Granular powder and production method therefor

Abstract

Provided are a granular powder with which a molded body having high strength can be obtained by a press molding method without necessarily requiring detailed composition control of organic components in a raw material powder slurry that is subjected to granulation, and / or an easy production method therefor. Provided is a ceramic granular powder comprising a ceramic powder and a binder, and having a peak top at 1730±20 cm-1 in a per-unit-mass infrared spectrum of the binder, the absorption peak intensity being 0.023 count or more.

Description

Granular powder and its manufacturing method

[0001] The present disclosure relates to ceramic granular powders and methods for producing the same.

[0002] Zirconia (zirconium dioxide, ZrO ２ Ceramics (sintered bodies) including ceramics (ceramics) are produced by molding raw material powders into a compact (green compact) and then sintering it (after calcining, if necessary). Press molding, in which raw material powders filled into a mold are pressed into a mold, is a commonly used method for molding raw material powders. Raw material powders usually have small secondary particle diameters of 1 μm or less and low fluidity. For this reason, the raw material powders are granulated to produce granular powders (granulated powders) with aggregate diameters of several tens of μm, which are then used for press molding. Granular powders containing the raw material powders and organic components such as binders are used to improve the fluidity and properties of the raw material powders during molding.

[0003] For example, Patent Document 1 discloses a granular powder containing an organic component, which is obtained by spray-drying an organic component consisting of an acrylic copolymer resin, polyvinyl alcohol, polyalkylene oxide, and stearic acid with a ceramic powder. Patent Document 1 discloses that such a granular powder can be used to obtain a molded body with excellent mold releasability during molding. Patent Document 2 discloses that a granular powder with a high average circularity can be obtained by controlling the bubble content, viscosity, surface tension, etc. of the slurry. Patent Document 2 also discloses that the granular powder of Patent Document 2 is a suitable raw material for molding laminates.

[0004] International Publication No. 2013 / 047413 International Publication No. 2018 / 056331

[0005] Patent Document 1 discloses that high-strength compacts can be obtained using granular powder by increasing the molding pressure. However, the granular powder disclosed in Patent Document 1 requires the use of a raw powder slurry in which the composition of organic components, including the binder, is precisely controlled. Furthermore, the inventors' investigations have confirmed that compacts obtained using the granular powder disclosed in Patent Document 1 are prone to defects, such as chipping of edges, during handling. Meanwhile, Patent Document 2 discloses that the circularity of granules can be controlled by adding organic components to the raw powder slurry. Thus, the properties of the resulting granular powder have traditionally been controlled by precisely controlling the composition of the organic components in the raw powder slurry used for granulation. While Patent Document 2 suggests the use of a dispersant to control the circularity of granular powders, it does not disclose any specific details about the dispersant or other conditions, nor does it disclose any specific methods for controlling circularity.

[0006] The present disclosure aims to provide at least one of a granular powder that can be used to obtain a molded body having strength that is less likely to crack or chip during handling by a press molding method, without requiring detailed compositional control of the organic components of the raw material powder slurry to be granulated, and a simple method for producing such a granular powder.

[0007] In the past, granular powders suitable for compaction were obtained by focusing on the slurry composition, such as the combination of raw material powders and organic components, or the composition of the slurry. In contrast, in the present disclosure, we have focused on the granulation conditions themselves to improve granule characteristics without relying on detailed control of the slurry composition. As a result, we have found that by controlling the granulation conditions themselves, we can obtain granular powders that give compacts with higher strength, and that this reduces the occurrence of defects at the edges of the resulting compacts.

[0008] That is, the present invention is as defined in the claims, and the gist of the present disclosure is as follows: [1] A ceramic powder and a binder are included, and the binder has a peak at 1730±20 cm in the infrared spectrum per mass of the binder. －１[2] A ceramic granular powder having an absorption peak intensity of 0.023 counts or more, having a peak top at [1]. [2] The granular powder according to the above [1], wherein the ceramic is zirconia. [3] The granular powder according to the above [2], wherein the zirconia is zirconia containing a stabilizing element. [4] The granular powder according to the above [3], wherein the stabilizing element is one or more selected from the group consisting of yttrium, magnesium, calcium, cerium, and erbium. [5] The granular powder according to any one of the above [1] to [4], wherein the binder is at least one of a polyvinylpyrrolidone-based resin and an acrylic-based resin. [6] The granular powder according to any one of the above [1] to [5], wherein the content of the binder is 0.1 mass% or more and 8 mass% or less. [7] A granular powder having a loose bulk density of 1.10 g / cm ３ [8] The granular powder according to any one of [1] to [6], wherein 15±0.5 g of the granular powder is filled into a cylindrical mold having a diameter of 25 mm and press-molded at a pressure of 49 MPa, and the measured density is 2.70 g / cm ３ The granular powder according to any one of [1] to [7] above, which is above. [9] A method for producing the granular powder according to any one of [1] to [8] above, comprising a step of spray-drying a slurry containing ceramic powder, a binder, and a solvent at a temperature where the difference between the hot air temperature and the exhaust air temperature is 55°C or more.

[10] The production method according to [9] above, wherein the hot air temperature is 300°C or less.

[11] A method for producing a molded body using the granular powder according to any one of [1] to [8] above.

[12] A method for producing a calcined body using the molded body according to

[11] above.

[13] A method for producing a sintered body using the molded body according to

[11] above or the calcined body according to

[12] above.

[0009] The present disclosure makes it possible to provide at least one of a granular powder that can be used by a press molding method to obtain a molded body that is strong enough to be less susceptible to cracking or chipping during handling, without requiring detailed compositional control of the organic components of the raw material powder slurry to be subjected to granulation, and a simple method for producing such a granular powder.

[0010] SEM observation image of granular powder of Example 2 (scale in the figure is 100 μm)

[0011] The granular powder of the present disclosure will be described with reference to an example embodiment. The configurations and parameters disclosed herein may be combined in any desired manner, and the upper and lower limits of the values ​​disclosed herein may be combined in any desired manner.

[0012] The "composition" is a substance having a certain composition, and examples thereof include one or more selected from the group consisting of powder, granules, a molded body, a calcined body, and a sintered body.

[0013] The term "powder" refers to a composition that is an aggregate of powder particles and has flowability. The term "zirconia powder" refers to a powder whose main component is zirconia, or a powder that essentially consists of zirconia.

[0014] "Granular powder" refers to a powder made up of granular particles, and "granular particles" are particles (tertiary particles, granulated particles) formed by the slow aggregation of powder particles (particularly, at least one of primary particles and secondary particles) by physical force, and may contain organic components.

[0015] A "green body" is a composition having a certain shape composed of powder particles agglomerated by physical force, and in particular, a composition in a state in which the composition has not been subjected to heat treatment after the shape has been imparted (e.g., after molding). A "zirconia green body" is a green body whose main component is zirconia, and is essentially made of zirconia. In this embodiment, the terms "green body" and "green compact" are used interchangeably.

[0016] The term "calcined body" refers to a composition having a certain shape and composed of fused particles, which is heat-treated at a temperature below the sintering temperature. The term "zirconia calcined body" refers to a calcined body containing zirconia as the main component, and essentially consisting of zirconia.

