JP2021120337A - Abrasion-resistant agent, coating agent, laminate, method for producing laminate, and method for coating substrate - Google Patents

Abstract

To provide an abrasion-resistant agent having abrasion resistance, a coating agent, a laminate to which the abrasion-resistant agent and the coating agent are applied, a method for producing the laminate, and a method for coating a substrate.SOLUTION: An abrasion-resistant agent containing plate-like alumina particles has a longitudinal relaxation time T1 of 5 seconds or more with respect to a peak of 6-coordinate aluminum of 10 to 30 ppm at a static magnetic field strength of 14.1 T in solid27 Al NMR analysis.SELECTED DRAWING: None

Description

The present invention relates to an abrasion resistant agent, a coating agent, a laminate, a method for producing the laminate, and a method for coating a base material.
The present application claims priority based on US62 / 912,650 provisionally filed in the United States on October 9, 2019, the contents of which are incorporated herein by reference.

It is common to form a coating film such as a resin composition on materials such as flooring materials, building materials, and automobile parts in order to impart wear resistance.

It is known that such a coating material contains inorganic particles in order to improve wear resistance. For example, Patent Document 1 discloses a floor plate in which a coating film made of a synthetic resin composition containing a ceramic fiber piece and a ceramic abrasion resistance improver in a resin is formed on the surface of a base material. Patent Document 2 discloses a fitting member coated with a coating film containing a synthetic resin and inorganic particles.

Japanese Unexamined Patent Publication No. 62-225278 Japanese Unexamined Patent Publication No. 2005-273821

However, there continues to be a demand for additional compositions to achieve the wear resistance effect.

The present invention has been made in view of the above circumstances, and provides an abrasion resistant agent having abrasion resistance, a coating agent, and a laminate to which they are applied, a method for producing the laminate, and a method for coating a base material. offer.

That is, the present invention includes the following aspects.
(1) Solid ²⁷ _{Al NMR analysis shows that the longitudinal relaxation time T 1} for the peak of 6-coordinated aluminum at 10 to 30 ppm at a static magnetic field strength of 14.1 T is 5 seconds or more, and the resistance to contain plate-like alumina particles. Abrasion agent.
(1) The wear-resistant agent according to (1) above, wherein the plate-shaped alumina particles contain silicon and / or germanium.
(3) The wear-resistant agent according to (2) above, wherein the plate-shaped alumina particles contain mullite on the surface layer.
(4) The wear-resistant agent according to any one of (1) to (3) above, wherein the plate-shaped alumina particles contain molybdenum.
(5) The abrasion resistant agent according to (4) above, wherein the content of molybdenum with respect to 100% by mass of the plate-shaped alumina particles is 0.1 or more and 1% by mass or less in terms of molybdenum trioxide.
(6) A coating agent containing the wear-resistant agent according to any one of (1) to (5) above.
(7) A laminate having a base material and a layer containing the coating agent according to (6) above.
(8) A method for producing a laminate, which comprises applying the coating agent according to (6) above to a base material.
(9) A method for coating a base material, which comprises applying the coating agent according to (6) above to the base material.

According to the wear-resistant agent, the coating agent, and the laminate according to the present invention, it is possible to provide the wear-resistant agent, the coating agent, and the laminate capable of exhibiting good wear resistance.
Further, according to the method for producing a laminate according to the present invention, it is possible to produce a laminate capable of exhibiting good wear resistance.
Further, according to the base material coating method according to the present invention, good wear resistance can be imparted to the base material.

Hereinafter, the abrasion resistant agent, the coating agent, the laminate, the method for producing the laminate, and the method for coating the base material according to the embodiment of the present invention will be described in detail.

<Abrasion resistant agent>
The wear-resistant agent according to one embodiment of the present invention (hereinafter, may be referred to as "wear-resistant agent of the embodiment" or simply "wear-resistant agent") contains plate-shaped alumina particles. The plate-shaped alumina particles have _{a longitudinal relaxation time T 1} for a peak of 6-coordinated aluminum of 10 to 30 ppm at a static magnetic field strength of 14.1 T, which is 5 seconds or more, as ^{determined by solid 27 Al NMR analysis.} The plate-shaped alumina particles have an aspect ratio of 5 to 500, and a solid ²⁷ _{Al NMR analysis shows that the longitudinal relaxation time T 1} for the peak of 6-coordinated aluminum at 10 to 30 ppm at a static magnetic field strength of 14.1 T is 5 seconds. The above is preferable.

The plate-like alumina particles contained in the wear-resistant agent of the present embodiment have the above-mentioned structure and have a dense crystal structure, and thus have high hardness. Therefore, the wear-resistant agent of the present embodiment has excellent wear resistance.

<Plate-shaped alumina particles>
The alumina particles of the present embodiment have a plate-like shape, and in solid ²⁷ _{Al NMR analysis, the longitudinal relaxation time T 1} with respect to the peak of 6-coordinated aluminum of 10 to 30 ppm at a static magnetic field strength of 14.1 T is 5. More than a second. The alumina particles of the present embodiment are also referred to as "plate-like alumina particles", "plate-like alumina", or simply "alumina particles".

In the present specification, "plate-like" means that the aspect ratio obtained by dividing the average particle size of the alumina particles by the thickness is 2 or more. In the present specification, "thickness of alumina particles" is an arithmetic of the thickness measured for at least 50 plate-shaped alumina particles randomly selected from images obtained by a scanning electron microscope (SEM). Take the average value. The "average particle size of alumina particles" is a value calculated as _{a volume-based median diameter D 50} from a volume-based cumulative particle size distribution measured by a laser diffraction particle size measuring device.

In the case of alumina particles, the conditions of thickness, particle size, and aspect ratio shown below can be combined in any way as long as they are plate-shaped. Further, the upper limit value and the lower limit value of the numerical range illustrated under these conditions can be freely combined.

The plate-shaped alumina particles preferably have a thickness of 0.01 μm or more and 5 μm or less, preferably 0.03 μm or more and 5 μm or less, preferably 0.05 μm or more and 5 μm or less, and 0.1 μm or more and 3 μm or less. It is more preferable that it is 0.15 μm or more and 1.5 μm or less.
When plate-shaped alumina particles having a larger particle size are used, the thickness is preferably 3 μm or more, and more preferably 5 μm or more and 60 μm or less.
Alumina particles having the above thickness are preferable because they have a high aspect ratio and excellent mechanical strength.

The average particle size (D ₅₀ ) of the plate-shaped alumina particles is preferably 0.1 μm or more and 500 μm or less, more preferably 0.5 μm or more and 100 μm or less, and further preferably 1 μm or more and 50 μm or less.
When plate-shaped alumina particles having a larger particle size are used, the average particle size (D ₅₀ ) is preferably 10 μm or more, more preferably 20 μm or more, more preferably 22 μm or more, and more preferably 25 μm. The above is more preferable, and 31 μm or more is particularly preferable. The upper limit of the above average particle size is not particularly limited, but as an example, the average particle size (D ₅₀ ) of the plate-shaped alumina particles of the embodiment is preferably 10 μm or more and 500 μm or less, and 20 μm or more. It is preferably 300 μm or less, more preferably 22 μm or more and 100 μm or less, further preferably 25 μm or more and 100 μm or less, and particularly preferably 31 μm or more and 50 μm or less.
_{Alumina particles having an average particle size (D 50} ) equal to or higher than the above lower limit value exhibit high wear resistance because the area of the upper surface or the lower surface of the plate-like alumina plate is large. _{Further, alumina particles having an average particle size (D 50} ) equal to or less than the above upper limit value are suitable for blending with a coating agent.

The plate-shaped alumina particles have an aspect ratio of 2 or more and 500 or less, which is a ratio of the average particle size to the thickness, preferably 5 or more and 500 or less, preferably 10 or more and 500 or less, and 13 or more. It is more preferably 300 or less, more preferably 15 or more and 300, and further preferably 20 or more and 100 or less.
When the aspect ratio of the plate-shaped alumina particles is 2 or more, it is preferable because it can have two-dimensional compounding characteristics, and when the aspect ratio of the plate-shaped alumina particles is 500 or less, it is preferable because it is excellent in mechanical strength. When the aspect ratio is 15 or more, high wear resistance is exhibited, which is preferable.
When plate-shaped alumina particles having a larger particle size are used, the aspect ratio, which is the ratio of the average particle size to the thickness, is preferably 2 or more and 50 or less, and more preferably 3 or more and 30 or less.

The plate-shaped alumina particles may have a circular plate shape or an elliptical plate shape, but the particle shape is preferably, for example, a polygonal plate shape from the viewpoint of handleability and ease of manufacture.

The plate-shaped alumina particles may be obtained based on any production method, but are molybdenum compounds (preferably) in that they have a higher aspect ratio, better dispersibility, and better productivity. Further, it is preferably obtained by firing the aluminum compound in the presence of the potassium compound) and the shape control agent. As the shape control agent, it is preferable to use at least one selected from the group consisting of silicon, a silicon compound, and a germanium compound. Since the shape control agent serves as a source of Si for mullite, which will be described later, it is more preferable to use silicon or a silicon compound containing a silicon element.
In the above production method, the molybdenum compound is used as a flux agent. Hereinafter, in the present specification, this production method using a molybdenum compound as a flux agent may be simply referred to as "flux method". The flux method will be described in detail later. By such firing, the molybdate compound reacts with the aluminum compound at a high temperature to form aluminum molybdate, and then when the aluminum molybdate is further decomposed into alumina and molybdenum oxide at a higher temperature, the molybdenum compound becomes a plate. It is considered that the compound is incorporated into the alumina particles. Molybdenum oxide can also be sublimated, recovered and reused.
When the plate-shaped alumina particles contain mullite in the surface layer, in this process, silicon or a compound containing a silicon atom blended as a shape control agent and an aluminum compound react with each other via molybdenum, so that the mullite becomes a plate. It is considered that the alumina particles are formed on the surface layer. More specifically, regarding the formation mechanism of mullite, the formation of Mo-O-Si by the reaction of molybdenum and Si atom and the formation of Mo-O-Al by the reaction of molybdenum and Al atom occur on the surface of the aluminum plate. It is considered that Mo is desorbed and mullite having a Si—O—Al bond is formed by firing at a high temperature.
Molybdenum oxide that is not incorporated into the plate-shaped alumina particles is preferably recovered by sublimation and reused. By doing so, the amount of molybdenum oxide adhering to the surface of the plate-like alumina can be reduced, and molybdenum oxide is mixed in the binder when it is dispersed in a medium to be dispersed such as an organic binder such as resin or an inorganic binder such as glass. It is possible to maximize the original properties of plate-like alumina.
In this specification, those having a sublimable property in the manufacturing method described later are referred to as a flux agent, and those which cannot be sublimated are referred to as a shape control agent.

By utilizing molybdenum and a shape control agent in the production of the plate-shaped alumina particles, the alumina particles have high crystallinity and high α crystallinity, and have an automorphic shape. High wear resistance can be achieved.

When the plate-shaped alumina particles contain mullite in the surface layer, the amount of mullite generated on the surface layer of the plate-shaped alumina particles can be controlled by the usage ratio of the molybdenum compound and the shape control agent, but particularly as a shape control agent. It can be controlled by the ratio of silicon used or a silicon compound containing a silicon element. The preferable value of the amount of mullite generated on the surface layer of the plate-shaped alumina particles and the preferable usage ratio of the raw material will be described in detail later.

The plate-shaped alumina particles are plate-shaped alumina particles having an aspect ratio of 5 to 500 from the viewpoint of improving wear resistance, and are arranged in 6 units of 10 to 30 ppm at a static magnetic field strength of 14.1 T ^{by solid-state 27 Al NMR analysis.} _{It is preferable that the longitudinal relaxation time T 1} with respect to the peak of the aluminum position is 5 seconds or more.

The fact that the longitudinal relaxation time T ₁ is 5 seconds or more means that the crystallinity of the plate-shaped alumina particles is high. It has been reported that when the longitudinal relaxation time in the solid state is large, the symmetry of the crystal is good and the crystallinity is high. Publishing Co., Ltd., p80-82)).

