hours to obtain an alumina-based fiber molding. (4) The obtained alumina-based fiber molding was cut to obtain a test piece (thickness 25 mm x width 50 mm x length 150 mm) for measuring three-point bending strength. From the scanning electron microscope image of the obtained molded body, 300 fibers were selected and their fiber diameters were measured. The average fiber diameter of the 300 fibers was calculated from the measured fiber diameters. Similarly, the fiber lengths were measured using an optical microscope. The aspect ratios of the 300 fibers were calculated from the measured fiber lengths and the calculated average fiber diameters.

[0067] [Example 2] An alumina fiber-containing molded body was obtained in the same manner as in Example 1, except that 15.0 kg of second alumina fiber as the first filler, 1.5 kg of colloidal silica, and 1.5 kg of starch were used.

[0068] [Example 3] An alumina-based fiber-containing molded body was obtained in the same manner as in Example 1, except that 15.0 kg of first alumina-based fiber as the third main material instead of the first main material, 15.0 kg of second alumina-based fiber as the first filler, 1.5 kg of colloidal silica, and 1.5 kg of starch were used.

[0069] [Example 4] Compared to the alumina-based fiber molding of Example 3, an alumina-based fiber-containing molding was obtained in the same manner as Example 3, except that 7.5 kg of first alumina-based fiber, 1.125 kg of colloidal silica, and 1.125 kg of starch were used as the third main material.

[0070] [Example 5] An alumina fiber-containing compact was obtained in the same manner as in Example 1, except that 15.0 kg of the first alumina fiber was used as the second main material instead of the first main material.

[0071] [Example 6] An alumina fiber-containing molded article was obtained in the same manner as in Example 5, except that 15.0 kg of second alumina fiber as the first filler, 1.5 kg of collidal silica, and 1.5 kg of starch were used.

[0072] [Example 7] Compared to the alumina-based fiber molding of Example 6, an alumina-based fiber-containing molding was obtained in the same manner as Example 6, except that 7.5 kg of first alumina-based fiber, 1.125 kg of colloidal silica, and 1.125 kg of starch were used as the second main material.

[0073] [Comparative Example 1] An alumina fiber-containing compact was obtained in the same manner as in Example 1, except that 7.5 kg of alumina particles were used as the second filler instead of the first filler.

[0074] Comparative Example 2 An alumina fiber-containing molded article was obtained in the same manner as in Comparative Example 1, except that 15.0 kg of alumina particles, 1.5 kg of colloidal silica, and 1.5 kg of starch were used as the second filler.

[0075] Comparative Example 3 An alumina fiber-containing compact was obtained in the same manner as in Comparative Example 1, except that 15.0 kg of the first alumina fiber was used as the second main material instead of the first main material.

[0076] Comparative Example 4 An alumina-based fiber-containing molded body was obtained in the same manner as in Comparative Example 3, except that 15.0 kg of alumina particles, 1.5 kg of colloidal silica, and 1.5 kg of starch were used as the second filler. The fiber length distribution and aspect ratio distribution of the alumina-based fibers contained in the molded bodies of the Examples and Comparative Examples are shown below:

[0077] [Table 2]

[0078] [Table 3]

[0079] 3-point bending test Test Method The molded articles prepared in the examples and comparative examples were subjected to a three-point bending test in accordance with the bending strength test of JIS R2575. Specifically, the test was carried out as follows: A flat plate-shaped specimen measuring 25 mm thick x 50 mm wide x 150 mm long is measured to the nearest 0.01 mm in thickness, width and length using a vernier caliper, and its weight is measured to the nearest 0.01 g using a weighing scale.

[0080] The three-point bending strength is calculated using the following formula based on the maximum load measured in a three-point bending test in which a load is applied at a head speed of 10 mm / min using a three-point bending tester.

[0081] Three-point bending strength (MPa) = {3 x maximum load (N) x distance between lower supports (mm)} / {2 x width of specimen (mm) x thickness of specimen (mm)} 2}

[0082] Testing machine: Minebea TG-5kN

[0083] The results are shown in Figure 1. As shown in Figure 1, it can be seen that the molded body of the example has a higher three-point bending strength than the molded body of the comparative example having the same bulk density.

Claims

1. A molded body comprising alumina-based fibers and an inorganic binder, wherein the proportion of alumina-based fibers having an aspect ratio of 50 or less is 10% or more.

2. The molded article according to claim 1, which satisfies at least one selected from the group consisting of the following requirements (i) to (iii): (i) The proportion of alumina-based fibers having an aspect ratio in the range of 10 to 30 is 10 to 50%. (ii) The proportion of alumina-based fibers having an aspect ratio in the range of 10 to 40 is 20 to 65%. (iii) The proportion of alumina-based fibers having an aspect ratio in the range of 10 to 50 is 25 to 75%.

3. A molded body comprising alumina-based fibers and an inorganic binder, wherein the proportion of alumina-based fibers having a fiber length of 250 μm or less is 5% or more.

4. The molded article according to claim 3, which satisfies at least one selected from the group consisting of the following requirements (iv) to (vii): (iv) The proportion of alumina-based fibers having a fiber length in the range of 50 to 100 μm is 5 to 30%. (v) The proportion of alumina-based fibers having a fiber length in the range of 50 to 150 μm is 10 to 40%. (vi) The proportion of alumina-based fibers having a fiber length in the range of 50 to 200 μm is 15 to 60%. (vii) The proportion of alumina-based fibers having a fiber length in the range of 50 to 250 μm is 20 to 70%.

5. A molded body containing alumina-based fibers and an inorganic binder, wherein the alumina-based fibers include first alumina-based fibers pulverized by a first pulverization method and second alumina-based fibers pulverized by a second pulverization method that can pulverize the fibers more finely than the first pulverization method, the FV value of the first alumina-based fiber is 50 to 500 ml / 5 g; A molded body, wherein the second alumina-based fiber has an FV value of 5 to 20 ml / 5 g.

6. The molded article according to any one of claims 1 to 5, for use as a heat insulating material.

7. The molded article according to any one of claims 1 to 5, having a three-point bending strength of 0.6 to 15.1 MPa.

8. A laminate comprising a layer made of the molded article according to any one of claims 1 to 5 and a layer made of an inorganic fiber aggregate.

9. The molded body has a strength of 170 kg / m ３ ~1000 kg / m ３ and having a bulk density of The inorganic fiber aggregate has a viscosity of 90 kg / m ３ ~200 kg / m ３ 9. The laminate of claim 8 having a bulk density of

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