Coating composition for snow-adhering surface and coating film forming method

Abstract

To provide a coating material for snow-adhering surfaces and a coating film forming method using the same, which can form a durable hydrophilic coating film whose hydrophilicity is not degraded by exposure to rain or solar radiation.SOLUTION: A coating composition for snow-adhering surfaces comprises a first liquid containing colloidal silica, an alkyl silicate, a solvent, and an acid, and a second liquid containing an acrylic polymer having a hydrophilic group and having an alkoxysilyl group or a silanol group at least at one terminal, and a solvent.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a paint for snow-covered surfaces and a coating film forming method. [Background technology]

[0002] In areas of Japan with heavy snowfall, removing snow from houses and other structures is essential in winter, but it is a very tough and dangerous job. Every year, there are reports of falling accidents during snow removal work, and there are also accidents in which people passing under a roof are caught up in avalanches of snow that have accumulated on the roof.

[0003] Therefore, paints have been developed that can be applied to surfaces such as roofs so that snow slides off without sticking. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 5-222064 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-111806 [Patent Document 3] Japanese Patent Application Laid-Open No. 2016-169384 Summary of the Invention [Problem to be solved by the invention]

[0005] Patent Document 1 discloses imparting hydrophilicity with a silicon-containing sulfobetaine compound. Patent Document 2 discloses a coating agent that is imparted with hydrophilicity by hydrolyzing and condensing hydrocarbyl silicates in a mixed solution of a basic catalyst solution, glycol ethers, and a lower alcohol having 1 to 4 carbon atoms. Patent Document 3 discloses a snow-drifting paint that contains an oxidatively curable resin component, a fluorine-based surfactant, and an organic solvent.

[0006] The methods of imparting hydrophilicity to substrates disclosed in the various patent documents have had problems such as the coating film imparted with hydrophilicity not being highly durable, requiring repainting at short intervals, and the coating film formed on the substrate not having sufficient adhesion, resulting in a decrease in hydrophilicity over time. Furthermore, there has been a problem of decreased snow sliding properties when the snow contains a lot of water. Therefore, the present invention aims to develop a paint for snow-covered surfaces that does not lose its hydrophilicity even after the snowfall period has passed, even when exposed to rain or sunlight, and that produces a highly durable hydrophilic coating film, and a coating film formation method using this paint. [Means for solving the problem]

[0007] The present inventors have found that the above problems can be solved by the following configuration.

[0008] <1> As the first liquid Contains colloidal silica, alkyl silicate, solvent, and acid. As second liquid The composition is characterized by comprising an acrylic polymer containing a hydrophilic group and an alkoxysilyl group or a silanol group at at least one end, and a solvent. Coating composition for snow-covered surfaces.

[0009] <2> The aforementioned <1> After the first liquid described in the above is applied and dried to form a coating film, the above-mentioned <1> 2. A method for forming a coating film for snow-covered surfaces, comprising applying the second liquid described in 1 above and drying it to form a coating film having a water contact angle of 20° or less on the surface.

[0010] <3> The aforementioned <1> After applying and drying the first liquid described in the above to form a transparent coating film, <1> A method for forming a coating film for snow-covered surfaces, comprising applying the second liquid described in the above and drying it to form a transparent coating film having a coating film transmittance of 70% or more. [Effects of the Invention]

[0011] The paint for snow-receiving surfaces according to the present invention and the coating film formed using this paint have strong adhesion to the substrate, excellent durability, and do not lose their hydrophilicity even when exposed to repeated rainfall and sunlight. As a result, snow does not accumulate on the coating film formed on the substrate during winter snowfall, eliminating the need to repaint the paint for snow-receiving surfaces for long periods of time. Furthermore, because both the first and second liquids are paints that harden at room temperature, a coating film can be formed by painting at any painting site, regardless of the painting environment. DETAILED DESCRIPTION OF THE INVENTION

[0012] The following describes the paint for snow-covered surfaces according to the present invention and a method for forming a coating film using this paint. The various configurations and combinations in the following embodiments are examples, and the present invention is not limited to these embodiments. In this specification, the symbol "to" is used to mean that the numerical values ​​before and after it are included as the lower limit and upper limit.

