Paint and method for producing painted metal sheet using said paint

Abstract

Painted metal sheets are mainly used for the exterior of buildings. Since painted metal sheets are thin, they are prone to raising the temperature inside the room due to sunlight. For this reason, it is known that a coating film can be formed on the back side (the side not exposed to sunlight) of the metal substrate to reduce heat radiation. However, when the painted metal sheet is processed, such as by bending, the coating film cannot withstand the processing, and peeling or cracking of the coating film occurs, and this has not been put to practical use. For this reason, we provide a paint that can form a coating film that has a high effect of reducing heat radiation and excellent flexibility, and a painted metal sheet using the paint. [Solution] A paint for coating metal substrates, comprising a vehicle, aluminum powder, a solvent, and an anti-settling agent, the vehicle being 100 parts by mass, the aluminum powder being 45 to 65 parts by mass, and the volatile components in the paint being 70% to 90% by mass; and a method for producing coated metal sheets using the paint.

Description

[Technical field]

[0001] The present invention relates to a paint, and more particularly to a paint that reduces thermal radiation when applied to a metal plate used for the exterior of a building or the like, and a method for producing a painted metal plate by applying the paint. [Background technology]

[0002] Painted metal sheets are metal substrates coated with paint, and are mainly used for the exterior of buildings. However, because painted metal sheets are relatively thin, they have the problem of easily raising the temperature inside the room when exposed to solar heat. For this reason, paint with a heat-shielding effect is applied to the metal substrate to impart a heat-shielding function. By imparting a heat-shielding function, the rise in the temperature inside the room can be suppressed, which leads to a reduction in the use of air conditioning equipment, and ultimately contributes to the prevention of global warming.

[0003] As a method for imparting a heat shielding function to a metal substrate, for example, a coated metal plate in which a coating film containing aluminum powder is formed on the back surface (the side not exposed to solar radiation) of a metal substrate is known. By forming a coating film containing aluminum powder on the back surface of a metal substrate, it is possible to reduce heat radiation into a room. However, unless the content of aluminum powder contained in the coating film is increased, it is not possible to sufficiently reduce heat radiation. However, if the content of aluminum powder is increased, when the coated metal substrate is processed, such as by bending, the coating film cannot withstand the processing, and problems occur in which the coating film peels off or cracks, and this has not been put to practical use.

[0004] For this reason, a coated metal plate is known in which the aluminum powder content in the coating film on the back surface of the metal substrate is reduced, flexibility is improved so as to prevent peeling or cracking of the coating film, and a solar reflective coating film is formed on the front surface of the metal substrate (the side receiving solar radiation) (see Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2001-89871 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, the coating film provided on the back surface of the metal substrate in Patent Document 1 does not have sufficient ability to reduce heat radiation, and merely forms a solar radiation reflective coating film on the front surface (the side receiving solar radiation) of the metal substrate, so the effect of reducing heat radiation from the back surface of the metal substrate cannot be said to be sufficient.

[0007] Furthermore, when forming a solar reflective coating on the surface of a metal substrate (the surface that receives solar radiation), it is necessary to include a solar reflective pigment, which limits the design possibilities, such as color tone. On the other hand, if the radiant heat reduction effect can be increased simply by applying it to the back surface, it is possible to sufficiently reduce heat intrusion by protecting the front surface with a general weather-resistant coating that is not solar reflective, and the design possibilities, such as color tone, can be freely chosen.

[0008] The present invention has been made in consideration of the problems associated with the conventional inventions, and an object of the present invention is to provide a coating material that has a high thermal radiation reduction effect and is capable of forming a coating film that has excellent flexibility. [Means for solving the problem]

[0009] In order to achieve the above object, the present invention has at least the following configuration or executes the following procedures.

[0010] An invention according to one aspect of the present invention is a paint for coating a metal substrate, comprising a vehicle, aluminum powder, a solvent, and an anti-settling agent, wherein the vehicle is 100 parts by mass, the aluminum powder is 45 to 65 parts by mass, and the paint contains 70% to 90% by mass of volatile components. This configuration makes it possible to form a coating film that has a high thermal radiation reducing effect and excellent flexibility.

