Dyed powder, paint composition, water-repellent film and water-repellent member, and method for manufacturing the dyed powder and water-repellent member.

Abstract

To provide dyeing powder capable of enhancing a degree of design freedom, a coating composition, a water repellent film and a water repellent member, as well as, a manufacturing method of the dyeing powder and the water repellent member.SOLUTION: Dyeing powder contains alumina as a main component and has a plurality of long particles having an elongated shape, and an inorganic dye compound is incorporated in the long particles. A method for manufacturing the dyeing powder includes a step of firing a plurality of precursor particles having the elongated shape containing at least one of alumina and aluminum hydroxide at 500°C or more and 1100°C or less to obtain a plurality of fired particles containing alumina as a main component, having the elongated shape and provided with meso fine pores, and a dyeing step for incorporating an inorganic dye compound into the meso fine pores of the plurality of the fired particles.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to dyeing powders, paint compositions, water-repellent coatings and water-repellent members, and methods for manufacturing dyeing powders and water-repellent members. [Background technology]

[0002] Water-repellent materials have low surface wettability and can easily repel water droplets that adhere to their surface. When a material's surface is water-repellent, water droplets easily slide off, making water-repellent materials suitable for materials that require waterproofing. In particular, the phenomenon in which the contact angle between the material's surface and the water droplet is 150° or more is called superhydrophobicity. Since it is difficult to achieve superhydrophobicity when the material's surface is smooth, it has been proposed to create irregularities on the material's surface.

[0003] Patent Document 1 discloses a component obtained by curing a composition containing a curable silicone rubber component and a filler. The filler has a three-dimensional shape with a core and needle-like portions extending from the core in four different axial directions, and the mass ratio of the filler content to the total content of the curable silicone rubber component and the filler in the composition is 0.70 or more. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2019-210401 [Overview of the project] [Problems that the invention aims to solve]

[0005] In the embodiment of Patent Document 1, the contact angle between the component surface and the water droplet is approximately 150°, confirming that the component has excellent water repellency. However, conventional fillers often exhibit a white appearance due to light scattering caused by their three-dimensional shape, which may limit design freedom.

[0006] The present invention has been made in view of the problems of such conventional technologies. And an object of the present invention is to provide a dyeing powder, a coating composition, a water-repellent film and a water-repellent member capable of enhancing the degree of freedom of design, and a method for producing the dyeing powder and the water-repellent member.

Means for Solving the Problems

[0007] The dyeing powder according to the first aspect of the present invention contains alumina as a main component and includes a plurality of long particles having a long shape, and an inorganic dye compound is incorporated into the long particles In this case, between the center of the long particle and the outer surface of the long particle therein.

[0008] The coating composition according to the second aspect of the present invention contains alumina as a main component, includes a plurality of long particles having a long shape, a solvent, and a water-repellent resin dissolved in the solvent, and a dye compound is incorporated into the long particles In this case, between the center of the long particle and the outer surface of the long particle [[ID=1,6]]therein.

[0009] The water-repellent film according to the third aspect of the present invention contains alumina as a main component, includes an aggregate including a plurality of long particles having a long shape and a coating layer formed of a water-repellent resin covering the surfaces of the plurality of long particles, and a dye compound is incorporated into the long particles In this case, between the center of the long particle and the outer surface of the long particle therein, the aggregate is such that a plurality of long particles are three-dimensionally aggregated, the outer surface of the aggregate is covered by the coating layer, and the aggregate holds a space communicating with the outside between the plurality of long particles covered by the coating layer.

[0010] The water-repellent member according to the fourth aspect of the present invention includes a base material and a water-repellent film covering the surface of the base material.

[0011] The method for producing a dyeing powder according to the fifth aspect of the present invention includes at least one of alumina and aluminum hydroxide, firing a plurality of precursor particles having a long shape at 500°C or higher and 1100°C or lower to obtain a plurality of fired particles containing alumina as a main component, having a long shape, and provided with mesopores (a firing step), and a dyeing step of incorporating an inorganic dye compound into the mesopores of the plurality of fired particles.

[0012] A method for manufacturing a water-repellent member according to a sixth aspect of the present invention involves applying a paint composition to the surface of a substrate to form a water-repellent film, wherein the water-repellent film comprises aggregates including a plurality of elongated particles and a coating layer formed of a water-repellent resin that covers the surface of the plurality of elongated particles. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide dyeing powders, paint compositions, water-repellent coatings and water-repellent members that can increase the degree of freedom in design, as well as methods for manufacturing dyeing powders and water-repellent members. [Brief explanation of the drawing]

[0014] [Figure 1] This is a scanning electron microscope (SEM) image of powder A1. [Figure 2] This is a magnified SEM image of Figure 1. [Figure 3] This is an SEM image of powder A2 observed using a scanning electron microscope. [Figure 4] This is a magnified SEM image of Figure 3. [Figure 5] This is an SEM image of powder A3 observed using a scanning electron microscope. [Figure 6] This is a magnified SEM image of Figure 5. [Figure 7] This is an SEM image of powder A4 observed using an SEM. [Figure 8] This is a magnified SEM image of Figure 7. [Figure 9] This is an SEM image of powder A5 observed using a scanning electron microscope. [Figure 10] This is a magnified SEM image of Figure 9. [Figure 11] This graph shows the relationship between pore size and pore volume for powders A2 to A5. [Figure 12] This is an SEM image of powder B5 observed using a scanning electron microscope. [Figure 13] This is a magnified SEM image of Figure 12. [Figure 14] Figure 13 shows a graph of the analysis of the portion indicated by the line using EDS. [Figure 15] This is an SEM image of the water-repellent material E6 observed using an SEM. [Figure 16] This is a magnified SEM image of Figure 15. [Figure 17] This is an SEM image of powder B5 observed using a scanning electron microscope. [Figure 18] This is a magnified SEM image of Figure 17. [Figure 19] This is an SEM image of the water-repellent material E2 observed using an SEM. [Figure 20] This is a magnified SEM image of Figure 19. [Modes for carrying out the invention]

[0015] The following description, with reference to the drawings, will detail the dyeing powder, the method for manufacturing the dyeing powder, the paint composition, the water-repellent film, the water-repellent member, and the method for manufacturing the water-repellent member according to this embodiment. This disclosure is not limited to the following embodiments. Furthermore, some or all of the components in the embodiments can be combined as appropriate.

[0016] [Dyeing powder] First, the dyeing powder according to this embodiment will be described. The dyeing powder according to this embodiment contains alumina as the main component and comprises a plurality of elongated particles having an elongated shape. A dye compound is incorporated into the elongated particles. The dyeing powder according to this embodiment allows for greater design freedom. As a result, when a water-repellent film is formed using the dyeing powder, the color tone of the water-repellent film can be improved. As will be described later, the dyeing powder can be manufactured by incorporating a dye compound into mesopores provided in calcined particles. The dyeing powder according to this embodiment will now be described in detail.

[0017] The elongated particles contain alumina as their main component. Alumina is difficult to dissolve even in an acidic atmosphere. Therefore, compared to using inorganic particles containing zinc oxide, etc., it is possible to suppress changes in the shape of the elongated particles even under acidic conditions. Here, "main component" means that each elongated particle contains 50% by mass or more of alumina. The elongated particles may contain 60% by mass or more, 70% by mass or more, or 80% by mass or more of alumina. Furthermore, the elongated particles may contain 90% by mass or more, 95% by mass or more, or 99% by mass or more of alumina. The elongated particles may also contain at least one selected from the group consisting of sodium oxide, aluminum hydroxide, and sodium aluminate, for example, derived from the manufacturing raw materials.

[0018] The elongated particles have an elongated shape. The elongated shape may be at least one shape selected from the group consisting of needle shape, scale shape, and plate shape. When the elongated particles have such shapes, spaces are easily formed between the elongated particles, which helps to suppress the decrease in water repellency when a water-repellent film is formed. Among these, it is preferable that the elongated particles are needle-shaped. Note that the needle shape means a shape that extends in a straight line, but it does not have to be strictly a needle shape. For example, the needle shape may have a pointed shape at the end, or it may not have a pointed shape at the end. That is, the elongated particles may have a columnar shape with a flat surface at the end. Also, the elongated particles may be prismatic particles with a polygonal cross-section, or they may have a cylindrical shape with a circular or elliptical cross-section. Furthermore, the needle shape only needs to be needle-like, and does not have to be, for example, strictly a straight line. The same applies to the scale shape and plate shape.

[0019] The average major diameter of multiple elongated particles may be between 1 μm and 40 μm. If the average major diameter is 1 μm or greater, even under polluting conditions where airborne particulate matter adheres to the water-repellent coating, it is possible to suppress the blockage of spaces between elongated particles by particulate matter or the complete surface of elongated particles being covered by particulate matter. Therefore, even under polluting conditions, a decrease in the water-repellent properties of the water-repellent coating can be suppressed. If the average major diameter is 40 μm or less, the elongated particles are less susceptible to deformation such as bending or breaking, resulting in excellent abrasion resistance. The average major diameter may be 3 μm or greater, or 7 μm or greater. Furthermore, the average major diameter may be 20 μm or less, 15 μm or less, or 11 μm or less. In this specification, the major diameter refers to the length of the part of the elongated particle with the largest diameter. For example, if the elongated particles are needle-shaped particles, the major diameter corresponds to the length of the needle-shaped particles. Also, in this specification, the average major diameter is the average value of the major diameters of 10 to 100 elongated particles observed in a secondary electron image of a scanning electron microscope (SEM).

[0020] The average minor diameter of the elongated particles may be between 0.01 μm and 5 μm. When the average minor diameter is 0.01 μm or greater, the elongated particles are less susceptible to deformation such as bending or breaking, resulting in excellent abrasion resistance. Furthermore, when the average minor diameter is 5 μm or less, even under contamination conditions where airborne particulate matter adheres to the water-repellent coating, it is possible to suppress the blockage of spaces between elongated particles by particulate matter or the complete covering of the surface of the elongated particles by particulate matter. Therefore, even under contamination conditions, a decrease in the water-repellent properties of the water-repellent coating can be suppressed. The average minor diameter may be 0.5 μm or greater, or 1 μm or greater. Also, the average minor diameter may be 3 μm or less, or 2.5 μm or less. In this specification, the minor diameter refers to the length of the part of the elongated particle with the smallest diameter. For example, if the elongated particles are needle-shaped particles, the minor diameter corresponds to the wire diameter of the needle-shaped particles. Furthermore, in this specification, the average minor axis is the average of the minor axes of 10 to 100 elongated particles observed in the secondary electron image of the SEM.

