Particle having space inside so as to be given thermal insulating properties and lightweight properties

Abstract

To provide a particle having a space inside, the particle including aluminum oxynitride and aluminum oxide.SOLUTION: The present invention provides a particle having a space inside. The particle includes aluminum oxynitride and aluminum oxide. The particle includes the aluminum oxynitride in an amount of 0.1 wt.% to 90 wt.% based on a total of the aluminum oxynitride and the aluminum oxide.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to particles having internal voids. More specifically, the particles contain aluminum oxynitride and aluminum oxide. Even more specifically, the particles have internal voids and are therefore lightweight and heat-insulating. [Background technology]

[0002] Hollow particles are generally known to have low thermal conductivity, and there are examples where aluminum oxide is used as the material for these hollow particles (for example, Pacific Random's hollow sphere fused alumina BL). Furthermore, 400,000 tons of aluminum dross is generated annually in Japan during aluminum refining. When this aluminum dross comes into contact with water, ammonia gas and hydrogen gas are generated, making it difficult to effectively utilize or store. For this reason, most aluminum dross is often disposed of as industrial waste. As an example of the utilization of aluminum dross, a method for manufacturing aluminum oxynitride refractories using aluminum dross is known (Japanese Patent Laid-Open Publication No. 261273 / 1986). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 61-261273 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the thermal conductivity of hollow particles containing aluminum oxide is not particularly low, so the first challenge was the need for particles with even lower thermal conductivity. Furthermore, Patent Document 1 only produces an aluminum oxynitride ingot, but does not have an internal space of the ingot. Therefore, as a second problem, when aiming to make a refractory material lightweight or to impart heat insulating properties, lightweight particles containing aluminum oxynitride with an internal space are needed. Therefore, an object of the present disclosure is to provide particles containing aluminum oxynitride and aluminum oxide and having internal voids. [Means for solving the problem]

[0005] The present disclosure provides particles having an internal space, the particles containing aluminum oxynitride and aluminum oxide, and the aluminum oxynitride content being 0.1 wt % to 90 wt % based on the total weight of the aluminum oxynitride and aluminum oxide.

[0006] The present disclosure also provides a thermal insulation material or a refractory material comprising the above particles as an aggregate.

[0007] The present disclosure also provides particles having internal spaces, which are obtained by air-milling a melt of aluminum dross or a melt mixture of aluminum dross and aluminum oxide.

[0008] The present disclosure also provides a method for producing particles having internal voids, the method comprising the steps of melting raw materials containing aluminum nitride and aluminum oxide, and air-pulverizing the melt.

[0009] The present disclosure also provides the use of aluminum dross in the production of particles comprising aluminum oxynitride and aluminum oxide and having internal voids. [Effects of the Invention]

[0010] The particles of the present disclosure contain aluminum oxynitride and aluminum oxide, and have internal spaces, thereby providing a heat insulating effect. [Brief explanation of the drawings]

[0011] [Figure 1]1 is an optical microscope photograph of particles of Example 1. [Figure 2] 1 is a SEM photograph of particles of Example 1. [Figure 3] 1 shows X-ray diffraction patterns of the particles of Example 1 (unsintered), the particles of Example 1-1 (sintered), corundum (main component: aluminum oxide), and aluminum oxynitride. [Figure 4] 1 is a graph showing the thermal conductivity of particles of Examples 1, 5, and 7 and Comparative Examples 1 and 2. [Figure 5] 1 is a graph showing the apparent porosity of particles of Examples 1 to 7 and Comparative Example 1. [Figure 6] 1 is a graph showing the thermal expansion coefficients of particles of Examples 1 to 5 and Comparative Examples 1 and 2. DETAILED DESCRIPTION OF THE INVENTION

[0012] <Particles of the present disclosure> The particles having internal spaces according to the present disclosure (also referred to simply as "particles according to the present disclosure" in this specification) contain aluminum oxynitride and aluminum oxide, and are characterized by containing 0.1 wt % to 90 wt % of aluminum oxynitride relative to the total weight of the aluminum oxynitride and aluminum oxide.

[0013] The particles of the present disclosure contain aluminum oxynitride and aluminum oxide and have a structure with internal voids, resulting in low overall thermal conductivity and high thermal insulation. Furthermore, because of the structure with internal voids, the density of the particles themselves is low, making them suitable for use as a raw material for lightweight materials. For example, they can be used as aggregate for lightweight insulation or refractories. The particles of the present disclosure contain at least one space inside the particle. The space may be a combination of open pores and closed pores, or may be closed pores only. In the present disclosure, open pores refer to the internal space of the particles of the present disclosure being connected to the outside through openings on the particle surface, and closed pores refer to the internal space of the particles of the present disclosure being a closed space that is not connected to the outside. It is preferable that the particles of the present disclosure have at least one closed pore as the internal space. The surface of the particles of the present disclosure may be smooth or may have irregularities, so long as the particle as a whole has a substantially spherical shape.

[0014] Aluminum oxynitride is a compound represented by the chemical formula AlON, and can be a solid solution of aluminum oxide (Al2O3) and aluminum nitride (AlN). In the present disclosure, aluminum oxynitride may be a solid solution obtained by mixing and melting aluminum oxide powder and aluminum nitride powder, or a solid solution obtained by melting a mixture containing aluminum oxide and aluminum nitride. In one embodiment, aluminum oxynitride is obtained as a solid solution by melting aluminum dross containing aluminum oxide and aluminum nitride. This embodiment is environmentally and economically advantageous because it allows for the effective use of aluminum dross, which is often disposed of as industrial waste. Aluminum dross will be described later.

[0015] Aluminum oxide is a compound represented by the chemical formula Al2O3, and may exist in the crystal systems of alpha alumina, beta alumina, and gamma alumina. In the present disclosure, the aluminum oxide may contain alpha alumina (corundum type) in an amount of 50% by weight or more, for example 60% by weight or more, more specifically 70% by weight or more, more specifically 80% by weight or more, and even more specifically 90% by weight or more.

