High solar reflectance paint and method for forming a high solar reflectance coating film
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- ATOM CHEM PAINT
- Filing Date
- 2024-11-13
- Publication Date
- 2026-05-25
AI Technical Summary
Existing high solar reflectance paints struggle to achieve dark colors with sufficient solar reflectance, as conventional methods either result in visible undercoat layers or pigment fading, and using multiple colored pigments leads to color variations and discoloration.
A high solar reflectance paint formulation incorporating a colored pigment with high near-infrared transmittance and a hollow filler with high solar reflectance, ensuring the coating film achieves dark colors while maintaining high solar reflectance.
The paint achieves high solar reflectance with dark colors by utilizing a hollow filler for near-infrared reflection and a colored pigment for color development, preventing pigment fading and maintaining color consistency.
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Abstract
Description
[Technical Field]
[0001] The present invention relates to a high solar reflectance paint and a method for forming a high solar reflectance coating film. [Background technology]
[0002] High solar reflectance paint is a type of functional paint that can suppress the temperature rise of the paint film and the object it is coated on by reflecting near-infrared light contained in sunlight at a high level, and is also called "heat-shielding paint." High solar reflectance paint aims to improve the solar reflectance of the paint film formed by incorporating light-reflecting fine particles such as titanium dioxide (see, for example, Patent Document 1).
[0003] However, paints containing light-reflecting particles such as titanium dioxide result in a brighter paint film and lighter hues. Therefore, currently, darker colors (for example, L) are preferred. * We are unable to meet the demand for high solar reflectance paints in hues (especially black) with a value of 25% or less.
[0004] While it is possible to obtain a dark-colored coating with high solar reflectance by forming a high-brightness undercoat layer on the surface of the object to be coated and then applying a dark-colored paint with high near-infrared transmittance, this requires the step of forming a high-brightness undercoat layer. Furthermore, in this case, if the coating made with high solar reflectance paint is worn or damaged, the high-brightness undercoat layer will become visible on the surface of the dark-colored coating, so even very slight wear or damage will significantly impair the initial requirement for a dark-colored surface.
[0005] One method involves creating a black color by mixing multiple colored pigments that absorb relatively little sunlight, rather than using pigments that absorb a lot of sunlight (such as carbon black). The combined reflectance and transmittance of these pigments then contribute to achieving a consistent overall solar reflectance. However, paint films using multiple colored pigments in this way cannot maintain their black color because the pigments have different lightfastness properties, leading to fading over time and the appearance of color variations. Furthermore, for the same reason, unnatural discoloration occurs as the color changes over time.
[0006] Another approach involves using a black pigment with near-infrared solar reflectance (e.g., chrome black) instead of a pigment with high solar absorption. However, even though black pigments have near-infrared solar reflectance, their reflectance is not very high, making it difficult to obtain sufficient solar reflectance in dark-colored regions where the pigment's own solar reflectance strongly influences the result. [Prior art documents] [Patent Documents]
[0007] [Patent Document 1] Japanese Patent Publication No. 2022-158089 [Overview of the project] [Problems that the invention aims to solve]
[0008] The present invention aims to provide a high solar reflectance paint and a method for forming a high solar reflectance paint film that can achieve a high solar reflectance while being dark in color using only the resulting coating film. [Means for solving the problem]
[0009] The above objective is achieved by the present invention as described below. That is, one aspect of the present invention is as follows.
