Heat-reflective coating and its application method

Abstract

The present invention aims to provide a heat-shielding coating film and a method for applying the same that can sufficiently reflect sunlight even if the rate of evaporation of volatile components during painting differs due to variations in outside temperature caused by seasonal differences, and that also possesses weather resistance. [Solution] The problem could be solved by a heat-shielding coating film applied to the exterior walls of a building, comprising a primer coating film applied to the exterior walls of a building and containing a primer binder and 55-70% by weight of titanium dioxide, and a topcoat coating film laminated on the primer coating film and containing a topcoat binder and 10-30% by weight of titanium dioxide, wherein the solar reflectance is greater than 85%.

Description

Technical Field

[0001] The present invention relates to a heat-insulating coating film applied to the surface of the outer wall of a building, which reflects heat rays from the sun and suppresses the temperature rise of the building, and a method for constructing the same.

Background Art

[0002] Conventionally, in order to suppress the temperature rise of a building by reflecting infrared rays of sunlight, etc., a paint applied to the exterior of a building is known as a heat-insulating paint. The heat-insulating paint, whose official name is called a high solar reflectance paint, is applied by increasing the film thickness to exhibit sufficient heat-insulating properties.

[0003] For example, in Patent Document 1, in order to form a coating film that efficiently reflects heat energy such as sunlight and prevents the intrusion of heat energy, a heat-insulating paint composition containing a binder, large particle size titanium dioxide powder having a predetermined particle size, and silica powder or silicate powder is disclosed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the heat-insulating paint composition described in Patent Document 1, although an effect of obtaining heat-insulating performance by causing large particle size titanium dioxide to float on the surface of the coating film with silica powder or silicate powder is described, depending on the speed at which the volatile components in the paint composition volatilize during painting in the heat-insulating paint compositions described in Examples 1 to Examples 5, the large particle size titanium dioxide may not be able to float sufficiently on the surface of the coating film, and there is a possibility that sunlight cannot be sufficiently reflected.

[0006] Therefore, the present invention aims to provide a heat-shielding coating film and a method for applying the same that can sufficiently reflect sunlight and have weather resistance, even if the rate of evaporation of volatile components in the paint composition differs during painting due to differences in outside temperature caused by seasonal variations. [Means for solving the problem]

[0007] [1] That is, the present invention is a heat-shielding coating film to be applied to the exterior wall of a building, comprising an undercoat coating film applied to the exterior wall of a building and containing an undercoat binder and 55 to 70% by weight of titanium dioxide, and a topcoat coating film laminated on the undercoat coating film and containing a topcoat binder and 10 to 30% by weight of titanium dioxide, characterized in that the solar reflectance is greater than 85%.

[0008] [2] The heat-shielding coating according to [1], characterized in that, of the titanium dioxide in the undercoat coating, needle-shaped titanium dioxide accounts for 5 to 15% by weight.

[0009] [3] The heat-shielding coating film according to [1] or [2], characterized in that the undercoat binder is an aqueous epoxy resin.

[0010] [4] The heat-shielding coating film according to [1] or [2], characterized in that the topcoat binder is an aqueous acrylic silicone resin.

[0011] [5] The method for applying a heat-shielding coating to the exterior wall of a building, comprising: a first means for applying a primer coating to the exterior wall of a building and forming a primer coating containing a primer binder and 55 to 70% by weight of titanium dioxide; and a second means for laminating a topcoat coating containing a topcoat binder and 10 to 30% by weight of titanium dioxide onto the primer coating. [Effects of the Invention]

[0012] The heat-shielding coating film and application method of the present invention, even if the rate of volatilization of volatile components differs during painting due to variations in outside temperature depending on the season, provides a multilayer structure in which titanium dioxide is contained in relatively large amounts in the undercoat film and relatively small amounts in the topcoat film. This allows for sufficient reflection of sunlight and results in a coating film with excellent weather resistance. [Modes for carrying out the invention]

[0013] Embodiments of the present invention will be described in detail below. Note that the "~" symbol indicating a range includes both an upper and lower limit.

[0014] The heat-shielding coating of the present invention comprises at least a primer coating applied to a substrate which is the exterior wall of a building, and a topcoat coating laminated on the primer coating.