[0017] A "sintered body" is a composition having a certain shape and composed of crystal grains, and is a composition in a state in which it has been heat-treated at a temperature equal to or higher than the sintering temperature. The shape of the sintered body of this embodiment can be, for example, at least one selected from the group consisting of spherical, approximately spherical, elliptical, disk-like, cylindrical, cubic, rectangular, polyhedral, and approximately polyhedral. Furthermore, any shape may be used to achieve a specific purpose, such as various applications. A "zirconia sintered body" is a sintered body containing zirconia as a main component, or further, a sintered body essentially consisting of zirconia.

[0018] The "stabilizing element" is an element that has the function of stabilizing the crystalline phase of zirconia by dissolving in zirconia.

[0019] The "BET specific surface area" is a value measured in accordance with JIS R 1626 by the BET multipoint method (5 points) using nitrogen as the adsorption gas under the following conditions: Adsorption medium: N ２ Adsorption temperature: -196°C Pretreatment conditions: Degassing in air at 250°C for 1 hour or more

[0020] The BET specific surface area can be measured using a common device (for example, Tristar II 3020, manufactured by Shimadzu Corporation).

[0021] The "average granule particle size" is the average particle size of granular powder measured by a dry method, and is the particle size (median diameter) corresponding to a volume fraction of 50% on a volume particle size distribution curve measured using a general particle size distribution analyzer (product name: MT3100II, manufactured by Microtrac Bell) under the following conditions: Measurement sample: granular powder Refractive index of zirconia: 2.17 Refractive index of air: 1.333 Measurement time: 10 seconds

[0022] The "loose bulk density" is the density measured by passing granular powder through a sieve with a mesh size of 500 μm and allowing it to fall freely from a height of 35 mm to a volume of 100 cm ３ The container is filled with granular powder, and the 100 cm ３The mass [g] of the container was measured using a balance, and then the mass [g] of the filled granular powder was calculated by subtracting the mass [g] of the container. ３ ] per mass [g / cm ３ ] can be calculated as follows.

[0023] The "powder X-ray diffraction pattern" is an XRD pattern of a composition obtained by powder X-ray diffraction (hereinafter also referred to as "XRD") measurement under the following conditions: Radiation source: CuKα radiation (λ=0.15418 nm) Measurement mode: Continuous scan Scan speed: 2° / min Measurement range: 2θ=26° to 33° Acceleration voltage / current: 40 kV / 40 mA Divergence vertical limiting slit: 10 mm Divergence / entrance slit: 1° Receiving slit: open Detector: Semiconductor detector (D / teX Ultra) Filter: Ni filter Goniometer radius: 185 mm

[0024] The XRD measurement can be performed using a general X-ray diffractometer (for example, Ultima IV, manufactured by RIGAKU Corporation). When the composition is a calcined body or a sintered body, the surface thereof may be polished to a surface roughness Ra≦0.02 μm, and the XRD measurement may be performed on the surface.

[0025] The XRD peaks corresponding to the crystal planes of zirconia measured in the above-mentioned XRD measurement include XRD peaks having peak tops at the following 2θ: XRD peak corresponding to monoclinic (111) plane: 2θ = 31 ± 0.5° XRD peak corresponding to monoclinic (11-1) plane: 2θ = 28 ± 0.5° XRD peak corresponding to tetragonal (111) plane: 2θ = 30 ± 0.5° XRD peak corresponding to cubic (111) plane: 2θ = 30 ± 0.5°

[0026] The XRD peak corresponding to the tetragonal (111) plane and the XRD peak corresponding to the cubic (111) plane are measured as a single overlapping peak. ｔ(111) + I ｃ The (111) can be determined from the integrated intensity of one XRD peak having a peak top at 2θ = 30 ± 0.5°. The integrated intensity of each crystal plane can be determined by profile fitting the XRD pattern after smoothing and background removal using a split pseudo-Voigt function. Analysis of the XRD pattern, such as smoothing, background processing, and calculation of integrated intensity, can be performed using an analysis program attached to the X-ray diffractometer (e.g., Integrated Powder X-ray Analysis Software PDXL Ver. 2.2, manufactured by RIGAKU Corporation).

[0027] "Atmospheric pressure sintering" is a method of sintering by heating an object to be sintered (such as a compact or calcined body) without applying an external force.

[0028] [Granular Powder] This embodiment contains ceramic powder and a binder, and has a wavelength of 1730±20 cm in the infrared spectrum per mass of the binder. －１ The ceramic granular powder has an absorption peak intensity of 0.023 counts or more, having a peak top at 1000 kJ / cm2. By press-molding a granular powder satisfying this constitution, a molded body having a strength that is resistant to cracking or chipping during handling (hereinafter also referred to as "chipping") can be obtained.

[0029] The granular powder of this embodiment includes ceramic powder and is composed of granular particles including a binder and ceramic powder particles. The "ceramic powder" in the granular powder of this embodiment means the ceramic that is the main component (matrix), and further, the ceramic that is contained in the largest amount in the granular powder of this embodiment. The ceramic is preferably an oxide ceramic. The oxide ceramic, for example, alumina (Al ２ O ３ ), zirconia (ZrO ２ ), silica (SiO ２ ), Germania (GeO ２ ) and ) are exemplified, and at least one of alumina and zirconia is preferred, with zirconia being more preferred.

[0030] Hereinafter, the granular powder of this embodiment will be described using an example in which the ceramic is zirconia (zirconia granular powder).

[0031] The zirconia contained in the granular powder of this embodiment is preferably zirconia containing a stabilizing element. The stabilizing element can be one or more selected from the group consisting of yttrium (Y), calcium (Ca), magnesium (Mg), scandium (Sc), cerium (Ce), and erbium (Er), and can be one or more selected from the group consisting of yttrium, calcium, magnesium, and cerium, or at least one of yttrium and cerium, with yttrium being preferred. The content of the stabilizing element may be an amount that stabilizes the zirconia in at least one of a cubic and a tetragonal crystal phase, and is preferably an amount that stabilizes the zirconia in a crystal phase having tetragonal crystals as the main phase. The content of the stabilizing element is preferably 1.5 mol% or more, 2.0 mol% or more, or 2.8 mol% or more, and 8.0 mol% or less, 6.0 mol% or less, or 4.2 mol% or less, and more preferably 1.5 mol% or more and 8.0 mol% or less, 2.0 mol% or more and 6.0 mol% or less, or 2.8 mol% or more and 4.2 mol% or less.

[0032] The content of the stabilizing element in this embodiment is the molar ratio (mol %) of the stabilizing element calculated as an oxide to the total of zirconia and the stabilizing element calculated as an oxide.