[0010] <1> The material comprises a colored pigment whose transmittance Tp value in the near-infrared wavelength range is 50% or more according to the following test X1, and a hollow filler whose solar reflectance Rfb value in the near-infrared wavelength range is 50% or more according to the following test X2. L of the coating film as determined by the following test X3 * High solar reflectance paint with a value of 35 or less. [Exam X1] A test paint P, consisting of the same amount of the colored pigment as the mixing ratio (mass%) to the high solar reflectance paint and the remainder being clear paint, is applied with an applicator to the black and white parts of the opacity test paper specified in JIS K5600-4-1 4.1.2 [Method B (Opacity Test Paper)] so that the dry film thickness is 100 ± 10 μm, and then dried to obtain a test plate. The solar reflectance in the near-infrared wavelength range is measured for each of the coating films on the black and white parts of the obtained test plate in accordance with Clause 7.8 (Solar Reflectance) of JIS K5675, and the solar reflectance Rpb (%) of the black part and the solar reflectance Rpw (%) of the white part are obtained. Furthermore, the solar reflectance in the near-infrared wavelength range is measured in accordance with Clause 7.8 (Solar Reflectance) of JIS K5675, using a blank opacity test paper with no coating on the black and white areas as specified in JIS K5600-4-1 4.1.2 [Method B (Opacity Test Paper)]. The solar reflectance Rbb (%) in the black area of the obtained blank and the solar reflectance Rbw (%) in the white area of the blank are then measured. From the obtained solar reflectance values Rpb(%), Rpw(%), Rbb(%), and Rbw(%), the transmittance Tp(%) in the near-infrared wavelength range is calculated using the following Equation 1. Tp=(Rpw-Rpb) / (Rbw-Rbb)×100...Equation 1 [Exam X2] A test paint F is prepared by mixing the hollow filler and the clear paint in an amount equal to the mixing ratio (mass %) of the hollow filler in the high solar reflectance paint. The test paint F is applied to the black portion of the hiding power test paper specified in Method B (hiding power test paper) of 4.1.2 of JIS K5600-4-1 using an applicator so that the dry film thickness is 100 ± 10 μm, and then dried to obtain a test plate. For the coating film of the obtained test plate, the solar reflectance in the near-infrared wavelength region is measured in accordance with Article 7.8 (Solar reflectance) of JIS K5675, and the result is defined as the solar reflectance Rfb (%) in the near-infrared wavelength region. [Test X3] Measure the L value of the coating film when it is applied to the black portion of the hiding power test paper specified in Method B (hiding power test paper) of 4.1.2 of JIS K5600-4-1 using an applicator so that the dry film thickness is 100 ± 10 μm and then dried. * Measure the value.
[0011] <2> The high solar reflectance paint according to <1>, wherein in Test X2, the solar reflectance Rb in the near-infrared wavelength region obtained by measuring in the same manner as in Test X2 except that the paint F is replaced with the high solar reflectance paint is 50% or more.
[0012] <3> The high solar reflectance paint according to <1>, wherein the diameter of the hollow filler is 10 μm or less. [Advantages of the Invention]
[0013] According to the high solar reflectance paint and the method for forming a high solar reflectance coating film of the present invention, it is possible to achieve a high solar reflectance with only the obtained coating film while being a dark color. [Embodiments for Carrying Out the Invention]
[0014] Hereinafter, a high solar reflectance paint according to an embodiment of the present invention (hereinafter, may be simply referred to as "paint" omitting "high solar reflectance") and a method for forming a high solar reflectance coating film will be described.
[0015] [[ID=ID=36]][High Solar Reflectance Paint] The high solar reflectance paint according to this embodiment contains a coloring pigment and a hollow filler, and includes other components as necessary in addition to the resin component and solvent constituting the paint.
[0016] (Coloring pigment and hollow filler) When the high solar reflectance paint according to this embodiment is contained in a coating film formed by coating, a coloring pigment with high transmittance in the near-infrared wavelength region and a hollow filler with high solar reflectance in the near-infrared wavelength region are blended. Thus, even though it is a dark color, a high solar reflectance can be realized only with the obtained coating film.
[0017] Regarding light in the near-infrared wavelength region, which contains a lot of energy and serves as a heat source, most of it passes through the coloring pigment and the hue of the coloring pigment is expressed. On the other hand, most of the hollow filler, which is a reflection component, is reflected and it does not affect the hue much itself. Therefore, the coloring pigment is responsible for the development of the dark color hue, and the hollow filler is responsible for the reflection of light in the near-infrared wavelength region, and a high solar reflectance is realized while being a dark color.
[0018] The hollow filler used in the high solar reflectance paint according to this embodiment contributes to near-infrared solar reflection with its hollow structure. By having a hollow structure, near-infrared solar reflection based on the hollow structure can be obtained, and reflection based on the material of the hollow filler occurs in the visible light region. Therefore, as the material of the hollow filler, materials with little reflection and absorption in visible light, such as glass and various resins, are preferable, and among them, an acrylic resin-based hollow filler with good light resistance is preferable.