[0011] An invention according to one aspect of the present invention is a method for producing a painted metal plate by applying a paint containing a vehicle, aluminum powder, a solvent, and an anti-settling agent, wherein the vehicle is 100 parts by mass, the aluminum powder is 45 to 65 parts by mass, and a volatile component is 70% to 90% by mass, and is characterized by comprising a coating step of applying the paint to the back surface of a metal substrate, which is the side that is not exposed to solar radiation, and a coating film formation step of drying the paint on the metal substrate to which the paint has been applied, to form a coating film with a thickness of 1.0 to 3.0 μm and an emissivity of 0.45 or less. With this configuration, a coated metal plate having a high thermal radiation reducing effect and excellent flexibility can be formed. Effect of the Invention

[0012] As described above, according to the present invention, it is possible to provide a painted metal sheet that has a high thermal radiation reduction effect and excellent flexibility, so that by using the painted metal sheet of the present invention for the exterior of a building, particularly on the roof, the amount of heat entering the room can be more reliably suppressed. [Brief description of the drawings]

[0013] [Figure 1] FIG. 2 is a cross-sectional view of an apparatus used in an experiment to evaluate the heat-shielding effect of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, an embodiment of the present invention will be described. Note that the embodiment described below is merely a specific example for carrying out the present invention, and is not to be construed as limiting the present invention.

[0015] <Paint> The paint according to the present invention is a paint for coating a metal substrate, and contains a vehicle, aluminum powder, a solvent, and a settling inhibitor. The ratio of each sample in the paint is 45 to 65 parts by mass of aluminum powder relative to 100 parts by mass of vehicle, and the volatile components in the paint according to the present invention account for 70% to 90% by mass. Here, the vehicle refers to a resin component and does not contain a solvent. The volatile components refer to a solvent and the like, and more specifically, refer to those that evaporate when the paint is heated at 200°C. When the paint is heated at 200°C, those that do not evaporate are referred to as solid components. In other words, the paint can be divided into solid components and volatile components.

[0016] In addition, the paint according to the present invention contains a large amount of aluminum powder, 45 to 65 parts by mass, per 100 parts by mass of vehicle, so the content of aluminum powder on the coating film surface can be increased, thereby enhancing the thermal radiation reduction effect. In addition, the paint according to the present invention contains a large amount of volatile components, 70% to 90% by mass, so the proportions of vehicle and aluminum powder in the paint can be reduced, and therefore the coating amount can be 10.0 to 20.0 g / m 2 When the coating composition is set to 100 parts by mass, the film thickness can be controlled to 1.0 to 3.0 μm, and the absolute amount of aluminum powder can be reduced. This makes it possible to form a coating film with excellent flexibility. In other words, the coating material according to the present invention has a vehicle of 100 parts by mass, aluminum powder of 45 to 65 parts by mass, and a volatile component of 70% by mass to 90% by mass, so that the aluminum powder and volatile component are high relative to the vehicle, and therefore the coating material is characterized by having a high thermal radiation reduction effect and being able to form a coating film with excellent flexibility.

[0017] As the vehicle, thermosetting resins such as polyester resin, acrylic resin, vinyl acetate resin, phthalate ester resin, epoxy resin, and urethane resin can be used. In particular, low molecular weight polyester resins are preferred, such as Beckolite 46-118. The reason for their preference is that they are excellent in hardness, flexibility, water resistance, chemical resistance, and adhesiveness. Here, the solid content of Beckolite 46-118 is 59.0% to 61.0% by mass at 107.5°C according to the manufacturer's value. In addition, the value measured when heated at 200°C is 57.6% by mass. Therefore, Beckolite 46-118 contains 42.4% by mass of volatile components. In addition, alkoxysiloxane, which has excellent heat resistance, may be used as the resin.

[0018] It is preferable to use a commercially available aluminum pigment as the aluminum powder. For example, aluminum paste 0810M from Toyo Aluminum Co., Ltd. can be used. Aluminum paste 0810M has an aluminum concentration of 66 to 69%, stearic acid of 3% or less, and mineral spirits of 28 to 33% by mass. In other words, 100 g of aluminum paste 0810M contains 66 to 69 g of aluminum powder. In addition, the value measured when heated at 200°C is 69.3% by mass. Therefore, this value was used as the aluminum content. However, since aluminum paste D462GR, which is a colored aluminum pigment, contains a colored pigment and a methacrylic resin, the aluminum content was set to 32.0%, which is the value stated in the SDS.

[0019] The solvent may be any commercially available solvent, such as ST3000FX, ST1000, or Anon, available from Chugai Shoko Co., Ltd.

[0020] If necessary, additives may be mixed in. Examples of additives that may be used include anti-settling agents such as Flonone SH-290 and Disparlon A603-20X, and anti-foaming agents such as Flonone AC-303HF.