[0016] The thermal conductivity of the particles of the present disclosure can be, for example, 0.24 W / m·K or less, more specifically 0.23 W / m·K or less, more specifically 0.23 W / m·K to 0.10 W / m·K, more specifically 0.22 W / m·K to 0.12 W / m·K, and more specifically 0.21 W / m·K to 0.14 W / m·K. The lower the thermal conductivity, the less heat is transferred inside the substance, so particles with low thermal conductivity have improved heat insulation. The thermal conductivity of the particles of the present disclosure may be measured by a known method, which can be appropriately selected by a person skilled in the art. Examples include the hot disc method (ISO / CD 2207-2), the probe method (JIS R 2616), the heat flow meter method (ASTM E1530), and the laser flash method (JIS R 1611). In one embodiment, the thermal conductivity is determined by the hot disc method. To briefly explain the hot disk method, the test material is filled into a stainless steel cylinder, leveled with a spatula, the end surface is smoothed, a measurement sensor is installed, a stainless steel cylinder is placed on top of it so that it matches the lower stainless steel cylinder, the test material is filled into the upper stainless steel cylinder, leveled with a spatula, the end surface is smoothed, and then the thermal conductivity is measured. For details, see ISO / CD 2207-2. The particles of the present disclosure contain aluminum oxynitride and aluminum oxide, and exhibit low thermal conductivity (compared to, for example, hollow particles of aluminum oxide) due to the presence of internal spaces. The bulk density of the particles of the present disclosure is, for example, 0.50 to 1.50 g / cm 3 More specifically, 0.60 to 1.40 g / cm 3 More specifically, 0.70 to 1.30 g / cm 3 More specifically, 0.80 to 1.20 g / cm 3 More specifically, 0.85 to 1.15 g / cm 3 If the particles of the present disclosure have a bulk density within the above range, they can be suitably used as a lightweight insulating material or an aggregate for refractories.

[0017] The ratio of aluminum oxynitride to the total of aluminum oxynitride and aluminum oxide in the particles of the present disclosure may be determined by prioritizing the heat insulating effect expected of the particles. When the heat insulating effect is prioritized, the ratio of aluminum oxynitride to the total of aluminum oxynitride and aluminum oxide is 0.1 to 90% by weight, preferably 0.5 to 90% by weight, more preferably 1.0 to 90% by weight, even more preferably 3.0 to 90% by weight, even more preferably 5.0 to 90% by weight, and even more preferably 10 to 90% by weight.

[0018] The ratio of aluminum oxynitride to the total of aluminum oxynitride and aluminum oxide in the particles of the present disclosure may be determined by prioritizing the fire-resistant effect expected of the particles. When the fire-resistant effect is prioritized, the ratio of aluminum oxynitride to the total of aluminum oxynitride and aluminum oxide is preferably 0.1 to 63% by weight, more preferably 0.1 to 45% by weight, particularly preferably 1.0 to 45% by weight, and most preferably 3.0 to 45% by weight.

[0019] In the particles of the present disclosure, the content of aluminum oxynitride and aluminum oxide can be, for example, 50% by weight or more, preferably 60% by weight or more, more preferably 70% by weight or more, more preferably 80% by weight or more, more preferably 90% by weight or more, and more preferably 95% by weight or more.

[0020] The particles of the present disclosure may be, for example, substantially spherical, which allows the particles of the present disclosure to be packed more densely as aggregate in, for example, a thermal insulating material or a fire-resistant material, thereby achieving higher thermal insulating properties or fire resistance. The particle size of the particles of the present disclosure is not particularly limited, but in the field of insulating aggregates and heat-resistant aggregates, it may be, for example, 0.05 to 10 mm, more specifically 0.1 to 7 mm, more specifically 0.2 to 5 mm, more specifically 0.5 to 5 mm, and even more specifically 0.5 to 2 mm. Furthermore, the particle size of the particles of the present disclosure has a range, and any particle size distribution may be possible as long as it is within that range. The particle size of the particles of the present disclosure can be adjusted by air crushing, which will be described later.

[0021] The refractoriness of the particles of the present disclosure can be a temperature at which the particles do not melt, for example, 1500°C or higher, preferably 1600°C or higher. Other methods for measuring fire resistance include, for example, Segel cone fire resistance. Segel cone refractoriness is expressed in SK~. For example, if it is 1500°C, it is SK18. If it is 1600°C, it is SK26. Japanese Patent Application Laid-Open No. 2013-18657 describes that the fire resistance can be estimated from the melting temperature (melting point).

[0022] The thermal expansion coefficient of the particles of the present disclosure may be measured by a known method, for example, by a TMA method or a laser interferometry. In one embodiment, the thermal expansion coefficient of the particles of the present disclosure is measured by a TMA method. To put it simply, the TMA method involves filling a container with a sample, covering it with an insulating tube, and heating it at 1500°C for 30 minutes, then measuring the amount of displacement due to thermal expansion to determine the thermal expansion coefficient. For details, see the examples below. When fire resistance is important, the particles of the present disclosure have a thermal expansion coefficient measured at 1500°C of, for example, -2.0% to 2.0%, preferably within the range of -1.5% to 1.5%, and a residual linear change rate preferably within the range of -2.0% to 2.0%.

[0023] The apparent porosity of the particles of the present disclosure is, for example, 7% to 60%, preferably 20% to 60%, and more preferably 30% to 60%. The apparent porosity can be measured by a known method, for example, JIS R 2205. In one embodiment, the apparent porosity of the particles of the present disclosure is measured by the boiling method of JIS R 2205. According to the boiling method of JIS R 2205, apparent porosity can be calculated simply by (1) drying a sample in an incubator and recording the mass when it reaches a constant weight as the dry mass W1 (g), (2) boiling the dried sample for at least 3 hours and cooling it to room temperature to record the saturated sample, (3) weighing the saturated sample while suspending it in water with a wire and subtracting the mass of the wire to record the saturated mass W2 (g), and (4) removing water droplets from the sample with a wet cloth and then weighing it to record the saturated mass W3 (g). These values ​​can be used to calculate the apparent porosity according to the following formula: (W3 - W1) / (W3 - W2) x 100%. For details, see JIS R 2205. In the particles of the present disclosure, the higher the apparent porosity, the larger the volume of the internal space of the particles of the present disclosure, and the more gas can be contained in the particles, which is preferable as it results in a lower thermal conductivity.