[0019] The hollow filler has an equivalent L * value, and those with a smaller particle diameter tend to have a larger solar reflectance. Also, the solar reflectance tends to increase according to the number of introduced hollow structures in the coating film. Therefore, L *A hollow filler with a small particle size is preferred because it is less likely to increase in value and allows for a greater number of hollow structures to be introduced within a given film thickness. Specifically, the diameter of the hollow filler used in the high solar reflectance coating according to this embodiment is preferably 10 μm or less, and more preferably in the range of 3 to 7 μm. Here, "particle size" refers to the number-average particle size.
[0020] As described above, compared to conventional technologies that incorporate titanium dioxide, which has high reflectivity even in the visible light region, the technology of this embodiment, which incorporates a hollow filler that can obtain reflection in the near-infrared region with a material that has low coloring power (reflection in the visible light region), is particularly advantageous when it is desired to obtain a dark-colored coating film.
[0021] The amount of hollow filler used in the high solar reflectance paint according to this embodiment should be such that the solar reflectance Rfb value in the near-infrared wavelength range, as determined by the aforementioned test X2, is 50% or more, assuming that the final paint has the necessary properties to be a paint. The actual amount to be added cannot be generalized as it depends on the type of hollow filler and the types and amounts of other components, but it is selected from a range of approximately 5% to 15% by mass of the paint solids content.
[0022] In this embodiment, the transmittance of the colored pigment used in the near-infrared wavelength range is, more specifically, a value of the transmittance Tp in the near-infrared wavelength range determined by test X1 below, which is 50% or more, preferably 60% or more, and more preferably 75% or more. However, it is necessary to consider that the desired coating film must have the required hue and opacity. In particular, as will be described later, the coating film made of the high solar reflectance paint that is ultimately obtained must have a predetermined L * Darker colors are selected to indicate the value.
[0023] [Exam X1] A test paint P, consisting of the same amount of the colored pigment as the mixing ratio (mass%) to the high solar reflectance paint and the remainder being clear paint, is applied with an applicator to the black and white parts of the opacity test paper specified in JIS K5600-4-1 4.1.2 [Method B (Opacity Test Paper)] so that the dry film thickness is 100 ± 10 μm, and then dried to obtain a test plate. The solar reflectance in the near-infrared wavelength range is measured for each of the coating films on the black and white parts of the obtained test plate in accordance with Clause 7.8 (Solar Reflectance) of JIS K5675, and the solar reflectance Rpb (%) of the black part and the solar reflectance Rpw (%) of the white part are obtained.
[0024] Furthermore, the solar reflectance in the near-infrared wavelength range is measured in accordance with Clause 7.8 (Solar Reflectance) of JIS K5675, using a blank opacity test paper with no coating on the black and white areas as specified in JIS K5600-4-1 4.1.2 [Method B (Opacity Test Paper)]. The solar reflectance Rbb (%) in the black area of the obtained blank and the solar reflectance Rbw (%) in the white area of the blank are then measured.
[0025] From the obtained solar reflectance values Rpb(%), Rpw(%), Rbb(%), and Rbw(%), the transmittance Tp(%) in the near-infrared wavelength range is calculated using the following Equation 1. Tp=(Rpw-Rpb) / (Rbw-Rbb)×100...Equation 1
[0026] Furthermore, the solar reflectance of the hollow filler used in this embodiment in the near-infrared wavelength range is, more specifically, 50% or more, preferably 55% or more, and more preferably 60% or more, as determined by the solar reflectance Rfb value in the near-infrared wavelength range in test X2 below. In this embodiment, the higher the value of the solar reflectance Rfb in the near-infrared wavelength range, the better; however, in practice, the level of solar reflectance should be set considering the hue to be obtained by mixing with the coloring pigment.
[0027] [Exam X2] A test paint F, prepared by mixing the hollow filler and the clear paint in an amount equal to the mixing ratio (mass%) for the high solar reflectance paint, is applied with an applicator to the black area of the opacity test paper specified in JIS K5600-4-1, 4.1.2 [Method B (Opacity Test Paper)], so that the dry film thickness is 100 ± 10 μm, and then dried to obtain a test plate. The solar reflectance in the near-infrared wavelength range of the obtained test plate is measured in accordance with Clause 7.8 (Solar Reflectance) of JIS K5675, and the result is defined as the solar reflectance Rfb (%) in the near-infrared wavelength range.