In the plate-shaped alumina particles, the longitudinal relaxation time T ₁ is preferably 5 seconds or longer, more preferably 6 seconds or longer, and even more preferably 7 seconds or longer.
In the plate-shaped alumina particles of the embodiment, _{the upper limit of the longitudinal relaxation time T 1} is not particularly limited, but may be, for example, 22 seconds or less, 15 seconds or less, and 12 seconds. It may be less than a second.
An example of the numerical range of the longitudinal relaxation time T ₁ illustrated above, may be less than 5 seconds and 22 seconds, may be less than 15 seconds 6 seconds, a 12 seconds or less than 7 seconds You may.

For the plate-shaped alumina particles, it is preferable that the peak of 4-coordinated aluminum at 60 to 90 ppm at a static magnetic field strength of 14.1 T is not detected by ^{solid 27 Al NMR analysis.} It is considered that such plate-shaped alumina particles are unlikely to be damaged or dropped due to the distortion of crystal symmetry due to the inclusion of crystals having different coordination numbers, and tend to be superior in shape stability. ..

Conventionally, the degree of crystallinity of an inorganic substance is generally evaluated by the result of XRD analysis or the like. However, according to the studies by the present inventors, it has been found that the evaluation of crystallinity for alumina particles can be performed with more accurate analysis results than the conventional XRD analysis by using _{the above-mentioned longitudinal relaxation time T 1 as an index.} rice field. It can be said that the plate-shaped alumina particles according to the embodiment have a _{large longitudinal relaxation time T 1} of 5 seconds or more, and the crystallinity of the alumina particles is high. That is, it is considered that the plate-like alumina particles according to the embodiment have high crystallinity, so that their chemical stability, strength and hardness are improved, and their wear resistance is excellent.

As compared with spherical alumina particles, it has been difficult to obtain highly crystalline alumina particles in the plate-shaped alumina particles. This is considered to be because, unlike the spherical alumina particles, the plate-shaped alumina particles need to be biased in the direction of crystal growth in the manufacturing process.
On the other hand, the above-mentioned _{plate-shaped alumina particles satisfying the value of the above-mentioned longitudinal relaxation time T 1} have a plate-like shape but high crystallinity. Therefore, it is very useful because it exhibits excellent chemical stability and further has improved coating film stability and mechanical strength.

Further, as an index of the plate shape, the plate-shaped alumina particles of the embodiment have 2θ = 41.6 ± 0 corresponding to the (006) plane of the diffraction peak obtained by the X-ray diffraction measurement using Cu—Kα rays. The ratio of the peak intensity I (006) of .3 degrees to the peak intensity I (113) of 2θ = 43.3 ± 0.3 degrees corresponding to the (113) plane, I (006) / I (113) ( Hereinafter, I (006) / I (113) is abbreviated as (006/113) ratio), but it may be preferably 0.2 or more and 30 or less, more preferably 1 or more and 20 or less, and further preferably 3. More than 10 or less, particularly preferably 7.5 or more and 10 or less. The plate-shaped alumina particles in this case have, for example, an average particle diameter (D ₅₀ ) of 10 μm or more and a thickness of 0.1 μm or more.

A large value of the (006/113) ratio means that the ratio of the (006) plane to the (113) plane is large, and the plane corresponding to the crystal in the orientation of the (006) plane has been remarkably developed. It is understood to mean that it is a flat alumina particle. The flat-plate-shaped alumina particles have a large area of the upper surface or the lower surface developed on the plate-shaped surface of the plate-shaped alumina, and the formation of the surface corresponding to the crystal in the orientation of the (113) plane is suppressed. Even if the mass per particle is small, it exhibits high wear resistance.

The pH of the isoelectric point of the plate-shaped alumina particles is, for example, in the range of 2 to 6, preferably in the range of 2.5 to 5, and more preferably in the range of 3 to 4. Plate-like alumina particles having an isoelectric point pH within the above range have a high electrostatic repulsive force, and by themselves can enhance dispersion stability when blended into the above-mentioned object to be dispersed. Modification by surface treatment such as a coupling treatment agent intended to improve performance becomes easier.

For the pH value of the isoelectric point, measure the zeta potential with a zeta potential measuring device (Zetasizer Nano ZSP, manufactured by Malvern), and use 20 mg of the sample and 10 mL of 10 mM KCl aqueous solution with Rentaro Awatori (Sinky, ARE-310). ) Stir in the stirring / defoaming mode for 3 minutes and allow the supernatant to stand for 5 minutes as the measurement sample, add 0.1N HCl to the sample using an automatic titrator, and measure the zeta potential in the range up to pH = 2. (Applied voltage 100V, Monomodl mode) and evaluate the pH of the isoelectric point where the potential becomes zero.

Tabular alumina particles, for example, a density of not more than 3.70 g / cm ³ or more 4.10 g / cm ^3, preferably a density of less 3.72 g / cm ³ or more 4.10 g / cm ^3, density More preferably, it is 3.80 g / cm ³ or more and 4.10 g / cm ^{3 or less.}
After pretreatment of the plate-like alumina particles under the condition of 300 ° C. for 3 hours, the density was measured using a dry automatic densitometer Accupic II 1330 manufactured by Micromeritix Co., Ltd. at a measurement temperature of 25 ° C. and helium was used as a carrier gas. Can be measured under conditions.

The plate-shaped alumina particles preferably have a specific surface area of, for example, 0.01 m ² / g or more and 50 m ² / g or less, ^{more preferably 0.1 m 2} / g or more and 20 m ² / g or less, and 0. further preferably 5 m ² / g or more ^{10 m} 2 / g or less, even more preferably at most 1.3 m ² / g or more ^{10 m} 2 / g.
The specific surface area can be determined as the surface area per 1 g of plate-shaped alumina particles measured by the nitrogen gas adsorption / desorption method by the BET method.
This specific surface area can be measured by JIS Z 8830: BET 1-point method (adsorbed gas: nitrogen) or the like.

[alumina]
The "alumina" contained in the plate-shaped alumina particles is aluminum oxide, and may be, for example, transition alumina in various crystalline forms such as γ, δ, θ, κ, etc., or alumina hydrate in the transition alumina. However, it is basically preferable to be in the α crystal form (α type) in terms of being more excellent in mechanical strength or thermal conductivity. The α crystal form is a dense crystal structure of alumina, which enhances the mechanical strength and chemical stability of plate-like alumina, which is advantageous for improving wear resistance.
It is preferable that the α crystallization rate is as close to 100% as possible because the original properties of the α crystal form can be easily exhibited. The α crystallization rate of the plate-shaped alumina particles is, for example, 90% or more, preferably 95% or more, and more preferably 99% or more.

[Silicon / Germanium]
The plate-like alumina particles of the embodiment may contain silicon and / or germanium.
The silicon or germanium may be derived from a silicon, a silicon compound, and / or a germanium compound that can be used as a shape control agent. By utilizing these, in the production method described later, plate-shaped alumina particles satisfying the value of the _{longitudinal relaxation time T 1 can be easily produced.}

(silicon)
The plate-like alumina particles of the embodiment may contain silicon. The plate-shaped alumina particles according to the embodiment may contain silicon in the surface layer.
Here, the "surface layer" means within 10 nm from the surface of the plate-shaped alumina particles according to the embodiment. This distance corresponds to the detection depth of XPS used for the measurement in the examples.

In the plate-shaped alumina particles, silicon may be unevenly distributed on the surface layer. Here, "unevenly distributed on the surface layer" means a state in which the mass of silicon per unit volume in the surface layer is larger than the mass of silicon per unit volume in other than the surface layer. The uneven distribution of silicon on the surface layer can be determined by comparing the results of the surface analysis by XPS and the overall analysis by XRF.

The silicon contained in the plate-shaped alumina particles may be a simple substance of silicon or may be silicon in a silicon compound. The plate-shaped alumina particles may _{contain at least one selected from the group consisting of mullite, Si, SiO 2} , SiO, and aluminum silicate produced by reacting with alumina as silicon or a silicon compound, and the above-mentioned substance. May be included in the surface layer. Mullite will be described later.

In the plate-shaped alumina particles, when silicon or a silicon compound containing a silicon element is used as the shape control agent, Si can be detected by XRF analysis. The plate-shaped alumina particles have a molar ratio of Si to Al [Si] / [Al] obtained by XRF analysis, for example, 0.04 or less, preferably 0.035 or less, preferably 0.02 or less. More preferably.
The value of the molar ratio [Si] / [Al] is not particularly limited, but is, for example, 0.003 or more, preferably 0.004 or more, and 0.005 or more. Is more preferable.
The plate-shaped alumina particles have a molar ratio [Si] / [Al] of Si to Al obtained by XRF analysis, for example, 0.003 or more and 0.04 or less, and 0.004 or more and 0.035 or less. Is preferable, and more preferably 0.005 or more and 0.02 or less.
The plate-shaped alumina particles in which the molar ratio [Si] / [Al] values obtained by the XRF analysis are within the above range are well formed in a plate-like shape. In addition, the deposits do not easily adhere to the surface of the plate-shaped alumina particles, and the quality is excellent. The deposits are considered to be _two SiO particles, and it is considered that the formation of mullite on the surface layer of the plate-like alumina particles is saturated and is generated from the excess Si.
When plate-shaped alumina particles having a larger particle size are used, the plate-shaped alumina particles have a molar ratio of Si to Al [Si] / [Al] of 0.0003 or more and 0.01, which is obtained by XRF analysis. It is preferably 0.0005 or more and 0.0025 or less, and more preferably 0.0006 or more and 0.001 or less.

The plate-shaped alumina particles can contain silicon, which corresponds to the silicon compound used in the production method or a silicon compound containing a silicon element. The content of silicon with respect to 100% by mass of the plate-shaped alumina particles is preferably 10% by mass or less, more preferably 0.001 to 5% by mass, and further preferably 0.01 to 4% by mass in terms of silicon dioxide. %, More preferably 0.3 to 2.5% by mass, and particularly preferably 0.6 to 2.5% by mass.
When the silicon content is within the above range, the plate-like shape is satisfactorily formed. In addition, _{deposits that appear to be two} SiO particles do not easily adhere to the surface of the plate-shaped alumina particles, and the quality is excellent.
When plate-shaped alumina particles having a larger particle size are used, the content of silicon with respect to 100% by mass of the plate-shaped alumina particles is preferably 10% by mass or less in terms of silicon dioxide, and more preferably 0. It is 001 to 3% by mass, more preferably 0.01 to 1% by mass, and particularly preferably 0.03 to 0.3% by mass.
The above silicon content can be determined by XRF analysis. The XRF analysis shall be performed under the same conditions as the measurement conditions described in Examples described later, or under compatible conditions in which the same measurement results can be obtained.

(Mullite)
The plate-like alumina particles of the embodiment may contain mullite. By including mullite in the surface layer of the plate-shaped alumina particles, for example, when a coating agent is produced by mixing with a resin, the coating agent has good compatibility with the resin, the adhesion is enhanced by the anchor effect, and the wear resistance is further excellent. Can provide a coating agent. Further, by including mullite having a low Mohs hardness in the surface layer of the plate-shaped alumina particles, it is possible to make it difficult to wear the equipment for producing the coating agent.
When mullite is contained in the surface layer of the plate-shaped alumina particles, a remarkable wear resistance effect and a wear reduction effect of the equipment are exhibited. The "mullite" that the plate-shaped alumina particles may contain in the surface layer is a composite oxide of Al and Si and _{is represented as Al X} Si _{YO z} , but the values of x, y, and z are not particularly limited. A more preferable range is Al ₂ Si ₁ O _{5 to Al 6} Si ₂ O ₁₃ . In the examples described later, the XRD peak intensities were confirmed by Al _2.85 Si ₁ O _6.3 , Al ₃ Si ₁ O _6.5 , Al _3.67 Si ₁ O _7.5 , and Al ₄ It contains _{Si 1} O ₈ or Al ₆ Si ₂ O _13. The plate-shaped alumina particles are Al _2.85 Si ₁ O _6.3 , Al ₃ Si ₁ O _6.5 , Al _3.67 Si ₁ O _7.5 , Al ₄ Si ₁ O ₈ and Al ₆ Si ₂ O. _The surface layer may contain at least one compound selected from the group consisting of 13. Here, the "surface layer" means within 10 nm from the surface of the plate-shaped alumina particles. This distance corresponds to the XPS detection depth. The surface layer of mullite is a very thin layer within 10 nm, and if there are many defects of mullite crystals on the surface and interface, the compatibility with the resin becomes better, and compared with mullite having no or few crystal defects. Further, the wear resistance effect can be remarkably exhibited.
In the plate-shaped alumina particles, it is preferable that mullite is unevenly distributed on the surface layer. Here, "unevenly distributed on the surface layer" means a state in which the mass of mullite per unit volume in the surface layer is larger than the mass of mullite per unit volume in other than the surface layer. The uneven distribution of mullite on the surface layer can be determined by comparing the results of surface analysis by XPS and overall analysis by XRF. By unevenly distributing mullite on the surface layer, the amount of mullite is smaller than that when mullite is present not only on the surface layer but also on other than the surface layer (inner layer). Can be demonstrated.