[0015] The undercoat film is formed by directly or indirectly applying paint to the substrate, which is the exterior wall of a building, via a primer layer. It is a coating film containing an undercoat binder and 55-70% by weight of titanium dioxide. The undercoat film is applied to the substrate for purposes such as reflecting light, including heat rays from the sun.

[0016] The resin component used as a primer binder in the primer coating is a binder for fixing titanium dioxide, and various resins such as epoxy resin, acrylic resin such as acrylic silicone, silicone, urethane, and fluororesin can be used. As will be described later, since the above various resins are diluted with a solvent such as water and applied as paint, it is preferable that they be water-soluble so that they dissolve uniformly in the solvent, and it is even more preferable that they be water-soluble epoxy resins. In addition, in order to impart gloss to the primer coating, a predetermined amount of siloxane can be included in the primer coating so that it is contained in 1 to 5% by weight.

[0017] The titanium dioxide used in the primer coating is dispersed almost uniformly within the coating, absorbing, shielding, or reflecting sunlight to minimize exposure of the substrate to sunlight. Specifically, particulate or needle-shaped titanium dioxide is preferred, and rutile-type titanium dioxide is preferred in terms of its crystalline structure. The titanium dioxide content in the primer coating is preferably 55-70% by weight, and more preferably 57-65% by weight. When the titanium dioxide content in the primer coating is within this range, the temperature rise of the substrate can be suppressed by absorbing or reflecting sunlight, the coloring by the titanium dioxide can be clearly seen, and it can be fixed to the resin component so that it does not peel off the substrate. Furthermore, the blending ratio of needle-shaped titanium dioxide in the titanium dioxide in the primer coating is preferably 5-15% by weight, and more preferably 7-13% by weight. By using needle-shaped titanium dioxide in the titanium dioxide within this range, cracking of the surface of the formed primer coating can be suppressed even if the titanium dioxide content in the primer coating is high.

[0018] The thickness of the undercoat film is preferably 10 to 100 μm, more preferably 20 to 80 μm, and most preferably 30 to 50 μm. When the thickness of the undercoat film is within this range, the temperature rise of the substrate can be suppressed by absorbing or reflecting sunlight, the coloring by titanium dioxide can be clearly seen, and differences in film thickness in different areas can be suppressed to prevent uneven coloring.

[0019] Furthermore, in order to form the undercoat film, a liquid paint is prepared in advance by mixing an undercoat binder and titanium dioxide with a solvent such as water or alcohol, and a dispersant to disperse the titanium dioxide. This paint is then applied to the substrate, and the solvent evaporates, leaving behind non-volatile components such as the undercoat binder and titanium dioxide, thus forming the undercoat film.

[0020] The topcoat film is formed by being laminated and painted on the undercoat film on the surface opposite to the substrate in the undercoat film, and is a film containing a topcoat binder and 10 to 30% by weight of titanium oxide. The topcoat film absorbs or reflects sunlight that penetrates into the undercoat film, so as to protect the undercoat film by minimizing the exposure of the undercoat film to sunlight, and by reducing the concentration of titanium oxide below the content ratio of titanium oxide in the undercoat film, deterioration of the topcoat film itself due to sunlight can be prevented.

[0021] The resin component used as the topcoat binder in the topcoat film is a binder for fixing titanium oxide. Similar to the resin component in the undercoat film, various resins such as epoxy resins, acrylic resins such as acrylic silicone, silicone, urethane, and fluororesins can be used. As will be described later, since the above various resins are diluted with a solvent such as water and painted as a paint, it is preferable that they are water-soluble so as to be uniformly dissolved in the solvent, and more preferably an aqueous acrylic silicone resin. Also, in order to impart a gloss or the like to the topcoat film, a predetermined amount of siloxane can be contained so as to be contained at 20 to 50% by weight in the topcoat film.