[0028] Furthermore, while it is desirable that the degree of darkness of the high solar reflectance paint according to this embodiment be a desired hue, in this embodiment, the L of the coating film according to the following test X3 * The value is 35% or less, preferably between 10 and 35, and more preferably between 15 and 30.
[0029] [Exam X3] The coating film was applied to the black area of the opacity test paper specified in JIS K5600-4-1 4.1.2 [Method B (Opacity Test Paper)] using an applicator to achieve a dry film thickness of 100 ± 10 μm, and the coating film after drying was measured in L. * Measure the value.
[0030] The clear coatings used in preparing the test coatings P and F in the above tests X1 and X2 are selected to have a transmittance of nearly 100% in the near-infrared wavelength range and a solar reflectance of nearly 0% in the near-infrared wavelength range for the coating film formed solely from the clear coating. Specifically, the transmittance influence Tce due to the clear coating, as determined in the following test X4, should be 3% or less, preferably 2% or less, and more preferably 1% or less.
[0031] [Exam X4] The clear coating C to be tested is applied to the black and white areas of the opacity test paper specified in JIS K5600-4-1, 4.1.2 [Method B (Opacity Test Paper)], using an applicator to obtain a test plate with a dry film thickness of 100 ± 10 μm. The black and white areas of the obtained test plate are then coated and dried to obtain a test plate. The solar reflectance in the near-infrared wavelength range is measured for each coating film in the black and white areas of the test plate in accordance with JIS K5675, Clause 7.8 (Solar Reflectance).
[0032] From the obtained solar reflectances Rcb(%) and Rcw(%) in the black and white areas, and the solar reflectances Rbb(%) in the black area of the blank and Rbw(%) in the white area of the blank determined in the above test X1, the transmittance Tc(%) in the near-infrared wavelength range by the clear coating C is calculated using the following formula 2. Tc=(Rcw-Rcb) / (Rbw-Rbb)×100 ··· Formula 2
[0033] From the transmittance Tc(%) due to clear coating C obtained by Equation 2, the influence of clear coating C on transmittance Tce(%) is calculated using the following Equation 3. Tce=|Tc-100| ··· Equation 3
[0034] Furthermore, most commercially available clear coatings can be used as they generally meet the conditions for the transmittance influence Tce without any problems. In addition, even coatings not specifically labeled as "clear coatings" can be used as clear coatings in tests X1 and X2 as long as they meet the conditions. Moreover, if the high solar reflectance coating to be obtained contains a clear coating, it is more preferable to use the clear coating that contains it.
[0035] Examples of hollow fillers used in this embodiment include Matsumoto Microspheres® FE series (FN-010E, etc.) manufactured by Matsumoto Oil & Fat Pharmaceutical Co., Ltd., and Cellspheres® manufactured by Taiheiyo Cement Corporation.
[0036] Examples of coloring pigments used in this embodiment include Chromofine Black A1103 (manufactured by Dainichi Seika Kogyo Co., Ltd.), Spectrasense™ Black EH8082 (manufactured by DIC Corporation), and Paliogen Black S 0084 (manufactured by BASF).
[0037] As for the coloring pigment, one with particularly excellent lightfastness is preferred. As an example of the lightfastness test results by the present inventors, when an accelerated lightfastness test of Chromofine Black A1103 was performed for 1947 hours on a coating film using the paint formulation described in the example below, the hue after the test was ΔL* / Δa* / Δb* = +6.45 / -0.71 / -2.63 compared to the hue before the test (L* / a* / b* = 4.05 / 2.30 / 0.68), and the black color was sufficiently maintained to the naked eye.
[0038] Furthermore, in the same lightfastness test as above, when 3% of the light stabilizer (HALS) Chinuvin 123-DW (manufactured by BASF) was added to the paint, ΔL* / Δa* / Δb* = 2.81 / -0.15 / -1.62 was obtained, confirming that sufficient lightfastness was achieved. In addition, when a clear coat of the same paint with UV-cutting properties was applied as a topcoat, ΔL* / Δa* / Δb* = 1.17 / -0.19 / 0.08 was obtained, and almost no discoloration was observed. Depending on the level of lightfastness required for the high solar reflectance paint as a final product, appropriate coloring pigments can be selected, light stabilizers can be used, or methods such as applying a clear coat as a topcoat can be chosen.