[0024] The bulk density of the particles of the present disclosure is, for example, 1.6 g / cm 3 or less, more specifically 1.4 g / cm 3 or less, more specifically 1.3 g / cm 3 or less, more specifically 1.2 g / cm 3 The lower limit is not particularly limited, but is, for example, 0.5 g / cm 3 That's it, more specifically 0.7 g / cm 3 That's all. The bulk density of the particles of the present disclosure can be measured by a known method, such as JIS R 1628. In one embodiment, the bulk density of the particles of the present disclosure is a tapped bulk density measured according to JIS R 1628. According to JIS R 1628, tapped bulk density is calculated simply by (1) filling a measuring container of known mass and volume with an appropriately sampled sample up to the top, repeating the filling and topping process until the change in mass of the sample due to tapping impact of the container is 0.3% or less, weighing the sample including the measuring container, subtracting the mass of the measuring container from the measured mass, and dividing the resulting mass by the volume of the measuring container. For details, see JIS R 1628. The particles of the present disclosure preferably have a lower bulk density, which means that the volume of the space inside the particle is larger and more gas can be contained inside the particle, resulting in a lower thermal conductivity. However, if the bulk density is too low, the particle becomes brittle.

[0025] The particles of the present disclosure may contain other substances as long as the effects of the invention are not impaired. Examples of other substances include Si (silicon), Mg (magnesium), Fe (iron), Na (sodium), Ca (calcium), K (potassium), Ti (titanium), Cr (chromium), Zr (zirconium), and compounds of these elements. Examples of compounds include oxides and nitrides.

[0026] From another viewpoint, the particles of the present disclosure are characterized in that they are obtained by air-pulverizing a melt of aluminum dross or a melt mixture of aluminum dross and aluminum oxide. The molten mixture of aluminum dross and aluminum oxide may be, for example, a molten mixture of more than 0 wt% but less than 100 wt% aluminum dross and more than 0 wt% but less than 100 wt% aluminum oxide; more specifically, a molten mixture of 1 wt% to less than 100 wt% aluminum dross and more than 0 wt% but less than 99 wt% aluminum oxide; more specifically, a molten mixture of 1 wt% to less than 100 wt% aluminum dross and more than 0 wt% but less than 99 wt% aluminum oxide; more specifically, a molten mixture of 10 wt% to less than 100 wt% aluminum dross and more than 0 wt% but less than 90 wt% aluminum oxide; more specifically, a molten mixture of 30 wt% to less than 100 wt% aluminum dross and more than 0 wt% but less than 70 wt% aluminum oxide; and more specifically, a molten mixture of 50 wt% to less than 100 wt% aluminum dross and more than 0 wt% but less than 50 wt% aluminum oxide. The particles of this embodiment can be obtained, for example, by the following production method.

[0027] <Insulation and Refractories> The heat insulating material or refractory material of the present disclosure is characterized by containing the above-described particles of the present disclosure as aggregate. Details of the constituent components and their mass ratios of the particles of the present disclosure are as described above.

[0028] According to JIS R 2001, refractories refer to, for example, "monolithic refractories with a maximum operating temperature of 1500°C or higher, monolithic refractories with a maximum operating temperature of 800°C or higher, fireproof mortar, and fireproof insulating bricks." The content of the particles of the present disclosure in the insulating material or refractory material can be, for example, 30% by weight or more, more specifically 40% by weight or more, more specifically 50% by weight or more, and even more specifically 60% by weight or more, based on 100% by weight of the total weight of the insulating material or refractory material. In addition to aggregate, the insulation or refractory material of the present disclosure may also include other materials such as binders and / or fillers and / or thickeners and / or hardeners known in the art, depending on the type of insulation or refractory material. Examples of other substances include silica stone, fused silica, calcined bauxite, aluminium shale, andalusite, electrofused mullite, chamotte, hard clay, pyrophyllite, zircon sand, haderite, electrofused zirconia, electrofused magnesia, chromium ore, electrofused magnesia chromium, synthetic dolomite, natural dolomite, electrofused spinel, magnesia, graphite, silicon carbide, silicon nitride, hydrated lime, calcined alumina, molasses, clay, water glass, iron oxide, calcium chloride, chromium oxide, resin, silicon, water, pulp waste liquor, CMC, phenolic resin, dextrin, amorphous silica (e.g., microsilica, silica flour, fumed silica, white carbon, etc.), aluminum phosphate, sodium phosphate, hydraulic alumina, alumina cement, boric acid, metal fibers, etc. The heat insulating material or refractory material of the present disclosure, including the insulating castable, can be produced by replacing aggregate components such as hollow alumina in known production methods with the particles of the present disclosure. For example, the method for producing a heat insulating castable material described in JP-A-2013-18657 can be used.

[0029] The apparent porosity of the refractory or thermal insulating material of the present disclosure can be measured by a known method, for example, JIS R 2205. In one embodiment, the apparent porosity of the refractory or thermal insulating material of the present disclosure is measured according to JIS R 2205.

[0030] The coefficient of linear thermal expansion of the refractory or insulating material of the present disclosure can be measured by a known method, for example, JIS R 2554. In one embodiment, it is measured according to JIS R 2554. According to JIS R 2554, the linear thermal expansion coefficient is calculated by measuring the length l0 of the prepared test piece before firing, measuring the length l1 of the test piece after firing, and then using the following formula: (l1-l0) / l0×100[%]. For details, please refer to JIS R 2554.

[0031] The dry bending strength and dry compressive strength of the refractory or thermal insulating material of the present disclosure can be measured by a known method, for example, JIS R 2553. In one embodiment, they are measured according to JIS R 2553. According to JIS R 2553, dry bending strength and dry compressive strength are calculated briefly as follows: The prepared sample is packed into a mold, cured for 24 hours at a temperature of 20±3°C and humidity of 80% or more, and then demolded to obtain a test specimen. Immediately after curing, the test specimen is dried at a temperature of 110°C±5°C for 24 hours or more, and then fired under certain conditions. The dimensions (width b and thickness d) of the fired test specimen are measured. A load is applied at a uniform rate to the center of the side of the test specimen when it is molded, and the maximum load W is calculated and used the following formula: (3×W×l) / (2×b×d 2 ) (l: center distance (100 mm) of the support roll of the bending strength tester used). Immediately after measuring the dry bending strength, a half of the test piece is cut and pressed at a uniform speed against the center of the test piece using a pressure plate, with both sides of the test piece used when it was molded as the pressing surface, to determine the maximum load W, and calculate it according to the following formula: W / (40 x b). For details, see JIS R 2553.