[0022] The titanium oxide used in the topcoat film is dispersed approximately uniformly in the topcoat film. By absorbing, shielding, or reflecting sunlight, it prevents the sunlight from reaching the primer coat film as much as possible, thereby protecting the primer coat film. Specifically, as the titanium oxide, similar to the titanium oxide in the primer coat film, particulate or acicular titanium oxide is preferred in terms of shape, and rutile-type titanium oxide is preferred in terms of crystal structure. The titanium oxide used in the topcoat film can have the same shape and the same crystal structure as the titanium oxide in the primer coat film. The content ratio of titanium oxide in the topcoat film is preferably 10 to 30% by weight, and more preferably 15 to 28% by weight. When the content ratio of titanium oxide in the topcoat film is within this range, it can prevent the substrate from being deteriorated by sunlight by absorbing or reflecting sunlight, can sufficiently visually recognize the coloring by titanium oxide, and can be fixed to the topcoat binder so as not to peel off from the substrate. And it prevents the sunlight from reaching the primer coat film as much as possible to protect the primer coat film, and by reducing the concentration of titanium oxide below the concentration of titanium oxide in the primer coat film, it can prevent the deterioration of the topcoat film itself caused by titanium oxide activated by absorbing the ultraviolet rays of sunlight. In addition, the topcoat film can contain coloring pigments such as black, blue, red, yellow, and white in addition to titanium oxide.

[0023] The film thickness of the topcoat film is preferably 10 to 40 μm, more preferably 15 to 30 μm, and most preferably 17 to 25 μm. When the film thickness of the topcoat film is within this range, the coating film can be formed quickly, the primer coat film can be protected by preventing the sunlight from reaching the primer coat film as much as possible, and the aging deterioration due to long-term exposure to sunlight can be prevented.

[0024] Also, in order to form the topcoat film, a liquid paint prepared by previously blending a solvent such as water or alcohol or a dispersant for dispersing titanium oxide into the topcoat binder and titanium oxide is used. The paint is applied to the primer coat film, and the solvent is volatilized so that non-volatile components such as the topcoat binder and titanium oxide remain, thereby forming a coating film.

[0025] Furthermore, it is also possible to form another coating film to cover the surface of the topcoat.

[0026] Furthermore, the paint composition used to produce the undercoat and topcoat films may contain a dispersant for dispersing titanium dioxide, a solvent such as a glycol compound like ethylene glycol or propylene glycol, water, a crosslinking agent, an antioxidant, an organic pigment, an ultraviolet absorber, a colorant, a leveling agent, and the like.

[0027] (Example 1) [Undercoat film] As titanium dioxide, 34.2 parts by weight of granular titanium dioxide (Chemours, product name: Typure R960) was used, along with 2.0 parts by weight of a composition mainly containing special ammonium polycarboxylate (Sunopco, Inc., product name: SN Dispersant 5027 <20% by weight of non-volatile components>) as a titanium dioxide dispersant, 17.8 parts by weight of water and 6.0 parts of ethylene glycol as solvents, and 40.0 parts by weight of a water-based epoxy resin (Daicel Ornex, Inc., product name: BECKOPOX EP2384w / 57WA <57% by weight of non-volatile components>) as a primer binder. These were mixed and stirred until uniform to prepare a primer coating. The primer coating was then applied to the substrate at a rate of 155 g / m². 2 When applied and dried, a white primer film with a film thickness of 40 μm was formed. In the primer film, the non-volatile components of the formed film consist of titanium dioxide, special polycarboxylate ammonium in the dispersant, and the non-volatile components of the water-based epoxy resin. Therefore, the weight percentage of non-volatile components in the primer film was 57.4% by weight, the weight percentage of titanium dioxide in the non-volatile components was 59.6%, and the specific gravity of the film was 2.2.

[0028] [Topcoat film] As titanium dioxide, 8.4 parts by weight of granular titanium dioxide (Chemours, product name: Typure R960) was used, along with 0.8 parts by weight of a composition mainly containing special ammonium polycarboxylate (Sunopco, Inc., product name: SN Dispersant 5027 <non-volatile components: 20% by weight>) as a titanium dioxide dispersant, 24.8 parts by weight of water and 10.0 parts of ethylene glycol as solvents, and 56.0 parts by weight of a water-based acrylic silicone resin (Nisshin Chemical Industry Co., Ltd., product name: Charline E-370 <non-volatile components: 45% by weight>) as a topcoat binder. These were mixed and stirred until uniform to form a topcoat coating. The topcoat coating was then applied to the surface of the undercoat at a rate of 82 g / m². 2 The paint was applied and dried to form a white topcoat with a film thickness of 20 μm, which was thinner than the undercoat. In the topcoat paint, the nonvolatile components of the formed film consisted of titanium dioxide, special polycarboxylate ammonium in the dispersant, and the nonvolatile components of the water-based acrylic silicone resin. Therefore, the weight percentage of the nonvolatile components of the topcoat paint was 33.76% by weight, the weight percentage of titanium dioxide in the nonvolatile components was 24.9% by weight, and the specific gravity of the film was 1.4. Furthermore, when an undercoat with a film thickness of 40 μm was formed on opacity test paper conforming to JIS K5600 using the above method, and a topcoat with a film thickness of 20 μm was formed on its surface, the opacity was measured and it was 95% or more.