[0021] The ratio of the average major axis to the average minor axis of multiple long particles (aspect ratio) may be 3 or greater. When the aspect ratio is 3 or greater, even under contamination conditions where airborne particulate matter adheres to the water-repellent coating, it is possible to suppress the blockage of spaces between long particles by particulate matter or the entire surface of long particles being covered with particulate matter. Therefore, even under contamination conditions, it is possible to suppress the decrease in the water repellency of the water-repellent coating. The aspect ratio may also be 4 or greater. There is no particular upper limit to the aspect ratio, but for example, it may be 100 or less. When the aspect ratio is 100 or less, the long particles are less likely to break, resulting in excellent abrasion resistance. The aspect ratio may be 60 or less, 30 or less, or 10 or less.

[0022] The dyeing powder may contain protruding particles (core-containing protruding particles) which include a core portion and a protrusion portion in which multiple elongated particles extend radially from the core portion toward the outer surface. The multiple elongated particles may be connected to the core portion. The space is enclosed by each of the multiple elongated particles and the core portion, and this space is retained in the protruding particles. Alternatively, the dyeing powder may contain protruding particles that do not contain a core portion and are aggregated in such a way that multiple elongated particles gather in a spherical shape and are arranged radially from the inside toward the outer surface (core-less protruding particles). The space is enclosed by each of the multiple elongated particles, and this space is retained in the protruding particles. Because the space is retained in the protruding particles, a Cassie-Baxter surface is formed in the water-repellent coating, and a water-repellent coating with high water repellency can be obtained. An example of a protruding particle is, for example, a chestnut-shaped particle. The chestnut-shaped particle includes needle-shaped elongated particles. The average major diameter, average minor diameter, and aspect ratio of the elongated particles in the protrusion portion may be the same as those described above.

[0023] The average particle diameter of the protruding particles may be between 1 μm and 100 μm. When the average particle diameter of the protruding particles is within the above range, when a water-repellent film is formed, coarse irregularities formed by the protruding particles and fine irregularities formed by the elongated particles are formed on the surface of the water-repellent film. As a result, a complex uneven structure is formed on the surface of the water-repellent film, and the contact area between the surface of the water-repellent film and water droplets becomes smaller, thus a highly water-repellent film can be obtained. The average particle diameter of the protruding particles may be 10 μm or more, 20 μm or more, or 30 μm or more. In addition, the average particle diameter of the protruding particles may be 80 μm or less, 70 μm or less, or 60 μm or less. In this specification, the average particle diameter of the protruding particles is the average value of the particle diameters of 10 to 100 aggregates observed in the secondary electron image of an SEM.

[0024] The core may be formed by a single large particle, or by a collection of multiple particles. The core may also be formed by a collection of multiple particles, including elongated particles. The core may contain alumina as its main component. Here, "main component" means that the core contains 50% by mass or more of alumina. The core may contain 60% by mass or more, 70% by mass or more, 80% by mass or more, 85% by mass or more, 90% by mass or more, or 93% by mass or more of alumina. The core may contain at least one substance selected from the group consisting of sodium oxide, aluminum hydroxide, and sodium aluminate, derived from the manufacturing raw materials.

[0025] The total number of elongated particles in a single protruding particle may be, for example, 10 or more, 20 or more, 50 or more, or 100 or more. The total number of elongated particles contained in the protrusion may be 10,000 or less, 5,000 or less, or 1,000 or less.

[0026] Long particles may have sealed portions formed by the sealing of mesopores. In the dyeing process described later, the dyeing compound is incorporated into the mesopores present in the calcined particles, and a hydration reaction occurs, sealing the mesopores and forming sealed portions into which the dyeing compound is incorporated. At this time, it is thought that byerite is mainly generated inside the mesopores present in the calcined particles containing alumina, thereby sealing the mesopores. The sealed portions may be provided in at least one of the surface and central portions of the long particles.

[0027] Dye compounds are incorporated into the elongated particles. The dye compounds only need to be incorporated into the sealing portion, and may be dye compounds that were adsorbed on the surface of the wall forming the mesopore and were incorporated along with the sealing. The dye compounds may be adsorbed near the surface of the sealing portion (the outer surface of the elongated particle) in the depth direction of the sealing portion, or adsorbed in the deeper part of the sealing portion (the deeper part of the elongated particle). The dye compounds may be incorporated only in the surface portion of the elongated particle, or they may be incorporated throughout the elongated particle. When the dye compounds are incorporated throughout the elongated particle, the dye compounds may be incorporated more in the surface portion than in the central portion. The surface portion referred to here is the portion at a distance of less than 50% from the outer surface with respect to the line segment connecting the center of the elongated particle and the outer surface. The above distance from the outer surface may be less than 40%, less than 30%, less than 20%, or less than 10%. The dye compounds may contain at least one of organic dye compounds and inorganic dye compounds. Among these, from the viewpoint of weather resistance or heat resistance, it is preferable that the dye compound contains an inorganic dye compound.

[0028] Organic dye compounds may have at least one unsaturated atomic group selected from the group consisting of nitro, diazo, sulfo, and carbonyl groups. Organic dye compounds may have an aromatic ring. Organic dye compounds may contain transition metal elements. Organic dye compounds may contain at least one element selected from transition metal elements, and may contain two or more elements. Organic dye compounds may contain at least one element selected from the group consisting of chromium, cobalt, copper, and nickel.

[0029] Inorganic dye compounds may contain transition metal elements. That is, dye compounds may contain transition metal elements. Inorganic dye compounds may contain at least one element selected from transition metal elements, and may contain two or more elements. Inorganic dye compounds may contain at least one element selected from the group consisting of iron, cobalt, and copper. These dye compounds have excellent dyeing properties, and the dye powder L * The value can be effectively reduced. Among these, the dye compound preferably contains iron. The inorganic dye compound does not have to have at least one unsaturated atomic group selected from the group consisting of nitro groups, azo groups, and carbonyl groups. The inorganic dye compound does not have to have an aromatic ring. The inorganic dye compound may contain at least one selected from the group consisting of ammonium iron oxalate, iron oxalate, cobalt oxalate, copper oxalate, iron acetate, cobalt acetate, copper acetate, iron sulfate, copper sulfate, cobalt sulfate, iron chloride, copper chloride, cobalt chloride, iron phosphate, copper phosphate, and cobalt phosphate.

[0030] The incorporation of dye compounds into elongated particles can be confirmed, for example, by detecting the presence of transition metal elements contained in the dye compounds. The presence of transition metal elements can be detected by methods such as energy dispersive X-ray spectroscopy (EDS), glow discharge optical emission spectrometry (GD-OES), electron probe microanalyzer (EPMA), and X-ray fluorescence spectroscopy (XRF).

[0031] L of dyeing powder * The value may be less than 90. (L of dyeing powder) * A value of less than 90 makes it possible to form a highly aesthetic water-repellent coating with reduced whiteness, even when using long particles. * The value may be less than 80, less than 70, less than 60, less than 50, or less than 45. L of the dyeing powder * The value can be obtained by measurement in accordance with geometric condition c of JIS Z8722:2009.

[0032] As described above, the dyeing powder according to this embodiment contains alumina as its main component and comprises a plurality of elongated particles. Dye compounds are incorporated within these elongated particles. As a result, the dyeing powder can exhibit a color due to the incorporated dye compounds. Therefore, by coating a substrate with a film containing the dyeing powder, the design freedom of the coated member can be increased. Furthermore, if the same dye compound is incorporated into the dyeing powder, the color tone of the coated member can be improved. In particular, when the dyeing powder incorporates an inorganic dye compound, a dyeing powder with excellent weather resistance or heat resistance can be provided. Moreover, by coating a substrate with a water-repellent film containing the dyeing powder and a water-repellent resin, the superhydrophobicity and stain resistance of the coated member can be increased, and the design freedom can be increased.

[0033] [Method for manufacturing dyed powder] Next, a method for producing the dyed powder according to this embodiment will be described. The method for producing the dyed powder according to this embodiment includes a calcination step and a dyeing step.

[0034] The calcination process involves calcining multiple precursor particles to obtain multiple calcined particles. Each precursor particle contains at least one of alumina and aluminum hydroxide and has an elongated shape. Each calcined particle contains alumina as its main component, has an elongated shape, and is provided with mesopores.

[0035] As described above, the precursor particles contain at least one of alumina and aluminum hydroxide. By calcining the precursor particles, calcined particles containing alumina as the main component are obtained. The alumina may contain at least one selected from the group consisting of α-alumina (corundum), χ-alumina, ε-alumina, ρ-alumina, κ-alumina, γ-alumina, δ-alumina, and θ-alumina. The aluminum hydroxide may contain at least one of alumina hydrate and alumina gel. The alumina hydrate may contain at least one of alumina monohydrate and alumina trihydrate. The alumina monohydrate may contain at least one of boehmite and diaspore. The alumina trihydrate may contain at least one selected from the group consisting of gibbsite, bayerite, and nordstrandite.

[0036] The elongated shape can be the same as that of the elongated particles described above. In addition, in the firing process, multiple precursor protrusion particles may be fired to obtain multiple fired protrusion particles. The shape of the precursor protrusion particles can be the same as that of the protrusion particles of the dyed powder described above. That is, the precursor protrusion particles may include a core portion and protrusions that extend radially from the core portion toward the outer surface. Alternatively, the precursor protrusion particles may not include a core portion and may include protrusion particles that are aggregated by multiple elongated particles gathering into a spherical shape and arranging radially from the inside toward the outer surface. The average major diameter, average minor diameter, and aspect ratio of the elongated particles in the protrusion portion may be the same as those described above. The precursor protrusion particles may also be chestnut-shaped particles.