[0033] The granular powder of this embodiment preferably contains, in addition to zirconia powder, a powder of one or more selected from the group consisting of alumina, silica, and germania (hereinafter also referred to as "additive component"), and more preferably contains alumina powder. The coexistence of zirconia and the additive component enables sintering of zirconia at a lower temperature. In this case, the content of the additive component may be 0% by mass or more, more than 0% by mass, or 0.01% by mass or more, and may be 20% by mass or less, 10% by mass or less, 5% by mass or less, or 0.1% by mass or less. The granular powder of this embodiment may not contain an additive component such as alumina (i.e., the content of the additive component is 0% by mass), but may contain alumina, and the alumina content may be more than 0% by mass but less than 20% by mass, 0.01% by mass or more but less than 10% by mass, or 0.01% by mass or more but less than 0.1% by mass. The content of the additive component in the granular powder of this embodiment can be determined from the mass ratio [mass %] of the additive component converted into oxide to the mass of the granular powder converted into oxide (hereinafter also referred to as "oxide mass"). ２ O ３ , silica is SiO ２ and germania is GeO ２ is.

[0034] The granular powder of this embodiment may contain a pigment component. By containing the pigment component, the granular powder of this embodiment can be used as a raw material for obtaining a sintered body of any color tone. The pigment component may be any compound capable of coloring ceramics, and examples thereof include transition metal oxides and composite oxides of transition metals. Examples of transition metal oxides include oxides of transition metals other than zirconium and hafnium, as well as oxides containing one or more selected from the group consisting of titanium (Ti), vanadium (V), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), niobium (Nb), palladium (Pd), and tungsten (W). Examples of composite oxides of transition metals include composite oxides containing two or more selected from the group consisting of titanium, vanadium, manganese, iron, cobalt, nickel, and copper, and composite oxides containing two or more selected from the group consisting of manganese, iron, cobalt, and nickel, and two or more selected from the group consisting of aluminum (Al), zinc (Zn), germanium (Ge), gadolinium (Gd), and tin (Pb). The shape of the pigment component contained in the granular powder of this embodiment is arbitrary, but may be a powder (or powder particles).

[0035] The types and contents of the pigment components may be any combination and content that results in a desired color tone. The granular powder of this embodiment may not contain a pigment component (i.e., the content of the pigment component is 0% by mass), but it may contain a pigment component and the content of the pigment component may be more than 0% by mass and not more than 10% by mass, 0.01% by mass or more and not more than 1% by mass, or 0.01% by mass or more and not more than 0.5% by mass. The content of the pigment component in the granular powder of this embodiment can be calculated from the mass ratio [mass%] of the pigment component converted into oxide relative to the oxide mass.

[0036] The granular powder of this embodiment may contain unavoidable impurities. Examples of unavoidable impurities in zirconia include hafnia (HfO ２ In this embodiment, when determining values ​​based on the composition such as content, hafnia may be calculated by regarding it as zirconia.

[0037] The granular powder of this embodiment contains a binder. Compared to a molded body that does not contain a binder, a molded body obtained by molding the granular powder of this embodiment has higher strength. The binder may be any binder that is applicable to ceramic powders used in dry press molding, and may further be any binder that can improve the properties of molded bodies obtained by dry press molding of ceramic powders. Examples of such binders include one or more selected from the group consisting of polyvinyl alcohol resins, polyvinylpyrrolidone resins, and acrylic resins. Because the resulting powder and molded body have improved storage properties and excellent crushability during molding, the binder is preferably at least one of polyvinylpyrrolidone resins and acrylic resins, and more preferably acrylic resins. The binder contained in the granular powder of this embodiment may be a commercially available binder for press molding (e.g., the Celander series, manufactured by HighChem; AS-1800, AS-2000, manufactured by Toa Gosei Co., Ltd., etc.).

[0038] The binder content of the granular powder of this embodiment may be 0.1% by mass or more, 0.5% by mass or more, or 1% by mass or more. This binder content range allows for a molded body with high strength to be obtained. Furthermore, the binder content may be an amount sufficient to allow for sufficient segregation on the granule surface, for example, 8% by mass or less, 6% by mass or less, 4% by mass or less, 3.5% by mass or less, or 3% by mass or less. Preferably, the binder content is 0.1% by mass or more and 8% by mass or less, 0.5% by mass or more and 6% by mass or less, 1% by mass or more and 4% by mass or less, 1% by mass or more and 3.5% by mass or less, or 1% by mass or more and 3% by mass or less. Increasing the binder content tends to increase the density of the resulting molded body.

[0039] In this embodiment, the binder content can be determined from the ratio (mass %) of the mass of the granular powder of this embodiment reduced after heat treatment when the granular powder is heat treated under the following conditions: Heat treatment atmosphere: air; Heat treatment temperature: 400°C; Heat treatment time: 5 hours; Heating rate: 50°C / hour

[0040] The heat treatment may be carried out in a general muffle furnace (for example, FO310, manufactured by Yamato Chemical Co., Ltd.) Prior to the heat treatment, the granular powder may be pretreated by drying in an air atmosphere at 110°C for 1 hour.

[0041] The granular powder of this embodiment may contain one or more selected from the group consisting of dispersants, lubricants, plasticizers and antifoaming agents, as long as the effects of the granular powder are not impaired, but it is not necessary to contain these.

[0042] The granular powder of this embodiment may contain, for example, a binder, alumina, and AB as a pigment component. ２ O ４ The composition of the granular powder made of yttrium-stabilized zirconia containing iron and a spinel oxide consisting of the above can be determined from the following: In the spinel oxide, A is a divalent metal element, and B is a trivalent metal element. Oxide mass [g] = Al ２ O ３ +A B ２ O ４ +Fe ２ O ３ +Y ２ O ３ + ZrO ２ Alumina content [mass%] = {Al ２ O ３ / (Al ２ O ３ +A B ２ O ４ +Fe ２ O ３ +Y ２ O ３ + ZrO ２ )}×100 Pigment component amount [mass%]={(AB ２ O ４ +Fe ２ O ３ ) / (Al ２ O ３ +A B ２ O ４ +Fe ２ O ３ +Y ２ O ３ + ZrO ２ )}×100 Iron content [mass%] = {Fe２ O ３ / (Al ２ O ３ +A B ２ O ４ +Fe ２ O ３ +Y ２ O ３ + ZrO ２ )} × 100 Spinel oxide amount [mass%] = {AB ２ O ４ / (Al ２ O ３ +A B ２ O ４ +Fe ２ O ３ +Y ２ O ３ + ZrO ２ )}×100 Stabilizing element amount [mol%]={Y ２ O ３ / (Y ２ O ３ + ZrO ２ ) x 100

[0043] The amount of binder can be calculated by the above-mentioned method. Due to differences in calculation methods, the mass percentage of the granular powder in this embodiment may differ from 100% by mass when the binder is taken into consideration (the binder may be treated as an external number).

[0044] The granular powder of this embodiment has a wavelength of 1730±20 cm in the infrared spectrum per mass of the binder. －１ The absorption peak intensity (hereinafter simply referred to as "unit absorption peak intensity") having a peak top at 1730±20 cm in the infrared spectrum is 0.023 counts or more. When the unit absorption peak intensity exhibits such a value, chipping of the resulting molded body is less likely to occur. One of the reasons for this is thought to be that the state of existence of the binder in the granular powder of this embodiment is different from that of conventional granular powders. That is, －１The absorption peak with a peak top (hereinafter also referred to as the "binder peak") is thought to correspond to a peak derived from the binder. Furthermore, a high binder peak relative to the mass of binder in the granular powder is thought to indicate that a large amount of binder is present on the surface of the particles (granule particles) that make up the granular powder. Therefore, the granular powder of this embodiment is thought to be a granular powder composed of granule particles having a structure in which the binder content on the surface is high relative to the binder content inside. This makes it easier for the binder between the granular particles to adhere to each other when pressed. As a result, it is thought that defects are less likely to occur even at the edges of the resulting molded body, resulting in higher strength.