[0013] <1st liquid> The first liquid of the paint for snow-adhering surfaces according to the present invention must contain colloidal silica, alkyl silicate, a solvent, and an acid.

[0014] The colloidal silica contained in the first liquid of the snow-retaining surface paint of the present invention is a colloidal dispersion consisting of spherical silica particles having a particle diameter of approximately 1 nm to 200 nm and a dispersant. In one embodiment, the dispersant in the colloidal silica is water or a hydrophilic organic solvent. Examples of hydrophilic organic solvents include, but are not limited to, lower alcohols such as methanol, ethanol, normal propyl alcohol, and isopropyl alcohol; glycols such as ethylene glycol and propylene glycol; and glycol ethers such as ethylene glycol monomethyl ether and propylene glycol monomethyl ether.

[0015] Colloidal silica includes those in which spherical silica particles are dispersed (referred to as "spherical colloidal silica"), those in which a plurality of spherical silica particles are connected in a ring shape like a pearl necklace (referred to as "pearl necklace-shaped colloidal silica"), and those in which a plurality of spherical silica particles are connected in a chain shape (referred to as "chain colloidal silica"), and any of these can be used. Of these, chain colloidal silica is preferred because it has a high hydrophilicity-imparting effect. Furthermore, using chain colloidal silica and spherical colloidal silica in combination is preferred because it can achieve the effect of imparting hydrophilicity as well as the effect of improving the strength of the coating.

[0016] Commercially available colloidal silica can be used. For example, Organosilicasol (manufactured by Nissan Chemical Industries, Ltd.) is commercially available as a dispersion in an organic solvent, and Snowtex (registered trademark) (manufactured by Nissan Chemical Industries, Ltd.) is commercially available as a dispersion medium in water stabilized with monovalent cations such as sodium or ammonium. Other colloidal silica that can be used include Ludox (manufactured by DuPont) and Cataloid (manufactured by JGC Catalysts and Chemicals).

[0017] Colloidal silica has the effect of imparting hydrophilicity to the coating. In addition, when the first liquid contains a compound that swells the organic substrate, colloidal silica penetrates the swollen organic substrate and forms a coating, thereby improving the adhesion between the organic substrate and the coating.

[0018] The content of colloidal silica in Liquid 1 is preferably 0.20 to 10.00 mass %, more preferably 0.50 to 5.00 mass %, in terms of silica solid content. If the content is less than this range, the hydrophilicity-imparting effect tends to be reduced, while if the content is more than this range, cracks or cloudiness may occur in the coating.

[0019] The alkyl silicate contained in the first liquid of the snow-retaining surface paint of the present invention refers to an alkyl silicate monomer represented by the general formula: Si(OR)4 (R is an alkyl group) and an alkyl silicate oligomer formed by condensation polymerization of 2 to 10, preferably 3 to 5, alkyl silicate monomers. The alkyl group (R) preferably has 1 to 4 carbon atoms, more preferably 1 to 3.

[0020] Specific examples of alkyl silicates include, but are not limited to, tetramethoxysilane, methyl polysilicate, tetraethoxysilane, and ethyl polysilicate, of which tetraethoxysilane and ethyl polysilicate are preferred from the viewpoints of reactivity, stability, and safety. The alkyl silicate imparts hydrophilicity and also functions as a film-forming aid.

[0021] The alkyl silicate content in the first liquid is preferably 0.50 to 5.00% by mass, and more preferably 1.00 to 5.00% by mass. When the alkyl silicate content is within this range, the fixation of colloidal silica can be improved and a film can be formed. If the content is less than 0.50% by mass, the film formation may be insufficient and the film may become brittle. On the other hand, if the content is more than 5.00% by mass, the hydrophilicity tends to decrease.

[0022] The solvent contained in the first liquid of the paint for snow-retaining surfaces according to the present invention can be an aqueous solvent. The aqueous solvent is a solvent containing at least one of water and a hydrophilic organic solvent, such as water, alcohol, or a mixture of water and alcohol, with water or a mixture of water and alcohol being preferred.