When the plate-shaped alumina particles according to the embodiment use silicon or a silicon compound containing a silicon element as a shape control agent and the surface layer contains mullite, Si is detected by XPS analysis. When the plate-shaped alumina particles according to the embodiment contain mullite, the value of the molar ratio [Si] / [Al] of Si to Al obtained in XPS analysis is preferably 0.15 or more, and 0. It is more preferably 20 or more, and further preferably 0.25 or more. According to the XPS results, the value of [Si] / [Al] increases as the amount of the _{raw material SiO 2 charged increases, but the value may reach a plateau to some extent.} This is considered to mean that the amount of Si on the plate-shaped alumina particles has become saturated. Therefore, it is considered that the surface of the plate-like alumina particles having a molar ratio [Si] / [Al] of 0.20 or more, particularly 0.25 or more, is covered with mullite. In the above-mentioned coated state, the entire surface of the plate-shaped alumina particles may be coated with mullite, or at least a part of the surface of the plate-shaped alumina particles may be coated with mullite.
The upper limit of the molar ratio [Si] / [Al] in the XPS analysis is not particularly limited, but is preferably 0.4 or less, more preferably 0.35 or less, and 0. It is more preferably 3 or less.
In the plate-shaped alumina particles according to the embodiment, the value of the molar ratio [Si] / [Al] of Si to Al obtained in XPS analysis is preferably 0.15 or more and 0.4 or less, and 0. It is more preferably 20 or more and 0.35 or less, and further preferably 0.25 or more and 0.3 or less.
The plate-like alumina particles in which the molar ratio [Si] / [Al] values obtained in the XPS analysis are in the above range have an appropriate amount of mullite contained in the surface layer, are excellent in quality, and have an abrasion resistance effect. And it is superior in the effect of reducing wear of equipment.
The XPS analysis shall be performed under the same conditions as the measurement conditions described in Examples described later, or under compatible conditions in which the same measurement results can be obtained.
In the present embodiment, in the method for producing plate-like alumina described later _{, silicon compounds containing silicon or silicon elements such as SiO 2} charged are converted into mullite with high efficiency, so that plate-like alumina of excellent quality is obtained. Is obtained.

In the plate-shaped alumina particles according to the embodiment containing mullite, a diffraction peak derived from mullite is detected by XRD analysis. The diffraction peak derived from mullite can be clearly distinguished from the diffraction peak of silicon or a silicon compound containing a silicon element, for example, SiO _2. In the plate-shaped alumina particles according to the embodiment, 2θ is 26.2 ± 0 with respect to the peak intensity of the (104) plane of α-alumina in which 2θ is recognized at 35.1 ± 0.2 °, which is obtained by XRD analysis. The ratio of the peak intensities of mullite observed at .2 ° may be, for example, 0.02 or more, 0.05 or more, or 0.1 or more.
The upper limit of the value of the ratio of the peak intensities is not particularly limited, but is, for example, 0.3 or less, preferably 0.2 or less, and more preferably less than 0.12.
In the plate-like alumina particles according to the embodiment, 2θ is 26.2 ± 0 with respect to the peak intensity of the (104) plane of α-alumina in which 2θ is recognized at 35.1 ± 0.2 °, which is obtained by XRD analysis. The ratio of the peak intensity of mullite observed at .2 ° may be, for example, 0.02 or more and 0.3 or less, 0.05 or more and 0.2 or less, and 0.1 or more and 0.12. It may be less than.

The presence or absence of mullite on the surface of the plate-shaped alumina particles can be analyzed using a wide-angle X-ray diffraction (XRD) apparatus such as Ultima IV manufactured by Rigaku Corporation.
For example, the sample is placed on a holder for a measurement sample having a depth of 0.5 mm, filled flat with a constant load, set in the wide-angle X-ray diffraction (XRD) apparatus, and Cu / Kα ray, 40 kV /. The measurement is performed under the conditions of 40 mA, a scanning speed of 2 degrees / minute, and a scanning range of 10 to 70 degrees.
Let A be the peak height of mullite observed at 2θ = 26.2 ± 0.2 degrees, and B be the peak height of α-alumina on the (104) plane observed at 2θ = 35.1 ± 0.2 degrees. With the baseline value of 2θ = 30 ± 0.2 degrees as C, the presence or absence of mullite can be determined from the following equation. The value of R may be, for example, 0.02 or more, 0.02 or more and 0.3 or less, 0.05 or more and 0.2 or less, and 0.1 or more and 0.12. It may be less than.
R = (AC) / (BC)
(R: Ratio of peak height A of mullite to peak height B of the (104) plane of α-alumina)
The plate-shaped alumina particles in which the value of the ratio of the peak intensities is within the above range have an appropriate amount of mullite, are excellent in quality, and are excellent in wear resistance effect and wear reduction effect of equipment.
The XRD analysis shall be performed under the same conditions as the measurement conditions described in Examples described later, or under compatible conditions in which the same measurement results can be obtained.

Si is detected by XRF analysis in the plate-shaped alumina particles according to the embodiment containing mullite.
The values of the molar ratio [Si] / [Al] obtained by the XRF analysis may be those exemplified above, and the plate-like alumina particles within the above range have an appropriate amount of mullite and are of good quality. Excellent, excellent in wear resistance effect and wear reduction effect of equipment.
The plate-shaped alumina particles according to the embodiment contain silicon corresponding to mullite based on silicon or a silicon compound containing a silicon element used in the production method. The content of silicon with respect to 100% by mass of the plate-shaped alumina particles according to the embodiment may be as exemplified above, and it is preferable that the content of silicon is within the above range because the amount of mullite is appropriate. The silicon content can be determined by XRF analysis.
The XRF analysis shall be performed under the same conditions as the measurement conditions described in Examples described later, or under compatible conditions in which the same measurement results can be obtained.

Further, the mullite on the surface layer may form a mullite layer, or may be in a state in which mullite and alumina are mixed. The interface between mullite and alumina on the surface layer may be in a state where mullite and alumina are in physical contact with each other, or mullite and alumina may form a chemical bond such as Si—O—Al. Compared to the combination of alumina and SiO ₂ , the combination containing alumina and mullite as essential components has a high degree of similarity in constituent atomic composition, and when the flux method is adopted, the above Si—O—Al is based on it. From the viewpoint of easiness of forming chemical bonds such as, alumina and mullite can be more firmly bonded and hard to be peeled off. From this, if the amount of Si is the same level, the combination of alumina and mullite as essential components is more preferable because it can exhibit the wear resistance effect and the wear reduction effect of the equipment for a long period of time. The technical effect of the combination of alumina and mullite as essential components can be expected with either alumina and mullite alone or with alumina, mullite and silica, but if anything, the former two combination is the level of technical effect. Will be higher.

(germanium)
The plate-like alumina particles of the embodiment may contain germanium. Further, the plate-shaped alumina particles may contain germanium in the surface layer. When the plate-shaped alumina particles contain germanium or a germanium compound, for example, when a coating agent is produced by mixing with a resin, the plate-like alumina particles have good compatibility with the resin, and the adhesion is enhanced by the anchor effect, further improving the wear resistance effect. An excellent coating agent can be provided. Further, by containing germanium or a germanium compound having a low Mohs hardness in the surface layer of the plate-shaped alumina particles, it is possible to make the equipment less likely to be worn.
Depending on the raw material used, the plate-like alumina particles can be used as germanium or germanium compounds, for example, Ge, GeO ₂ , GeO, GeCl ₂ , GeBr ₄ , GeI ₄ , GeS ₂ , AlGe, GeTe, GeTe _3, As _2. , GeSe, GeS ₃ As, SiGe, Li ₂ Ge, FeGe, SrGe, GaGe and the like, and at least one selected from the group consisting of oxides thereof and the like may be contained, and the above-mentioned substance is contained in the surface layer. You may be.
The "germanium or germanium compound" contained in the plate-shaped alumina particles and the "raw material germanium compound" used as the shape control agent of the raw material may be the same type of germanium compound. For example, GeO ₂ may be detected in a plate-like alumina particles produced by the addition of raw materials GeO _2.

When the germanium or the germanium compound is contained in the surface layer of the plate-like alumina particles, a remarkable wear resistance effect and a wear reduction effect of the equipment are exhibited. Here, the "surface layer" means within 10 nm from the surface of the plate-shaped alumina particles.
The plate-like alumina particles preferably have germanium or a germanium compound unevenly distributed on the surface layer. Here, "unevenly distributed on the surface layer" means a state in which the mass of germanium or germanium compound per unit volume in the surface layer is larger than the mass of germanium or germanium compound per unit volume other than the surface layer. The uneven distribution of germanium or germanium compound on the surface layer can be determined by comparing the results of surface analysis by XPS and overall analysis by XRF. By unevenly distributing the germanium or germanium compound on the surface layer, the abrasion resistance based on the germanium or germanium compound is smaller and at the same level as compared with the case where the germanium or germanium compound is present not only on the surface layer but also on other than the surface layer (inner layer). The effect and the effect of reducing the wear of the equipment can be exhibited.

When the germanium or the germanium compound is contained in the surface layer of the plate-like alumina particles, a remarkable wear resistance effect and a wear reduction effect of the equipment are exhibited. Here, the "surface layer" means within 10 nm from the surface of the plate-shaped alumina particles according to the embodiment. The surface layer containing germanium is a very thin layer within 10 nm. For example, in the case of germanium dioxide, if there are many defects in the germanium dioxide structure on the surface and the interface, the compatibility with the resin is further improved. Therefore, as compared with germanium dioxide having no or few structural defects, the wear resistance effect and the wear reduction effect of the equipment can be remarkably exhibited.
In the plate-like alumina particles according to the embodiment, it is preferable that germanium or a germanium compound is unevenly distributed on the surface layer. Here, "unevenly distributed on the surface layer" means a state in which the mass of germanium or germanium compound per unit volume in the surface layer is larger than the mass of germanium or germanium compound per unit volume other than the surface layer. The uneven distribution of germanium or germanium compound on the surface layer can be determined by comparing the results of surface analysis by XPS and overall analysis by XRF. By unevenly distributing the germanium or germanium compound on the surface layer, the abrasion resistance based on the germanium or germanium compound is smaller and at the same level as compared with the case where the germanium or germanium compound is present not only on the surface layer but also on other than the surface layer (inner layer). The effect and the effect of reducing the wear of the equipment can be exhibited.

The plate-shaped alumina particles according to the embodiment contain germanium or a germanium compound in the surface layer, so that Ge is detected by XPS analysis. In the plate-shaped alumina particles according to the embodiment, the value of the molar ratio [Ge] / [Al] of Ge to Al obtained in the XPS analysis is preferably 0.005 or more, preferably 0.01 or more. More preferably, it is more preferably 0.02 or more, and particularly preferably 0.03 or more. By increasing the amount of the raw material GeO ₂ charged, the value of [Ge] / [Al] increases, but the value may reach a plateau to some extent. This is considered to mean that the amount of Ge on the plate-shaped alumina particles has become saturated. The entire surface of the plate-shaped alumina particles may be coated with germanium or a germanium compound, or at least a part of the surface of the plate-shaped alumina particles may be coated with germanium or a germanium compound.
The upper limit of the molar ratio [Ge] / [Al] in the XPS analysis is not particularly limited, but may be 0.3 or less, 0.25 or less, or 0.2. It may be less than or equal to, 0.17 or less, or 0.1 or less.
In the plate-shaped alumina particles according to the embodiment, the value of the molar ratio [Ge] / [Al] of Ge to Al obtained in the XPS analysis may be 0.005 or more and 0.3 or less, and 0. It may be 005 or more and 0.25 or less, 0.01 or more and 0.2 or less, 0.02 or more and 0.17 or less, or 0.03 or more and 0.1 or less. May be good.
The plate-like alumina particles in which the molar ratio [Ge] / [Al] values obtained in the XPS analysis are in the above range have an appropriate amount of germanium or germanium compound contained in the surface layer, and have a plate-like shape. Is well formed, excellent in quality, and excellent in wear resistance effect and wear reduction effect of equipment.
The XPS analysis shall be performed under the same conditions as the measurement conditions described in Examples described later, or under compatible conditions in which the same measurement results can be obtained.
In the present embodiment, in the method for producing plate-like alumina described later, a _{raw material germanium compound such as GeO 2} charged as a shape control agent is formed as a layer containing germanium on the surface layer of plate-like alumina with high efficiency. , Excellent quality plate-like alumina can be obtained.