[0037] The precursor protrusion particles may specifically be gibbsite. Gibbsite can be obtained by adding aluminum hydroxide, which will serve as a seed crystal, to a sodium aluminate solution, and then continuously or intermittently adding the sodium aluminate solution at a predetermined rate while controlling the supersaturation concentration. The aluminum hydroxide, which will serve as the seed crystal, contains gibbsite. The sodium aluminate solution may be prepared by dissolving bauxite using the Bayer process.

[0038] The sodium oxide (Na2O) content in the sodium aluminate solution may be 25 g / L or more. When the sodium oxide content is 25 g / L or more, crystallization proceeds faster, and more burr-shaped gibbsite crystals are obtained. The sodium oxide content in the sodium aluminate solution may be 100 g / L or less. When the sodium oxide content is 100 g / L or less, excessive crystallization can be prevented, and the generation of gibbsite crystals that are not burr-shaped can be suppressed. The sodium oxide content may be 50 g / L or less.

[0039] The aluminum oxide (Al2O3) content in the sodium aluminate solution may be 25 g / L or more. When the aluminum oxide content is 25 g / L or more, crystallization proceeds more rapidly, and a larger amount of burr-shaped gibbsite is obtained. The aluminum oxide content in the sodium aluminate solution may be 100 g / L or less. When the aluminum oxide content is 100 g / L or less, excessive crystallization can be prevented, and the generation of gibbsite crystals with shapes other than burr-shaped can be suppressed. The aluminum oxide content may be 50 g / L or less.

[0040] The molar ratio of sodium oxide dissolved in the sodium aluminate solution to aluminum oxide may be between 1.5 and 3. When the molar ratio is 1.5 or higher, the formation of gibbsite crystals with shapes other than chestnut burrs can be suppressed. When the molar ratio is 3 or lower, the dissolution of aluminum hydroxide, which will become seed crystals, into the sodium aluminate solution can be suppressed. The molar ratio may also be 2 or lower.

[0041] The temperature of the sodium aluminate solution to which aluminum hydroxide is added may be 50°C or higher and 80°C or lower. When the temperature is 50°C or higher, it becomes easier to control the supersaturation concentration. Also, when the temperature is 50°C or higher, the generation of hexagonal gibbsite crystals, the generation of particles in which excessively long particles are aggregated, and the aggregation of seed crystals can be suppressed. The temperature may be 70°C or higher. Further, when the temperature is 80°C or lower, the dissolution of seed crystals can be suppressed. Incidentally, the temperature of the sodium aluminate solution to which aluminum hydroxide is added may be a constant temperature, but for example, it may be gradually decreased as the sodium aluminate solution is added from a predetermined temperature such as 80°C. In this case, the yield of spherical gibbsite is improved.

[0042] The average particle diameter (Dp50) of the aluminum hydroxide serving as the seed crystal may be 0.1 μm or more and 1 μm or less. When the average particle diameter is 0.1 μm or more, the yield of spherical gibbsite is improved. When the average particle diameter is 1 μm or less, the short diameter of the long particles of the obtained spherical gibbsite can be made thinner. Incidentally, the average particle diameter represents the particle diameter when the cumulative value of the particle size distribution based on the number is 50%, and can be measured by the laser diffraction / scattering method.

[0043] The BET specific surface area of the aluminum hydroxide serving as the seed crystal may be 15 m 2 / g or more. When the BET specific surface area is 15 m 2 / g or more, the generation of hexagonal general-purpose gibbsite crystals can be suppressed. The BET specific surface area may be 30 m 2 / g or more. Also, the BET specific surface area may be 50 m 2 / g or less. When the BET specific surface area is 50 m 2 / g or less, the yield of spherical gibbsite is improved.

[0044] The aluminum hydroxide serving as the seed crystal may be added so that the BET specific surface area is 0.05 m 2 or more and 1 m 2 or less per liter of the sodium aluminate solution. When the addition amount of aluminum hydroxide is 0.05 m2 If the above conditions are met, the yield of burr-shaped gibbsite will improve. The amount of aluminum hydroxide added is 1 m 2 The following conditions can suppress the formation of particles in which excessively long particles have aggregated. The BET specific surface area can be measured in accordance with JIS R1626:1996.

[0045] The supersaturated concentration of aluminum oxide may be between 3 g / L and 15 g / L. When the supersaturated concentration is 3 g / L or higher, the yield of burr-shaped gibbsite improves. When the supersaturated concentration is 15 g / L or lower, the formation of excessively long aggregated particles and the generation of gibbsite crystals with shapes other than burr-shaped can be suppressed. The supersaturated concentration may also be 10 g / L or lower. The supersaturated concentration can be determined by the following formula derived from White's equation (Light Metals, 1984, pp. 237-253). X=AC×exp[6.2106-{(2486.7-1.0876C) / (T+273)}] In the above formula, X represents the supersaturation concentration (g / L), A represents the dissolved Al2O3 concentration (g / L), C represents the dissolved Na2O concentration (g / L), and T represents the solution temperature (°C).

[0046] The precursor particles are calcined at a temperature between 500°C and 1100°C. By calcining the precursor particles at a temperature of 500°C or higher, mesopores are formed in the calcined particles. Therefore, the calcined particles can be effectively dyed in the dyeing process described later. Furthermore, by calcining the precursor particles at a temperature of 1100°C or lower, it is possible to suppress the calcined particles from becoming brittle and breaking due to heat, or from the calcined particles becoming compacted and losing their mesopores. The calcination temperature may be 550°C or higher, 600°C or higher, 650°C or higher, 700°C or higher, 750°C or higher, or 800°C or higher. Also, the calcination temperature may be 1050°C or lower, 1000°C or lower, 950°C or lower, 900°C or lower, 850°C or lower, or 800°C or lower. The calcination time for the precursor particles may be 0.5 hours or longer, or 1 hour or longer. Furthermore, the calcination time for the precursor particles may be 10 hours or less, or 3 hours or less.

[0047] The calcined particles are provided with mesopores. The presence of mesopores in the calcined particles allows for effective staining in the staining process described later. Mesopores are pores with a diameter between 2 and 50 nm. Mesopores may be present in at least one of the surface and central portions of the calcined particles. The pore diameter of the calcined particles can be obtained by the BJH method in accordance with JIS Z8831-2:2010. A specific method for measuring the average pore diameter of the calcined particles will be described later. In this disclosure, calcined particles provided with mesopores have an average pore diameter of 2 to 50 nm and a pore volume (cumulative pore volume) of 0.03 cm³. 3 The BET specific surface area is 10m² or more, and the BET specific surface area is 10m² or more. 2 This refers to items weighing 1g or more.

[0048] The pore volume (cumulative pore volume) of multiple calcined particles is 0.03 cm³. 3 It may be greater than or equal to / g. Pore volume of 0.03 cm³ 3By increasing the concentration to 1 / g or higher, the calcined particles can be stained even more effectively. The pore volume of multiple calcined particles is 0.04 cm³. 3 It may be more than / g, and 0.1cm 3 It may be more than / g, and 0.2cm 3 It may be more than / g, and 0.25cm 3 It may be greater than or equal to / g. Furthermore, there is no particular upper limit to the pore volume, and the pore volume is 10 cm³. 3 It may be less than / g, 1cm 3 It may be less than / g, and 0.5cm 3 The value may be less than / g. The pore volume of the calcined particles can be obtained by the BJH method in accordance with JIS Z8831-2:2010. The specific method for measuring the pore volume of the calcined particles will be described later.

[0049] The BET specific surface area of ​​multiple calcined particles is 10 m². 2 The BET specific surface area may be 10 m² or more. 2 By setting the amount to 1 / g or more, the calcined particles can be stained even more effectively. The BET specific surface area of ​​multiple calcined particles is 20 m². 2 It may be more than / g, 30m 2 It may be more than / g, 50m 2 It may be more than / g, 100m 2 It may be greater than / g. Also, there is no particular upper limit on the BET specific surface area, 1000m 2 It may be less than / g, and 500m 2 It may be less than / g, and 200m 2 It may be less than / g. The BET specific surface area of ​​the calcined particles can be obtained by measuring it using nitrogen gas in accordance with JIS Z8830:2013.

[0050] In the dyeing process, the dye compound is incorporated into the mesopores of multiple calcined particles. By bringing multiple calcined particles into contact with the dye through mixing or immersion, the dye compound can be incorporated into the mesopores. The dye compounds can be those described above. When multiple calcined particles are mixed with or immersed in the dye, the multiple calcined particles may be filtered to obtain a dyed powder.

[0051] The dye may include at least one selected from the group consisting of azo dyes, anionic dyes, anthraquinone dyes, basic dyes, carbonium dyes, quinoline dyes, quinone imine dyes, metal complex dyes, fluorescent dyes, acid dyes, direct dyes, natural dyes, reactive dyes, vat dyes, mordant dyes, phthalocyanine dyes, disperse dyes, methine dyes, sulfur dyes, and vat dyes. Examples of azo dyes include naphthol dyes. Examples of carbonium dyes include xanthene dyes such as rhodamine dyes, acridine dyes, and triphenylmethane dyes. Examples of quinone imine dyes include oxazine dyes and thiazine dyes. Examples of vat dyes include leucoester dyes. Examples of methine dyes include cyanine dyes such as merocyanine dyes, azomethine dyes, and polymethine dyes.

[0052] The dye may contain at least one of an organic dye and an inorganic dye. The organic dye is a dye containing the organic dye compounds described above. The inorganic dye is a dye containing the inorganic dye compounds described above. The organic dye may contain at least one of a chromium complex salt azo acid dye and a cobalt complex salt azo acid dye. The inorganic dye may contain at least one of ammonium iron oxalate and cobalt acetate.

[0053] The contact temperature between the fired particles and the dye depends on the state of the fired particles and the dye, but may be between 0°C and 100°C. The contact temperature may be 20°C or higher, or 40°C or higher. The contact temperature may be 80°C or lower, or 70°C or lower. The contact time between the fired particles and the dye depends on the state of the fired particles and the dye, but may be between 1 minute and 1000 minutes. The contact time may be 10 minutes or higher, or 20 minutes or higher. The contact time may be 100 minutes or lower, or 70 minutes or lower.