[0023] The water content in the mixture of water and alcohol is preferably 50% by mass or more and less than 100%, and more preferably 70% by mass or more and less than 100%. Examples of alcohol include hydrophilic solvents such as water, lower alcohols such as methanol, ethanol, propanol, and isopropanol, glycols such as ethylene glycol and propylene glycol, and glycol ethers such as ethylene glycol monomethyl ether and propylene glycol monomethyl ether.

[0024] The aqueous solvent used in the first liquid is not limited to these, but hydrophilic solvents such as water, lower alcohols such as methanol, ethanol, propanol, and isopropanol, glycols such as ethylene glycol and propylene glycol, and glycol ethers such as ethylene glycol monomethyl ether and propylene glycol monomethyl ether may be used alone or in combination of two or more.

[0025] The content of the solvent in the first liquid is preferably 60.00 to 99.00 mass%, more preferably 65.00 to 95.00 mass%, and even more preferably 65.00 to 90.00 mass%, and the content of water therein is preferably 1.00 to 35.00 mass%, more preferably 2.00 to 30.00 mass%, and even more preferably 3.00 to 25.00 mass%.

[0026] The content of alcohols is preferably 5.00 to 90.00 mass%, more preferably 20.00 to 85.00 mass%, and even more preferably 30.00 to 80.00 mass%, and the content of glycols and glycol ethers is preferably 20.00 to 60.00 mass%, and even more preferably 40.00 to 60.00 mass%.

[0027] Methanol and ethanol swell or partially dissolve the surface of the organic substrate, increasing the adhesion strength of the first coating formed by the first liquid to the organic substrate, and also function as a dispersing solvent for colloidal silica. Isopropyl alcohol, normal propyl alcohol, liquors, and glycol ethers swell or partially dissolve the surface of the organic substrate, increasing the adhesion strength of the first coating formed by the first liquid to the organic substrate, and also function as a dispersing solvent for colloidal silica, and further adjust the drying speed when dried at room temperature after application. If the content of these ingredients is too low, the drying speed may be too fast, resulting in an uneven coating film.

[0028] The acid contained in the first liquid of the paint for snow-retaining surfaces of the present invention catalyzes the condensation polymerization reaction of alkyl silicate and promotes the formation of a film of alkyl silicate. The type of acid is not particularly limited, and may be an organic acid or an inorganic acid. For example, but not limited to, formic acid, acetic acid, hydrochloric acid, sulfuric acid, nitric acid, etc. may be used.

[0029] Of these, nitric acid is preferred from the viewpoints of reactivity and low corrosiveness. The content of the acid in the first liquid is preferably 0.01 to 0.10 mass %.

[0030] In addition to the above-mentioned compounds, the first liquid may contain other components, such as tetrahydrofuran, boric acid, water glass (No. 3 sodium silicate), organic resins (acrylic resin, methacrylic resin, acrylic urethane resin, urethane resin, etc.), and silane coupling agents.

[0031] When other components are contained, the content of the other components is preferably 3.2 mass % or less of the entire first liquid composition.

[0032] Tetrahydrofuran swells or partially dissolves the surface of the organic substrate, thereby enhancing the adhesive strength of the first coating formed by the first liquid to the organic substrate. In particular, it promotes swelling of the surface of polycarbonate resins and polyester resins, which are difficult to swell with lower alcohols or glycols alone. The content of tetrahydrofuran is preferably 0.10 to 3.00% by mass, and more preferably 0.10 to 1.00% by mass.

[0033] Boric acid acts to increase the adhesive strength of the first coating formed by the first liquid to the organic substrate. The content of boric acid is preferably 0.02 to 0.40 mass %, more preferably 0.03 to 0.10 mass %. If the content is too high, the hydrophilicity of the first coating may decrease and the coating may whiten.