[0032] The dry bulk density of the refractory or insulating material of the present disclosure can be measured by a known method, for example, JIS R 2655. In one embodiment, it is measured according to JIS R 2655. According to JIS R 2655, the dry bulk density of a refractory or heat insulating material is calculated by drying and cooling the prepared test piece, immediately measuring the mass W to the nearest 0.5g, measuring the dimensions of the test piece (length L, width M, and thickness T) as the length of the line connecting the approximate midpoints of each side, and then calculating according to the following formula: W / (L×M×T). For details, please refer to JIS R 2655.

[0033] <Method for producing particles with internal spaces> In one respect, the present disclosure relates to a method for producing particles having internal voids. The manufacturing method of the present disclosure is characterized by including a step of melting raw materials containing aluminum nitride and aluminum oxide, and a step of air-crushing the molten material. Details of the particle shape, constituent components, and mass ratios thereof of the present disclosure are as described above.

[0034] The raw material containing aluminum nitride and aluminum oxide may contain aluminum nitride and aluminum oxide as a whole, and may be a raw material containing both aluminum nitride and aluminum oxide, a raw material containing aluminum nitride and aluminum oxide separately, or a combination of a raw material containing both aluminum nitride and aluminum oxide and a raw material containing at least one of aluminum nitride and aluminum oxide. The raw material containing both aluminum nitride and aluminum oxide may be, for example, a raw material containing aluminum dross, more specifically, aluminum dross. The raw material containing aluminum dross may contain other substances as long as the effects of the present invention are not impaired. In one embodiment, the raw material containing aluminum nitride and aluminum oxide is a raw material containing aluminum dross. In another embodiment, the raw material containing aluminum nitride and aluminum oxide is aluminum dross. In another embodiment, the raw material containing aluminum nitride and aluminum oxide consists of aluminum dross and aluminum oxide.

[0035] Aluminum nitride is a compound represented by AlN, and can produce aluminum oxynitride by melting it together with aluminum oxide.

[0036] Aluminum oxide is a compound represented by Al2O3 and can be produced by oxidizing aluminum.

[0037] In the present disclosure, when the raw material containing aluminum dross consists of aluminum dross and aluminum oxide, it contains 1 wt% or more and less than 100 wt% aluminum dross and more than 0 wt% and 99 wt% or less aluminum oxide, preferably 5 wt% or more and less than 95 wt% aluminum dross and more than 5 wt% and 95 wt% or less aluminum oxide, particularly preferably 10 wt% or more and less than 90 wt% aluminum dross and more than 10 wt% and 90 wt% or less aluminum oxide, and most preferably 30 wt% or more and less than 70 wt% aluminum dross and more than 30 wt% and 70 wt% or less aluminum oxide.

[0038] Aluminum dross is a by-product generated during the melting process in the manufacturing process of aluminum materials, and is a substance whose main components are metallic aluminum, aluminum oxide, aluminum nitride, oxides of alloying elements, halides added during dross treatment, etc. The aluminum dross used in the present invention is a mixture containing aluminum nitride. The types of aluminum dross include raw dross, primary dross, secondary dross, etc. In the present invention, any of them can be used as long as they contain aluminum nitride. The composition of aluminum dross generated during the manufacturing process of aluminum material varies depending on the manufacturing method of the aluminum material. Therefore, to homogenize the composition of the particles of the present disclosure, it is possible to use aluminum dross generated by the same manufacturing method, or to use an aluminum dross mixture whose composition is adjusted by mixing aluminum dross generated by different manufacturing methods. The total proportion of aluminum and / or aluminum compounds (Al2O3 and AlN) in the aluminum dross used in the present invention is 60% by weight or more, preferably 70% by weight or more, and particularly preferably 80% by weight or more. In addition to Al (aluminum), elements that can be contained in aluminum dross include Si (silicon), Mg (magnesium), Fe (iron), Na (sodium), Ca (calcium), K (potassium), Ti (titanium), Cr (chromium), Zr (zirconium), etc. Furthermore, these elements may exist as simple elements or as compounds.

[0039] The ratio of aluminum to aluminum compounds (Al2O3 and AlN) contained in the aluminum dross is, for example, 5 to 80 weight % of metal Al, 15 to 55 weight % of Al2O3, and 3 to 25 weight % of AlN. This element ratio is an example and is not limited to this. The proportion of aluminum dross used in the raw material can be 0% by weight to 100% by weight, for example, 1% by weight to 100% by weight, preferably 10% by weight to 100% by weight, more preferably 30% by weight to 100% by weight, and more preferably 50% by weight to 100% by weight. When the proportion of aluminum dross used as raw material is increased, aluminum dross, which is often disposed of as industrial waste, can be effectively utilized, which is environmentally and economically beneficial.

[0040] When the amount of aluminum dross used as a raw material in producing the particles of the present disclosure is 70% by weight or less, the particles of the present disclosure can be used as an aggregate for refractories. If the particles have undergone the firing process described below, the particles of the present disclosure can be used as aggregate for refractories even if the amount of aluminum dross used as a raw material is 70% by weight or more.

[0041] In the present disclosure, the aluminum oxide used may be aluminum oxide obtained by oxidizing aluminum, aluminum oxide contained in aluminum dross, or aluminum oxide obtained by oxidizing aluminum oxynitride. When aluminum dross is used to obtain aluminum oxide, aluminum dross, which is often disposed of as industrial waste, can be effectively utilized, which is environmentally and economically advantageous.

[0042] The aluminum oxide may be used as a raw material containing aluminum oxide in the form of a composition as long as it contains a required amount of aluminum oxide. The aluminum oxide content is, for example, 50% by weight or more, more specifically 60% by weight or more, and even more specifically 70% by weight or more. For example, an aluminum oxide (alumina)-based aggregate such as Espar (registered trademark, Yamakawa Sangyo Co., Ltd.) can be used as the raw material containing aluminum oxide. When aluminum oxide is used as a raw material, the usage ratio can be more than 0% by weight and less than 100% by weight, for example, more than 0% by weight and not more than 99% by weight, more specifically more than 0% by weight and not more than 90% by weight, more specifically more than 0% by weight and not more than 70% by weight, and even more specifically more than 0% by weight and not more than 50% by weight. The raw materials used in the method of the present disclosure may contain other substances, such as SiO2, Fe2O3, CaO, MgO, K2O, TiO2, etc., as long as the effects of the invention are not impaired.