[0029] (Example 2) [Undercoat film] As titanium dioxide, 23.0 parts by weight of granular titanium dioxide (Chemours, product name: Typure R960) and 25.6 parts by weight of needle-shaped titanium dioxide dispersion (Inui Co., Ltd., product name: Cellmuse <non-volatile component: 10% by weight>) were mixed together. As a titanium dioxide dispersant, 2.0 parts by weight of a composition mainly containing special ammonium polycarboxylate (Sunopco Co., Ltd., product name: SN Dispersant 5027 <non-volatile component: 20% by weight>) was mixed together. As solvents, 13.4 parts by weight of water and 6.0 parts of ethylene glycol were mixed together. As a primer binder, 30.0 parts by weight of a water-based epoxy resin (Daicel Ornex Co., Ltd., product name: BECKOPOX EP2384w / 57WA <non-volatile component: 57% by weight>) was mixed together. These were stirred until uniform to prepare a primer coating. Then, 204 g / m² of the primer coating was applied to the substrate. 2 When applied and dried, a white primer film with a film thickness of 40 μm was formed. In the primer film, the non-volatile components of the formed film were titanium dioxide, special polycarboxylate ammonium in the dispersant, and the non-volatile components of the water-based epoxy resin. Therefore, the weight percentage of non-volatile components in the primer film was 43.1% by weight, the weight percentage of titanium dioxide in the non-volatile components was 59.4%, and the specific gravity of the film was 2.2.

[0030] [Topcoat film] The topcoat coating was prepared with the same composition as the topcoat coating in Example 1. Then, 82 g / m² of the topcoat coating was applied to the surface of the undercoat coating. 2 The paint was applied and dried to form a white topcoat with a thickness of 20 μm, which was thinner than the undercoat. Since the composition was the same as the topcoat in Example 1, the weight percentage of non-volatile components in the topcoat paint, the weight percentage of titanium dioxide in the non-volatile components, and the specific gravity of the coating were the same as in Example 1. Furthermore, when an undercoat with a thickness of 40 μm was formed on opacity test paper conforming to JIS K5600 using the above method, and a topcoat with a thickness of 20 μm was formed on its surface, the opacity was measured and was found to be 95% or higher.

[0031] (Comparative Example 1) [Undercoat film] As titanium dioxide, 22.8 parts by weight of granular titanium dioxide (Chemours, product name: Typure R960) was used, along with 2.0 parts by weight of a composition mainly containing special ammonium polycarboxylate (Sunopco, Inc., product name: SN Dispersant 5027 <20% by weight of non-volatile components>) as a titanium dioxide dispersant, 9.2 parts by weight of water and 6.0 parts of ethylene glycol as solvents, and 60.0 parts by weight of a water-based epoxy resin (Daicel Ornex, Inc., product name: BECKOPOX EP2384w / 57WA <57% by weight of non-volatile components>) as a primer binder. These were mixed and stirred until uniform to prepare a primer coating. The primer coating was then applied to the substrate at a rate of 32 g / m². 2 When applied and dried, a white primer film with a film thickness of 10 μm was formed. In the primer film, the non-volatile components of the formed film consist of titanium dioxide, special polycarboxylate ammonium in the dispersant, and the non-volatile components of the water-based epoxy resin. Therefore, the weight percentage of the non-volatile components of the primer film was 57.4% by weight, the weight percentage of titanium dioxide in the non-volatile components was 39.7%, and the specific gravity of the film was 1.8.