[0034] The water glass (No. 3 sodium silicate) functions as a coating film forming aid. The content of water glass (No. 3 sodium silicate) is preferably 0.01 to 0.20 mass%, more preferably 0.01 to 0.10 mass%. If the content of water glass is too high, the first liquid will gel, making it difficult to apply to the substrate and potentially resulting in an uneven coating film.

[0035] The organic resin functions as an agent for improving the adhesion of the first coating to the substrate. The type of organic resin is not limited to, but may be, for example, an acrylic resin, a methacrylic resin, an acrylic urethane resin, or a urethane resin. Specifically, a resin that dissolves or disperses even in a polar solvent containing water is preferred. The content of the organic resin is preferably 0.01 to 1.00% by mass.

[0036] The silane coupling agent functions as an agent for improving adhesion of the first coating to the substrate, and the content of the silane coupling agent is preferably 0.10 to 1.00% by mass.

[0037] In addition to the above, the first liquid may contain various additives that are commonly used in paints, such as a leveling agent, a viscosity modifier, and an antifoaming agent.

[0038] <2nd liquid> The second liquid of the paint for snow-adhering surfaces according to the present invention must contain an acrylic polymer containing a hydrophilic group and an alkoxysilyl group or silanol group at at least one end, and a solvent.

[0039] The acrylic polymer contained in the second liquid of the paint for snow-adhering surfaces according to the present invention is an acrylic polymer having at least one of an alkoxysilyl group and a silanol group, and a hydrophilic group.

[0040] When the acrylic polymer is a linear polymer, at least one of an alkoxysilyl group and a silanol group may be present at at least one end of the acrylic polymer. The alkoxysilyl group is preferably a group represented by the following formula (A).

[0041] [ka]

[0042] In formula (A), Rx and Ry each independently represent an alkyl group. When a plurality of Rx and Ry are present, they may be the same or different. n represents 1, 2, or 3. * represents the bonding position. The alkyl group represented by Rx and Ry may be linear or branched. The number of carbon atoms in the alkyl group represented by Rx and Ry is not particularly limited, and may be, for example, 1 to 10.

[0043] The acrylic polymer has a hydrophilic group, such as an alkoxysilyl group, a silanol group, or a betaine group. The acrylic polymer preferably contains a repeating unit represented by the following formula (1).

[0044] The viscosity average molecular weight of the acrylic polymer having a repeating unit represented by formula (1) and an alkoxysilyl group or a silanol group at at least one end is preferably 100 or more, more preferably 500 or more, and from the viewpoint of increasing the solubility of the polymer, is preferably 100,000 or less.

[0045] The viscosity average molecular weight can be determined by measuring the viscosity of a polymer solution at 25°C using an Ubbelohde viscometer (manufactured by Sogo Rikagaku Glass Works, Ltd., product number: U-0327-26), or by gel permeation chromatography.

[0046] [ka]

[0047] In formula (1), R1 and R2 each independently represent a hydrogen atom or a substituent. When R1 and R2 represent a substituent, examples of the substituent include an alkyl group, a cycloalkyl group, and an aryl group, and the alkyl group, the cycloalkyl group, and the aryl group may be substituted with a substituent such as an alkoxysilyl group, a silanol group, or a hydrophilic group.

[0048] The concentration of the acrylic polymer is preferably adjusted to about 0.05 to 5.00% by mass, more preferably about 1.00 to 3.00% by mass, and even more preferably about 1.00 to 2.00% by mass.

[0049] The solvent contained in the second liquid of the snow-retaining surface paint of the present invention may be, but is not limited to, water; lower alcohols such as methanol, ethanol, normal propyl alcohol, and isopropyl alcohol; glycols such as ethylene glycol and propylene glycol; ketones such as acetone and methyl ethyl ketone; ethers such as diethyl ether and tetrahydrofuran; aromatic hydrocarbon compounds such as benzene, toluene, and xylene; aliphatic hydrocarbon compounds such as n-hexane; alicyclic hydrocarbon compounds such as cyclohexane; and acetate esters such as methyl acetate and ethyl acetate, which may be used alone or in combination of two or more.