[0043] The melting method used in the method of the present disclosure is not particularly limited, and examples thereof include flame melting, electric melting, melting by laser irradiation, melting by plasma, etc. In one embodiment, the electric melting method is used. The reaction furnace used in the melting step is not particularly limited, and examples thereof include an arc furnace, a crucible furnace, an induction furnace (such as a high-frequency furnace or a low-frequency furnace), a resistance furnace, a reverberatory furnace, a rotary furnace, a vacuum melting furnace, a cupola furnace, etc. In one embodiment, the reaction furnace is an arc furnace. The melting temperature in the melting step may be raised to a temperature at which the aluminum oxide and aluminum nitride in the raw materials melt, for example, 1800°C or higher, more specifically 1900°C or higher, and preferably 2000°C or higher. The melting time in the melting step may be any time long enough to sufficiently melt the aluminum oxide and aluminum nitride in the raw materials, and is, for example, 5 minutes or more, preferably 10 minutes or more, and more preferably 20 minutes or more. In the melting step of the present disclosure, when there are two or more kinds of raw materials, the raw materials may be mixed in advance and then charged, or they may be charged separately. When the raw materials are charged separately, the raw materials charged first may or may not be melted. The gas atmosphere in the melting step of the present disclosure is not particularly limited, but examples thereof include a nitrogen atmosphere, an oxygen atmosphere, an oxygen-containing gas atmosphere (e.g., air), etc. In the present invention, melting in an oxygen-containing gas atmosphere is preferred, and melting in air is particularly preferred.

[0044] In the present disclosure, air pulverization refers to dropping a molten material and blowing an air current onto the falling molten material to simultaneously pulverize the molten material and rapidly cool it to form fine particles. The air current blowing angle is not particularly limited, but may be, for example, in the range of obliquely upward (specifically, 45° upward) to obliquely downward (specifically, 45° downward), more specifically in the range of 45° upward to 15° downward, and even more specifically in the range of 30° upward to horizontal (90° relative to the axis of drop). The method of blowing is not particularly limited, as long as the airflow is blown at a constant flow rate, and compressed air is preferably used. The airflow blowing rate is, for example, 20 m / s to 180 m / s, more specifically, 40 m / s to 160 m / s, more specifically, 60 m / s to 140 m / s, and even more specifically, 80 m / s to 120 m / s. The temperature of the airflow is not particularly limited, but is, for example, 0°C to 50°C, and more specifically, 10°C to 40°C. After the melt is air-crushed, the particles may or may not be further rapidly cooled. A method for rapidly cooling the particles is, for example, immersion in water.

[0045] The manufacturing methods of the present disclosure can be used to make the particles of the present disclosure.

[0046] The manufacturing method of the present disclosure may further include a calcination step of calcining the particles obtained by air-milling. The calcination method is not particularly limited, but may be air calcination, etc. In the present invention, air calcination is preferred. The firing temperature is 1200°C or higher, preferably 1300°C or higher, more preferably 1400°C or higher, and particularly preferably 1500°C or higher. The firing time of the present invention may be determined depending on the firing temperature, and may be, for example, 4 hours or more, preferably 8 hours or more, if the firing temperature is 1200°C or higher, for example, 1 hour or more, preferably 2 hours or more, if the firing temperature is 1300°C or higher, for example, 15 minutes or more, preferably 30 minutes or more, if the firing temperature is 1400°C or higher.

[0047] <Use of aluminum dross in particle production> In yet another aspect, the present disclosure relates to the use of aluminum dross in producing particles comprising aluminum oxynitride and aluminum oxide and having internal voids. Details of the constituents of the particles containing aluminum oxynitride and aluminum oxide and having internal voids are as described above in <Particles of the Present Disclosure>. The aluminum dross is as described above in <Particles of the Present Disclosure>. The aluminum dross of the present disclosure may be used in any specific manner or form as long as it is used in the production of particles containing aluminum oxynitride and aluminum oxide and having internal voids, but is preferably used in the production of the particles of the present disclosure described above, and more preferably used in the production method of the present disclosure described above.

[0048] Specific embodiments of the present invention are described below. [Section 1] A particle having an internal space, the particles include aluminum oxynitride and aluminum oxide; Particles containing 0.1% by weight to 90% by weight of aluminum oxynitride based on the total weight of the aluminum oxynitride and aluminum oxide. [Section 2] Item 1. The particles according to item 1, wherein the particles have a thermal conductivity of 0.23 W / m·K or less. [Section 3] Item 3. The particles according to Item 1 or 2, containing 0.5% by weight to 90% by weight of aluminum oxynitride based on the total weight of the aluminum oxynitride and aluminum oxide. [Section 4] Item 4. The particles according to any one of Items 1 to 3, wherein the particles have a substantially spherical shape. [Section 5] Item 5. The particles according to any one of items 1 to 4, having a refractoriness of 1500° C. or higher. [Section 6] Item 6. The particles according to any one of items 1 to 5, wherein the particles have an apparent porosity of 7% to 60%. [Section 7] Item 7. A heat insulating material or refractory material containing the particles according to any one of items 1 to 6 as aggregate. [Section 8] Particles with internal spaces obtained by air granulation of molten aluminum dross or a molten mixture of aluminum dross and aluminum oxide. [Section 9] A method for producing particles having internal spaces, comprising the steps of melting a raw material containing aluminum nitride and aluminum oxide, and air-crushing the melt. [Section 10] Item 10. The manufacturing method according to Item 9, wherein the raw material containing aluminum nitride and aluminum oxide is a raw material containing aluminum dross. [Section 11] Item 11. The method according to Item 9 or 10, wherein the particles having internal voids contain aluminum oxynitride and aluminum oxide, and the aluminum oxynitride content is 0.1 wt % to 90 wt % based on the total weight of the aluminum oxynitride and aluminum oxide. [Section 12] Item 12. The method according to any one of items 9 to 11, further comprising a firing step. [Section 13] Use of aluminum dross in producing particles containing aluminum oxynitride and aluminum oxide and having internal voids. [Example]

[0049] Examples of the present invention will be described below, but the present invention is not limited to the following examples.