[0045] The unit absorption peak intensity may be 0.023 counts or more, and preferably 0.025 counts or more or 0.028 counts or more. It is believed that the higher the unit absorption peak intensity, the higher the proportion of binder on the surface of the granule particles constituting the granule powder, and the stronger the resulting molded body is likely to be. It is believed that the granule particles constituting the granule powder of this embodiment have a higher amount of binder on the surface relative to the amount of binder inside the granule particles. In other words, the granule powder is composed of granule particles with a binder content gradient composition, in which the binder concentration decreases from the surface to the interior of the granule particles. Furthermore, as the unit absorption peak intensity increases, the maximum strain described below tends to increase, making the granule powder more likely to have excellent moldability.

[0046] On the other hand, the unit absorption peak intensity does not need to be excessively high, and may be 0.045 counts or less, 0.042 counts or less, 0.040 counts or less, or 0.035 counts or less. The unit absorption peak intensity of the granular powder of this embodiment is preferably 0.023 counts or more and 0.045 counts or less, 0.028 counts or more and 0.042 counts or less, or 0.028 counts or more and 0.040 counts or less. Since the granular powder of this embodiment is likely to have a particularly high granule compressibility (described later), the unit absorption peak intensity is preferably more than 0.028 counts, more preferably more than 0.028 counts and not more than 0.040 counts, and even more preferably more than 0.029 counts and not more than 0.036 counts.

[0047] The infrared spectrum in this embodiment is a value measured by a single-reflection ATR method under the following conditions. The single-reflection ATR method may be performed using a general Fourier transform infrared spectrophotometer (for example, IRXross, manufactured by Shimadzu Corporation) and a single-reflection total reflection measurement device with an integrated sample chamber (for example, QATR-10, manufactured by Shimadzu Corporation). Resolution: 4 cm －１ Number of measurements: 40 Wavenumber range: 4000-1500 cm －１ Apodization function: SqrTriangle

[0048] The measurement sample may be a granular powder adhered to a diamond prism having a diameter of 2 mm.

[0049] The unit absorption peak intensity can be calculated from the obtained infrared spectrum using the following formula:

[0050] D ｕｎｉ = (D １ -D ｒｅｆ ) / W In the above formula, D ｕｎｉ is the unit absorbance peak intensity [count], D １ is the measurement sample's 1730 ± 20 cm －１ Peak intensity [count] of the peak having a peak top at D ｒｅｆ is the standard sample's 1730±20 cm －１ is the peak intensity [count] of the peak having a peak top at 1730±20 cm, and W is the binder content [mass%] of the measurement sample. －１ When there are multiple peaks with a peak top at 1000 kJ / s, the intensity of the peak with the greatest peak intensity should be used. The standard sample was a commercially available zirconia granular powder (product name: TZ-3YS, manufactured by Tosoh Corporation).

[0051] The shape of the granular particles constituting the granular powder of this embodiment is arbitrary, and the granular powder of this embodiment may be composed of granular particles having one or more shapes selected from the group consisting of amorphous, spherical, approximately spherical, and elliptical, and further one or more shapes selected from the group consisting of spherical, approximately spherical, and elliptical. Furthermore, the granular powder of this embodiment may include granular particles having a spherical, approximately spherical, or elliptical shape with a depression, or may include granular particles having a crushed shape of these.

[0052] The average granule particle size of the granular powder of this embodiment is 30 μm or more or 40 μm or more, and may be 80 μm or less, 60 μm or less, or 50 μm or less, and is preferably 30 μm or more and 80 μm or less, 40 μm or more and 60 μm or more, or 40 μm or more and 50 μm or less. By having such an average granule particle size, the density of the compact obtained by press molding it tends to be high.

[0053] The loose bulk density of the granular powder of this embodiment is 1.10 g / cm ３ Above, 1.20g / cm ３ or more or 1.25 g / cm ３ or more, and 1.50 g / cm ３ or less or 1.35 g / cm ３ and 1.10 g / cm ３ 1.50g / cm or more ３ Below, 1.20g / cm ３ 1.35g / cm or more ３ or less, or 1.25 g / cm ３ 1.35g / cm or more ３ It is preferable that:

[0054] The granular powder of this embodiment preferably has high moldability, and when 15±0.5 g of the granular powder is filled into a cylindrical mold having a diameter of 25 mm and press-molded at a pressure of 49 MPa, the measured density (hereinafter also referred to as "molded density") is 2.70 g / cm ３ Above, 2.80g / cm ３ or more or 2.85 g / cm ３ or more, and 3.20 g / cm ３ Below, 3.00g / cm ３ or less than 2.90 g / cm ３and 2.70 g / cm ３ 3.20g / cm or more ３ Below, 2.80g / cm ３ 3.00g / cm or more ３ or less, or 2.85 g / cm ３ 2.90g / cm or more ３ It is preferable that the unit absorption peak intensity is satisfied and the molding density is 2.80 g / cm or less. ３ 2.90g / cm or more ３ The granular powder of this embodiment described below can provide a molded body that has strength and is less prone to defects, even when compared with granular powder that does not satisfy the unit absorption peak intensity and has a higher molding density.

[0055] The granular powder of this embodiment preferably has a strength that does not crumble during handling and is easily compressed during press molding. The strength of the granular powder of this embodiment (hereinafter also referred to as "granule strength") is preferably 0.1 MPa or more, 0.4 MPa or more, or 0.5 MPa or more, and is preferably 2 MPa or less, 1.5 MPa or less, 1.2 MPa or less, or 1.0 MPa or less. Examples of the granular strength of the granular powder of this embodiment include 0.1 MPa or more and 2 MPa or less, 0.1 MPa or more and 1.2 MPa or less, and 0.4 MPa or more and 1.0 MPa or less. Furthermore, by having a strength of 0.4 MPa or more and 0.5 MPa or less, a molded body that is less prone to defects can be obtained.

[0056] Granule strength is the strength at which a granular powder is crushed, and is a value determined by a method conforming to JIS R 1639-5. Specifically, it can be measured using a general instrument (for example, MCT-510, manufactured by Shimadzu Corporation) in the following manner. That is, ten samples of granular particles constituting the granular powder are extracted, and the longest and shortest lengths of each granular particle are measured at a 10x objective lens magnification using a length measurement kit attached to the measuring instrument, and the average of these lengths is regarded as the granule particle size (deemed granule particle size). Next, a stress-strain curve is measured while pressing an indenter against each granular particle under the following conditions: Indenter: FLAT200 Test force: 30 mN Load rate: 30 (0.1487 mN / sec)

[0057] The granule strength of each granule particle is calculated from the inflection point of the obtained stress-strain curve using the following formula, and the average value is taken as the granule strength of the granule powder.