[0032] [Topcoat film] As titanium dioxide, 16.8 parts by weight of granular titanium dioxide (Chemours, product name: Typure R960) was added, along with 1.0 part by weight of a composition mainly containing special ammonium polycarboxylate (Sunopco, Inc., product name: SN Dispersant 5027 <non-volatile components: 20% by weight>) as a titanium dioxide dispersant, 16.2 parts by weight of water and 10.0 parts of ethylene glycol as solvents, and 56.0 parts by weight of a water-based acrylic silicone resin (Nisshin Chemical Industry Co., Ltd., product name: Charline E-370 <non-volatile components: 45% by weight>) as a topcoat binder. These were mixed and stirred until uniform to form a topcoat coating. Then, 260 g / m² of the topcoat coating was applied to the surface of the undercoat. 2The paint was applied and dried to form a white topcoat with a film thickness of 60 μm, which was thinner than the undercoat. In the topcoat paint, the nonvolatile components of the formed film were titanium dioxide, special polycarboxylate ammonium in the dispersant, and the nonvolatile components of the water-based acrylic silicone resin. Therefore, the weight percentage of nonvolatile components in the topcoat paint was 42.2% by weight, the weight percentage of titanium dioxide in the nonvolatile components was 39.8% by weight, and the specific gravity of the film was 1.8. Furthermore, when an undercoat with a film thickness of 40 μm was formed on opacity test paper conforming to JIS K5600 using the above method, and a topcoat with a film thickness of 20 μm was formed on its surface, the opacity was measured and found to be 85%.

[0033] (Comparative Example 2) [Undercoat film] The primer coating was prepared with the same composition as the primer coating used in Comparative Example 1. Then, 32 g / m² of the primer coating was applied to the substrate. 2 When applied and dried, a white primer film with a film thickness of 10 μm was formed. Since the composition was the same as that of the primer film in Comparative Example 1, the weight percentage of non-volatile components in the primer paint, the weight percentage of titanium dioxide in the non-volatile components, and the specific gravity of the film were the same as in Comparative Example 1.

[0034] [Topcoat film] As titanium dioxide, 31.0 parts by weight of granular titanium dioxide (Chemours, product name: Typure R960) was used, along with 2.0 parts by weight of a composition mainly containing special ammonium polycarboxylate (Sunopco, Inc., product name: SN Dispersant 5027 <non-volatile components: 20% by weight>) as a titanium dioxide dispersant, 16.0 parts by weight of water and 5.0 parts of ethylene glycol as solvents, and 46.0 parts by weight of a water-based acrylic silicone resin (Nisshin Chemical Industry Co., Ltd., product name: Charline E-370 <non-volatile components: 45% by weight>) as a topcoat binder. These were mixed and stirred until uniform to form a topcoat coating. The topcoat coating was then applied to the surface of the undercoat at a rate of 254 g / m². 2The paint was applied and dried to form a white topcoat with a film thickness of 60 μm, which was thinner than the undercoat. In the topcoat paint, the non-volatile components of the formed film were titanium dioxide, special polycarboxylate ammonium in the dispersant, and the non-volatile components of the water-based acrylic silicone resin. Therefore, the weight percentage of non-volatile components in the topcoat paint was 52.1% by weight, the weight percentage of titanium dioxide in the non-volatile components was 59.5% by weight, and the specific gravity of the film was 2.2. Furthermore, when an undercoat with a film thickness of 10 μm was formed on opacity test paper conforming to JIS K5600 using the above method, and a topcoat with a film thickness of 60 μm was formed on its surface, the opacity was measured and it was 95% or more.

[0035] For each example and comparative example, the heat-shielding coating film obtained was visually inspected, and its solar reflectance, carbon black contamination test, and weather resistance were evaluated and judged. In addition, the surface condition of the primer coating film during molding was evaluated and judged for each example. The evaluation methods are described below.

[0036] [Finished appearance] The color of the coating film obtained in each example and comparative example was confirmed by visual inspection. In all examples and comparative examples, the color was white.

[0037] [Solar reflectance] The coating films obtained in each example and comparative example, prepared using opacity test paper as a substrate, were measured for solar reflectance using a spectrophotometer (NF-555, manufactured by Nippon Denshoku Industries Ltd.) in accordance with JIS K5602-2008 under conditions of 25°C and 60 RH% humidity. A solar reflectance of 85% or more was evaluated as ○, indicating that it reflects sunlight well and can suppress the temperature rise of the substrate. A solar reflectance of 60% or more but less than 85% was evaluated as △, indicating that it reflects sunlight moderately and can suppress the temperature rise of the substrate to some extent. A solar reflectance of less than 60% was evaluated as ×, indicating that it does not reflect sunlight well and cannot suppress the temperature rise of the substrate. ○ was judged as good, and △ and × as poor. Examples 1, 2, and Comparative Example 2 had a solar reflectance greater than 85%, while Comparative Example 1 had a solar reflectance of less than 60%.