When a germanium compound is used as the shape control agent in the plate-shaped alumina particles according to the embodiment, Ge can be detected by XRF analysis. In the plate-shaped alumina particles according to the embodiment, the molar ratio of Ge to Al [Ge] / [Al] obtained by XRF analysis is, for example, 0.08 or less, preferably 0.05 or less, and is 0. It is more preferably 0.03 or less.
The value of the molar ratio [Ge] / [Al] is not particularly limited, but is, for example, 0.0005 or more, preferably 0.001 or more, and 0.0015 or more. Is more preferable.
The plate-shaped alumina particles according to the embodiment have a molar ratio of Ge to Al [Ge] / [Al] obtained by XRF analysis, for example, 0.0005 or more and 0.08 or less, 0.003) 1 or more and 0. It is preferably 0.05 or less, and more preferably 0.0015 or more and 0.03 or less.
The plate-like alumina particles in which the molar ratio [Ge] / [Al] values obtained by the XRF analysis are within the above range have an appropriate amount of germanium or germanium compound contained, and the plate-like shape is good. It is formed in the above, has excellent quality, and is excellent in wear resistance effect and wear reduction effect of equipment.

The plate-shaped alumina particles contain germanium corresponding to the raw material germanium compound used in the production method. The content of germanium with respect to 100% by mass of the plate-shaped alumina particles is preferably 10% by mass or less, more preferably 0.001 to 5% by mass, and further preferably 0.01 in terms of germanium dioxide. It is ~ 4% by mass, and particularly preferably 0.1 to 3.0% by mass. When the content of germanium is within the above range, the amount of germanium or germanium compound is appropriate, and a plate-like shape is satisfactorily formed, which is preferable. The germanium content can be determined by XRF analysis.
The XRF analysis shall be performed under the same conditions as the measurement conditions described in Examples described later, or under compatible conditions in which the same measurement results can be obtained.

Further, the germanium or the germanium compound on the surface layer may form a layer, or may be a state in which the germanium or the germanium compound and alumina are mixed. The interface between the germanium or the germanium compound and the alumina on the surface layer may be in a state where the germanium or the germanium compound and the alumina are in physical contact with each other, and the germanium or the germanium compound and the alumina are chemically bonded to each other such as Ge-O-Al. May be formed.

[molybdenum]
The plate-like alumina particles of the embodiment may contain molybdenum. Further, the plate-shaped alumina particles preferably contain molybdenum in the surface layer thereof.
The molybdenum may be derived from the molybdenum compound used as the flux agent in the method for producing alumina particles described later.

Molybdenum has a catalytic function and an optical function. Further, by utilizing molybdenum, plate-like alumina particles having a plate-like shape but high crystallinity and excellent wear resistance can be produced by a production method described later.

By increasing the amount of molybdenum used, the particle size and the above-mentioned (006/113) ratio values are satisfied, and the abrasion resistance of the obtained alumina particles tends to be further improved. Furthermore, by utilizing molybdenum, the formation of mullite is promoted, and plate-like alumina particles having a high aspect ratio and excellent wear resistance can be produced.

The molybdenum is not particularly limited, and includes molybdenum metal, molybdenum oxide, a partially reduced molybdenum compound, molybdate, and the like.
It may be contained in the plate-like alumina particles in any or a combination of possible polymorphs of the molybdenum compound, and is contained in the plate-like alumina particles as α-MoO ₃ , β-MoO ₃ , MoO ₂ , MoO, molybdenum cluster structure and the like. May be.

The molybdenum-containing form is not particularly limited, and may be contained in a form of adhering to the surface of the plate-shaped alumina particles, or may be contained in a form of being replaced with a part of aluminum having a crystal structure of alumina. , These may be a combination thereof.

The content of molybdenum with respect to 100% by mass of plate-shaped alumina particles obtained in the XRF analysis is preferably 10% by mass or less in terms of molybdenum trioxide, and the firing temperature, firing time, and sublimation rate of the molybdenum compound are adjusted. By doing so, it is more preferably 0.001 to 5% by mass, further preferably 0.01 to 5% by mass, further preferably 0.1 to 1.5% by mass, and particularly preferably 0. It is 1 to 1% by mass. When the molybdenum content is 10% by mass or less, it is preferable because it improves the α single crystal quality of alumina.
When plate-shaped alumina particles having a larger particle diameter are used, the content of molybdenum with respect to 100% by mass of the plate-shaped alumina particles according to the embodiment is preferably 10% by mass or less in terms of molybdenum trioxide, and is fired. By adjusting the temperature, firing time, and sublimation rate of the molybdenum compound, it is more preferably 0.1 to 5% by mass, and further preferably 0.3 to 1% by mass.
The molybdenum content can be determined by XRF analysis. The XRF analysis shall be performed under the same conditions as the measurement conditions described in Examples described later, or under compatible conditions in which the same measurement results can be obtained.

Further, the analysis of the amount of Mo on the surface of the alumina particles can be performed using the above-mentioned X-ray photoelectron spectroscopy (XPS) apparatus.

[potassium]
The plate-shaped alumina particles may further contain potassium.

Potassium may be derived from potassium that can be used as a flux agent in the method for producing alumina particles described later.
By utilizing potassium, the particle size of the alumina particles can be appropriately improved in the method for producing alumina particles described later.

The potassium is not particularly limited, but includes potassium oxide, a partially reduced potassium compound, and the like, in addition to potassium metal.

The form of potassium is not particularly limited, and even if it is contained in a form of adhering to the surface of flat alumina of plate-like alumina particles, it is contained in a form of being replaced with a part of aluminum having a crystal structure of alumina. It may be a combination of these.

Acquired in XRF analysis, the content of potassium to the alumina particles 100 mass%, with potassium oxide _(K 2 O) in terms, preferably at least 0.01 wt%, 0.01 to 1.0 mass %, More preferably 0.03 to 0.5% by mass, and particularly preferably 0.05 to 0.3% by mass. Alumina particles having a potassium content within the above range are preferable because they have a plate-like shape and a value such as an average particle size is suitable.

(Other atoms)
Other atoms are those intentionally added to alumina particles for the purpose of imparting mechanical strength or electrical or magnetic functions as long as the effects of the present invention are not impaired.

Examples of other atoms include, but are not limited to, zinc, manganese, calcium, strontium, yttrium and the like. These other atoms may be used alone or in combination of two or more.

The content of other atoms in the alumina particles is preferably 5% by mass or less, more preferably 2% by mass or less, based on the mass of the alumina particles.

[Inevitable impurities]
Alumina particles may contain unavoidable impurities.

Inevitable impurities are derived from metal compounds used in manufacturing, are present in raw materials, or are inevitably mixed with alumina particles in the manufacturing process. It means impurities that do not affect the characteristics of alumina particles.

The unavoidable impurities are not particularly limited, and examples thereof include magnesium, calcium, strontium, barium, scandium, yttrium, lanthanum, cerium, and sodium. These unavoidable impurities may be contained alone or in combination of two or more.

The content of unavoidable impurities in the alumina particles is preferably 10,000 ppm or less, more preferably 1000 ppm or less, and even more preferably 10 to 500 ppm, based on the mass of the alumina particles.

[Organic compounds]
In one embodiment, the plate-like alumina particles may contain an organic compound. The organic compound exists on the surface of the plate-shaped alumina particles and has a function of adjusting the surface physical characteristics of the plate-shaped alumina particles. For example, since the plate-shaped alumina particles having an organic compound on the surface have an improved affinity with the resin, the function of the plate-shaped alumina particles can be maximized as an abrasion resistant agent.

The organic compound is not particularly limited, and examples thereof include organic silane, alkylphosphonic acid, and polymer.

Examples of the organic silane include methyltrimethoxysilane, dimethyldimethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, iso-propyltrimethoxysilane, and iso-propyltri. Alkyltrimethoxysilanes or alkyltrichlorosilanes with alkyl groups from 1 to 22 such as ethoxysilane, pentiltrimethoxysilane, hexyltrimethoxysilane, 3,3,3-trifluoropropyltrimethoxysilane, trideca Fluoro-1,1,2,2-tetrahydrooctyl) trichlorosilanes, phenyltrimethoxysilanes, phenyltriethoxysilanes, p-chloromethylphenyltrimethoxysilanes, p-chloromethylphenyltriethoxysilanes and the like can be mentioned.

Examples of the phosphonic acid include methylphosphonic acid, ethylphosphonic acid, propylphosphonic acid, butylphosphonic acid, pentylphosphonic acid, hexylphosphonic acid, heptylphosphonic acid, octylphosphonic acid, decylphosphonic acid, dodecylphosphonic acid, octadecylphosphonic acid, and the like. Examples thereof include 2_ethylhexylphosphonic acid, cyclohexylmethylphosphonic acid, cyclohexylethylphosphonic acid, benzylphosphonic acid, phenylphosphonic acid and dodecylbenzenephosphonic acid.

As the polymer, for example, poly (meth) acrylates can be preferably used. Specifically, polymethyl (meth) acrylate, polyethyl (meth) acrylate, polybutyl (meth) acrylate, polybenzyl (meth) acrylate, polycyclohexyl (meth) acrylate, polyt-butyl (meth) acrylate, polyglycidyl (meth). Acrylate, polypentafluoropropyl (meth) acrylate and the like, and general-purpose polymers such as polystyrene, polyvinyl chloride, polyvinyl acetate, epoxy resin, polyester, polyimide and polycarbonate can be mentioned.

The organic compound may be contained alone or may contain two or more kinds.

The contained form of the organic compound is not particularly limited, and may be linked to alumina by a covalent bond or may be coated with alumina.

The content of the organic compound is preferably 20% by mass or less, more preferably 10% by mass or more and 0.01% by mass or less, based on the mass of the alumina particles. When the content of the organic compound is 20% by mass or less, it is preferable because the physical properties derived from the plate-like alumina particles can be easily expressed.

<Manufacturing method of plate-shaped alumina particles>
The method for producing the plate-shaped alumina particles is not particularly limited, and known techniques can be appropriately applied, but from the viewpoint that alumina having a high α crystallization rate at a relatively low temperature can be preferably controlled, it is preferable. A production method by the flux method using a molybdenum compound can be applied.

More specifically, a preferred method for producing plate-like alumina particles includes a step of firing an aluminum compound (calcination step) in the presence of a molybdenum compound and a shape control agent. The firing step may be a step of firing the mixture obtained in the step of obtaining the mixture to be fired (mixing step).

[Mixing process]
The mixing step is a step of mixing an aluminum compound, a molybdenum compound, and a shape control agent to form a mixture. The mixture preferably further contains a potassium compound. The contents of the mixture will be described below.

(Aluminum compound)
The aluminum compound is a raw material for the plate-like alumina particles of the present embodiment, and is not particularly limited as long as it becomes alumina by heat treatment. For example, aluminum chloride, aluminum sulfate, basic aluminum acetate, aluminum hydroxide, boehmite, etc. Pseudo-boemite, transition alumina (γ-alumina, δ-alumina, θ-alumina, etc.), α-alumina, mixed alumina having two or more kinds of crystal phases, etc. can be used, and the shape and particles of the aluminum compound as these precursors. The physical form such as diameter and specific surface area is not particularly limited.

According to the flux method described in detail below, the shape of the aluminum compound may be, for example, spherical, amorphous, a structure with an aspect (wire, fiber, ribbon, tube, etc.), a sheet, or the like. Can be used.