[0054] The method for producing the dyed powder may include a drying step after the dyeing step in which the dyed particles are dried. The drying temperature of the dyed powder may be 30°C or higher, or 40°C or higher. The drying time may be 80°C or lower, or 60°C or lower. The drying time of the dyed powder may be 0.1 hours or more, or 1 hour or more. The drying time may be 10 hours or less, 5 hours or less, or 3 hours or less.

[0055] The method for producing the dyed powder may include a sealing step to seal the mesopores after the dyeing and drying steps. In the sealing step, known sealing treatments such as treating the dyed powder with boiling water, pressurized steam, nickel salts, or chromate salts can be used. By forming alumina hydrate on the surface of the long particles through the sealing step, the mesopores that have incorporated the dyeing compound are sealed more reliably.

[0056] As described above, the dyeing powder manufacturing method according to this embodiment makes it possible to produce the dyeing powder described above.

[0057] [Paint composition] Next, a paint composition according to this embodiment will be described. The paint composition according to this embodiment contains a plurality of elongated particles, a solvent, and a water-repellent resin. Alternatively, the paint composition contains a plurality of protruding particles, a solvent, and a water-repellent resin. By using such a paint composition, a water-repellent film, as described later, can be formed. Dye compounds are incorporated into the elongated particles. That is, the paint composition contains the dye powder described above as either elongated particles or protruding particles. The elongated particles and protruding particles can be any of the dye powders listed above.

[0058] The content of elongated particles and protruding particles relative to the solid content in the paint composition may be 10% by mass or more and 90% by mass or less. When the content of elongated particles and protruding particles is 10% by mass or more, the rigidity of the water-repellent film is increased. Furthermore, when the content of elongated particles and protruding particles is 90% by mass or less, the water-repellent resin can be more uniformly coated onto the elongated particles and protruding particles. The content of elongated particles and protruding particles may be 20% by mass or more, 30% by mass or more, or 40% by mass or more. Furthermore, the content of elongated particles and protruding particles may be 80% by mass or less, 70% by mass or less, or 60% by mass or less.

[0059] The content of water-repellent resin relative to the solid content in the paint composition may be 10% by mass or more and 90% by mass or less. When the water-repellent resin content is 10% by mass or more, the water-repellent resin can be more uniformly coated onto long particles and protruding particles. Also, when the water-repellent resin content is 90% by mass or less, the rigidity of the water-repellent film is increased. The water-repellent resin content may be 20% by mass or more, 30% by mass or more, or 40% by mass or more. Also, the water-repellent resin content may be 80% by mass or less, 70% by mass or less, or 60% by mass or less.

[0060] The ratio of the water-repellent resin content to the content of long particles and protruding particles may be between 0.1 and 10. When the ratio is 0.1 or higher, the water-repellent resin can be more uniformly coated onto the long particles and protruding particles. When the ratio is 10 or lower, the rigidity of the water-repellent film increases. The ratio may also be 0.4 or higher, or 0.8 or higher. Furthermore, the ratio may be 8 or lower, or 6 or lower.

[0061] The total content of long particles and water-repellent resin relative to the solid content in the paint composition may be 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, 95% by mass or more, or 99% by mass or more. The total content of protruding particles and water-repellent resin relative to the solid content in the paint composition may be 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, 95% by mass or more, or 99% by mass or more.

[0062] The solvent is used to dissolve the water-repellent resin and form a coating layer on the surface of the long particles and protruding particles. The solvent is not particularly limited as long as it can dissolve the water-repellent resin, and for example, an organic solvent can be used. Examples of organic solvents include acetic acid esters such as methyl acetate, ethyl acetate, and butyl acetate. These organic solvents may be used individually or in combination of two or more. The solvent content is not particularly limited, but for example, it may be 10 to 99 parts by mass per 100 parts by mass of the paint composition.

[0063] The water-repellent resin is not particularly limited as long as it is a resin that has water-repellent properties, but it may contain at least one of silicone resins and fluororesins. Among water-repellent resins, these resins have particularly high water repellency, so a water-repellent film with good water repellency can be obtained.

[0064] Silicone resins are polymers having a three-dimensional network structure with a siloxane-bonded main skeleton. Silicone resins can be produced, for example, by polymerizing organohalosilanes or organoalkoxysilanes. Examples of organohalosilanes include at least one silane selected from the group consisting of methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, ethyltrichlorosilane, diethyldichlorosilane, and triethylchlorosilane. Examples of organoalkoxysilanes include at least one silane selected from the group consisting of organomonoalkoxysilanes, organodialkoxysilanes, and organotrialkoxysilanes. Silicone resins may also contain at least one silicone resin selected from the group consisting of vinyl silicone resins, phenyl silicone resins, and fluorinated silicone resins. A typical example of a silicone resin is polydimethylsiloxane (PDMS).

[0065] The fluororesin may contain, for example, at least one selected from the group consisting of polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), tetrafluoroethylene perfluoroalkyl vinyl ether (PFA), tetrafluoroethylene hexafluoropropylene (FEP), ethylene tetrafluoroethylene (ETFE), and ethylene chlorotrifluoroethylene (ECTFE).

[0066] The water-repellent resin may further contain, in addition to at least one of silicone resins and fluororesins, auxiliary resins other than silicone resins and fluororesins, such as polyester. The auxiliary resin functions as a binder that holds long particles and maintains the structure of aggregates. The content of at least one of silicone resins and fluororesins relative to the water-repellent resin may be 20% by mass or more. The content of at least one of silicone resins and fluororesins relative to the water-repellent resin may be 50% by mass or more, 80% by mass or more, or 90% by mass or more. In addition to the water-repellent resin, the water-repellent resin may further contain additives having various functions. Examples of additives include antioxidants, antistatic agents, ultraviolet absorbers, flame retardants, pigments, and dyes. These additives may be used individually or in combination of two or more.

[0067] According to the paint composition of this embodiment, a water-repellent film, as described later, can be formed well.

[0068] [Water-repellent coating] Next, the water-repellent coating according to this embodiment will be described. The water-repellent coating according to this embodiment comprises an aggregate including a plurality of elongated particles and a coating layer that covers the surface of the plurality of elongated particles. The elongated particles incorporate a dye compound. That is, the water-repellent coating contains the dye powder described above as elongated particles or protruding particles.

[0069] The aggregate consists of multiple elongated particles aggregated three-dimensionally. The outer surface of the aggregate is covered by a coating layer. The aggregate maintains spaces between the multiple elongated particles covered by the coating layer that communicate with the outside of the water-repellent film. The spaces between the multiple elongated particles covered by the coating layer and the elongated particles covered by the coating layer form an uneven structure on the surface of the water-repellent film, forming a Cassie-Baxter surface. Therefore, even when water droplets are dropped onto the surface of the water-repellent film, a void is formed between the surface of the water-repellent film and the water droplet, reducing the contact area between the water-repellent film and the water droplet, thus resulting in a highly water-repellent film.

[0070] The aggregates have a structure in which long particles are aggregated together. Furthermore, the water-repellent coating has aggregates formed by the aggregation of multiple long particles. For example, when aggregates containing long particles are formed, the long particles may directly aggregate with respect to the substrate, resulting in aggregates having a structure in which multiple long particles are arranged on the surface of the substrate. The water-repellent coating of this disclosure may contain aggregates having such a structure in which long particles are arranged on a substrate, but it has at least on its outer surface aggregates having a three-dimensional structure composed of long particles, formed by the three-dimensional aggregation of long particles. The water-repellent coating is formed by the presence of such aggregates, formed by the three-dimensional aggregation of long particles, on the surface of the substrate.

[0071] The aggregate includes elongated particles as unit particles constituting the aggregate. For example, when an aggregate containing elongated particles is formed, it is conceivable that the aggregate has a structure in which some of the particles have a structure similar to that of elongated particles, and the aggregate as a whole has a structure in which non-elongated unit particles are aggregated. The water-repellent coating of this disclosure may include aggregates having a structure made up of such non-elongated unit particles, but it is preferable that the aggregate has at least an aggregate made up of elongated particles formed by the aggregation of elongated particles as unit particles on its outer surface.

[0072] The aggregate has a three-dimensional aggregated structure formed by multiple elongated particles. Here, "three-dimensional" means that the elongated particles do not aggregate only in a linear (one-dimensional) or planar (two-dimensional) manner, but rather have a structure in which they aggregate in a spatial manner defined by three mutually perpendicular axes. In particular, it is preferable that adjacent elongated particles do not oriented in the same direction, but aggregate with different orientations. The aggregate may also have protruding particles in which multiple elongated particles are assembled in a spherical shape, with the elongated particles arranged as protrusions facing outwards. The aggregate may include a core portion as described above, and have protruding particles in which elongated particles are aggregated so as to be arranged radially from the core portion toward the outer surface. The aggregate may also not include a core portion, and have protruding particles in which elongated particles are aggregated so as to be arranged radially from the inside toward the outer surface. Furthermore, the aggregate may have a three-dimensional network structure in which elongated particles form a three-dimensional network.

[0073] The water-repellent coating may be a single large aggregate, or it may be a secondary aggregate formed by the aggregation of multiple primary aggregates containing multiple elongated particles. Furthermore, the water-repellent coating may be a single large aggregate spread planarly, or a single large aggregate spread with an uneven surface. Also, the water-repellent coating may be formed by the aggregation of multiple primary aggregates, with the aforementioned protruding particles acting as primary aggregates. In this case, the aggregation of multiple approximately spherical primary aggregates may result in the formation of a water-repellent coating by the aggregation of spherically missing primary aggregates. In this case, a space communicating with the outside of the water-repellent coating can be maintained on the spherical caps of the primary aggregates between the multiple elongated particles covered by the coating layer.