[0058] CS=2.48×[{CS １ / (πD １ ２ ) + CS ２ / (πD ２ ２ )+ ・・・・+CS １０ / (πD １０ ２ )} / 10] In the above formula, CS is the granule strength [MPa], CS １ ~CS １０ is the compressive strength of each granule particle [mN], and D １ or D １０ is the assumed granule diameter [μm] of each granule particle.

[0059] The granular powder of this embodiment preferably has a granule compression ratio of 0.1% or more, 2% or more, 5% or more, or 6% or more, and preferably 15% or less, 12% or less, or 10% or less. The granule compression ratio of the granular powder of this embodiment can be, for example, 0.1% to 15%, 2% to 12%, 5% to 12%, 6% to 12%, or 6% to 10%. This makes it easier to obtain a tough compact, and the resulting compact is less likely to break.

[0060] The granule compressibility can be calculated from the stress-strain curve obtained by the same measurement method as for the granule strength, using the following formula: Granule compressibility = Indenter displacement when granules are crushed / Granule diameter C = {(C １ / D １ +C ２ / D ２ +...+C １０ / D １０ ) / 10}×100 In the above formula, C is the granule compressibility [%], C １ ~C １０ is the distance [μm] that the indenter moves from the zero point (initial position) to the inflection point on the stress-strain curve of each granule particle, and D １ or D１０ is the assumed granule diameter [μm] of each granule particle.

[0061] The granular powder of this embodiment preferably satisfies at least one of the following conditions: a granule strength of more than 0.3 MPa and a granule compression rate of 6% or more. This results in a powder with high handleability, making the resulting molded body less susceptible to defects. Furthermore, since the granular powder of this embodiment tends to have high crushability, it is preferable that the granular powder of this embodiment has a granule strength of 0.3 MPa or more and a granule compression rate of 6% or more, preferably a granule strength of 0.4 MPa or more and a granule compression rate of 6% or more, and more preferably a granule strength of 0.5 MPa or more and a granule compression rate of 6% or more.

[0062] [Method for Producing Granular Powder] A preferred method for producing the granular powder of this embodiment includes a step of spray-drying a slurry containing ceramic powder, a binder, and a solvent at a temperature where the difference between the hot air temperature and the exhaust air temperature is 55° C. or more. This produces the granular powder of this embodiment, which produces a molded product that is less prone to defects such as cracks and chips.

[0063] In the step of spray-drying a slurry containing ceramic powder, a binder, and a solvent by setting the difference between the hot air temperature and the exhaust air temperature to 55°C or more (hereinafter also referred to as the "spray-drying step"), a slurry containing ceramic powder, a binder, and a solvent (hereinafter also referred to as the "raw material slurry") is provided. The ceramic powder and binder contained in the raw material slurry may be any suitable for the purpose, and may be any of the ceramic powder and binder types described above.

[0064] The BET specific surface area of ​​the ceramic powder contained in the slurry is 5 m ２ / g or more or 6m ２ / g or more, and ２ / g or less or 20m ２ / g or less, and ２ / g or more 25m ２ / or less, or 6m ２ / g or more 20m ２ / g or less is preferable.

[0065] The ceramic powder may have any particle size that allows it to be formed into granules by drying, and examples of such particle sizes include 0.05 μm to 1.5 μm, and even 0.1 μm to 0.5 μm.

[0066] The solvent contained in the raw material slurry may be any solvent in which the ceramic powder and binder are uniformly dispersed, and examples thereof include at least one of an aqueous solvent and a non-aqueous solvent, at least one of water and alcohol, or at least one of water and ethanol, with water being preferred.

[0067] The raw material slurry may contain, in addition to the ceramic powder, binder, and solvent, one or more selected from the group consisting of the additive component, pigment component, dispersant, lubricant, plasticizer, and antifoaming agent described above.

[0068] In this embodiment, "spray drying" refers to an operation in which droplets of the raw material slurry are brought into contact with a high-temperature carrier gas to rapidly evaporate the solvent, thereby removing the solvent from the droplets of the raw material slurry and obtaining a granular powder composed of granular particles containing ceramic powder and a binder. Spray drying is performed using a spray dryer. In this embodiment, the raw material slurry is formed into droplets, which are introduced into the spray dryer together with a high-temperature carrier gas, and the resulting granular powder is recovered from the spray dryer together with the carrier gas, thereby performing spray drying.

[0069] In the spray drying process, the difference between the hot air temperature and the exhaust air temperature (hereinafter referred to as the "inlet / outlet temperature difference") is set to 55°C or higher. This results in a granular powder composed of granular particles with a structure in which the binder content is higher on the surface than in the interior. Spray drying instantaneously evaporates the solvent from the raw slurry. Therefore, conventionally, a hot air temperature suitable for solvent removal, i.e., the inlet temperature of the carrier gas into the spray dryer, has been set. Meanwhile, the resulting granular powder is transported and recovered by the carrier gas, but the temperature of the carrier gas decreases as it passes through the spray dryer. Therefore, the exhaust air temperature, i.e., the outlet temperature of the carrier gas from the spray dryer, has not been purposefully controlled, but has been set to an arbitrary temperature depending on the size of the spray dryer. In contrast, in this embodiment, we have discovered that the state of the binder changes while the granular powder is transported by the carrier gas. Furthermore, by maintaining a temperature difference between the hot air and exhaust air above a certain level, most of the solvent is instantly removed, but the removal of the remaining solvent promotes the diffusion of the binder in each granular particle constituting the granular powder. As a result, it was found that a granular powder composed of granular particles having a structure in which the binder content on the surface is higher than the binder content inside can be obtained. The inlet / outlet temperature difference needs only to be 55°C or higher, and is preferably 60°C or higher or 80°C or higher. On the other hand, the upper limit of the inlet / outlet temperature difference can be 150°C or lower, 120°C or lower, or 100°C or lower. The inlet / outlet temperature difference is preferably 55°C or higher and 150°C or lower, 60°C or higher and 120°C or lower, 80°C or higher and 120°C or lower, or 80°C or higher and 100°C or lower.

[0070] The inlet / outlet temperature difference can be controlled by adjusting the hot air temperature and exhaust air temperature using the temperature control function of the spray dryer.

[0071] The hot air temperature may be any temperature at which the solvent is removed from the raw material slurry, such as 120°C or higher, 150°C or higher, over 150°C, or over 180°C, and 300°C or lower, 250°C or lower, or 200°C or lower. Examples include 120°C or higher and 300°C or lower, 120°C or higher and 250°C or lower, 150°C or higher and 200°C or lower, over 150°C or lower and 250°C or lower, or 180°C or higher and 200°C or lower. A hot air temperature within this range and at a moderately low temperature (e.g., 210°C or lower) suppresses the amount of solvent that instantly evaporates, further promoting the diffusion of the binder in each granule particle constituting the granular powder as the remaining solvent is removed. This tends to increase the difference in binder concentration between the surface and the interior of the granule particle, resulting in increased strength of the resulting molded body.