Similarly, according to the flux method described in detail below, a solid aluminum compound having a particle size of several nm to several hundred μm can be preferably used.

The specific surface area of the aluminum compound is also not particularly limited. Since the molybdenum compound acts effectively, it is preferable that the specific surface area is large, but any specific surface area can be used as a raw material by adjusting the firing conditions and the amount of the molybdenum compound used.

Further, the aluminum compound may be composed of only the aluminum compound or may be a complex of the aluminum compound and the organic compound. For example, an organic / inorganic composite obtained by modifying an aluminum compound with an organic silane, an aluminum compound composite on which a polymer is adsorbed, or the like can be preferably used. When these complexes are used, the content of the organic compound is not particularly limited, but from the viewpoint of efficiently producing plate-like alumina particles, the content is preferably 60% by mass or less, and is preferably 30. It is more preferably mass% or less.

(Shape control agent)
A shape control agent can be used to form the plate-like alumina particles according to the embodiment. The shape control agent plays an important role in the plate-like crystal growth of alumina by calcining the alumina compound in the presence of the molybdenum compound.

The state of existence of the shape control agent is not particularly limited, and for example, a shape control agent, an aluminum compound and a physical mixture, and a complex in which the shape control agent is uniformly or localized on the surface or inside of the aluminum compound are preferably used. be able to.

Further, the shape control agent may be added to the aluminum compound, but may be contained as an impurity in the aluminum compound.

The shape control agent plays an important role in plate crystal growth. In the molybdenum oxide flux method, molybdenum oxide reacts with an aluminum compound to form aluminum molybdate, and then the change in chemical potential in the process of decomposition of this aluminum molybdate is the driving force for crystallization. Hexagonal bipyramidal polyhedron particles with a developed automorphic surface (113) are formed. In the production method of the embodiment, the shape control agent is localized near the particle surface in the α-alumina growth process, so that the growth of the automorphic surface (113) is significantly inhibited, and as a result, the plane direction is relatively relative. It is considered that the crystal orientation of the (001) plane or the (006) plane grows faster and the plate-like morphology can be formed. By using the molybdenum compound as a flux agent, plate-like alumina particles containing molybdenum having a high α crystallization rate can be more easily formed.

It should be noted that the above mechanism is only speculative, and even if the effect of the present invention is obtained by a mechanism different from the above mechanism, it is included in the technical scope of the present invention.

The type of shape control agent is selected from the group consisting of silicon, silicon compounds, and germanium compounds because it is possible to produce plate-shaped alumina particles having a higher aspect ratio, better dispersibility, and better productivity. It is preferable to use at least one of these. Silicon or a silicon compound and a germanium compound can be used in combination. From the viewpoint of being a supplier of Si for mullite and being able to efficiently produce mullite, it is preferable to use silicon or a silicon compound containing a silicon element as a shape control agent. Further, it is preferable to use a germanium compound as a shape control agent from the viewpoint that plate-shaped alumina particles having a higher aspect ratio and a larger particle size can be produced than when silicon or a silicon compound is used.
By the above-mentioned flux method using silicon or a silicon compound as a shape control agent, plate-like alumina particles containing mullite in the surface layer can be easily produced.
Plate-like alumina particles containing germanium or a germanium compound can be easily produced by the above-mentioned flux method using a raw material germanium compound as a shape control agent.

-Silicon or silicon compound The silicon compound containing silicon or a silicon element is not particularly limited, and known compounds can be used. Specific examples of silicon compounds containing silicon or silicon elements include artificial synthetic silicon compounds such as metallic silicon, organic silane, silicon resin, silica fine particles, silica gel, mesoporous silica, SiC, and mulite; and natural silicon compounds such as biosilica. Can be mentioned. Of these, organic silane, silicone resin, and silica fine particles are preferably used from the viewpoint of being able to form a composite and a mixture with an aluminum compound more uniformly. The silicon compound containing silicon or a silicon element may be used alone or in combination of two or more. In addition, it may be used in combination with other shape control agents as long as the effects in the present invention are not impaired.

The shape of silicon or a silicon compound containing a silicon element is not particularly limited, and for example, spherical, amorphous, aspected structures (wires, fibers, ribbons, tubes, etc.), sheets, and the like can be preferably used.

-Germanium compound The raw material germanium compound used as a shape control agent is not particularly limited, and known ones can be used. Specific examples of the raw material germanium compound include germanium metal, germanium dioxide, germanium monoxide, germanium tetrachloride, and an organic germanium compound having a Ge—C bond. The raw material germanium compound may be used alone or in combination of two or more. In addition, it may be used in combination with other shape control agents as long as the effects in the present invention are not impaired.

The shape of the raw material germanium compound is not particularly limited, and for example, a spherical, amorphous, aspected structure (wire, fiber, ribbon, tube, etc.), a sheet, or the like can be preferably used.

(Molybdenum compound)
The molybdenum compound contains a molybdenum element and functions as a flux agent in the α crystal growth of alumina, as will be described later.
The molybdenum compound is not particularly limited, and examples thereof include molybdenum oxide and a compound containing an _{acid root anion (MoO x} ^{n-) in which a molybdenum metal is bonded to oxygen.}

The compound containing the acid radical anion (MoO _x ^n-), is not particularly limited, molybdate, sodium molybdate, potassium molybdate, lithium _{molybdate, H 3 PMo 12 O 40,} H 3 SiMo 12 O 40, Examples _{include NH 4} Mo ₇ O ₁₂ , molybdenum disulfide and the like.

It is also possible to include silicon in the molybdenum compound, in which case the molybdenum compound containing silicon serves as both a flux agent and a shape control agent.

Among the above-mentioned molybdenum compounds, it is preferable to use molybdenum oxide from the viewpoint of easy sublimation and cost. Further, the above-mentioned molybdenum compound may be used alone or in combination of two or more.

Further, potassium molybdate _{(K 2 Mo n O 3n +} 1, n = 1~3) is for containing potassium may also have a function as described below potassium compound. In the production method of the embodiment, using potassium molybdate as a flux agent is synonymous with using a molybdenum compound and a potassium compound as a flux agent.

(Potassium compound)
A potassium compound may be further used in combination with the shape control agent.
The potassium compound is not particularly limited, but is limited to potassium chloride, potassium chlorate, potassium chlorate, potassium sulfate, potassium hydrogen sulfate, potassium sulfite, potassium hydrogen sulfite, potassium nitrate, potassium carbonate, potassium hydrogen carbonate, potassium acetate, potassium oxide. , Potassium bromide, potassium bromide, potassium hydroxide, potassium silicate, potassium phosphate, potassium hydrogen phosphate, potassium sulfide, potassium hydrogen sulfide, potassium molybdate, potassium tungstate and the like. At this time, the potassium compound contains an isomer as in the case of the molybdenum compound. Of these, potassium carbonate, potassium hydrogencarbonate, potassium oxide, potassium hydroxide, potassium chloride, potassium sulfate, and potassium molybdate are preferably used, and potassium carbonate, potassium hydrogencarbonate, potassium chloride, potassium sulfate, and potassium molybdenate are used. It is more preferable to use it.

The above-mentioned potassium compounds may be used alone or in combination of two or more.

The potassium compound contributes to the efficient formation of mullite on the surface layer of alumina. In addition, the potassium compound contributes to the efficient formation of a layer containing germanium on the surface layer of alumina.

The potassium compound is also preferably used as a flux agent together with the molybdenum compound.

Of the above, potassium molybdate contains molybdenum, and therefore may also have a function as the above-mentioned molybdenum compound. When potassium molybdate is used as a flux agent, the same action as when a molybdenum compound and a potassium compound are used as a flux agent can be obtained.

As a potassium compound used during the preparation of raw materials or generated in the reaction of the temperature rising process during firing, a water-soluble potassium compound, for example, potassium molybdenumate, does not vaporize even in the firing temperature range and can be easily recovered by washing after firing. The amount of the molybdenum compound released to the outside of the firing furnace is also reduced, and the production cost can be significantly reduced.

When a molybdenum compound and a potassium compound are used as a flux agent, the molar ratio of the molybdenum element to the potassium element of the potassium compound (molybdenum element / potassium element) is preferably 5 or less, preferably 0.01 to 3. It is more preferable, and 0.5 to 1.5 is more preferable because the production cost can be further reduced. When the molar ratio (molybdenum element / potassium element) is within the above range, plate-like alumina particles having a large particle size can be obtained, which is preferable.

(Metal compound)
The metal compound may have a function of promoting crystal growth of alumina, as will be described later. The metal compound can be used at the time of firing, if desired. Since the metal compound has a function of promoting the crystal growth of α-alumina, it is not essential for the production of the plate-shaped alumina particles according to the present invention.

The metal compound is not particularly limited, but preferably contains at least one selected from the group consisting of Group II metal compounds and Group III metal compounds.

Examples of the Group II metal compound include magnesium compounds, calcium compounds, strontium compounds, barium compounds and the like.

Examples of the Group III metal compound include scandium compounds, yttrium compounds, lanthanum compounds, and cerium compounds.

The above-mentioned metal compound means an oxide, a hydroxide, a carbon oxide, or a chloride of a metal element. For example, in the case of a yttrium compound, yttrium oxide (Y ₂ O ₃ ), yttrium hydroxide, and yttrium carbonate can be mentioned. Of these, the metal compound is preferably an oxide of a metal element. In addition, these metal compounds contain isomers.

Of these, the metal compound of the 3rd period element, the metal compound of the 4th period element, the metal compound of the 5th period element, and the metal compound of the 6th period element are preferable, and the metal compound of the 4th period element and the metal compound of the 4th period element. It is more preferably a metal compound of a 5-period element, and even more preferably a metal compound of a 5-period element. Specifically, it is preferable to use a magnesium compound, a calcium compound, an yttrium compound, and a lanthanum compound, more preferably a magnesium compound, a calcium compound, and an yttrium compound, and particularly preferably to use an yttrium compound.

The addition rate of the metal compound is preferably 0.02 to 20% by mass, more preferably 0.1 to 20% by mass, based on the mass conversion value of the aluminum atom in the aluminum compound. When the addition rate of the metal compound is 0.02% by mass or more, the crystal growth of α-alumina containing molybdenum can proceed favorably, which is preferable. On the other hand, when the addition rate of the metal compound is 20% by mass or less, plate-like alumina particles having a low content of impurities derived from the metal compound can be obtained, which is preferable.

[yttrium]
When the aluminum compound is fired in the presence of the yttrium compound as the metal compound, crystal growth proceeds more preferably in this firing step, and α-alumina and a water-soluble yttrium compound are produced. At this time, since the water-soluble yttrium compound is likely to be localized on the surface of α-alumina, which is a plate-shaped alumina particle, if necessary, washing with water, alkaline water, a warm liquid or the like is performed. This makes it possible to remove the yttrium compound from the plate-like alumina particles.

The amount of the above aluminum compound, molybdenum compound, silicon or silicon compound, germanium compound, potassium compound and the like is not particularly limited, but for example, when the total amount of the raw material converted to oxide is 100% by mass, the following mixture is fired. To do.
1) In _{terms of Al 2} O ₃ , preferably 50% by mass or more of aluminum compound, more preferably 70% by mass or more and 99% by mass or less of aluminum compound, and further preferably 80% by mass or more and 94.5% by mass or less of aluminum compound. When,
In _{terms of MoO 3} , preferably 40% by mass or less of molybdenum compound, more preferably 0.5% by mass or more and 20% by mass or less of molybdenum compound, and further preferably 1% by mass or more and 7% by mass or less of molybdenum compound.
In terms of _{SiO 2 or GeO 2} , preferably 0.1% by mass or more and 10% by mass or less of silicon, silicon compound or germanium compound, more preferably 0.5% by mass or more and less than 7% by mass of silicon, silicon compound or germanium. Compounds, more preferably 0.8% by mass or more and 4% by mass or less of silicon, silicon compounds, or germanium compounds.
, A mixed mixture.

More from the viewpoint of obtaining a large plate-like alumina particles with a particle size, in the mixture, MoO ₃ terms, preferably 40 wt% 7 wt% or more of the following molybdenum compounds, more preferably 9% by weight to 30% by weight It is preferable to use the following molybdenum compounds, more preferably 10% by mass or more and 17% by mass or less.