[0039] There are no particular restrictions on the amount of coloring pigment used in this embodiment, but it is preferably in the range of 5% to 20% by mass of the resin solids content in the paint, and more preferably in the range of 8% to 15% by mass. Furthermore, there are no particular restrictions on the amount of hollow filler used in this embodiment, provided that the final paint has the necessary properties to function as a paint, but it should be an amount that results in a solar reflectance Rfb value in the near-infrared wavelength range of 50% or more, as determined by the aforementioned test X2. In practice, the amount is preferably in the range of 5% to 20% by mass of the resin solids content in the paint, and more preferably in the range of 8% to 15% by mass.
[0040] (Resin components and solvents) The high solar reflectance paint according to this embodiment includes resin components and solvents that constitute the paint. Depending on the type and form of the resin components and solvents, it can be an organic solvent-based paint or a water-based paint, and in this embodiment, either type of paint is acceptable.
[0041] As resin components that can be used in the high solar reflectance paint according to this embodiment, various resin materials that have been conventionally used as resin components in paints can be used. For example, inorganic resins such as silicone resins and silicate resins, acrylic resins, urethane resins, acrylic-urethane resins, epoxy resins, polyester resins, melamine resins, phenolic resins, butyral resins, vinyl ester resins, unsaturated polyester resins, and mixtures or emulsions thereof, as well as water-soluble resins such as polyvinyl alcohol, polyacrylic acid, and polyvinylpyrrolidone.
[0042] In the case of resins that harden when the main component and hardener are mixed, the two components should be kept separate until application, then mixed to form a single component, and applied immediately. In the case of such two-component paints, in this embodiment, the mixed single-component coating solution will be treated as a "high solar reflectance paint" (for example, the proportions of each component).
[0043] There are no particular restrictions on the amount of resin component used in this embodiment, but it is preferably in the range of 40% to 95% by mass of the total solid content of the paint, and more preferably in the range of 70% to 90% by mass.
[0044] On the other hand, when using organic solvents, examples include acetone, methyl ethyl ketone, methyl isobutyl ketone, isopropyl alcohol, n-butanol, isobutanol, ethyl acetate, butyl acetate, toluene, xylene, etc., and these can be appropriately selected depending on the purpose. Of course, it is also acceptable to use a mixture of several of these.
[0045] Furthermore, if the resin is water-soluble or a water-dispersible emulsion, an aqueous medium such as water, methanol, or ethanol may be used. If the film-forming component is in the form of an emulsion, a high-boiling point solvent, whether water-soluble or non-water-soluble, may be used as a film-forming aid. Moreover, if the organic solvent is a water-soluble solvent, the water-soluble solvent and the aqueous medium may be mixed and used together.
[0046] The amount of solvent used in this embodiment depends on the type and form of the resin and solvent (two-component type, emulsion, etc.), the application method, etc., but it is preferably in the range of 30 to 200 parts by mass, and more preferably in the range of 50 to 150 parts by mass, per 100 parts by mass of total solids.
[0047] (Other ingredients) The high solar reflectance paint according to this embodiment may contain various conventionally known components as paint components. Specifically, examples include fluorescent agents, crosslinking agents, antioxidants, ultraviolet inhibitors, preservatives, fungicides, dispersion stabilizers, and the like.
[0048] (Other manufacturing methods) The high solar reflectance paint according to this embodiment can also be obtained, for example, by adding a predetermined amount of a coloring pigment and a hollow filler to a commercially available clear paint. At this time, the clear paint to be used is not limited in terms of the value of the transmittance influence degree Tce obtained in the aforementioned Test X4, but is preferably within 3%, more preferably within 2%, and even more preferably within 1%.
[0049] (Properties of the coating film of the high solar reflectance paint) The coating film formed by the high solar reflectance paint according to this embodiment can achieve a high solar reflectance with only the obtained coating film while being dark in color. The method of forming the coating film using the high solar reflectance paint will be described in the next section, "Method of forming the high solar reflectance coating film".
[0050] First, the coating film formed by the high solar reflectance paint according to this embodiment is dark in color. The characteristic that the high solar reflectance paint according to this embodiment is dark in color is derived from the characteristics of the coloring pigment. In other words, the coloring pigment is appropriately selected so that the high solar reflectance paint according to this embodiment has a predetermined darkness.