[0050] The amount of solvent is not particularly limited, but is usually adjusted so that the concentration of the acrylic polymer in a solution obtained by dissolving an acrylic polymer having a hydrophilic group and an alkoxysilyl group or a silanol group at at least one end in a solvent is about 0.05 to 5.00 mass%, more preferably about 1.00 to 3.00 mass%, and even more preferably about 1.00 to 2.00 mass%.

[0051] The second liquid may contain other components in addition to those described above. Examples of other components include acids, alkalis, and additives commonly used in paints.

[0052] The second liquid may contain an acid or alkali. Adding an acid or alkali is particularly preferable when using an acrylic polymer having an alkoxysilyl group at the end. Adding an acid or alkali promotes hydrolysis of the alkoxysilyl group, converting it to a silanol group.

[0053] The type of acid is not particularly limited, and may be an organic acid or an inorganic acid. For example, but not limited to, formic acid, acetic acid, hydrochloric acid, sulfuric acid, nitric acid, etc. can be used. Among them, nitric acid is preferred from the viewpoint of reactivity and low corrosiveness. The type of alkali is also not particularly limited, and sodium hydroxide, potassium hydroxide, ammonia, etc. can be used.

[0054] In addition to the above, the second liquid may contain various additives commonly used in paints. For example, it may contain salts such as sodium sulfate, sodium chloride, potassium chloride, and ammonium sulfate in an amount of about 0.01 to 0.05% by mass. These salts play a role in improving the dissolution stability of the acrylic polymer.

[0055] <Production of paint for snow-retaining surfaces> The snow-retaining surface paint of the present invention can be produced by conventionally known paint production methods and production processes, using a high-speed blade-type mixer, an open or pressure kneader, a roll mill, a grain mill, or other paint production equipment.

[0056] <Painting for snow-retaining surfaces> The paint for snow-adhered surfaces of the present invention can be applied by conventionally known coating methods, such as brush coating, roller coating, sponge coating, flow coating, trowel coating, air spray coating, airless spray coating, and various on-site coating machines, as well as electrostatic coating and various in-plant line coating machines such as various roll coater coating.

[0057] Substrates to which the snow-adhering surface paint of the present invention can be applied include roofing materials of any material, such as various metal roofs, various slate roofs, various tile roofs, etc. In addition, it is also possible to apply the paint to glass, thermoplastic resins, and thermosetting resins.

[0058] The dry coating film thickness formed by the paint for snow-receiving surfaces of the present invention is preferably 350 μm to 1000 μm. If it is less than 350 μm, the required water contact angle may not be obtained on the coating film surface. If it exceeds 1000 μm, problems such as the coating film taking a long time to dry and forming may occur, and the coating film transmittance may decrease.

[0059] The coating amount of each of the first and second liquids of the paint for snow-receiving surfaces of the present invention is 15 g / m 2 ~20g / m 2 It is desirable that the thickness is 15g / m 2 If the coating thickness is less than 20 g / m, the required water contact angle may not be obtained on the coating surface. 2 If the temperature exceeds this range, problems such as a long drying time for the coating film may occur, and the transmittance of the coating film may decrease.

[0060] The coating film surface of the snow-receiving surface paint consisting of the first and second liquids of the present invention, immediately after application and drying to form a film, must have a water contact angle of 20° or less. If the water contact angle of the coating film surface exceeds 40°, the coating film surface will not be sufficiently hydrophilic, and snow may continue to adhere to the coating film surface. If the water sliding angle of the coating surface exceeds 90°, snow adhering to the coating may not slide off quickly and may accumulate.

[0061] If the coating film surface immediately after application and drying of the snow-receiving surface paint consisting of the first and second liquids of the present invention has a coating film transmittance of less than 70%, the original color tone of the roofing material may be altered. For this reason, the coating film transmittance must be 70% or higher. [Example]

[0062] The present invention will be described in more detail below with reference to the following examples. The materials, amounts used, proportions, treatment contents, treatment procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention.