[0072] The exhaust air temperature may be any temperature that results in the above-mentioned inlet / outlet temperature difference, and is lower than the hot air temperature, and is 65°C or higher, 95°C or higher, over 100°C or 105°C or higher, and is 245°C or lower, 195°C or lower, 145°C or lower, or 120°C or lower, and examples thereof include 65°C or higher and 245°C or lower, 65°C or higher and 195°C or lower, 95°C or higher and 145°C or lower, 105°C or higher and 145°C or lower, or 105°C or higher and 120°C or lower.

[0073] The carrier gas in spray drying may be, for example, one or more selected from the group consisting of nitrogen, argon, and air, and air is preferred. The spraying method in spray drying may be any method as long as it converts the raw material slurry into droplets, but at least either an atomizer or a spray nozzle may be used. A spraying method in which the raw material slurry is converted into droplets using an atomizer disk is preferred, as this method produces granular powder with a sharp particle size distribution.

[0074] [Methods for producing a compact, a calcined body, and a sintered body] The granular powder of this embodiment can be used as a precursor for a compact, a calcined body, and a sintered body. For example, the granular powder of this embodiment can be used in a method for producing a compact, which includes a step of compacting the granular powder of this embodiment.

[0075] A molded body is obtained by a step of molding the granular powder of this embodiment (hereinafter also referred to as the "molding step"). The molding method can be one or more selected from the group consisting of known molding methods, press molding, cold isostatic pressing, injection molding, slip casting, and slip casting, but the molding method in the molding step is preferably press molding. Furthermore, cold isostatic pressing may be performed after press molding.

[0076] The press molding conditions may be any conditions depending on the purpose, but for example, molding may be performed at a molding pressure of 15 MPa to 100 MPa, and the molding pressure may be maintained. This allows the granular powder of this embodiment to be appropriately crushed, making it easier to obtain a molded body with high strength. In this case, the holding time can be, for example, 5 seconds to 60 seconds.

[0077] The compacts obtained from the granular powder of this embodiment preferably have a strength that makes them less susceptible to chipping during handling. One indicator of strength during handling is the strength (hereinafter also referred to as "chipping strength") measured using a standard autograph (e.g., AGS-10KNX STD 0.5 class, manufactured by Shimadzu Corporation) equipped with a 10 kN load cell, which is obtained by filling 15±0.5 g of the granular powder into a cylindrical mold with a diameter of 25 mm and uniaxially press-molding the resulting compact at a pressure of 49 MPa. This measurement can confirm the likelihood of defects occurring in the compacts obtained from the granular powder. Chipping strength is measured by applying a 1.8 mm diameter indenter along the circumferential direction of the measurement sample and applying a load at 0.1 mm / min, and determining the pressure at the maximum load. Five measurements are taken for one compact, and the average value obtained is taken as the chipping strength. The distance traveled by the indenter during this measurement is taken as the "maximum strain." The maximum strain is one of the indicators of the toughness of the molded body. The larger the maximum strain, the more resistant the molded body tends to be to breakage. The maximum strain of the molded body obtained from the granular powder of this embodiment is preferably greater than 0.05 mm, and is preferably 0.06 mm or more or 0.08 mm or more. The upper limit of the maximum strain can be 0.25 mm or less, 0.20 mm or less, 0.16 mm or less, 0.15 mm or less, or 0.12 mm or less. The maximum strain of the molded body obtained from the granular powder of this embodiment can be, for example, greater than 0.05 mm and 0.25 mm or less, 0.06 mm or more and 0.20 mm or less, 0.06 mm or more and 0.15 mm or less, 0.08 mm or more and 0.16 mm or less, or 0.08 mm or more and 0.12 mm or less.

[0078] The density of the compact obtained from the granular powder of this embodiment may be an actually measured density similar to the above-mentioned compact density.

[0079] The chipping strength of the molded body obtained from the granular powder of this embodiment is 11 MPa or more, 13 MPa or more, or 14 MPa or more, and can be 25 MPa or less, 18 MPa or less, or 15 MPa or less, for example, 11 MPa or more and 25 MPa or less, or 13 MPa or more and 18 MPa or less.

[0080] The compact obtained from the granular powder of this embodiment can be used in a method for producing a calcined body. The calcined body can be obtained by a method for producing a calcined body, which includes a step of calcining the compact. The calcination may be a heat treatment that gives the compact a strength suitable for processing, or a heat treatment at a temperature below the temperature at which densification of ceramics progresses, such as a heat treatment in an air atmosphere at 800°C or higher but lower than 1200°C, or even 1000°C or higher but 1150°C or lower. The calcination time may be adjusted appropriately depending on the size of the compact to be subjected to calcination and the performance of the calcination furnace, and may be, for example, 30 minutes to 5 hours, or 1 hour to 3 hours.

[0081] A molded body obtained from the granular powder of this embodiment, or a calcined body obtained from the sintered body, can be used in a method for producing a sintered body. The sintered body can be produced by a production method including a step of sintering at least one of the molded body and the calcined body. The sintering may be a heat treatment at a temperature equal to or higher than the temperature at which densification of the ceramic proceeds. Pressureless sintering is preferred, and heat treatment is preferably performed in an air atmosphere at 1200°C to 1700°C, more preferably 1400°C to 1550°C. The sintering time may be adjusted as appropriate depending on the size of the molded body to be sintered and the performance of the sintering furnace, and may be, for example, 10 minutes to 5 hours, or 1 hour to 3 hours.

[0082] The present disclosure will be specifically described below with reference to examples and comparative examples, but the present disclosure is not limited to these examples.

[0083] (BET Specific Surface Area) The BET specific surface area was measured using an automatic specific surface area / pore distribution measuring device (device name: Tristar II 3020, manufactured by Shimadzu Corporation) by the BET multipoint method (5 points) in accordance with JIS R 1626. Prior to the measurement, the powder sample was pretreated by degassing in an air atmosphere at 250°C for 1 hour or more but less than 12 hours. Adsorption medium: N ２ Adsorption temperature: -196°C Pretreatment conditions: Degassing in air at 250°C for 1 hour or more

[0084] (Average Granule Particle Size) The average granule particle size was measured by a dry method. That is, a particle size distribution meter (product name: MT3100II, manufactured by Microtrac Bell) was used to measure the volume particle size distribution curve of the granule powder under the following conditions. The particle size (median diameter) corresponding to a volume ratio of 50% on the obtained cumulative volume particle size distribution curve was taken as the average granule particle size. Measurement sample: Granule powder Refractive index of zirconia: 2.17 Refractive index of air: 1.333 Measurement time: 10 seconds

[0085] (Low bulk density) The granular powder was passed through a sieve with an opening of 500 μm. The granular powder that had passed through the sieve was then allowed to fall freely from a height of 35 mm to a volume of 100 cm. ３ The powder was filled into a container. ３ I used enough to overflow the container. ３ The top surface of the container was leveled off using a leveling plate to remove the powder that had overflowed from the container. ３ The mass of the container was measured using a balance, and the mass and loose bulk density of the filled granular powder were determined by subtracting the mass of the container.