[0074] The aggregate may be an agglomerate (weak aggregate) formed by the weak aggregation of long particles. Aggregates or assemblies formed by multiple particles can be classified into agglomerates (weak aggregates), aggregates (strong aggregates), and flocculates (assemblies). In this specification, an agglomerate is an aggregate of multiple particles formed by the bonding of particles, in which the multiple particles are weakly aggregated three-dimensionally, and the particles are coarsely aggregated so that the volume of the voids created by the multiple particles is large. An aggregate is an aggregate of multiple particles formed by the bonding of particles, in which the multiple particles are strongly aggregated, and the particles are densely aggregated so that the volume of the voids created by the multiple particles is small. A flocculate is an assembly of multiple particles formed via a dispersion medium that disperses particles, in which the multiple particles are aggregated by inter-particle interactions such as inter-ion interactions, hydrogen bonds, dipole interactions, and van der Waals forces. The aggregates of this disclosure preferably have agglomerates, and it is more preferable that the surface structure of the aggregate consists of agglomerates. The aggregation pattern of aggregates can be determined from the shape of the object obtained from secondary electron images observed by SEM.

[0075] When aggregates formed by elongated particles are agglomerates, adjacent elongated particles do not oriented in the same direction, but rather aggregate with their orientations differing from one another. Furthermore, adjacent elongated particles aggregate in a state where they are in contact at points and intersect. In addition, spaces communicating with the outside of the water-repellent film are maintained between multiple elongated particles coated by the coating layer. Then, elongated particles coated with the water-repellent resin aggregate so that they are arranged radially from the inside toward the outer surface, forming aggregates with protrusions on the surface. When aggregates formed by elongated particles are agglomerates, the voids created between multiple elongated particles facilitate the formation of a Cassie-Baxter surface, improving water repellency and stain resistance.

[0076] When aggregates formed by elongated particles are aggregates, adjacent elongated particles are oriented in the same direction, and aggregates with their orientations aligned. Furthermore, adjacent elongated particles aggregate in contact with each other along their edges or surfaces. This results in elongated particles coated with the water-repellent resin forming bundle-like, plate-like, strip-like, planar, or columnar aggregates. When aggregates formed by elongated particles are aggregates, voids are less likely to form between multiple elongated particles, making it difficult to create a Cassie-Baxter surface. Therefore, water repellency and stain resistance are less likely to improve.

[0077] When the water-repellent coating is a secondary aggregate composed of multiple primary aggregates, the average particle diameter of the primary aggregates may be between 1 μm and 100 μm. When the average particle diameter of the aggregates is within the above range, the surface of the water-repellent coating is formed with coarse irregularities formed by multiple primary aggregates and fine irregularities formed by multiple elongated particles. As a result, a complex uneven structure is formed on the surface of the water-repellent coating, and the contact area between the surface of the water-repellent coating and water droplets becomes smaller, thus obtaining a highly water-repellent coating. The average particle diameter of the primary aggregates may be 10 μm or more, 20 μm or more, or 30 μm or more. In addition, the average particle diameter of the primary aggregates may be 80 μm or less, 70 μm or less, or 60 μm or less. In this specification, the average particle diameter of the primary aggregates is the average value of the particle diameters of 10 to 100 aggregates observed in the secondary electron image of an SEM.

[0078] The thickness of the coating layer may be, for example, 2 μm or less. When the thickness of the coating layer is 2 μm or less, spaces are more easily maintained between the long particles, and many voids are formed on the surface of the water-repellent film. Therefore, even if airborne particles adhere to the water-repellent film, the contact area between the water-repellent film and the droplets remains small, and the water-repellency of the water-repellent film can be maintained for a long period of time. The lower limit of the thickness of the coating layer is not particularly limited as long particles are covered, but for example, it is 0.01 μm or more. The thickness of the coating layer can be measured by observing the cross-section of the water-repellent film with a microscope such as a SEM.

[0079] The outer surface of the aggregate is covered by a coating layer. The coating layer only needs to cover a portion of the aggregate's surface, but it is preferable that it covers the entire surface of the aggregate. The coating layer may cover the entire surface of each of the multiple elongated particles constituting the aggregate, or it may cover the entire outer surface of multiple elongated particles without covering the parts where adjacent elongated particles are in contact with each other. Furthermore, each of the multiple elongated particles may be bonded to each other via the coating layer. However, if the coating layer covers the multiple elongated particles in a planar manner, preventing the formation of an uneven structure on the surface of the water-repellent film, the water repellency will decrease. For this reason, the coating layer covers the elongated particles in such a way that it maintains spaces between the multiple elongated particles that communicate with the outside of the water-repellent film. In other words, the coating layer covers the elongated particles in such a way that the outer surface of the aggregate covered by the coating layer has portions that are exposed to the outside. In this way, the spaces between the multiple elongated particles covered by the coating layer are open to the outside of the water-repellent film.

[0080] The coating layer is formed of a water-repellent resin. The water-repellent resin coating, in conjunction with the Cassie-Baxter surface structure, enhances the water repellency of the coating. Furthermore, the water-repellent resin also functions as a binder, holding long particles and maintaining the aggregate structure. As described above, the water-repellent resin may contain at least one of either a silicone resin or a fluororesin. In addition to at least one of the silicone resin or fluororesin, the water-repellent resin may further contain auxiliary resins other than silicone resin and fluororesin, such as polyester. That is, the outer surface of the aggregate may be coated with a coating layer formed of a water-repellent resin containing an auxiliary resin, in addition to at least one of the silicone resin or fluororesin.

[0081] The aggregate may contain the aforementioned protruding particles. As described above, spaces are maintained between the protruding particles. Furthermore, multiple protruding particles may be bonded to each other via a coating layer. Because the water-repellent coating has multiple protruding particles, a Cassie-Baxter surface is formed on the water-repellent coating, thus providing a highly water-repellent coating as described above.

[0082] The outer surface of the protruding particles may be covered with a coating layer. Specifically, a portion of the outer surface of the core and several elongated particles included in the protrusions may be covered with a coating layer. However, the outer surface of the core may not be covered with a coating layer at the connection point where the core and the elongated particles are connected.

[0083] The content of elongated particles and protruding particles in the water-repellent coating may be 10% by mass or more and 90% by mass or less. When the content of elongated particles and protruding particles is 10% by mass or more, the rigidity of the water-repellent coating increases. Furthermore, when the content of elongated particles and protruding particles is 90% by mass or less, the water-repellent resin can be more uniformly coated onto the elongated particles and protruding particles. The content of elongated particles and protruding particles may be 20% by mass or more, 30% by mass or more, or 40% by mass or more. Furthermore, the content of elongated particles and protruding particles may be 80% by mass or less, 70% by mass or less, or 60% by mass or less.

[0084] The water-repellent resin content in the water-repellent coating may be 10% by mass or more and 90% by mass or less. When the water-repellent resin content is 10% by mass or more, the water-repellent resin can be more uniformly coated onto long particles and protruding particles. Also, when the water-repellent resin content is 90% by mass or less, the rigidity of the water-repellent coating increases. The water-repellent resin content may be 20% by mass or more, 30% by mass or more, or 40% by mass or more. Also, the water-repellent resin content may be 80% by mass or less, 70% by mass or less, or 60% by mass or less.

[0085] The ratio of the water-repellent resin content to the content of long particles and protruding particles may be between 0.1 and 10. When the ratio is 0.1 or higher, the water-repellent resin can be more uniformly coated onto the long particles and protruding particles. When the ratio is 10 or lower, the rigidity of the water-repellent film increases. The ratio may also be 0.4 or higher, or 0.8 or higher. Furthermore, the ratio may be 8 or lower, or 6 or lower.

[0086] The total content of long particles, protruding particles, and the coating layer in the water-repellent film may be 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, 95% by mass or more, or 99% by mass or more.

[0087] The amount of alumina in the inorganic components of the water-repellent coating may be 80% by mass or more, 90% by mass or more, 95% by mass or more, or 99% by mass or more.

[0088] The thickness of the water-repellent coating may be between 10 μm and 500 μm. If the thickness of the water-repellent coating is 10 μm or more, water repellency can be maintained even if the coating is worn away. If the thickness of the water-repellent coating is 500 μm or less, the formation of the water-repellent coating is easy. The thickness of the water-repellent coating may be 15 μm or more, or 20 μm or more. Furthermore, the thickness of the water-repellent coating may be 400 μm or less, or 300 μm or less.

[0089] As described above, the water-repellent coating according to this embodiment comprises an aggregate containing alumina as the main component and a plurality of elongated particles having an elongated shape, and a coating layer formed of a water-repellent resin that covers the surface of the plurality of elongated particles. Dye compounds are incorporated into the elongated particles. The aggregate is formed by the three-dimensional aggregation of the plurality of elongated particles. The outer surface of the aggregate is covered by the coating layer. The aggregate maintains spaces between the plurality of elongated particles covered by the coating layer that communicate with the outside of the water-repellent coating.

[0090] In the water-repellent coating according to this embodiment, the aggregate maintains spaces between multiple elongated particles covered by the coating layer that communicate with the outside of the water-repellent coating. Therefore, an uneven structure is formed on the surface of the water-repellent coating by the elongated particles covered by the coating layer and the above spaces, forming a Cassie-Baxter surface. As a result, even when a water droplet is dropped onto the surface of the water-repellent coating, a void is formed between the surface of the water-repellent coating and the water droplet, reducing the contact area between the water-repellent coating and the water droplet. Furthermore, the outer surface of the aggregate is covered by a coating layer, which is made of a water-repellent resin. Therefore, the water repellency of the water-repellent coating is enhanced by the combined effect of the surface structure of the water-repellent coating and the water-repellent resin.

[0091] Furthermore, the water-repellent coating according to this embodiment has a structure in which multiple elongated particles are aggregated three-dimensionally. Therefore, the elongated particles, which are aggregated while maintaining spaces between them, can further aggregate while maintaining spaces between other elongated particles, thereby achieving three-dimensional aggregation. In addition, since the water-repellent coating is formed by aggregates with elongated particles as unit particles, the aggregates can be easily stacked in the height direction, thereby increasing the surface area in the height direction. As a result, as the structure in which elongated particles are aggregated three-dimensionally expands, the spaces that communicate with the outside of the water-repellent coating, which are maintained between multiple elongated particles covered by the coating layer, can also be expanded three-dimensionally. Consequently, a Cassie-Baxter surface is more easily formed on the surface of the water-repellent coating, and the water repellency of the water-repellent coating is more easily enhanced.