[0051] As the degree of darkness of the high solar reflectance paint according to this embodiment, the L * value of the coating film according to the following Test X3 is required to be 35 or less, preferably 30 or less, and more preferably 25 or less. The L * value of the coating film of the dark high solar reflectance paint being 35 or less has not been easily achieved conventionally.
[0052] [Test X3] For the coating film when applied and dried with an applicator so that the dry film thickness becomes 100 ± 10 μm on the black part of the hiding power test paper specified in 4.1.2 [Method B (hiding power test paper)] of JIS K5600-4-1, measure the L * value.
[0053] Furthermore, the coating film formed with the high solar reflectance paint according to this embodiment has high solar reflectance. The high solar reflectance characteristic of the high solar reflectance paint according to this embodiment is due to the characteristics of the hollow filler. As previously described, the hollow filler used in this embodiment has a solar reflectance Rfb in the near-infrared wavelength range measured by test X2 at a predetermined value (50%) or higher.
[0054] The solar reflectance of the high solar reflectance paint according to this embodiment is preferably 40% or more, more preferably 50% or more, and even more preferably 60% or more, as measured by the following test X2′, which is the same as in the previously described test X2 except that paint F is replaced with the high solar reflectance paint according to this embodiment.
[0055] [Exam X2'] The high solar reflectance coating according to this embodiment is applied with an applicator to the black portion of the opacity test paper specified in JIS K5600-4-1, 4.1.2 [Method B (Opacity Test Paper)], so that the dry film thickness is 100 ± 10 μm, and then dried to obtain a test plate. The solar reflectance in the near-infrared wavelength range of the coating film on the obtained test plate is measured in accordance with Clause 7.8 (Solar Reflectance) of JIS K5675, and the result is defined as the solar reflectance Rb (%) in the near-infrared wavelength range.
[0056] [Method for forming a high solar reflectance coating] (High solar reflectance paint application process) By having a high solar reflectance coating step in which the high solar reflectance coating according to this embodiment is applied to the object to be coated, a high solar reflectance coating film can be formed. As described above, the characteristics of the formed high solar reflectance coating film are that, despite being dark in color, it can achieve high solar reflectance with the resulting coating film alone.
[0057] Therefore, without including a step to form a high-brightness undercoat layer on the surface of the object to be coated prior to the high-solar-reflectance paint coating step, high solar reflectance can be achieved even with a dark color simply by directly applying the high-solar-reflectance paint according to this embodiment to the surface of the object to be coated in the high-solar-reflectance paint coating step. Of course, the surface of the object to be coated may be high-brightness and have high solar reflectance itself. Regardless of the surface condition of the object to be coated, the high-solar-reflectance paint according to this embodiment can achieve high solar reflectance with only the resulting coating film, even with a dark color.
[0058] There are no particular restrictions on the method of applying the high solar reflectance coating according to this embodiment to the object to be coated. Any conventionally known coating method, such as dipping, spraying, roll coating, spin coating, curtain coating, brush coating, or applicator coating, can be used. The coating method should be appropriately selected depending on the liquid state of the high solar reflectance coating according to this embodiment, the material and shape of the object to be coated, the desired film thickness, and various performance characteristics.
[0059] (Undercoating process) Prior to the above-mentioned high solar reflectance paint application process, there may be an priming step in which a primer paint is applied to the surface of the object to be painted to form a primer layer. However, the paint film of the primer layer formed in the priming step does not need to be high in brightness. Even if the paint film of the primer layer is not high in brightness, the paint film formed in the high solar reflectance paint application process will be dark in color but will have high solar reflectance.
[0060] Therefore, the solar reflectance Ra in the near-infrared wavelength range measured in accordance with Clause 7.8 (Solar Reflectance) of JIS K5675 for the undercoat film formed by the undercoating process may be 40% or less. The solar reflectance Ra of a typical black surface is about 5%. Of course, the undercoat film may be highly light and have a high solar reflectance itself, i.e., a solar reflectance Ra exceeding 40%. The high solar reflectance paint according to this embodiment can achieve high solar reflectance with only the resulting paint film, even if it is a dark color, regardless of the condition of the undercoat film.