[0086] (Infrared Spectrum Measurement) Infrared spectra were measured under the following conditions using a Fourier transform infrared spectrophotometer (device name: IRXross, manufactured by Shimadzu Corporation) and a sample chamber-integrated single reflection total reflection measurement device (QATR-10, manufactured by Shimadzu Corporation).

[0087] Disassembly: 4cm －１ Number of measurements: 40 Wavenumber range: 4000-1500 cm －１ Apodization function: SqrTriangle The measurement sample was a granular powder that was brought into close contact with a diamond prism having a diameter of 2 mm.

[0088] The unit absorption peak intensity was calculated from the obtained infrared spectrum using the following formula:

[0089] D ｕｎｉ= (D １ -D ｒｅｆ ) / W In the above formula, D ｕｎｉ is the unit absorbance peak intensity [count], D １ is the measurement sample's 1730 ± 20 cm －１ Peak intensity [count] of the peak having a peak top at D ｒｅｆ is the standard sample (TZ-3YS, manufactured by Tosoh Corporation) of 1730 ± 20 cm －１ is the peak intensity [count] of the peak having a peak top at 1730±20 cm, and W is the binder content [mass%] of the measurement sample. －１ When there are multiple peaks with peak tops, the intensity of the peak with the maximum peak intensity was used.

[0090] (Granule Strength) Granule strength was determined by a method in accordance with JIS R 1639-5. That is, 10 samples of granule particles constituting the granule powder were extracted. Using a length measurement kit attached to a measuring device (MCT-510, manufactured by Shimadzu Corporation) and an objective lens magnification of 10x, the longest and shortest lengths of each extracted granule particle were measured, and the average was regarded as the granule particle size (deemed granule particle size). Next, a stress-strain curve was measured while pressing an indenter against each granule particle under the following conditions:

[0091] Indenter: FLAT200 Test force: 30 mN Loading speed: 30 (0.1487 mN / sec) From the inflection point of the obtained stress-strain curve, the granule strength of each granule particle was calculated using the following formula, and the average value was taken as the granule strength of the granule powder.

[0092] CS=2.48×[{CS １ / (πD １ ２ ) + CS ２ / (πD ２ ２ )+ ・・・・+CS １０ / (πD １０ ２ )} / 10] In the above formula, CS is the granule strength [MPa], CS １ ~CS １０ is the compressive strength of each granule particle [mN], and D１ or D １０ is the assumed granule diameter [μm] of each granule particle.

[0093] (Granule Compressibility) The granule compressibility was calculated from the stress-strain curve obtained by the same measurement method as for granule strength, using the following formula.

[0094] Granule compression ratio = indenter displacement when granules are crushed / granule diameter C = {(C １ / D １ +C ２ / D ２ +...+C １０ / D １０ ) / 10}×100 In the above formula, C is the granule compressibility [%], C １ ~C １０ is the distance [μm] that the indenter moves from the zero point (initial position) to the inflection point on the stress-strain curve of each granule particle, and D １ or D １０ is the assumed granule diameter [μm] of each granule particle.

[0095] (Chipping strength and maximum strain) An autograph equipped with a 10 kN load cell (device name: AGS-10KNX STD 0.5 grade, manufactured by Shimadzu Corporation) was used. 15 ± 0.5 g of granular powder was filled into a cylindrical mold with a diameter of 25 mm and uniaxially press-molded at a pressure of 49 MPa to obtain a compact, which was used as the measurement sample. An indenter with a diameter of 1.8 mm was applied along the circumferential direction of the measurement sample, and the pressure at the maximum load when a load was applied at 0.1 mm / min was determined, and the average value of five points was used as the chipping strength. The travel distance of the indenter at that time was used as the maximum strain.

[0096] (Molded body density) 15±0.5 g of the granular powder was filled into a cylindrical mold with a diameter of 25 mm and uniaxially press-molded at a pressure of 49 MPa to obtain a molded body. The mass of the obtained molded body sample was measured with a balance, and the volume was measured with a vernier caliper to determine the dimensions. The actual density was calculated from the obtained mass and volume, and this was used as the molded body density.

[0097] Example 1 A slurry containing alumina-containing yttrium-stabilized zirconia powder and pure water, with an alumina content of 0.05 mass% and an yttrium content of 5.5 mol%, and a slurry containing alumina-containing yttrium-stabilized zirconia powder and pure water, with an alumina content of 0.05 mass% and an yttrium content of 2.5 mol%, were mixed so that the yttrium content was 4.0 mol%, to obtain a mixed slurry. The BET specific surface area of ​​the powder in the mixed slurry was 10.1 m ２ / g.

[0098] The mixed slurry was mixed with 2.0% by mass of an acrylic binder as a binder and pure water to obtain a dried slurry with a solids concentration (mass ratio of powder in the mixed slurry) of 40% by mass. The dried slurry was granulated and dried using an atomizer-type spray dryer equipped with a pin-type disk at a hot air temperature (inlet temperature) of 200°C and an exhaust air temperature (outlet temperature) of 105°C (inlet / outlet temperature difference of 95°C). This resulted in a granular powder made of yttrium-stabilized zirconia containing an acrylic binder and alumina, with a binder content of 2.0% by mass, alumina content of 0.05% by mass, and yttrium content of 4.0 mol%, which was designated as the granular powder of this example. The loose bulk density of the granular powder of this example was 1.22 g / cm. ３ The granule strength was 0.4 MPa and the granule compressibility was 6.1%.

[0099] Comparative Example 1 A granular powder made of yttrium-stabilized zirconia containing an acrylic binder and alumina, with a binder content of 2.0 mass%, alumina content of 0.05 mass%, and yttrium content of 4.0 mol%, was obtained in the same manner as in Example 1, except that the dried slurry was granulated and dried at a hot air temperature of 150°C and an exhaust air temperature of 100°C (inlet / outlet temperature difference: 50°C). The granular powder of this comparative example had a granule strength of 0.3 MPa and a granule compression ratio of 5.5%.

[0100] Example 2 A granular powder made of yttrium-stabilized zirconia containing an acrylic binder and alumina, with a binder content of 3.4 mass%, alumina content of 0.05 mass%, and yttrium content of 4.0 mol%, was obtained in the same manner as in Example 1, except that the mixed slurry, acrylic binder, and pure water were mixed so that the acrylic binder content was 3.4 mass%, to obtain a dried slurry. This was designated as the granular powder of this example. The loose bulk density of the granular powder of this example was 1.28 g / cm. ３ The granule strength was 0.3 MPa and the granule compressibility was 7.9%.

[0101] An SEM image of the granular powder of this example is shown in Figure 1. The granular powder of this example contained, in addition to granular particles having a substantially spherical shape, substantially spherical granular particles having depressions, and granular particles having a crushed substantially spherical shape.

[0102] Example 3 A granular powder made of yttrium-stabilized zirconia containing an acrylic binder and alumina, with a binder content of 2.0 mass%, an alumina content of 0.05 mass%, and an yttrium content of 4.0 mol%, was obtained in the same manner as in Example 1, except that the mixed slurry, an acrylic binder, and pure water were mixed so that the acrylic binder content was 2.0 mass% to obtain a dried slurry, and the dried slurry was granulated and dried with a hot air temperature of 220°C and an exhaust air temperature of 105°C (inlet / outlet temperature difference: 115°C). This was used as the granular powder of this example.