[0038] [Carbon black contamination test] A carbon black suspension prepared at a predetermined concentration was uniformly applied to the coating film obtained in each example and comparative example, and the suspension was dried to fix the carbon black. Then, the carbon black that had adhered was washed off with a certain amount of water for a predetermined time. At this time, the degree of contamination of the coating film by carbon black was visually checked. A ○ was evaluated as having almost no contamination on the coating film, a △ was evaluated as having a slight contamination on the coating film, and a × was evaluated as having a clearly visible contamination on the coating film. ○ was judged as good, and △ and × were judged as poor. Examples 1 and 2 were hardly contaminated, comparative example 1 showed a slight contamination, and comparative example 2 showed significant contamination.

[0039] [Weather resistance] For each example and comparative example, the coating obtained was subjected to an accelerated weathering test using metal weathering (DW-R8PL, manufactured by Daipla Wintes Co., Ltd.), with 50 cycles of irradiation and darkness (rest) as one cycle. The surface condition after the test was visually inspected. A ○ was given to those with no change in the coating, a △ to those with slight chalking, and a × to those with clear chalking. ○ was judged as good, and △ and × as poor. No change was observed in Examples 1 and 2, while clear chalking was observed in Comparative Examples 1 and 2.

[0040] We judged all of these factors—solar reflectance, carbon black contamination test, and weather resistance—to be good overall, while all others were judged to be poor overall.

[0041] [Surface condition of a 60 μm thick undercoat coating] Furthermore, using the primer coating paints from each example, a 60 μm thick primer coating, thicker than the 40 μm coating produced in each example, was created in a single application rather than in multiple applications. The surface condition of the primer coating was then visually inspected. A primer coating with no cracks at all was rated ○, one with some cracks △, and one with many cracks ×. The fewer cracks a coating had, the better it was judged to be. Some cracks were observed in the coating of Example 1, but no cracks were observed in Example 2, indicating that the coating of Example 2 was better than that of Example 1.

[0042] Table 1 shows the composition and proportions of the primer paint for forming the primer film and the topcoat paint for forming the topcoat film obtained in each example and comparative example. Table 2 shows a list of the composition and proportions of the non-volatile components in the primer film and the performance of the resulting coating film.

[0043] [Table 1]

[0044] [Table 2]

[0045] From the results in Tables 1 and 2, it was found that, as shown in each example, by providing a primer coating containing a primer binder and a predetermined proportion of titanium dioxide, and a topcoat coating laminated on the primer coating containing a topcoat binder and a predetermined proportion of titanium dioxide, it is possible to obtain a heat-shielding coating that can sufficiently reflect sunlight and has excellent weather resistance. Furthermore, from the surface condition test results of the primer coating with a thickness of 60 μm in Examples 1 and 2, it was found that cracking of the formed coating can be suppressed by including needle-shaped titanium dioxide in a predetermined proportion of titanium dioxide.

Claims

1. A heat-shielding coating applied to the exterior walls of a building, Painted on the exterior walls of buildings, the primer film contains a primer binder and 55-70% by weight of titanium dioxide, The above-mentioned undercoat film is laminated with a topcoat film containing a topcoat binder and 10 to 30% by weight of titanium dioxide, A heat-shielding coating characterized by a solar reflectance greater than 85%.

2. The heat-shielding coating according to claim 1, characterized in that, of the titanium dioxide in the undercoat coating, needle-shaped titanium dioxide accounts for 5 to 15% by weight.

3. The heat-shielding coating film according to claim 1 or 2, characterized in that the aforementioned undercoat binder is a water-based epoxy resin.

4. The heat-shielding coating film according to claim 1 or 2, characterized in that the topcoat binder is an aqueous acrylic silicone resin.

5. A method for applying a heat-shielding coating to the exterior walls of a building, A first means for forming an undercoat coating film that is applied to the exterior walls of a building and contains an undercoat binder and 55-70% by weight of titanium dioxide, A method for applying a heat-shielding coating, characterized by comprising a second means of forming a topcoat coating film containing a topcoat binder and 2 to 5% by weight of titanium dioxide on the undercoat coating film.

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