[0050] Measurement of aluminum dross The raw material aluminum dross used in the following examples was analyzed by the FP method using an X-ray fluorescence analyzer (Primus II, Rigaku Corporation). The results are shown in Table 1. [Table 1]

[0051] This X-ray fluorescence analysis can measure elements with atomic numbers larger than F (fluorine), so it was found that the raw material aluminum dross contains the above elements in the proportions shown in Table 1. However, the components of aluminum dross are not limited to those shown in Table 1. In the table, Al includes at least aluminum, aluminum nitride, and aluminum oxide.

[0052] Creation of particles with internal spaces Example 1 Five kg of aluminum dross (see Table 1 for composition) was placed in an arc melting furnace (Laboratory Arc Furnace ALF-3, Ando Industries Co., Ltd.) and heated until the aluminum dross melted. After the aluminum dross melted, it was heated at that temperature (approximately 2000°C (measured with a Chino digital radiation thermometer IR-AHS2)) for 20 minutes. The arc melting furnace was then tilted to allow the aluminum dross melt to flow out. While the eluate was falling, compressed air was supplied perpendicularly to the eluate using a compressed air supply device (Engine Compressor PDS265S, Hokuetsu Industries Co., Ltd.) at an air volume of 7.5 m. 3 / min and a blowing pressure of 0.4 MPa (velocity 80-120 m / s) to obtain air-breaking particles.

[0053] Observation of appearance using an optical microscope The appearance of the particles obtained in Example 1 was observed using an optical microscope (Digital Microscope VHX-6000, Keyence Corporation). The results are shown in Figure 1. As can be seen from Figure 1, the obtained particles were found to be rounded. The black scale bar is 0.5 mm. The rounded particles are thought to be the result of the molten material being atomized by compressed air and agglomerating due to surface tension.

[0054] Observation of appearance using SEM The appearance of the particles obtained in Example 1 was observed using an SEM (scanning electron microscope JSM-IT700HR, JEOL Ltd.). The results are shown in Figure 2. The white scale bar is 200 µm. There were openings on the surface of the particles, which were very small compared to the size of the particles and appeared to have originated from inside the particles, suggesting that there was space inside the particles. The space inside the particles is thought to be caused by the generation of nitrogen gas when aluminum oxynitride is produced from aluminum oxide and aluminum nitride contained in the raw materials.

[0055] Example 1-1 1 kg of the particles obtained in Example 1 was placed in a Nikkato alumina firing container and fired at 1550°C for 30 minutes using a high-temperature atmosphere furnace (PART-3, Seishin Enterprise Co., Ltd.) to obtain fired particles. There was no change in the shape of the particles before and after firing.

[0056] Particle identification by X-ray diffraction (XRD) The particles obtained in Example 1 and Example 1-1 were pulverized in an XRF mill (high-speed vibration sample mill TI-100, CMT Scientific Co., Ltd.) and subjected to XRD analysis using CuKα radiation (1.5418 Å) with an X-ray diffractometer (desktop X-ray diffractometer MiniFlex II, Rigaku Corporation). The results are shown in Figure 3, labeled "3" (Example 1) and "4" (Example 1-1), respectively. The X-ray diffraction patterns of corundum (main component: aluminum oxide) and aluminum oxynitride are also shown in Figure 3, labeled "5" (corundum) and "6" (aluminum oxynitride), respectively. Furthermore, Table 2 shows the ratio of aluminum oxide to aluminum oxynitride in the particles of Example 1 and Example 1-1 relative to the total weight of both components.

[0057] [Table 2]

[0058] Peaks of aluminum oxide and aluminum oxynitride were detected in the X-ray diffraction patterns of the particles of Example 1 and Example 1-1, which revealed that the particles of Example 1 and Example 1-1 were mixtures containing aluminum oxide and aluminum oxynitride. It was found that the particles of Example 1 had a high proportion of aluminum oxynitride, which is thought to be the result of aluminum nitride contained in the raw material forming a solid solution (aluminum oxynitride) with aluminum oxide. It was found that the particles of Example 1-1 had a high proportion of aluminum oxide, which is thought to be the result of nitrogen being released from the aluminum nitride in the aluminum oxynitride contained in the particles before firing, and the remaining aluminum reacting with oxygen to produce aluminum oxide.

[0059] Creation of particles with internal spaces Example 2 Particles having internal voids were obtained in the same manner as in Example 1, except that aluminum dross and a raw material containing aluminum oxide but not aluminum nitride (Espearl #35L (component ratios are shown in Table 3 below), Yamakawa Sangyo Co., Ltd.) were added in a weight ratio of 70:30 instead of aluminum dross.

[0060] [Table 3]

[0061] Example 3 Particles having internal voids were obtained in the same manner as in Example 1, except that aluminum dross and a raw material containing aluminum oxide but not aluminum nitride (Espearl #35L, Yamakawa Sangyo Co., Ltd.) were added in a weight ratio of 50:50 instead of aluminum dross.

[0062] Example 4 Particles having internal voids were obtained in the same manner as in Example 1, except that aluminum dross and a raw material containing aluminum oxide but not aluminum nitride (Espearl #35L, Yamakawa Sangyo Co., Ltd.) were added in a weight ratio of 30:70 instead of aluminum dross.

[0063] Example 5 Particles having internal voids were obtained in the same manner as in Example 1, except that aluminum dross and a raw material containing aluminum oxide but not aluminum nitride (Espearl #35L, Yamakawa Sangyo Co., Ltd.) were added in a weight ratio of 10:90 instead of aluminum dross.

[0064] Example 6 Particles having internal voids were obtained in the same manner as in Example 1, except that aluminum dross and a raw material containing aluminum oxide but not aluminum nitride (Espearl #35L, Yamakawa Sangyo Co., Ltd.) were added in a weight ratio of 5:95 instead of aluminum dross.

[0065] Example 7 Particles having internal voids were obtained in the same manner as in Example 1, except that aluminum dross and a raw material containing aluminum oxide but not aluminum nitride (Espearl #35L, Yamakawa Sangyo Co., Ltd.) were added in a weight ratio of 1:99 instead of aluminum dross.

[0066] Comparative Example 1 Particles were obtained in the same manner as in Example 1, except that a raw material containing aluminum oxide but not aluminum nitride (Espearl #35L, Yamakawa Sangyo Co., Ltd.) was added instead of aluminum dross.

[0067] Comparative Example 2 As a comparative example of particles, hollow spherical fused alumina BL (Pacific Random Co., Ltd.) containing no aluminum oxynitride was prepared.