[0061] The embodiments described above are merely representative forms of the present invention, and the present invention is not limited to these embodiments. That is, those skilled in the art can implement the invention in various ways without departing from the core principles, in accordance with prior art knowledge. As long as such modifications still possess the configuration of the high solar reflectance paint and the method for forming a high solar reflectance coating film of the present invention, they are of course included within the scope of the present invention. [Examples]
[0062] The present invention will be described below with reference to examples, but the present invention is not limited to the following examples.
[0063] (Preparation of paints in the examples and comparative examples) The materials were mixed according to the formulations shown in Table 1 below to prepare the paints for the examples and comparative examples. Table 1 also includes the formulations of the clear coatings (hereinafter referred to as "evaluation clear coatings") used to prepare the test coatings P and F in Test X1 and Test X2 (see the "Clear" column). All numerical values in the table are in parts by mass.
[0064] [Table 1]
[0065] The details of each component in Table 1 above are as follows: • Black organic pigment A: Chromofine Black: A1103 (manufactured by Dainichi Seika Kogyo Co., Ltd.) • Black organic pigment B: Spectrasense™ Black EH8082 (manufactured by DIC Corporation) • Black inorganic pigment: Black 6350 (manufactured by Asahi Chemical Industries, Ltd.) • Carbon Black: AF Black E-2B (manufactured by Dainichi Seika Kogyo Co., Ltd., pigment content 30%) • Hollow filler A: Matsumoto Microsphere (registered trademark) FN-010E (manufactured by Matsumoto Oil & Fat Pharmaceutical Co., Ltd.) • Hollow filler B: Matsumoto Microspheres (registered trademark) F-65SE (manufactured by Matsumoto Oil & Fat Pharmaceutical Co., Ltd.) • Titanium dioxide: TITANIX JR-805 (manufactured by Teika Co., Ltd.) • Acrylic urethane resins: Barnock WD551 / Barnock DNW5100 (manufactured by DIC Corporation), Saibinol YC-330 (manufactured by Saiden Chemical Co., Ltd.) • Dispersant: AFCONA4570 (manufactured by AFCONA), AFCONA6226 (manufactured by AFCONA) • Thickeners: Disparon AQ607 (manufactured by Kusumoto Kasei Co., Ltd.), SN Thickener 665T (manufactured by Sunopco Co., Ltd.) • Antifoaming agent: TEGO FOAMEX852 (manufactured by EVONIC) • Humectant: BYK345 (manufactured by BYK) • Scratch protector: AQUACER515 (manufactured by BYK)
[0066] The values of the transmittance Tp in the near-infrared wavelength range for the colored pigments used in Test X1, and the values of the solar reflectance Rfb in the near-infrared wavelength range for the reflective components used in Test X2, are summarized in Table 2 below. The clear coating used for evaluation had a transmittance influence Tce of 0.8% as determined in Test X4. Although titanium dioxide is not a hollow filler, it was included as a reflective component similar to that of a hollow filler in the comparative example, so the value of the solar reflectance Rfb in the near-infrared wavelength range was determined in accordance with Test X2 for hollow fillers.
[0067] [Table 2]
[0068] (Evaluation test) • Evaluation Test 1 For each of the coatings in Examples 1-2 and Comparative Examples 1-11, as well as the clear coating for evaluation (in the "Clear" column), the L of the coating film was evaluated according to the above test X3. * The value was measured. The same process was also performed on the blank (unpainted surface) L. * The values were measured (in the "Blank" column). The results are summarized in Table 3 below.
[0069] • Evaluation Test 2 The solar reflectance Rb was measured for each of the coatings in Examples 1-2 and Comparative Examples 1-11, as well as the evaluation clear coating (in the "Clear" column), using the above test X2' method. Similarly, the solar reflectance Rbb was measured for the blank (unpainted surface) (in the "Blank" column). The results are summarized in Table 3 below.
[0070] • Evaluation Test 3 For each of the coatings in Examples 1-2 and Comparative Examples 1-11, as well as the evaluation clear coating (in the "Clear" column), the solar reflectance Rw (%) in the near-infrared wavelength range was measured by changing the coated surface in Test X2' from the black area to the white area of the opacity test paper, and otherwise performing the same procedure. The solar reflectance Rbw was also measured in the same manner for the blank (unpainted surface) (in the "Blank" column). The results are summarized in Table 3 below.