[0063] [1st liquid] The first liquid of the paint for snow-prone surfaces contained 2.7% by mass of amorphous silica as colloidal silica, 31.6% by mass of ethanol, 25% by mass of normal propyl alcohol, 25% by mass of propylene glycol monomethyl ether, 5% by mass of methanol, 5% by mass of isopropyl alcohol, 5% by mass of water, and 0.5% by mass of tetrahydrofuran as solvents, and 0.1% by mass of boric acid and 0.1% by mass of nitric acid as acids.

[0064] [Second liquid] The second liquid was an acrylic polymer having a betaine group as a hydrophilic group and containing an alkoxysilyl group or a silanol group at at least one end. An aqueous solution of this acrylic polymer (LAMBIC-771W, manufactured by Osaka Organic Chemical Industry Ltd., solids concentration 10% by mass) was diluted five times with ion-exchanged water to a solids concentration of 2.0% by mass.

[0065] Comparative Examples 1 to 3 Comparative Example 1 was a 3 mm thick glass plate with no paint applied to the surface, Comparative Example 2 was a commercially available general roof paint (silicone resin-based), and Comparative Example 3 was a commercially available snow-proof paint "Rakuyuki Paint" (manufactured by Kansai Paint Co., Ltd.).

[0066] [Preparation of evaluation test plates using glass plates] Example 1 The first liquid of the paint for snow-adhering surfaces according to the present invention was used as Comparative Example 1 on a glass plate, and 15 g / m 2 ~20g / m 2 The coating was then dried at room temperature for 24 hours to obtain a coating film having an average thickness of 500 μm. Onto this coating film, the second liquid of the paint for snow-receiving surfaces according to the present invention was applied using a sponge at a rate of 15 g / m. 2 ~20g / m 2 The coating was applied and dried at room temperature for 24 hours to obtain a coating film having an average thickness of 300 μm, which was designated as Example 1.

[0067] [Creating test panels for evaluating water contact angle and water slide-off using roofing materials] <Example 2> A metal roofing plate was used as the coating substrate, and the first liquid of the paint for snow-receiving surfaces according to the present invention was applied to the plate using a sponge at a rate of 15 g / m. 2 ~20g / m 2 The coating was then dried at room temperature for 24 hours to obtain a coating film having an average thickness of 400 μm. Onto this coating film, the second liquid of the paint for snow-receiving surfaces according to the present invention was applied using a sponge at a rate of 15 g / m. 2 ~20g / m 2 The coating was applied and dried at room temperature for 24 hours to obtain a coating film having an average thickness of 300 μm, which was designated as Example 2.

[0068] <Comparative Example 2> A metal roofing sheet was used as the coating substrate, and the paint of Comparative Example 2 was applied in an amount of 260 g / m using an air spray. 2 ~320g / m 2 After painting and drying at room temperature for 24 hours, a coating film of 150 μm on average was obtained.

[0069] <Comparative Example 3> A metal roofing sheet was used as the coating substrate, and the paint of Comparative Example 3 was applied using an air spray at 70 g / m 2 ~82g / m 2 The coating was applied and dried at room temperature for 24 hours to obtain a coating film of 50 μm.

[0070] <Measurement method (paint film transmittance)> Measurements are made in accordance with JIS R 3212 Automotive Safety Glass.

[0071] <Measurement method (water contact angle)> In accordance with JIS R 3257, 3 μl of pure water was dropped onto each test plate, and the contact angle was measured 10 seconds after the drop at a measurement temperature of 25°C using a CA-X monitor (Kyowa Interface Science Co., Ltd.). Evaluation was based on the average value of five measurements.

[0072] <Measurement method (sliding angle)> 20 μl of pure water was dropped onto each test plate, and the sliding angle was measured 10 seconds after dropping at a measurement temperature of 25°C by looking at the monitor of the CA-X model (Kyowa Interface Science Co., Ltd.). This is the average value of three measurements.

[0073] [Evaluation test result 1: Coating transmittance through glass plate] Table 1 shows the results of measuring and evaluating the transmittance of the coating film. The values ​​in the table are the maximum, minimum, and average values ​​for each transmittance. The values ​​in parentheses are the difference from the value of the glass alone.