[0021] <Painted metal plate> Next, a coated metal plate produced by applying the paint according to the present invention to a metal substrate will be described. When the paint according to the present invention is applied to the back surface of a metal substrate, a coated metal plate having a high thermal radiation reduction effect and excellent flexibility can be formed. Here, the surface of the coated metal plate refers to the side that receives solar radiation when the coated metal plate is used for the exterior of a building, and the back surface of the coated metal plate refers to the side opposite to the side that receives solar radiation. Since the surface of the metal substrate (the surface that receives solar radiation) is affected by rainwater and ultraviolet rays, it is desirable to apply a weather-resistant paint. In addition, if it is desired to further increase the heat shielding effect, a solar radiation reflective coating film may be formed on the surface of the coated metal plate. In addition, the coating film formed on the surface of the coated metal plate is called a weather-resistant coating film, and the coating film formed on the back surface of the coated metal plate is called an aluminum-containing coating film. Here, an important point in the present invention is that the coating film (aluminum-containing coating film) formed by applying the paint according to the present invention to the back surface reduces heat radiation to the indoor side.

[0022] The metal substrate may be made of a metal required for the application. Specific examples include aluminum-zinc alloy plated steel sheet (Galvalume Steel Sheet (registered trademark)), iron sheet, copper sheet, steel sheet, aluminum sheet, etc.

[0023] When forming a coating film on the surface of a coated metal plate, it is preferable to use a paint containing a mixture of resin and pigment for the weather-resistant coating film. Additives may be mixed as necessary. When forming a weather-resistant coating film, the thickness of the coating film is in the range of 10 μm to 60 μm. The thickness may be changed as necessary.

[0024] Resins that can be used for the weather-resistant coating film include polyester resins, acrylic resins, vinyl acetate resins, phthalate ester resins, epoxy resins, urethane resins, etc. In particular, polyester resins are preferred. The reason why polyester resins are preferred is that they are excellent in terms of high hardness, weather resistance, flexibility, water resistance, chemical resistance, adhesiveness, etc.

[0025] The aluminum-containing coating film formed on the back surface of the coated metal sheet of the present invention is formed by applying the coating material of the present invention at 10.0 to 20.0 g / m2. When the applied coating material is dried, the coating thickness is in the range of 1.0 to 3.0 μm.

[0026] The thickness of the aluminum-containing coating film is in the range of 1.0 to 3.0 μm. Within this range, the aluminum-containing coating film has excellent flexibility and is unlikely to be damaged even when the coated metal sheet is subjected to bending processing, etc. In addition, when a coating film of this thickness is formed by applying the paint according to the present invention, the coating film has an emissivity of 0.45 or less and has an excellent radiant heat reducing effect.

[0027] Next, a method for producing a coated metal plate by applying the coating material according to the present invention to a metal substrate will be described. To form an aluminum-containing coating film, the method includes a coating step of applying the coating material according to the present invention to the back surface of the metal substrate, which is the side not exposed to solar radiation, at 10.0 to 20.0 g / m2, and a coating film forming step of drying the coating material on the metal substrate to which the coating material has been applied to form a coating film having a thickness of 1.0 to 3.0 μm or less. This makes it possible to form a coating film having an emissivity of 0.45 or less. Specifically, the coating is performed using a roll coater, but the method is not limited thereto and may be applied using a brush, roller, or the like. Also, the coating may be applied by a spray method. EXAMPLES

[0028] Next, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0029] The experiment was carried out using a prototype heating box 1 made of a wooden plywood 2 with sides of 30 cm and a painted metal plate 3 as shown in Figure 1. To ensure a steady state, the sides were covered with an aluminum laminate sheet on the outside. A 25 mm thick expanded polystyrene was placed on the bottom as a heat insulator, and heat dissipation from the bottom was ignored and considered to be from the sides only. In a steady state, the amount of heat entering and dissipating is equal, so the amount of heat dissipating from the sides was considered to be the amount of heat entering. Heat was radiated from a heating lamp 4 placed above the painted metal plate 3, and each item was measured. Two 270 W heating lamps 4 were used, with the lamp irradiation distances set to 116 mm and 154 mm. This is based on the solar radiation on a midsummer day (temperature 30°C). The evaluation of the amount of radiated heat was conducted on the entire side surface except the top plate and bottom surface after confirming the steady state. As a condition at that time, the side emissivity of the heating box was determined to be emissivity ε = 0.02 based on the actual measurement value. The total area of ​​the side surface was set to 0.33 m2. The evaluation of temperature and WBGT (heat index) was conducted on the average value of 1 hour 3 to 4 hours after the start of lamp irradiation after confirming the steady state. A thermocouple sensor and a Memory HiLogger LR8400 (HIOKI EE Corporation) were used for temperature measurement, and a FUSO-87595SD (FUSO Corporation) was used for WBGT measurement. The metal plate 3 had a white surface and a beige back surface, and the metal plate with the paint of Examples 1 and 10 applied to the back surface and Comparative Example 6 (blank) were used to confirm the difference in the amount of heat entering (Table 1). Furthermore, in order to confirm the effect of the color tone of the metal substrate surface, the surface of the metal plate 3 was painted black and the same confirmation was carried out. At this time, one lamp 4 with a specification of 270 W was used, and the lamp irradiation distance was set to 220 mm (Table 2). The measurement results are shown in Tables 1 and 2. The average temperature on the underside of the tabletop is the surface temperature on the inside of the tabletop. WBGT and the average space temperature were measured at position A, 10 cm from the bottom at the center of the prototype heating box 1. In Example 1, the temperature of the underside of the top plate was higher than that of the uncoated Comparative Example 6 (blank). However, when actually conditioning the interior, the space temperature is important, and when humans are working, the WBGT is important. In particular, the electricity cost of air conditioning is a large expense, so reducing this is the first objective. In addition, the reduction rate of heat penetration was about the same regardless of the surface color tone of the solar reflective coating, etc., indicating that there is no effect on the surface color tone.