[0103] The results are shown in Table 1.

[0104]

[0105] Example 1 and Comparative Example 1 have the same composition. Nevertheless, compared to Comparative Example 1, where the inlet / outlet temperature difference is 50°C, Example 1, where the inlet / outlet temperature difference is 95°C, has a higher chipping strength, and it was confirmed that the Example produced a molded body that is less prone to defects during handling. Furthermore, the granular powder of Example 1 had a larger maximum strain than the granular powder of Comparative Example 1, and was confirmed to be a granular powder with high crushability during press molding. It was also confirmed that the granular powder of Example 2, which contains a higher binder content, produced a higher molded body density than Example 1. It was also confirmed that Example 1, where the hot air temperature was lower than Example 3, produced a higher chipping strength.

[0106] Example 4 A mixed slurry was obtained by mixing an alumina-containing yttria-stabilized zirconia powder containing 0.25% by weight of alumina and 3.0 mol% by weight of yttria with pure water. The mixed slurry, acrylic binder, and pure water were mixed to obtain a dried slurry with a solids concentration of 48% so that the acrylic binder was 5.0% by weight. The dried slurry was then granulated and dried at a hot air temperature of 185°C and an exhaust air temperature of 125°C (inlet / outlet temperature difference: 60°C). A granulated powder was obtained from yttrium-stabilized zirconia containing an acrylic binder and alumina, with a binder content of 5.0% by weight, alumina content of 0.25% by weight, and yttrium content of 3.0 mol%. This was designated the granulated powder of this example.

[0107] The granular powder of this example had an average granule diameter of 42 μm, a unit absorption peak intensity of 0.038 counts, a granule strength of 0.5 MPa, and a granule compressibility of 13.2%.

[0108] Example 5 Alumina-containing yttrium-stabilized zirconia powder containing 0.05 mass % alumina and 3.0 mol % yttrium was mixed with pure water to obtain a slurry. The BET specific surface area of ​​the powder in the obtained slurry was 12.8 m. ２ / g.

[0109] The obtained slurry was mixed with 2.0 mass% of an acrylic binder and pure water to obtain a dry slurry with a solid content of 40 mass%. In the same manner as in Example 1, except that a granular powder made of yttrium-stabilized zirconia containing an acrylic binder and alumina, with a binder content of 2.0 mass%, an alumina content of 0.05 mass%, and an yttrium content of 3.0 mol%, was obtained, and this was used as the granular powder of this example.

[0110] The granular powder of this example had an average granule size of 45 μm and a unit absorption peak intensity of 0.028 counts.

[0111] In addition, the compact density and maximum strain of the granular powder of this example were similar to those of Example 1, and were 2.85 g / cm ３ and 0.07 mm.

[0112] Example 6 Alumina-containing yttrium-stabilized zirconia powder containing 0.05 mass % alumina and 5.5 mol % yttrium was mixed with pure water to obtain a slurry. The BET specific surface area of ​​the powder in the obtained slurry was 9.7 m. ２ / g.

[0113] The obtained slurry was mixed with 2.0 mass% of an acrylic binder and pure water to obtain a dry slurry with a solid content of 40 mass%. In the same manner as in Example 1, except that a granular powder made of yttrium-stabilized zirconia containing an acrylic binder and alumina, with a binder content of 2.0 mass%, an alumina content of 0.05 mass%, and an yttrium content of 5.5 mol%, was obtained, and this was used as the granular powder of this example.

[0114] The granular powder of this example had an average granule particle size of 43 μm, a unit absorption peak intensity of 0.029 counts, a granule strength of 0.3 MPa, and a granule compressibility of 6.5%.

[0115] In addition, the compact density and maximum strain of the granular powder of this example were similar to those of Example 1, and were 2.84 g / cm ３ and 0.07 mm.

[0116] Example 7 Alumina-containing yttrium-stabilized zirconia powder (product name: 3YS-E, manufactured by Tosoh Corporation) having an alumina content of 0.25 mass% and an yttrium content of 3.0 mol% and a Co—Al—Fe—Zn composite oxide as a black pigment were mixed with pure water to obtain a slurry.

[0117] The resulting slurry was mixed with 5.0% by mass of an acrylic binder and pure water to obtain a dried slurry with a solids concentration of 48% by mass, and the dried slurry was granulated and dried at a hot air temperature of 210 ° C. and an exhaust air temperature of 110 ° C. (inlet / outlet temperature difference 100 ° C.) in the same manner as in Example 1, except that a binder amount of 5.0% by mass, an alumina amount of 0.25% by mass, and an yttrium amount of 3.0 mol% were obtained. A granular powder consisting of yttrium-stabilized zirconia containing an acrylic binder, alumina, and a Co-Al-Fe-Zn composite oxide was obtained, and this was designated as the granular powder of this example. The granular powder of this example had an average granule diameter of 42 μm, a unit absorption peak intensity of 0.035 count, a granule strength of 0.5 MPa, and a granule compressibility of 11.5%.

[0118] Furthermore, the granular powder of this example had a chipping strength of 14.9 MPa and a maximum distortion of 0.15 mm, and it was confirmed that distortion was more likely to occur as the amount of binder increased.

[0119] The entire contents of the specification, claims, drawings and abstract of Japanese Patent Application No. 2023-131187, filed on August 10, 2023, are hereby incorporated by reference as the disclosure of the specification of the present disclosure.

Claims

1. Ceramic powder and binder, and a wavelength of 1730 ± 20 cm in the infrared spectrum per mass of the binder －１ The ceramic granule powder has an absorption peak intensity of 0.023 counts or more having a peak top at 2. The granular powder according to claim 1, wherein the ceramic is zirconia.

3. The granular powder according to claim 2, wherein the zirconia is zirconia containing a stabilizing element.

4. The granular powder according to claim 3, wherein the stabilizing element is one or more selected from the group consisting of yttrium, magnesium, calcium, cerium and erbium.

5. The granular powder according to any one of claims 1 to 4, wherein the binder is at least one of a polyvinylpyrrolidone-based resin and an acrylic-based resin.

6. A granular powder according to any one of claims 1 to 5, wherein the binder content is 0.1% by mass or more and 8% by mass or less.

7. Lightly packed bulk density is 1.10 g / cm ３ The granular powder according to any one of claims 1 to 6.

8. 15±0.5 g of the granular powder was filled into a cylindrical mold having a diameter of 25 mm and press-molded at a pressure of 49 MPa. The measured density was 2.70 g / cm ３ The granular powder according to any one of claims 1 to 7.

9. A method for producing granular powder according to any one of claims 1 to 8, comprising a step of spray-drying a slurry containing ceramic powder, a binder and a solvent at a temperature difference between hot air and exhaust air of 55°C or more.

10. The method according to claim 9, wherein the hot air temperature is 300° C. or less.

11. A method for producing a molded body using the granular powder according to any one of claims 1 to 8.

12. A method for producing a calcined body using the molded body according to claim 11.

13. A method for producing a sintered body using the molded body according to claim 11 or the calcined body according to claim 12.

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