[0068] Measurement of thermal conductivity (hot disk method) The particles of Examples 1, 5, and 7 and Comparative Examples 1 and 2 were sieved through a 600 μm sieve, and the particles that passed through were further sieved through a 425 μm sieve to obtain the particles remaining on the sieve (hereinafter referred to as "425 μm mono-particle size particles" or "test sample"). The test sample was packed into a φ50 × 50 mm stainless steel cylinder and smoothed with a spatula to make the end surface smooth. A measurement sensor was installed on the smoothed end surface. Another identical cylinder was placed on top of the sensor so that it was aligned with the lower cylinder. The upper cylinder was filled with the test sample and smoothed with a spatula to make the end surface smooth. Thermal conductivity was then measured using a TPS-1500 hot disc thermophysical property measurement system (Kyoto Electronics Manufacturing Co., Ltd.). The results are shown in Table 4 and Figure 4.

[0069] [Table 4]

[0070] The thermal conductivities of the particles of Comparative Examples 1 and 2, which did not contain aluminum nitride as a raw material, were 0.2596 W / m K and 0.2562 W / m K, respectively, which were higher than the thermal conductivities of the particles of Examples 1, 5, and 7. This suggests that the particles of the present disclosure have internal spaces and contain aluminum oxynitride, which reduces their thermal conductivity. Therefore, the particles of the present disclosure have a lower thermal conductivity than the particles of Comparative Example 2 (hollow sphere fused alumina BL), which are already sold for use in insulating bricks and lightweight refractories and whose use as an insulating refractory is described in JP 2013-18657 A.

[0071] Apparent porosity measurement The particles of Examples 1 to 7 and Comparative Example 1 were sieved through a 5 mm sieve, and the particles that passed through were then sieved through a 1 mm sieve to obtain the particles remaining on the sieve (also referred to as 1-5 mm particles). The dry mass W1 (g), submerged mass W2 (g), and saturated mass W3 (g) of the 1-5 mm particles were measured according to the boiling method of JIS R 2205, and the apparent porosity ((W3-W1) / (W3-W2) x 100%) was calculated from these values. The results are shown in Table 5 and Figure 5.

[0072] [Table 5]

[0073] From Table 5, it was observed that the apparent porosity tended to decrease as the proportion of aluminum dross in the raw material (and therefore the proportion of aluminum nitride in the raw material) decreased (Examples 1 to 7). It was found that Comparative Example 1, which did not contain aluminum nitride in the raw material, had an apparent porosity of 0 (i.e., had no internal voids). From this, it is believed that the particles of the present disclosure have internal voids due to nitrogen gas derived from aluminum nitride.

[0074] Measurement of thermal expansion coefficient As described above, 425 μm mono-particle size particles (hereinafter also referred to as "test samples") were obtained from the particles obtained in Examples 1 to 5 and Comparative Examples 1 and 2. The test samples were packed into a container (sample container) consisting of an HB (mullite) protective tube with an outer diameter of 8 mm, an inner diameter of 5 mm, and a length of 21 mm, with a 9 × 9 × 1 mm SSA-S (aluminum oxide) plate attached to the bottom. The container was covered with a 1 mm thick insulating tube, and the thermal expansion coefficient was measured using a TMA (ThermoPlus TMA8310, Rigaku Corporation) when heated to 1500 °C for 30 minutes. The results are shown in Table 6 and Figure 6.

[0075] [Table 6]

[0076] The particles of Example 1 had the highest thermal expansion coefficient of 2.26%, while the particles of Comparative Example 1 had the lowest thermal expansion coefficient of 0%. The higher the proportion of aluminum dross in the raw material, the higher the thermal expansion coefficient, so it is thought that aluminum oxynitride produced by melting the aluminum dross is involved in the thermal expansion coefficient. The expansion coefficients of the particles of Examples 4 and 5 were almost the same as that of the particles of Comparative Example 2. From the viewpoints of thermal conductivity and thermal expansion coefficient, therefore, at least the particles of Examples 4 and 5 can be used as aggregate for refractories.

[0077] Example 1-2 Calcined particles were obtained in the same manner as in Example 1-1, except that the particles obtained in Example 1 were calcined at 1200° C. for 8 hours.

[0078] Examples 1-3 Calcined particles were obtained in the same manner as in Example 1-1, except that the particles obtained in Example 1 were calcined at 1300° C. for 120 minutes. Examples 1-4 Calcined particles were obtained in the same manner as in Example 1-1, except that the particles obtained in Example 1 were calcined at 1400° C. for 30 minutes.

[0079] Particles with a single particle size of 425 μm were obtained from the particles obtained in Examples 1, 1-2, 1-3, and 1-4 (hereinafter referred to as "test samples"). The test samples were packed into a container (sample container) consisting of an HB (mullite) protective tube with an outer diameter of 8 mm, an inner diameter of 5 mm, and a length of 21 mm, and a 9 × 9 × t1 SSA-S plate attached to the bottom. The container was covered with a 1 mm thick insulating tube, and the thermal expansion coefficient was measured using a TMA (ThermoPlus TMA8310, Rigaku Corporation) when heated to 1500 °C for 30 minutes. The results are shown in Table 7.

[0080] [Table 7]

[0081] The table shows that the thermal expansion coefficient decreased due to sintering. This decrease is thought to be due to the nitrogen in the aluminum nitride in the aluminum oxynitride particles before sintering being released during sintering, and the remaining aluminum reacting with oxygen to produce aluminum oxide. Furthermore, when the firing temperature was high, particles with a low thermal expansion coefficient were obtained even with a short firing time. This suggests that the higher the temperature, the more easily the reaction of converting aluminum oxynitride to aluminum oxide proceeds. Note that no change in shape was observed between the particles of Examples 1-2 to 1-4 and the particles of Example 1-1.