From the viewpoint of obtaining plate-shaped alumina particles having a larger particle size, in the above mixture, in _{terms of SiO 2} and / or GeO ₂ , the amount is preferably 0.4% by mass or more and less than 10% by mass, more preferably 0. It is preferable to use 5% by mass or more and 10% by mass or less, particularly preferably 1% by mass or more and 3% by mass or less of silicon, a silicon compound and / or a germanium compound.

The silicon, silicon compound and / or germanium compound of the shape control agent may be silicon or a silicon compound, or may be a germanium compound.
As the above-mentioned shape control agent, only silicon or a silicon compound may be used, only a germanium compound may be used, or only silicon or a silicon compound and a germanium compound may be used in combination.
When a germanium compound is used as the shape control agent, when the total amount of the raw material converted to oxide is 100% by mass, it is preferably 0.4% by mass or more and less than 1.5% by mass, more preferably in terms of _{GeO 2.} A germanium compound of 0.7% by mass or more and 1.2% by mass or less may be blended in the mixture.

The above conditions for the raw material composition (mass%) may be freely combined for each raw material, and the lower limit value and the upper limit value for each raw material composition (mass%) can also be freely combined.

The use of various compounds within the above range, satisfy the vertical values of relaxation time T ₁ of the above can be easily produced excellent tabular alumina particles wear resistance.

Wherein said mixture, if further containing the above potassium compounds, the amount of the potassium compound is not particularly limited, a raw material total amount in terms oxide upon 100% by weight, preferably from 5% by mass K _{2 O} in terms Hereinafter, a potassium compound of 0.01% by mass or more and 3% by mass or less, more preferably 0.05% by mass or more and 1% by mass or less can be mixed.
It is considered that potassium molybdate formed by the reaction with the molybdenum compound by the use of the potassium compound exerts the effect of Si diffusion and contributes to the promotion of mullite formation on the surface of the plate-shaped alumina particles.
Similarly, it is considered that potassium molybdate formed by the reaction with the molybdenum compound by the use of the potassium compound exerts the effect of diffusing the raw material germanium and contributes to the promotion of the formation of germanium or the germanium compound on the surface of the plate-shaped alumina particles.
As a potassium compound used during the preparation of raw materials or generated in the reaction of the temperature rising process during firing, a water-soluble potassium compound, for example, potassium molybdenumate, does not vaporize even in the firing temperature range and can be easily recovered by washing after firing. The amount of the molybdenum compound released to the outside of the firing furnace is also reduced, and the production cost can be significantly reduced.

In the flux method, it is also preferable to use a molybdenum compound and a potassium compound as a flux agent.
The compound containing molybdenum and potassium as a flux agent can be produced, for example, from a molybdenum compound and a potassium compound, which are cheaper and more easily available, in the firing process. Here, the case where the molybdenum compound and the potassium compound are used as the flux agent, the case where the compound containing molybdenum and potassium is used as the flux agent, and the case where both are used together and the molybdenum compound and the potassium compound are used as the flux agent are taken as an example. explain.

From the viewpoint of obtaining plate-shaped alumina particles having a larger particle size, the amount of the aluminum compound, molybdenum compound, potassium compound, and silicon or silicon compound used is 100% by mass based on the total amount of the raw material converted into oxide. In some cases, it can be preferably as follows.
2) Aluminum compound of 10% by mass or more in terms of _{Al 2} O ₃ , molybdenum compound of 20% by mass or more in terms of _{MoO 3} , potassium compound of 1% by mass or more in terms of _{K 2} O, and 1% by mass in terms of _{SiO 2.} A mixture of less than silicon or a silicon compound.
In terms of being able to further increase the content of high-quality hexagonal plate-shaped alumina, the following mixture can be more preferably used when the total amount of the raw material converted to oxide is 100% by mass.
3) An aluminum compound of 20% by mass or more and 70% by mass or less in terms of _{Al 2} O ₃ , a molybdenum compound of 30% by mass or more and 80% by mass or less in terms of _{MoO 3} , and 5% by mass or more and 30% by mass in terms of _{K 2 O.} A mixture of the following potassium compounds and silicon or a silicon compound of 0.001% by mass or more and 0.3% by mass or less in terms of _{SiO 2.}
In terms of being able to further increase the content of hexagonal plate-shaped alumina, the following mixture can be more preferably used when the total amount of the raw material converted to oxide is 100% by mass.
4) An aluminum compound of 25% by mass or more and 40% by mass or less in terms of _{Al 2} O ₃ , a molybdenum compound of 45% by mass or more and 70% by mass or less in terms of _{MoO 3} , and 10% by mass or more and 20% by mass in terms of _{K 2 O.} A mixture of the following potassium compounds and silicon or a silicon compound of 0.01% by mass or more and 0.1% by mass or less in terms of _{SiO 2.}
In order to maximize the content of hexagonal plate-shaped alumina and to promote crystal growth more preferably, the following mixture can be particularly preferably used.
5) upon the 100% by mass in terms of oxide raw material total volume, _Al 2 _{O 3} and 40 mass% of aluminum compound more than 35 wt% in terms of, MoO ₃ in terms of the following 65 wt% 45 wt% or more of molybdenum compound and, _{K 2} O potassium 10 to 20 mass% in terms of compound, mixture with SiO ₂ silicon 0.02 wt% or more 0.08 mass% or less in terms or silicon compound, was mixed.

By blending various compounds in the above range, it is possible to produce plate-shaped alumina particles having a plate shape, a large particle size, and more excellent wear resistance. In particular, by increasing the amount of molybdenum used and decreasing the amount of silicon used to some extent, the particle size and crystallite diameter can be further increased, and hexagonal plate-shaped alumina particles can be easily obtained. By blending various compounds in the above-mentioned more preferable range, hexagonal plate-shaped alumina particles can be easily obtained, the content thereof can be further increased, and the obtained alumina particles have further excellent wear resistance. Tends to be.

When the mixture further containing the above yttrium compound, the amount of the yttrium compound is not particularly limited, a raw material total amount in terms oxide upon 100 mass%, 5 mass preferably in terms _of Y ₂ O ₃ % Or less, more preferably 0.01% by mass or more and 3% by mass or less of the yttrium compound can be mixed. To advance the crystal growth more suitably, more preferably, upon the raw material total amount in terms oxide is 100 mass%, the Y ₂ O ₃ in terms of at least 0.1 wt% 1 wt% or less of yttrium compound Can be mixed.

The numerical range of the amount of each raw material used can be appropriately combined as long as the total content thereof does not exceed 100% by mass.

[Baking process]
The firing step is a step of firing an aluminum compound in the presence of a molybdenum compound and a shape control agent. The firing step may be a step of firing the mixture obtained in the mixing step.

Plate-like alumina particles can be obtained, for example, by firing an aluminum compound in the presence of a molybdenum compound and a shape control agent. As mentioned above, this manufacturing method is called the flux method.

The flux method is classified as a solution method. More specifically, the flux method is a method of crystal growth utilizing the fact that the crystal-flux two-component phase diagram shows a eutectic type. The mechanism of the flux method is presumed to be as follows. That is, as the mixture of solute and flux is heated, the solute and flux become a liquid phase. At this time, since the flux is a flux, in other words, since the solute-flux two-component phase diagram shows a eutectic type, the solute melts at a temperature lower than its melting point to form a liquid phase. It becomes. If the flux is evaporated in this state, the concentration of the flux decreases, in other words, the effect of the flux on lowering the melting point of the solute is reduced, and the evaporation of the flux acts as a driving force to cause crystal growth of the solute (flux). Evaporation method). The solute and flux can also cause crystal growth of the solute by cooling the liquid phase (slow cooling method).

The flux method has merits such as being able to grow a crystal at a temperature much lower than the melting point, being able to precisely control the crystal structure, and being able to form a crystal having an automorphic shape.

In the production of α-alumina particles by the flux method using a molybdenum compound as the flux, the mechanism is not always clear, but it is presumed that the mechanism is as follows, for example. That is, when the aluminum compound is fired in the presence of the molybdenum compound, aluminum molybdate is first formed. At this time, the aluminum molybdate grows α-alumina crystals at a temperature lower than the melting point of alumina, as can be understood from the above description. Then, for example, alumina particles can be obtained by accelerating crystal growth through decomposition of aluminum molybdate, evaporation of flux, and the like. That is, the molybdenum compound functions as a flux, and α-alumina particles are produced via an intermediate called aluminum molybdate.

In the production of α-alumina particles by the flux method when a potassium compound is further used as the flux agent, the mechanism is not always clear, but it is presumed that the mechanism is as follows, for example. First, the molybdenum compound and the aluminum compound react to form aluminum molybdate. Then, for example, aluminum molybdate is decomposed into molybdenum oxide and alumina, and at the same time, the molybdenum compound containing molybdenum oxide obtained by the decomposition reacts with the potassium compound to form potassium molybdate. The plate-like alumina particles according to the embodiment can be obtained by crystal growth of alumina in the presence of the molybdenum compound containing potassium molybdate.

By the above-mentioned flux method, _{plate-like alumina particles satisfying the above-mentioned value of the longitudinal relaxation time T 1} and having excellent wear resistance can be produced.

The firing method is not particularly limited, and can be performed by a known and commonly used method. When the firing temperature exceeds 700 ° C., the aluminum compound reacts with the molybdenum compound to form aluminum molybdate. Further, when the firing temperature becomes 900 ° C. or higher, aluminum molybdate is decomposed and plate-like alumina particles are formed by the action of the shape control agent. Further, in the plate-shaped alumina particles, it is considered that the molybdenum compound is incorporated into the aluminum oxide particles when the aluminum molybdate decomposes into alumina and molybdenum oxide.
Further, when the firing temperature is 900 ° C. or higher, it is considered that the molybdenum compound (for example, molybdenum trioxide) obtained by decomposing aluminum molybdate reacts with the potassium compound to form potassium molybdate.
_{Further, when the firing temperature becomes 1000 ° C. or higher, Al 2} O _{3 on the} surface of the plate-shaped alumina particles reacts with SiO ₂ along with the crystal growth of the plate-shaped alumina particles in the presence of molybdenum to form mullite with high efficiency. it is conceivable that.
Similarly, when the firing temperature is 1000 ° C. or higher, in the presence of molybdenum, along with crystal growth of the plate-shaped alumina particles, Al ₂ O _{3 on the} surface of the plate-shaped alumina particles reacts with the Ge compound, and germanium dioxide and Ge are highly efficient. It is considered to form a compound or the like having −O—Al.

Further, at the time of firing, the states of the aluminum compound, the shape control agent, and the molybdenum compound are not particularly limited, and the molybdenum compound and the shape control agent may exist in the same space where they can act on the aluminum compound. Specifically, it may be a simple mixing of the powder of the molybdenum compound, the shape control agent and the aluminum compound, a mechanical mixing using a crusher or the like, or a mixing using a mortar or the like, and is in a dry state. , May be mixed in a wet state.

The conditions of the firing temperature are not particularly limited, and _{the value of the vertical relaxation time T 1} of the target plate-shaped alumina particles, the value of the (006/113) ratio, the average particle size, the aspect ratio, the formation of mullite, and the dispersibility. Etc., and it is determined as appropriate. Generally, the maximum firing temperature _{is preferably 900 ° C or higher, which is the decomposition temperature of aluminum molybdenate (Al 2} (MoO ₄ ) ₃ ), and 1000 ° C or higher, at which mullite or germanium compounds are formed with high efficiency. It is preferable that the longitudinal relaxation time T ₁ is 1200 ° C. or higher at which plate-like alumina particles having a longitudinal relaxation time T 1 of 5 seconds or longer (highly crystalline) can be easily obtained.

Generally, in order to control the shape of α-alumina obtained after firing, it is necessary to perform high-temperature firing at 2000 ° C. or higher, which is close to the melting point of α-alumina. There is a big problem for industrial use.

The production method of the embodiment can be carried out even at a high temperature of more than 2000 ° C., but even at a temperature of 1600 ° C. or lower, which is considerably lower than the melting point of α-alumina, α regardless of the shape of the precursor. It is possible to form α-alumina having a plate-like shape having a high crystallization rate and a high aspect ratio.