[0092] Furthermore, particulate matter such as DEP (diesel exhaust particulate matter), which is mainly composed of carbon, is suspended in the atmosphere. Of the DEP, the most numerous are particles with a diameter of 0.1 μm or less called PM0.1 (ultrafine particles), which have recently become a source of concern regarding their impact on health. When such ultrafine particles adhere to the surface of a water-repellent coating with a fine uneven structure, the spaces forming the Cassie-Baxter surface may become blocked by the ultrafine particles, or the surface of the coating layer formed by the water-repellent resin may become covered, potentially reducing water repellency. However, in the water-repellent coating according to this embodiment, multiple elongated particles are used. Therefore, even if ultrafine particles adhere to the water-repellent coating, the ultrafine particles will only adhere to a portion of the elongated particles, or they will be dispersed and adhere from the tip to the base of the elongated particles, so the spaces between the elongated particles are not blocked, and the Cassie-Baxter surface is maintained. Furthermore, because the ultrafine particles only adhere to a portion of the elongated particles, or because they are dispersed and adhere from the tip to the base of the elongated particles, the surface of the coating layer covering multiple elongated particles is prevented from being completely covered with ultrafine particles. Therefore, even under contaminated conditions, the deterioration of the water-repellent coating can be suppressed for a long period of time.

[0093] Furthermore, the long particles mainly contain alumina. Since alumina and boehmite are not easily dissolved in acidic solutions, the long particles do not easily deform even when the water-repellent coating is placed under acidic conditions. As a result, the water-repellent coating maintains the Cassie-Baxter surface for a long period of time, even under acidic conditions. Therefore, the water-repellent coating according to this embodiment exhibits high water repellency even under acidic conditions.

[0094] Furthermore, the elongated particles aggregate three-dimensionally, and the aggregates are arranged to maintain spaces that communicate with the outside of the water-repellent coating between multiple elongated particles covered by the coating layer. Therefore, even if the surface of the water-repellent coating is worn away, spaces exist along the thickness direction of the coating. Consequently, even if the surface of the water-repellent coating is worn away, a new Cassie-Baxter surface is revealed, making it easier to maintain water repellency.

[0095] As described above, the water-repellent coating according to this embodiment has excellent water repellency and stain resistance, and by coating a substrate with the water-repellent coating, the water repellency and stain resistance of the coated member can be enhanced. Furthermore, the water-repellent coating according to this embodiment can not only enhance water repellency and stain resistance but also exhibit a color derived from the dye compound incorporated into the dyeing powder. For example, it is possible to exhibit a darker color compared to conventional water-repellent members that exhibited white. Therefore, the water-repellent coating according to this embodiment can enhance the superhydrophobicity and stain resistance of the coated member, as well as increase the freedom of design. Moreover, in the water-repellent coating according to this embodiment, the dyeing powder incorporating the dye compound is coated with a water-repellent resin. This makes it possible to keep the dye compound inside the water-repellent coating without it leaking out to the outside. In addition, it is possible to reduce the interaction between the dye compound and external substances and suppress the deterioration of the dye compound. Therefore, the water-repellent coating according to this embodiment can stably retain the dye compound and make it easier to exhibit color over a long period of time.

[0096] [Water-repellent material] Next, a water-repellent member will be described. The water-repellent member comprises a base material and the water-repellent coating that covers the surface of the base material. The water-repellent coating only needs to cover at least a portion of the surface of the base material, it may cover only a portion of the surface of the base material, or it may cover the entire surface of the base material.

[0097] The shape of the base material is not particularly limited and can be selected according to the purpose, for example, it may be a plate, sphere, rod, tube, honeycomb, fiber, membrane, polygon, or porous body. The length, width, thickness, and diameter of the base material should be of an optimal size depending on the application. Furthermore, the material forming the base material is not particularly limited and may be, for example, metal, glass, resin, ceramics, paper, fiber, wood, cement, leather, or a composite thereof.

[0098] The water-repellent component can be any material that requires water repellency. Specific examples of water-repellent components include building materials, vehicles, vehicle parts, clothing, rain gear, antennas, power lines, radar, and ship hulls. These water-repellent components can contribute to preventing the adhesion of water droplets and ice and snow, and facilitating their removal.

[0099] [Method for manufacturing water-repellent material] The method for manufacturing the water-repellent member involves applying the above-mentioned coating composition to the surface of a substrate to form a water-repellent film. The water-repellent film produced by the method for manufacturing the water-repellent member of this disclosure is the same as that described above, so its description is omitted. The substrate can be the material described above.

[0100] The method of applying the paint composition to the surface of the substrate is not particularly limited and can be used by methods such as spray painting, brush painting, bar coating, spin coating, dipping, gravure printing, reverse gravure printing, offset printing, flexographic printing, screen printing, and squeegeeing. The paint composition only needs to be applied to at least a portion of the surface of the substrate. Among the above application methods, spray painting allows for easy application of the paint composition to any desired portion.

[0101] After applying the paint composition to the surface of the substrate, it may be dried as needed to remove the solvent in the paint composition. The drying conditions are not particularly limited as long as the solvent is removed, and heating may be used as needed. In addition, since the water-repellent film according to this embodiment has multiple voids and good breathability, the solvent can be easily evaporated without heating.

[0102] [others] The water-repellent coating may be formed by coating the outermost surface of the aggregate with a coating layer containing at least one of a water-repellent resin, either a silicone resin or a fluororesin. Alternatively, the water-repellent coating may have an intermediate layer formed on the surface of the elongated particles, with a layer containing an auxiliary resin forming as an intermediate layer, and a further outermost layer containing at least one of a water-repellent resin, either a silicone resin or a fluororesin. In other words, it may have a multilayer structure in which elongated particles, a layer containing an auxiliary resin coating the elongated particles, and a layer containing at least one of a water-repellent resin, either a silicone resin or a fluororesin, are laminated in this order. When manufacturing such a water-repellent coating, a coating composition containing a plurality of elongated particles or a plurality of protruding particles, a solvent, and an auxiliary resin can be used. Alternatively, a coating composition in which a water-repellent resin is dissolved in a solvent can be used. For example, a water-repellent member may be manufactured by applying a coating composition containing a plurality of elongated particles or a plurality of protruding particles, a solvent, and an auxiliary resin to the surface of a substrate, drying it, baking it if necessary, and then applying a coating composition in which a water-repellent resin is dissolved in a solvent and drying it. [Examples]

[0103] The embodiment will be described in more detail below with reference to examples, comparative examples, and reference examples, but the embodiment is not limited to these.

[0104] First, the raw materials, powders A1 to A5, were prepared as follows.

[0105] <Preparation of precursor particles> [Powder A1] (Comparative Example 1) 2250 ml of sodium aluminate solution, prepared to have a concentration of 50 g / L for both Na2O and Al2O3, was kept warm at 80°C. 0.5 m³ per 1 L of sodium aluminate solution 2 Aluminum hydroxide seed crystals (Dp50: 0.28 μm, BET specific surface area: 37.5 m²) are prepared to achieve the following BET specific surface area. 2The amount of seed crystal ( / g) was added to the sodium aluminate solution and stirred. While continuously stirring the sodium aluminate solution with the added seed crystal, 2250 mL of the sodium aluminate solution prepared as described above was added to the sodium aluminate solution with the added seed crystal. The sodium aluminate solution was added continuously at a rate of 10-20 cc / hour so that the supersaturated concentration of Al2O3 was 15 g / L or less, as determined by analyzing the liquid in the reaction vessel. The resulting crystallized material was filtered, washed with warm pure water, and dried to produce powder A1 containing multiple chestnut-shaped gibbsite particles. SEM images of powder A1 are shown in Figures 1 and 2. SEM observation was performed using a scanning electron microscope (Hitachi High-Tech Science Corporation, S-4700). As shown in Figures 1 and 2, it was confirmed that the chestnut-shaped gibbsite particles 1 have multiple elongated particles 2. Furthermore, XRD (X-ray Diffraction) measurements confirmed that powder A1 contains gibbsite.

[0106] The Dp50 of the aluminum hydroxide seed crystal was measured as follows. First, the seed crystal powder was pre-treated by dispersing it using a homogenizer (US-600T, Nippon Seiki Seisakusho Co., Ltd.) at 40W, 20kHz, and for 1 minute. Then, the Dp50 was measured using a laser diffraction / scattering particle size analyzer (Microtrac MT3300, Nikkiso Co., Ltd.). The BET specific surface area of ​​the aluminum hydroxide seed crystal was obtained using an automatic specific surface area measuring device (Flowsorb II 2300, Micrometrics) in accordance with JIS R1626:1996. Specifically, nitrogen gas was adsorbed at 23°C using the constant volume method, and the BET specific surface area was calculated using the BET single-point method.

[0107] <Preparation of calcined particles> [Powder A2] Powder A2 was prepared by calcining 4 g of powder A1 in an electric furnace at 600°C for 5 hours. SEM images of powder A2 are shown in Figures 3 and 4. XRD measurements confirmed that powder A2 contains χ-alumina and γ-alumina.

[0108] [Powder A3] Powder A3 was prepared by calcining 4 g of powder A1 in an electric furnace at 800°C for 5 hours. SEM images of powder A3 are shown in Figures 5 and 6. XRD measurements confirmed that powder A3 contains χ-alumina and γ-alumina.

[0109] [Powder A4] Powder A4 was prepared by calcining 4 g of powder A1 in an electric furnace at 1000°C for 5 hours. SEM images of powder A4 are shown in Figures 7 and 8. XRD measurements confirmed that powder A4 contains κ-alumina, θ-alumina, and corundum.

[0110] [Powder A5] Powder A5 was prepared by calcining 4 g of powder A1 in an electric furnace at 1200°C for 5 hours. SEM images of powder A5 are shown in Figures 9 and 10. XRD measurements confirmed that powder A5 contains corundum.