[0082] Bulk density measurement As described above, 425 μm monoparticle size particles (hereinafter also referred to as test samples) were obtained from the particles obtained in Examples 1, 5, and 7 and Comparative Examples 1 and 2. According to JIS R 1628, the test samples were filled to a predetermined level in a measuring container of known mass and volume, and the mass of the test sample of the predetermined volume was measured to determine the bulk density. The obtained bulk densities are shown in Table 8. [Table 8]

[0083] The bulk density of the particles of Comparative Example 1, which were produced using a raw material containing aluminum oxide but not aluminum nitride, was 1.89 g / cm 3 On the other hand, the bulk density of the particles of Examples 1, 5 and 7 was 1.08 g / cm3. 3 , 0.90 g / cm 3 and 1.06 g / cm 3 Yes, approximately 1.0±0.1 g / cm 3 Therefore, it was found that the particles of the present disclosure have a relatively low density. This is probably because the particles have internal spaces due to nitrogen generated when aluminum oxynitride is produced from aluminum oxide and aluminum nitride in the raw materials. Furthermore, when the bulk density of the particles of Comparative Example 2 was compared with the bulk density of the particles of Examples 1, 5 and 7, it was found that they were approximately the same.

[0084] As described above, the hollow fused alumina BL used as the particles in Comparative Example 2 is sold for use in insulating bricks and lightweight refractories, and examples of its use as insulating refractories have also been shown. Comparing the thermal conductivity of the particles in Examples 1, 5, and 7 with that of Comparative Example 2, the particles in Examples 1, 5, and 7 have lower thermal conductivity. Furthermore, the particles in Examples 1, 5, and 7 have similar bulk densities to the particles in Comparative Example 2. Furthermore, a thermal expansion coefficient of 1.5% or less at 1500°C is suitable for use as an aggregate for refractories. Therefore, it was found that the particles of the present disclosure are suitable for use as an aggregate for insulating materials and refractories.

[0085] <Production of heat insulating castable refractories> Example 8 Using the particles obtained in Example 1, a heat insulating castable was produced by a method known in the art. Using the produced heat insulating castable, a test piece specified in JIS R2553 was obtained. For the obtained test piece, the length l0 before firing and the length l1 after firing were measured in accordance with JIS R 2554, and the linear thermal expansion coefficient ((l1-l0) / l0×100) was calculated. The obtained test piece was also dried in an atmosphere at 110°C for 24 hours. For the dried test piece, its dry mass W1 (g), submerged mass W2 (g), and saturated mass W3 (g) were measured in accordance with the boiling method of JIS R2205, and these values ​​were used to calculate the apparent porosity ((W3-W1) / (W3-W2)×100%). Furthermore, according to JIS R 2553, the dimensions (width b and thickness d) of the fired test piece were measured, and the maximum load W during the bending test was calculated. M and maximum load W during compression test C Calculate the dry bending strength ((3 × W M ×l) / (2×b×d 2 )) and dry compressive strength (W C The measurement results of Example 8 are shown in Table 9. [Table 9]

[0086] The apparent porosity results revealed that the heat insulating castable of Example 8 had heat insulating properties.

[0087] Example 9 Using the particles obtained in Example 1-1, a heat insulating castable was produced by a method known in the art. Using the produced heat insulating castable, a test piece specified in JIS R2553 was obtained. For the obtained test piece, the length l0 before firing and the length l1 after firing were measured in accordance with JIS R 2554, and the linear thermal expansion coefficient ((l1-l0) / l0×100) was calculated. The obtained test piece was also dried in an atmosphere at 110°C for 24 hours. For the dried and cooled test piece, the mass W and dimensions (length L, width M, and thickness T) were immediately measured in accordance with JIS R 2655, and the dry bulk density (W / (L×M×T)) was calculated. Furthermore, in accordance with JIS R 2553, the dimensions (width b and thickness d) of the fired test piece were measured, and the maximum load W during the bending test was calculated. M and maximum load W during compression test C Calculate the dry bending strength ((3 × W M ×l) / (2×b×d 2 )) and dry compressive strength (W C / (40×b)) was calculated.

[0088] Comparative Example 3 Test pieces were obtained and various parameters were determined in the same manner as in Example 9, except that hollow fused alumina BL (Pacific Random Co., Ltd.) was used instead of the particles obtained in Example 1-1.

[0089] The measurement results for the heat insulating material of Example 9 and the heat insulating material of Comparative Example 3 are shown in Table 10. [Table 10]

[0090] The dry bending strength, dry compressive strength, and dry bulk density values ​​of the test piece of the insulating castable of Example 9 were similar to those of the test piece of the insulating castable of Comparative Example 3. In addition, the linear thermal expansion coefficient at 1500°C was less than 1.5%, which indicated that the insulating castable of Example 9 was fire-resistant. This result, expressed in Segel cone refractoriness, is at least SK18 or higher. [Explanation of symbols]

[0091] 3: XRD data spectrum of particles of Example 1, 4: XRD data spectrum of particles of Example 1-1, 5: Standard spectrum of XRD data of aluminum oxide, 6: Standard spectrum of XRD data of aluminum oxynitride

Claims

1. A particle having an internal space, the particles include aluminum oxynitride and aluminum oxide; Particles containing 0.1% by weight to 90% by weight of aluminum oxynitride based on the total weight of the aluminum oxynitride and aluminum oxide.

2. The particles according to claim 1 , wherein the particles have a thermal conductivity of 0.23 W / m·K or less.

3. 2. The particles according to claim 1, comprising 0.5% to 90% by weight of aluminum oxynitride relative to the total of the aluminum oxynitride and aluminum oxide.

4. The particle of claim 1 , wherein the particle has a generally spherical shape.

5. The particles of claim 1 having a refractoriness of 1500°C or greater.

6. 10. The particle of claim 1, wherein the particle has an apparent porosity of 7% to 60%.

7. A heat insulating material or refractory material comprising the particles of claim 1 as aggregate.

8. Particles with internal spaces obtained by air granulation of molten aluminum dross or a molten mixture of aluminum dross and aluminum oxide.

9. A method for producing particles having internal spaces, comprising the steps of melting a raw material containing aluminum nitride and aluminum oxide, and air-crushing the melt.

10. The method according to claim 9, wherein the raw material containing aluminum nitride and aluminum oxide is a raw material containing aluminum dross.

11. The method according to claim 9, wherein the particles having internal voids contain aluminum oxynitride and aluminum oxide, and the content of aluminum oxynitride is 0.1 wt % to 90 wt % based on the total weight of the aluminum oxynitride and aluminum oxide.

12. The method according to any one of claims 9 to 11, further comprising a firing step.

13. Use of aluminum dross in producing particles containing aluminum oxynitride and aluminum oxide and having internal voids.

Images