According to one embodiment of the present invention, even when the maximum firing temperature is 900 to 1600 ° C., plate-like alumina particles having a high aspect ratio and an α crystallization rate of 90% or more can be formed at low cost. It can be performed efficiently, firing at a maximum temperature of 950 to 1500 ° C. is more preferable, firing in a maximum temperature range of 1000 to 1400 ° C. is further preferable, and firing at a maximum temperature of 1200 to 1400 ° C. is most preferable. ..

Regarding the firing time, it is preferable that the heating time to the predetermined maximum temperature is performed in the range of 15 minutes to 10 hours, and the holding time at the maximum firing temperature is performed in the range of 5 minutes to 30 hours. In order to efficiently form the plate-shaped alumina particles, it is more preferable that the firing holding time is about 10 minutes to 15 hours.
By selecting the conditions of the maximum temperature of 1000 to 1400 ° C. and the firing holding time of 10 minutes to 15 hours, dense α-crystal-shaped polygonal plate-shaped alumina particles are difficult to aggregate and can be easily obtained.
By selecting the conditions of the maximum temperature of 1200 to 1400 ° C. and the firing holding time of 10 minutes to 15 hours _{, plate-like alumina particles having the longitudinal relaxation time T 1} of 5 seconds or more (high crystallinity) can be easily obtained. ..

The atmosphere of firing is not particularly limited as long as the effects of the present invention can be obtained, but for example, an oxygen-containing atmosphere such as air or oxygen or an inert atmosphere such as nitrogen, argon or carbon dioxide is preferable, and the cost aspect is improved. When considered, the air atmosphere is more preferable.

The device for firing is not necessarily limited, and a so-called firing furnace can be used. The firing furnace is preferably made of a material that does not react with sublimated molybdenum oxide, and it is preferable to use a highly airtight firing furnace so that molybdenum oxide can be used efficiently.

The alumina particles are preferably obtained by firing the aluminum compound in the presence of the molybdenum compound and the shape control agent, or in the presence of the molybdenum compound, the shape control agent, the potassium compound and the metal oxide.

That is, a preferred method for producing alumina particles includes a step of firing an aluminum compound (calcination step) in the presence of a molybdenum compound and a shape control agent, or in the presence of a molybdenum compound, a shape control agent, and a potassium compound. The mixture preferably further contains the above metal compound. As the metal compound, a yttrium compound is preferable.

[Cooling process]
When the molybdenum compound and the potassium compound are used as the flux agent, the method for producing the alumina particles may include a cooling step. The cooling step is a step of cooling the alumina crystal-grown in the firing step. More specifically, it may be a step of cooling the composition containing the alumina and the liquid phase flux agent obtained in the firing step.

The cooling rate is not particularly limited, but is preferably 1 to 1000 ° C./hour, more preferably 5 to 500 ° C./hour, and even more preferably 50 to 100 ° C./hour. When the cooling rate is 1 ° C./hour or more, the production time can be shortened, which is preferable. On the other hand, when the cooling rate is 1000 ° C./hour or less, the firing container is less likely to be cracked by heat shock and can be used for a long time, which is preferable.

The cooling method is not particularly limited, and a cooling device may be used even if it is naturally allowed to cool.

[Post-treatment process]
The method for producing plate-shaped alumina particles according to the embodiment may include a post-treatment step. The post-treatment step is a post-treatment step for the plate-shaped alumina particles and is a step of removing the flux agent. The post-treatment step may be performed after the above-mentioned firing step, after the above-mentioned cooling step, or after the firing step and the cooling step. Moreover, you may repeat it twice or more if necessary.

Post-treatment methods include cleaning and high temperature treatment. These can be done in combination.

The cleaning method is not particularly limited, but it can be removed by cleaning with water, an aqueous ammonia solution, an aqueous sodium hydroxide solution, or an acidic aqueous solution.

At this time, the molybdenum content can be controlled by appropriately changing the concentrations of the water used, the aqueous ammonia solution, the aqueous sodium hydroxide solution, and the acidic aqueous solution, the amount used, the cleaning site, the cleaning time, and the like.

Further, as a method of high temperature treatment, a method of raising the temperature above the sublimation point or boiling point of the flux can be mentioned.

[Crushing process]
In the fired product, plate-like alumina particles may aggregate and may not meet the suitable particle size range. Therefore, the plate-shaped alumina particles may be pulverized so as to satisfy a suitable particle size range, if necessary.
The method for crushing the fired product is not particularly limited, and conventionally known crushing methods such as ball mills, jaw crushers, jet mills, disc mills, spectromills, grinders, and mixer mills can be applied.

[Classification process]
The plate-shaped alumina particles are preferably classified in order to adjust the average particle size, improve the fluidity of the powder, or suppress the increase in viscosity when blended in a binder for forming a matrix. .. The "classification process" refers to an operation of grouping particles according to the size of the particles.
The classification may be either wet or dry, but from the viewpoint of productivity, the dry classification is preferable. Dry classification includes classification by sieving and wind classification by the difference between centrifugal force and fluid drag. From the viewpoint of classification accuracy, wind classification is preferable, and an air flow classer using the Coanda effect. This can be performed using a classifier such as a swirling air flow type classifier, a forced vortex centrifugal classifier, or a semi-free vortex centrifugal classifier.
The above-mentioned pulverization step and classification step can be performed at a necessary stage including before and after the organic compound layer forming step described later. For example, the average particle size of the obtained plate-shaped alumina particles can be adjusted by the presence or absence of pulverization and classification and selection of the conditions thereof.

As for the plate-shaped alumina particles of the embodiment or the plate-shaped alumina particles obtained by the production method of the embodiment, those having little or no agglomeration are likely to exhibit their original properties and are superior in their own handleability. It is preferable from the viewpoint of being more excellent in dispersibility when it is used by being dispersed in a medium to be dispersed. In the method for producing plate-shaped alumina particles, if the above-mentioned pulverization step or classification step is not performed and a substance having little or no aggregation is obtained, it is not necessary to perform the step on the left, and the desired properties are excellent. It is preferable because the plate-like alumina having the above can be produced with high productivity.

[Organic compound layer forming step]
In one embodiment, the method for producing plate-like alumina particles may further include an organic compound layer forming step. The organic compound layer forming step is usually performed after the firing step or the post-treatment step.

The method for forming the organic compound layer is not particularly limited, and a known method can be appropriately adopted. For example, a method of bringing a liquid containing an organic compound into contact with plate-like alumina particles containing molybdenum and drying the particles can be mentioned.

As the organic compound that can be used for forming the organic compound layer, for example, the above-mentioned ones can be used.

<Coating agent>
The wear resistant agent of the present embodiment is suitably blended in the coating agent. As one embodiment of the present invention, a coating agent containing the wear resistant agent of the embodiment (hereinafter, may be referred to as "coating agent of the embodiment" or simply "coating agent") can be provided. The coating agent is preferably used for materials such as flooring materials, building materials, and automobile parts, and is particularly preferably used for flooring materials.

The coating agent of the present embodiment may contain various optional components in addition to the above-mentioned plate-shaped alumina particles, if necessary. Examples of the optional component include a solvent, a resin, a drying accelerator, a curing agent, a curing accelerator, a thickener, an anti-settling agent, an anti-repellent agent, an anti-sagging agent, a spreading agent, an antifoaming agent, and an ultraviolet absorber. , Light stabilizers, other pigments that do not correspond to the above-mentioned plate-shaped alumina particles, and the like.
Examples of other pigments that do not correspond to the plate-shaped alumina particles include various pigments such as coloring pigments and extender pigments.
As the coloring pigment, conventionally known pigments can be appropriately used according to the desired hue and performance. For example, azo-based, benzimidazolone-based, isoindolinone / isoindoline-based, phthalocyanine-based, quinacridone-based, and dioxazine. Organic pigments such as diketopyrrolopyrrole, quinophthalone, perylene / perinone, thioindigo, anthraquinone, slene, etc., and inorganic pigments such as iron oxide, carbon black, titanium oxide, zinc sulfide, etc. Examples of the extender pigment include barium sulfate, calcium carbonate, talc, kaolin and the like.
Further, various metals such as zinc powder and aluminum powder or metal salts may be used in combination.

As one embodiment of the present invention, a coating agent containing the plate-shaped alumina particles of the embodiment, a solvent, and a resin can be provided.

From the viewpoint of reducing the viscosity of the coating agent and facilitating the application, it is preferable that the coating agent contains a solvent. The solvent can disperse the plate-shaped alumina particles. The solvent can disperse or dissolve the above optional components.
Examples of the solvent include alcohol solvents such as ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol and isobutyl alcohol; ester solvents such as ethyl acetate, propyl acetate and butyl acetate, methyl ethyl ketone and methyl butyl ketone. Ketone solvents such as cyclohexanone; ether ester solvents such as methyl cellosolve acetate and butyl cellosolve acetate; amide solvents such as dimethylformamide and dimethylacetamide; aromatic hydrocarbon solvents such as toluene and xylene; hexane, heptane, white spirits and the like The aliphatic hydrocarbon solvent of the above; a mixed solvent of aromatic hydrocarbons such as mineral spirit and an aliphatic hydrocarbon; water, a mixture thereof and the like, but are not limited thereto.

The content ratio of the solvent with respect to the total mass 100% by mass of the coating agent may be, for example, 3 to 90% by mass, or 5 to 85% by mass.

The content ratio of the solid content (component excluding volatile components such as solvent) to 100% by mass of the total mass of the coating agent may be, for example, 10 to 97% by mass, or 15 to 95% by mass.

It is preferable that the coating agent contains a resin from the viewpoint of binding the plate-shaped alumina particles contained in the coating agent to each other and enhancing the adhesion between the base material and the coating agent.
As the resin, any resin that can be blended in the paint can be used, and conventionally known resins may be used. Examples of the resin include acrylic resin, polyester resin, alkyd resin, urethane resin, epoxy resin, vinyl chloride copolymer resin, polyamide resin, melamine resin, cellulose resin and the like. As the resin, one type may be used alone, or two or more types may be used in combination.
The content ratio of the resin (solid content) in the coating agent may be 5% by mass or more with respect to 100% by mass of the total mass of the solid content (component excluding volatile components such as solvent) of the coating agent. It may be 10 to 97% by mass, or 30 to 80% by mass.

From the viewpoint of effectively improving the wear resistance, the content ratio of the plate-like alumina particles in the coating agent may be 1 to 15% by mass or more with respect to 100% by mass of the total mass of the coating agent. It may be 10% by mass, 2.5 to 8% by mass, or 3 to 7% by mass.

The coating agent of the present embodiment can be produced, for example, by a method including mixing the above-mentioned plate-shaped alumina particles and, if necessary, the above-mentioned optional components. Examples of the mixer that can be used at that time include a sand mill, a homomixer, a homogenizer, a colloid mill, a microfluidizer, a sonolator, and a cavitron.

<Laminated body>
The base material coated with the coating agent of the embodiment can be provided as a laminate having the base material and the layer containing the coating agent of the embodiment. Such a laminate is a useful one in which the base material is endowed with abrasion resistance. Examples of the layer containing the coating agent include a cured product of the coating agent of the embodiment. The cured product of the coating agent can be formed, for example, by drying or heat-curing the coating film of the coating agent applied to the base material at room temperature.

As an example, the dry film thickness of the layer containing the above coating agent is preferably 50 to 700 μm, more preferably 60 to 300 μm. When the dry film thickness is within the above range, wear resistance is satisfactorily exhibited.

The base material is not particularly limited, and examples thereof include a resin base material and a metal base material, and more specifically, materials such as flooring materials, building materials, and automobile parts can be exemplified.

<Method>
The coating agent of this embodiment can be applied to a base material and used. That is, in one embodiment, the present invention provides a method for producing a laminate, which comprises applying the coating agent to a substrate. According to the method for producing a laminate of the present embodiment, the above-mentioned laminate having wear resistance can be produced.
The method of applying the coating agent is not particularly limited, and can be applied by roll coating, spray, brush, spatula, bar coater, or dip coating. As a post-treatment method after painting, normal temperature drying to heat curing can be performed. The heating temperature for heat curing is preferably in the range of 50 to 250 ° C, particularly preferably in the range of 60 to 230 ° C. The heating time is preferably in the range of 2 to 30 minutes, particularly preferably in the range of 5 to 20 minutes.