[0111] For powders A1 to A5 (precursor particles or calcined particles) obtained as described above, the BET specific surface area, pore volume, average pore diameter, aggregated particle diameter, average major axis, average minor axis, and aspect ratio were measured as follows. These measurement results are shown in Table 1. Figure 11 shows a graph illustrating the relationship between pore diameter and pore volume. Note that since the pore volume of powder A1 is lower than that of powders A2 to A5, if we were to plot the relationship between the pore diameter and pore volume of powder A1 on the graph, it would be plotted almost on the horizontal axis and would overlap with the graph of powder A5, making it difficult to distinguish between the two. Therefore, Figure 11 shows the relationship between the pore diameter and pore volume of powders A2 to A5.

[0112] (BET specific surface area) The BET specific surface area of ​​the particles contained in the powder was obtained using a Micrometrics TriStar3000 automatic specific surface area / pore distribution analyzer in accordance with JIS Z8830:2013. Specifically, nitrogen gas was adsorbed at 23°C using the constant volume method, and the BET specific surface area was calculated using the BET multi-point method.

[0113] (pore volume) The pore volume of particles contained in the powder was measured using a Micrometrics TriStar3000 automatic specific surface area / pore distribution analyzer. Specifically, adsorption isotherms were measured using the constant volume method with nitrogen gas at 23°C in accordance with JIS Z8831-2:2010, and the pore size distribution was calculated from the adsorption isotherms using the BJH method to determine the pore volume.

[0114] (Average pore diameter) The average pore size of the particles contained in the powder was measured using a Micrometrics TriStar3000 automatic specific surface area / pore size distribution analyzer. Specifically, adsorption isotherms were measured using the constant volume method with nitrogen gas at 23°C in accordance with JIS Z8831-2:2010. The pore size distribution was calculated from the adsorption isotherms using the BJH method, and the most frequent pore size was determined as the average pore size.

[0115] (Agglomerated particle size) The aggregated particle size of the powder was measured using a Carl Zeiss FE-SEM ULTRAplus scanning electron microscope. The aggregated particle size was obtained by measuring the particle size of 10 chestnut-shaped gibbsite particles from the SEM image and calculating the average of these measurements.

[0116] (Average major axis, average minor axis, and aspect ratio) The average major and minor diameters of elongated particles contained in burr-shaped gibbsite were measured using a Carl Zeiss FE-SEM ULTRAplus scanning electron microscope. The average major and minor diameters were obtained by measuring the major and minor diameters of 10 elongated particles from SEM images of the burr-shaped gibbsite and calculating the average values ​​of these measurements. The major diameter of the elongated particles in the burr-shaped gibbsite was measured from the center of the burr-shaped gibbsite, i.e., from the base of the elongated particle to the tip of the elongated particle. The minor diameter of the elongated particles in the burr-shaped gibbsite was measured from the middle portion of the elongated particle. The aspect ratio was calculated by dividing the average major diameter by the average minor diameter.

[0117] [Table 1]

[0118] As shown in Table 1, powders A2 to A4, which were calcined at 600°C to 1000°C, have a larger BET specific surface area and pore volume compared to uncalcined powders A1 or powders A5, which were calcined at 1200°C. Furthermore, as can be seen from Table 1 and Figure 11, it was confirmed that the pore state differs between powders A1 or A5 and powders A2 to A4. Specifically, powders A2 to A4 had an average pore diameter in the range of 2 to 50 nm, and their pore volume and BET specific surface area were high, confirming the presence of mesopores. In contrast, powders A1 or A5 had an average pore diameter in the range of 2 to 50 nm, but their pore volume and BET specific surface area were low. This is thought to be because, when fired at 600°C to 1000°C, mesopores are formed in the long particles, but when fired at 1200°C, the mesopores formed in the long particles are sintered and disappear.

[0119] As shown in Table 1, the average major axis decreases with increasing firing temperature. This is thought to be because firing makes the long particles brittle and prone to breaking. On the other hand, comparing powders A2 to A4, there is no significant difference in the average minor axis, but the average minor axis of powder A5 is shorter than that of powders A2 to A4. Furthermore, the aspect ratio of powders A2 to A4 tends to decrease with increasing firing temperature from 600°C to 1000°C, while the aspect ratio of powder A5, fired at 1200°C, increases as the average minor axis decreases.

[0120] <Preparation of stained powder> Next, dyed powders B1 to B12 according to the examples and comparative examples were prepared using powders A1 to A5 prepared as described above as raw materials.

[0121] [Powder B1] (Example 1) First, a suspension was prepared by mixing 1 g of powder A2, 0.125 g of dye (TAC-BLACK BLH from Okuno Pharmaceutical Co., Ltd.), and 25 mL of water. TAC-BLACK BLH contains chromium complex salt azo acid dye and cobalt complex salt azo acid dye. Next, the suspension was stirred in a 60°C water bath for 60 minutes, and the suspension after stirring was filtered and washed. Powder B1 was prepared by drying the washed filtrate in a 50°C drying oven for more than 2 hours.

[0122] [Powder B2] (Example 2) Powder B2 was prepared in the same manner as powder B1, except that powder A3 was used instead of powder A2.

[0123] [Powder B3] (Example 3) Powder B3 was prepared in the same manner as powder B1, except that powder A4 was used instead of powder A2.

[0124] [Powder B4] (Example 11) A suspension was prepared by mixing 1 g of powder A2, 0.625 g of dye (ammonium iron oxalate), and 25 mL of water. Next, the suspension was stirred in a 50°C water bath for 30 minutes, and the suspension after stirring was filtered and washed. The washed filtrate was dried in a 50°C drying oven for more than 2 hours. Powder B4 was prepared in the same manner as powder B1, except for the above.

[0125] [Powder B5] (Example 12) Powder B5 was prepared in the same manner as powder B4, except that powder A3 was used instead of powder A2.

[0126] [Powder B6] (Example 13) Powder B6 was prepared in the same manner as powder B4, except that powder A4 was used instead of powder A2.

[0127] [Powder B7] (Example 4) Powder B7 was prepared in the same manner as powder B1, except that a suspension was prepared by mixing 1 g of powder A3, 0.125 g of dye (TAC-FIERY RED GBM from Okuno Pharmaceutical Co., Ltd.), and 25 mL of water.

[0128] [Powder B8] (Example 5) Powder B8 was prepared in the same manner as powder B1, except that a suspension was prepared by mixing 1 g of powder A3, 0.125 g of dye (TAC-BLUE BRL from Okuno Pharmaceutical Co., Ltd.), and 25 mL of water.

[0129] [Powder B9] (Comparative Example 2) A suspension was prepared by mixing 1 g of powder A1, 0.625 g of dye (TAC-BLACK BLH from Okuno Pharmaceutical Co., Ltd.), and 25 mL of water. Next, the suspension was stirred in a 50°C water bath for 30 minutes, and the suspension after stirring was filtered and washed. Powder B9 was prepared by drying the washed filtrate in a 50°C drying oven for more than 2 hours.

[0130] [Powder B10] (Comparative Example 3) Powder B10 was prepared in the same manner as powder B1, except that powder A5 was used instead of powder A2.

[0131] [Powder B11] (Comparative Example 11) Powder B11 was prepared in the same manner as powder B4, except that powder A1 was used instead of powder A2.

[0132] [Powder B12] (Comparative Example 12) Powder B12 was prepared in the same manner as powder B4, except that powder A5 was used instead of powder A2.

[0133] [evaluation] The color and L of the powder obtained as described above * a * b * The values ​​were evaluated as follows, and these results are shown in Tables 2 to 4. In addition, samples in which powder B5 was embedded in resin and processed with a cross-section polisher (registered trademark) were observed with an SEM, and the results of analysis by EDS (Energy Dispersive X-ray Spectroscopy) are shown in Figures 12 to 14.

[0134] (color) The color of the powder was determined by visual inspection.

[0135] (L * a * b * value) L of powder * value, a * Value and b * The values ​​were measured using a colorimeter (CR400, manufactured by Konica Minolta Japan, Inc.) in accordance with geometric condition c of JIS Z8722:2009. Colorimetric measurements were performed using a diffuse illumination vertical reception method (D / 0), with a D65 light source, and observed using CIE 2° field-of-view color matching function approximation.

[0136] (SEM, EDS) Powder B5 was embedded in resin, and cross-sections of long, burr-shaped gibbsite particles were observed using backscattered electron imaging with a scanning electron microscope (SEM) and analyzed by EDS.

[0137] [Table 2]

[0138] [Table 3]

[0139] [Table 4]

[0140] As shown in Table 2, powders B1 to B3 are L * The value became smaller. Also, as shown in Table 3, powders B4 to B6 are L smaller than powders A1, B11, and B12. * The value became smaller. Also, as shown in Table 4, powders B7 to B8 had a low L * It had a value. From these results, when powders A2 to A4 that were fired at 600°C to 1000°C were dyed, compared to when unfired powder A1 and powder A5 that was fired at 1200°C were dyed, L *A decrease in the value was confirmed. In powders B1 to B3 and B4 to B6, the dye compound is incorporated into the calcined particles with mesopores, resulting in L * The value appears to have decreased.

[0141] Figure 12 is an SEM image of powder B5 observed with an SEM. Figure 13 is a magnified SEM image of Figure 12. Figure 14 is a graph of the analysis of the area indicated by the line in Figure 13 by EDS. As shown in Figure 13, the surface portion of the long particles appears whiter compared to the central portion. Backscattered electron images tend to show whiter for elements with larger atomic numbers. Therefore, it is thought that iron, which has a larger atomic number and originates from the dye, is more ubiquitous in the surface portion of the long particles than aluminum, which originates from the raw material of the long particles, rather than in the central portion. Furthermore, as shown in Figure 14, the EDS analysis results show that iron is present throughout the long particles. In addition, as shown in Figure 14, the detection intensity of iron is higher in the surface portion of the long particles than in the central portion. From these results, it is thought that iron, which is a dyeing component, penetrates to the central portion of the long particles through mesopores, but tends to be more ubiquitous in the surface portion than in the central portion.