[0074] [Table 1]

[0075] [Evaluation test result 2: Water contact angle with glass plate] Table 2 shows the results of water contact angle measurement evaluation using glass substrates (glass plates). The initial contact angle was measured immediately after the coating film was formed in Example 1. The measurements after 1 month and 10 months were taken after the coated and uncoated glass plates were exposed to outdoor exposure on a test bench.

[0076] [Table 2]

[0077] [Evaluation test result 3: Water contact angle and water sliding angle of roofing materials] Table 3 shows the evaluation results of the accelerated weathering test for Example 2, Comparative Example 2, and Comparative Example 3. The accelerated weathering test was performed using an accelerated weathering tester that uses irradiation with a xenon lamp. The initial contact angle and initial sliding angle were measured immediately after the formation of the coating film for Example 1, Comparative Example 2, and Comparative Example 3. After Xe 900 hours, the respective coating films were measured after a 900-hour accelerated weathering exposure test using the accelerated weathering tester.

[0078] [Table 3]

[0079] In Comparative Example 3, loss of hydrophilicity and water slippage was observed after 900 hours of accelerated weather resistance, whereas in Example 1, water slippage was maintained. A sliding angle of 10° or less was maintained up to 3,000 hours, and a significant improvement in durability is expected.

[0080] [Evaluation test result 4] The snow was exposed to the outdoors for seven months (November 2021 to June 2022) in Niseko, Hokkaido, and snow sliding was evaluated. The number of snow slides was calculated by reading the plate temperature transition of the test plate. In other words, the sudden rise in plate temperature is evaluated as a phenomenon caused by the disappearance of snow on the surface of the test plate due to snow slide. As an example, the plate temperature transition of Example 2 on February 24, 2022 is shown in Evaluation Test Results 4-1, the plate temperature transition of Comparative Example 2 on the same day is shown in 4-2, and the plate temperature transition of Comparative Example 3 on the same day is shown in 4-3.

[0081] Evaluation test results 4-1 TIFF2025158650000006.tif5078

[0082] Evaluation test results 4-2 TIFF2025158650000007.tif5077

[0083] Evaluation test results 4-3 TIFF2025158650000008.tif5078

[0084] Next, Table 4 shows the number of times that Example 2, Comparative Example 2, and Comparative Example 3 went snowboarding by month from November to March.

[0085] [Table 4]

[0086] Example 2 exhibited the best snow sliding in all months, with the total number of times it slid on snow being 2.2 times greater than that of Comparative Example 3. This demonstrates the excellent snow sliding properties of the coating surface formed by the present invention.

[0087] The contact angles before and after outdoor exposure are shown in Table 5. In Example 2, the initial high hydrophilicity was maintained, and the same tendency as in the results of the accelerated weather resistance test shown in Table 3 was observed.

[0088] [Table 5]

[0089] Other Embodiments The above-described embodiments are merely examples of the present invention, and the present invention is not limited to these examples. These examples may be combined with well-known, commonly used, or publicly known technologies, or may be partially replaced. Modified inventions that would be easily conceived by a person skilled in the art are also included in the present invention.

Claims

1. As the first liquid Contains colloidal silica, alkyl silicate, solvent, and acid. As the second liquid The composition is characterized by comprising an acrylic polymer containing a hydrophilic group and an alkoxysilyl group or a silanol group at at least one end, and a solvent. Coating composition for snow-covered surfaces.

2. A method for forming a coating film for snow-covered surfaces, comprising applying and drying the first liquid described in claim 1 to form a coating film, and then applying and drying the second liquid described in claim 1 on top of this coating film to form a coating film having a water contact angle of 20° or less on the surface of the coating film.

3. A method for forming a coating film for snow-covered surfaces, comprising applying and drying the first liquid described in claim 1 to form a transparent coating film, and then applying and drying the second liquid described in claim 1 on top of this transparent coating film to form a transparent coating film having a coating film transmittance of 70% or more.

Images