As described above, the coating agent of the present embodiment has an appropriate hardness and good wear resistance by containing the plate-shaped alumina particles.
Further, when the plate-shaped alumina particles contain mullite in the surface layer, the adhesion with the resin is improved and the wear resistance is further improved.

Hereinafter, the present invention will be described with reference to Examples, but the present invention is not limited to the following Examples.

<Synthesis of plate-shaped alumina particles>
[Synthesis Example 1] Synthesis of plate-shaped alumina particles 145.2 g of aluminum hydroxide (manufactured by Nippon Light Metal Co., Ltd., average particle diameter 2 μm), 0.90 g of silicon dioxide (manufactured by Kanto Chemical Co., Inc., special grade), and molybdenum trioxide. (Manufactured by Taiyo Koko Co., Ltd.) 4.7 g and was mixed in a dairy pot to obtain a mixture. The obtained mixture was placed in a crucible, heated to 1200 ° C. in a ceramic electric furnace under the condition of 5 ° C./min, and held at 1200 ° C. for 10 hours for firing. Then, the temperature was lowered to room temperature under the condition of 5 ° C./min, and then the crucible was taken out to obtain 98.0 g of a light blue powder. The obtained powder was crushed in a mortar until it passed through a 106 μm sieve.
Subsequently, 98.0 g of the obtained light blue powder was dispersed in 150 mL of 0.5% aqueous ammonia, the dispersion solution was stirred at room temperature (25 to 30 ° C.) for 0.5 hours, and then the aqueous ammonia was filtered. The particles were washed with water and dried to remove molybdenum remaining on the particle surface, and 95.0 g of a light blue powder was obtained. It was confirmed by SEM observation that the obtained powder had a polygonal plate shape, very few aggregates, and plate-shaped particles having excellent handleability. Furthermore, when XRD measurement was performed, sharp peak scattering derived from α-alumina appeared, and alumina crystal system peaks other than the α crystal structure were not observed, and it was confirmed that the plate-like alumina had a dense crystal structure. .. The pregelatinization rate was 99% or more (almost 100%). Furthermore, from the results of the fluorescent X-ray quantitative analysis, it was found that the obtained particles contained 0.2% by mass of molybdenum in terms of molybdenum trioxide and 0.70% by mass of silicon in terms of silicon dioxide. confirmed. The molar ratio [Si] / [Al] of Si to Al determined from the XPS analysis result was 0.23. The molar ratio [Si] / [Al] of Si to Al determined from the XRF analysis result was 0.007. _{The longitudinal relaxation time T 1} for the peak of 6-coordinated aluminum was 9 seconds.

[Synthesis Example 2] Synthesis of plate-shaped alumina particles _{7.0 g of aluminum sulfate (manufactured by Kanto Chemical Co., Inc., Al 2} (SO ₄ ) ₃ , 14-18 crystalline water) and potassium sulfate (manufactured by Kanto Chemical Co., Inc., K ₂₎ SO ₄ ) 10 g was uniformly mixed to obtain a mixture. The obtained mixture was placed in a crucible, heated in a ceramic electric furnace at 5 ° C./min to 950 to 1100 ° C., and held at 950 to 1100 ° C. for 5 hours for firing. Then, the temperature was lowered to room temperature at 5 ° C./min, and then the crucible was taken out to obtain 11.5 g of white powder. Subsequently, the obtained white powder was washed with water and dried to obtain plate-like alumina.

<Evaluation of plate-like alumina particles obtained in the synthetic example>
[Measurement of particle size L]
Using the plate-shaped alumina particles obtained in the synthesis example as a sample, using a laser diffraction type particle size distribution meter HELOS (H3355) & RODOS (manufactured by Nippon Laser Co., Ltd.), the median diameter D ₅₀ (with a dispersion pressure of 3 bar and a pulling pressure of 90 mbar). μm) was determined and the particle size was L.

[Measurement of thickness D]
For the prepared sample, the average value obtained by measuring the thickness of 50 pieces using a scanning electron microscope (SEM) was adopted, and the thickness was taken as D (μm).

[Aspect ratio L / D]
The aspect ratio of the plate-shaped alumina particles was calculated using the following formula.

Aspect ratio = average particle size of plate-shaped alumina particles L / thickness of plate-shaped alumina particles D

[Measurement of specific surface area]
The prepared sample was pretreated under the condition of 300 ° C. for 3 hours, and then the specific surface area of the pretreated sample was measured using TriStar3000 manufactured by Micromeritics.

[Analysis of XRD peak intensity ratio and presence / absence of mullite]
The prepared sample is placed on a holder for a measurement sample having a depth of 0.5 mm, filled flat with a constant load, and set in a wide-angle X-ray diffraction (XRD) apparatus (Ultima IV manufactured by Rigaku Co., Ltd.). The measurement was performed under the conditions of Cu / Kα ray, 40 kV / 40 mA, a scan speed of 2 degrees / minute, and a scanning range of 10 to 70 degrees.
Let A be the peak height of mullite observed at 2θ = 26.2 ± 0.2 degrees, and B be the peak height of α-alumina on the (104) plane observed at 2θ = 35.1 ± 0.2 degrees. With the baseline value of 2θ = 30 ± 0.2 degrees as C, the presence or absence of mullite was determined from the following formula.
When the value was 0.02 or more, mullite was judged to be "yes", and when the value was less than 0.02, mullite was judged to be "absent".

[Analysis of pregelatinization rate]
Place the prepared sample on a holder for a measurement sample with a depth of 0.5 mm, fill it so that it becomes flat with a constant load, set it in a wide-angle X-ray diffractometer (Ultima IV manufactured by Rigaku Co., Ltd.), and use Cu / Kα rays. The measurement was performed under the conditions of 40 kV / 40 mA, a scan speed of 2 degrees / minute, and a scanning range of 10 to 70 degrees. The pregelatinization rate was calculated from the ratio of the strongest peak heights of α-alumina and transition alumina.

[Amount of Si on the surface layer of plate-shaped alumina particles]
Using the X-ray photoelectron spectroscopy (XPS) device Quantera SXM (ULVAC-PHI), the prepared sample was press-fixed on double-sided tape, and the composition was analyzed under the following conditions.

(Measurement condition)
・ X-ray source: monochromatic AlKα, beam diameter 100 μmφ, output 25 W ・ Measurement: area measurement (1000 μm square), n = 3
-Charge correction: C1s = 284.8eV

[Si] / [Al] obtained from the XPS analysis results was defined as the amount of Si in the surface layer of the plate-shaped alumina particles.

[Analysis of the amount of Si contained in the plate-shaped alumina particles]
Using a fluorescent X-ray (XRF) analyzer Primus IV (manufactured by Rigaku Co., Ltd.), about 70 mg of the prepared sample was taken on a filter paper and covered with a PP film for composition analysis.
[Si] / [Al] obtained from the XRF analysis result was defined as the amount of Si in the plate-shaped alumina particles.
The amount of silicon determined from the XRF analysis result was determined by silicon dioxide conversion (mass%) with respect to 100% by mass of plate-shaped alumina particles.

[Analysis of the amount of Mo contained in plate-shaped alumina]
Using a fluorescent X-ray analyzer Primus IV (manufactured by Rigaku Co., Ltd.), about 70 mg of the prepared sample was taken on a filter paper, covered with a PP film, and the composition was analyzed.
The amount of molybdenum determined from the XRF analysis result was determined by molybdenum trioxide conversion (mass%) with respect to 100% by mass of plate-like alumina particles.

[Measurement of coordination number by NMR]
^{A solid 27} Al NMR analysis was performed using JEM-ECA600 manufactured by JEOL RESONANCE at a static magnetic field strength of 14.1 T. Each sample was collected in a φ4 mm solid-state NMR sample tube and measured. After measuring the 90-degree pulse width for each sample, relaxation time measurement and single pulse measurement by the saturation recovery method were performed.

When the peak top of 6-coordinated aluminum of the commercially available reagent γ-alumina (Kanto Chemical Co., Ltd.) is 14.6 ppm, the peak detected at 10 to 30 ppm is the peak of 6-coordinated aluminum, and the peak detected at 60 to 90 ppm. Was estimated to be the peak of 4-coordinated aluminum.

The conditions are as follows.
・ MAS rate: 15kHz
-Probe: SH60T4 (manufactured by JEOL RESONANCE)

The measurement conditions for single pulse measurement at 14.1T are as follows.
-Pulse delinquency time (seconds): _{(T 1} (seconds) x 3 obtained by the relaxation recovery method)
-Pulse width (μsec): 90 degree pulse width (μsec) of 6-coordinated aluminum of each sample / 3
・ Number of integrations: 8 times ・ Temperature: 46 ℃

[Measurement of longitudinal relaxation time _{T 1} by NMR]
The relaxation recovery method in 14.1 T, was determined longitudinal relaxation time _{T 1} to the peak of the 6-coordinated aluminum was detected in 10 to 30 ppm.

The conditions are as follows.
-Pulse delinquency time (seconds): 0.5
・ Waiting time after saturation (seconds): 0.5 to 100, Exponetic interval 16 points ・ Number of integrations: 1 time ・ Temperature: 46 ° C

Table 1 shows the oxide-equivalent formulation of the raw material compound (the total is 100% by mass) and the above evaluation results. In Table 1, "ND" is an abbreviation for not detected and indicates that it is not detected.

<Preparation of coating agent>
[Example 1]
Centrifugal stirring of the plate-shaped alumina particles obtained in Synthesis Example 1 and the cellulose acetate butyrate resin solution (solid content concentration: 32%) at a ratio of plate-shaped alumina particles: cellulose butyrate acetate resin solution = 1/19. It was put into a machine (manufactured by Fractec) and stirred at 3000 rpm for 1 minute to obtain a coating agent (A1).

[Comparative Example 1]
A coating agent (A2) was obtained in the same manner as in Example 1 except that the plate-shaped alumina particles obtained in Synthesis Example 1 were changed to the plate-shaped alumina particles obtained in Synthesis Example 2.

[Comparative Example 2]
The plate-shaped alumina particles were not mixed with the cellulose acetate resin solution (solid content concentration: 32%) to prepare a coating agent (A3).

<Evaluation of wear resistance>
The coating agent obtained in each example was applied onto a paper substrate so as to have a film thickness of 76.2 μm to obtain a test piece. Attach the obtained test piece to the test stand of the Sutherland type wear tester, attach plain paper to a 2 kg weight, reciprocate the weight 50 times so as to rub the plain paper against the test piece, and then wear resistance according to the following criteria. Gender was evaluated. The results are shown in Table 2.
◯: The surface of the test piece was almost not damaged.
Δ: The scratches on the surface of the test piece were conspicuous.
X: The surface of the test piece was full of scratches.

From the results shown in Table 2, it was confirmed that the coating agent of Example 1 had better wear resistance than the coating agents of Comparative Examples 1 and 2.

Each configuration in each embodiment and a combination thereof are examples, and the configuration can be added, omitted, replaced, and other changes are possible without departing from the spirit of the present invention. Moreover, the present invention is not limited to each embodiment, but is limited only to the scope of claims.

According to the wear-resistant agent of the present embodiment, it is possible to provide a wear-resistant agent having good wear resistance.

Claims (9)

Solid ^{27 An} wear resistant agent containing plate-like alumina particles, which has _{a longitudinal relaxation time T 1} for a peak of 10 to 30 ppm 6-coordinated aluminum at a static magnetic field strength of 14.1 T in 5 seconds or more in Al NMR analysis. The wear-resistant agent according to claim 1, wherein the plate-shaped alumina particles contain silicon and / or germanium. The wear-resistant agent according to claim 2, wherein the plate-shaped alumina particles contain mullite on the surface layer. The wear-resistant agent according to any one of claims 1 to 3, wherein the plate-shaped alumina particles contain molybdenum. The wear-resistant agent according to claim 4, wherein the content of molybdenum with respect to 100% by mass of the plate-shaped alumina particles is 0.1 or more and 1% by mass or less in terms of molybdenum trioxide. A coating agent containing the wear resistant agent according to any one of claims 1 to 5. A laminate having a base material and a layer containing the coating agent according to claim 6. A method for producing a laminate, which comprises applying the coating agent according to claim 6 to a base material. A method for coating a base material, which comprises applying the coating agent according to claim 6 to the base material.