[0142] Next, paint compositions and water-repellent members according to the examples, comparative examples, and reference examples were prepared using the powders prepared as described above and newly prepared powders D1 and D2.

[0143] <Preparation of paint composition> [Composition C1] (Example 21) First, 0.5 g of water-repellent resin was added to 5 mL of solvent and stirred with a magnetic stirrer for 1 minute to uniformly mix the water-repellent resin and solvent. PDMS (polydimethylsiloxane) DOWSIL® HC2100, manufactured by Dow-Toray Industries, Inc., was used as the water-repellent resin. Ethyl acetate, special grade, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., was used as the solvent. 0.5 g of powder B2 was added to this mixture and stirred with a magnetic stirrer for a further 10 minutes to prepare composition C1.

[0144] [Composition C2] (Example 22) Composition C2 was prepared in the same manner as composition C1, except that powder B5 was used instead of powder B2.

[0145] [Composition C3] (Comparative Example 21) Composition C3 was prepared in the same manner as composition C1, except that powder D1 was used instead of powder B2 and the amount of solvent was set to 10 mL. As powder D1, spherical or ellipsoidal (approximately spherical) aluminum particles (product name: 14-0132, average particle size (Dp50): 11.2 μm) manufactured by Toyo Aluminum Co., Ltd. were used.

[0146] [Composition C4] (Reference Example 1) Composition C4 was prepared in the same manner as composition C1, except that powder A1 was used instead of powder B2.

[0147] [Composition C5] (Reference Example 2) Composition C5 was prepared in the same manner as composition C1, except that powder A2 was used instead of powder B2.

[0148] [Composition C6] (Reference Example 3) Composition C6 was prepared in the same manner as composition C1, except that powder A3 was used instead of powder B2.

[0149] [Composition C7] (Reference Example 4) Composition C7 was prepared in the same manner as composition C1, except that powder A4 was used instead of powder B2 and the amount of solvent was set to 20 mL.

[0150] [Composition C8] (Reference Example 5) Composition C8 was prepared in the same manner as composition C1, except that powder A5 was used instead of powder B2 and the amount of solvent was set to 10 mL.

[0151] [Composition C9] (Comparative Example 22) Composition C9 was prepared in the same manner as composition C1, except that powder D2 was used instead of powder B2 and the amount of solvent was changed to 20 mL. As powder D2, Panatetra(registered trademark) WZ-0501 (tetrapod-shaped zinc oxide) manufactured by Amtec Co., Ltd. was used.

[0152] <Fabrication of water-repellent materials> A 0.3 mm thick A3003 sheet material was prepared as the base material. Vinyl tape was attached to both ends of the base material to create a step. Compositions C1 to C9 prepared as described above were dropped onto the base material, spread evenly with a glass rod, and applied using the squeegee method, then dried at room temperature for 30 minutes. In this way, water-repellent members E1 to E9 were prepared, each having a water-repellent film formed on the surface of the base material.

[0153] [evaluation] The contact angle immediately after painting and the contact angle after the stain resistance test of the water-repellent material obtained as described above were evaluated as follows, and the results are shown in Table 5.

[0154] (Contact angle immediately after painting) The contact angles of the water-repellent coating surface obtained as described above were measured using a solid-liquid interface analyzer, DropMaster700, manufactured by Kyowa Interface Chemical Co., Ltd. Specifically, 2.5 μL of deionized water was dropped onto the water-repellent coating surface at three different locations, and the contact angles of the water droplets formed on the surface were measured. A Teflon® coated needle 28G was used to drop the deionized water. A "○" was given if all three contact angles were 150° or higher or if no droplets were deposited; a "△" was given if one or two contact angles were 150° or higher and the contact angles at the other locations were less than 150°; and a "×" was given if all three contact angles were less than 150°.

[0155] (Contact angle after stain resistance test) To reproduce contamination of superhydrophobic surfaces by the adhesion of ultrafine atmospheric particles such as DEP, a contamination resistance test was conducted. Specifically, carbon was deposited onto the surface of the water-repellent film obtained as described above using a carbon coater VC-100 manufactured by Vacuum Device Co., Ltd. Specifically, a replacement carbon core SLC-30 was set in the electrode section, the water-repellent material was placed on the stage, the chamber was evacuated to approximately 2 Pa, and then current was passed between the electrodes for several seconds until the core burned out to deposit carbon onto the surface of the water-repellent film. When carbon is deposited, ultrafine carbon particles with a primary particle diameter of several nanometers precipitate on the surface of the deposited material. The water-repellent material with the deposited carbon was removed from the chamber, and the contact angle was measured in the same manner as described above. If all three contact angles were 145° or higher or no droplets were deposited, it was evaluated as "○", if one or two contact angles were 145° or higher and the contact angles of the other locations were less than 145°, it was evaluated as "△", and if all three contact angles were less than 145°, it was evaluated as "×".

[0156] [Table 5]

[0157] As shown in Table 5, water-repellent members E1 to E2 and E4 to E9 did not exhibit superhydrophobicity, as no droplets adhered immediately after painting. On the other hand, water-repellent member E3 did not exhibit superhydrophobicity even immediately after painting because long particles were not used. However, water-repellent member E9 is formed from zinc oxide, and it has not been confirmed whether it can be colored using this method.

[0158] Furthermore, in water-repellent members E1, E2, and E6, dyed powders B2 and B5, and powder A3, respectively, were used, but all exhibited superhydrophobicity without droplet adhesion immediately after coating and after the stain resistance test. From this, it is considered that the presence or absence of powder dyeing does not have a significant effect on the contact angle immediately after coating and the contact angle after the stain resistance test. When water-repellent members E6 and E2 were examined by SEM, as shown in Figures 15, 16, 19, and 20, it was confirmed once again that the presence or absence of powder dyeing between firing and treatment with water-repellent resin did not affect the surface shape of the water-repellent members. In addition, when powder B5 and water-repellent member E2 were examined by SEM, as shown in Figures 17 to 20, it was confirmed once again that the presence or absence of treatment with water-repellent resin after firing and dyeing did not affect the surface shape of the water-repellent members.

[0159] As shown in Figures 19 and 20, the water-repellent member E2 had a Cassie-Baxter surface, and spaces communicating with the outside were maintained between multiple elongated particles covered by a coating layer formed of water-repellent resin. On the other hand, although not shown, the surface of the water-repellent member E3 had voids filled with water-repellent resin, and no Cassie-Baxter surface was formed. For this reason, it is thought that the water-repellent member E2 exhibited superhydrophobicity, while the water-repellent member E3 did not.

[0160] Powders B1 to B8 are produced by dyeing powders A2 to A4. Therefore, it is expected that water-repellent components made from powders B1 to B8 will exhibit superhydrophobicity immediately after coating, similar to water-repellent components E5 to E7.

[0161] Although this embodiment has been described above with reference to examples, comparative examples, and reference examples, this embodiment is not limited to these, and various modifications are possible within the scope of the gist of this embodiment.

Claims

1. It contains alumina as its main component and comprises multiple elongated particles having an elongated shape. A dyed powder in which an inorganic dye compound is incorporated between the center of the elongated particle and the outer surface of the elongated particle.

2. L ＊ The dyeing powder according to claim 1, wherein the value is less than 90.

3. The dyeing powder according to claim 1 or 2, wherein the inorganic dye compound contains a transition metal element.

4. The dyeing powder according to any one of claims 1 to 3, wherein the elongated shape is at least one shape selected from the group consisting of needle shape, scale shape and plate shape.

5. The dyeing powder according to any one of claims 1 to 4, wherein the average major diameter of the plurality of elongated particles is 1 μm or more and 40 μm or less.

6. The dyeing powder according to any one of claims 1 to 5, wherein the ratio of the average major axis to the average minor axis of the plurality of long particles is 3 or more.

7. It contains alumina as its main component and multiple elongated particles, Solvents and, A water-repellent resin dissolved in the aforementioned solvent, It contains, A paint composition in which a dye compound is incorporated between the center of the elongated particle and the outer surface of the elongated particle.

8. The paint composition according to claim 7, wherein the dye compound contains a transition metal element.

9. The aggregate comprises a plurality of elongated particles having an elongated shape and a coating layer formed of a water-repellent resin covering the surface of the plurality of elongated particles, Within the elongated particle, a dye compound is incorporated between the center of the elongated particle and the outer surface of the elongated particle. The aggregate is formed by the three-dimensional aggregation of the plurality of elongated particles. The outer surface of the aggregate is covered by the coating layer, The aggregate is a water-repellent coating that maintains spaces communicating with the outside between the plurality of elongated particles covered by the coating layer.

10. Substrate and A water-repellent coating according to claim 9 that covers the surface of the substrate, A water-repellent component equipped with the following features.

11. A calcination step comprising: calcining a plurality of elongated precursor particles containing at least one of alumina and aluminum hydroxide at a temperature of 500°C to 1100°C to obtain a plurality of calcined particles containing alumina as the main component, having an elongated shape, and having mesopores; A dyeing step in which an inorganic dye compound is incorporated into the mesopores of the plurality of calcined particles, A method for producing dyeing powders, including the following:

12. The pore volume of the aforementioned plurality of calcined particles is 0.03 cm³. ３ A method for producing a dyeing powder according to claim 11, wherein the amount is 1g or more.

13. The BET specific surface area of ​​the aforementioned plurality of calcined particles is 10 m². ２ A method for producing a dye powder according to claim 11 or 12, wherein the amount is 1 / g or more.

14. The coating composition described in claim 7 is applied to the surface of the substrate to form a water-repellent film. A method for manufacturing a water-repellent member, wherein the water-repellent film comprises an aggregate including a plurality of elongated particles and a coating layer formed of the water-repellent resin that covers the surface of the plurality of elongated particles.

15. The aggregate is formed by the three-dimensional aggregation of the plurality of elongated particles. The outer surface of the aggregate is covered by the coating layer, The method for manufacturing a water-repellent member according to claim 14, wherein the aggregate maintains a space between the plurality of elongated particles covered by the coating layer that communicates with the outside of the water-repellent coating.

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