[0071] ·Transmittance Tc From the values of solar reflectance Rb(%), Rw(%), Rbb(%), and Rbw(%) obtained in Evaluation Test 2 and Evaluation Test 3, the transmittance Tc(%) in the near-infrared wavelength range for each paint was determined using the following Equation 4. Tc=(Rw-Rb) / (Rbw-Rbb)×100...Equation 4 The results are summarized in Table 3 below.
[0072] • Results of the evaluation test [Table 3]
[0073] • Analysis of the results As can be seen in Table 3, in the example paint, L * The value is well below 30, indicating a sufficiently dark color, yet the solar reflectance Rb in the near-infrared wavelength range exceeds 60%, demonstrating high heat shielding properties. In contrast, the paint in the comparative example shows L * If you lower the value to 35% or less to make it darker, you will not be able to satisfy the solar reflectance Rb of 60% or more in the near-infrared wavelength range, and if you try to satisfy the solar reflectance Rb of 60% or more in the near-infrared wavelength range to achieve a high solar reflectance, L* The value significantly exceeded 35%, making it impossible to achieve sufficient color intensity.
Claims
1. The material comprises a colored pigment whose transmittance Tp value in the near-infrared wavelength range is 50% or more according to the following test X1, and a hollow filler whose solar reflectance Rfb value in the near-infrared wavelength range is 50% or more according to the following test X2. L of the coating film as determined by the following test X3 ＊ High solar reflectance paint with a value of 35 or less. [Test X1] A test paint P, consisting of the same amount of the coloring pigment as the mixing ratio (mass%) in the high solar reflectance paint and the remainder being clear paint, is applied with an applicator to the black and white parts of the opacity test paper specified in JIS K5600-4-1 4.1.2 [Method B (Opacity Test Paper)] so that the dry film thickness is 100 ± 10 μm, and then dried to obtain a test plate. The solar reflectance in the near-infrared wavelength range is measured for each of the coating films on the black and white parts of the obtained test plate in accordance with Clause 7.8 (Solar Reflectance) of JIS K5675, and the solar reflectance Rpb (%) of the black part and the solar reflectance Rpw (%) of the white part are obtained. Furthermore, the solar reflectance in the near-infrared wavelength range is measured in accordance with Clause 7.8 (Solar Reflectance) of JIS K5675, using a blank opacity test paper with no coating on the black and white areas as specified in JIS K5600-4-1, 4.1.2 [Method B (Opacity Test Paper)]. The solar reflectance Rbb (%) in the black area of the obtained blank and the solar reflectance Rbw (%) in the white area of the blank are then measured. From the obtained solar reflectance values Rpb (%), Rpw (%), Rbb (%), and Rbw (%), the transmittance Tp (%) in the near-infrared wavelength range is calculated using the following Equation 1. Tp=(Rpw-Rpb) / (Rbw-Rbb)×100... Formula 1 [Test X2] A test paint F is prepared by mixing the hollow filler and the clear paint in an amount equal to the mixing ratio (mass%) of the high solar reflectance paint. This test paint F is then applied with an applicator to the black portion of the opacity test paper specified in JIS K5600-4-1, 4.1.2 [Method B (Opacity Test Paper)], so that the dry film thickness reaches 100 ± 10 μm, and then dried to obtain a test plate. The solar reflectance in the near-infrared wavelength range is measured on the paint film of the obtained test plate in accordance with Clause 7.8 (Solar Reflectance) of JIS K5675, and the result is defined as the solar reflectance Rfb (%) in the near-infrared wavelength range. [Test X3] The coating film was applied to the black area of the opacity test paper specified in JIS K5600-4-1, 4.1.2 [Method B (Opacity Test Paper)], using an applicator to achieve a dry film thickness of 100 ± 10 μm, and then dried. ＊ Measure the value.
2. The high solar reflectance paint according to claim 1, wherein the solar reflectance Rb in the near-infrared wavelength range obtained by measurement in the same manner as in test X2, except that the paint F is replaced with the high solar reflectance paint, is 50% or more.
3. The high solar reflectance paint according to claim 1, wherein the diameter of the hollow filler is 10 μm or less.