[0030] TIFF0007665262000002.tif34166

[0031] TIFF0007665262000003.tif34166

[0032] As the painted metal sheets, metal substrates coated with the paints of Examples 1 to 12 on the back side were used. As comparative examples, metal substrates coated with the paints of Comparative Examples 1 to 5 were used. As Comparative Example 6, a commercially available colored steel sheet was used for reference. This colored steel sheet had a white front surface and a cream back surface. An aluminum-zinc alloy plated steel sheet (Galvalume Steel Sheet (registered trademark)) with a thickness of 0.27 mm was used as the metal substrate. The painted metal sheets of the examples were manufactured using the method for manufacturing a painted metal sheet according to the present invention.

[0033] <Examples 1, 3 to 10, 12> The vehicles used were Beckolite 46-118, Beckolite 46-119, Acrydic 56-728, and EPICLON H-360 manufactured by DIC Corporation, the aluminum pigments used were Aluminum Paste 0810M, Aluminum Paste 4640NS, Aluminum Paste 5660NS, Aluminum Paste Z460, and Aluminum Paste D462GR manufactured by Toyo Aluminum Co., Ltd., the solvents used were ST-3000FX, ST-1000, and Anon manufactured by Chugai Shoko Co., Ltd., the anti-settling agents used were Flonone SH-290 and Disparlon A603-20X, and the defoamer used was Flonone AC-303HF. The coated metal plate was prepared by baking the paint at 200°C for 60 seconds.

[0034] <Example 2> The coated metal plate was prepared in the same manner as in Example 1, except that the surface was painted with a matte black spray.

[0035] <Example 11> The coated metal plate was prepared in the same manner as in Example 10, except that the surface was painted with a matte black spray.

[0036] <Comparative Examples 1 to 5> The vehicle used was Beckolite 46-118 manufactured by DIC Corporation, the aluminum pigment was Aluminum Paste 0810M manufactured by Toyo Aluminum Co., Ltd., the solvent was ST3000FX and Anon manufactured by Chugai Shoko Co., Ltd., the anti-settling agent was Flonone SH-290, and the defoamer was Flonone AC-303HF. The coated metal plate was prepared by baking the paint at 200°C for 60 seconds.

[0037] <Comparative Example 6> A commercially available color steel plate was used, which was not coated with the paint according to the present invention.

[0038] <Comparative Example 7> A commercially available color steel plate was used, the front side of which was painted with a matte black spray paint, and the back side of which was not coated with the paint according to the present invention.

[0039] These paints were applied to a colored steel plate (150 x 150 x 0.5 mm) and placed on a heater. The surface temperature of the heater was measured using a thermocouple attached to the heater, and the effect of reducing thermal emissivity was estimated by comparing the results with the radiation temperature measured by a non-contact thermometer. The principle of this measurement is explained below.

[0040] Radiant heat is basically considered to be the amount of infrared radiation emitted from a surface. A thermometer measures this amount of infrared radiation and inversely determines the surface temperature. However, because the amount of emitted heat is a function of the surface temperature and emissivity, the surface temperature cannot be determined from a thermometer unless the emissivity is known. For this reason, thermometers are calibrated using a pseudo-blackbody. Because they are calibrated using a blackbody, if a surface with a lower emissivity is measured, the measured temperature will naturally be lower than the actual temperature. For example, even if the actual surface temperature is 200°C, if the emissivity is 0.64, the thermometer will display 160°C.

[0041] Normally, when measuring a person's body temperature with a thermometer, the surface to be measured (such as human skin) is first measured with a thermocouple for correction. In this case, correction is performed using a blackbody, so the thermometer measures a lower temperature. The ratio of the surface temperature measured by the thermometer to the contact surface temperature measured by the thermocouple is the emissivity of the surface.

[0042] The room temperature was set at 23°C, the heater was set at 100°C, and the surface temperature of the metal plates prepared in the examples and comparative examples was measured using a contact thermocouple and a non-contact blackbody-corrected thermometer to determine the emissivity. The amount of radiant heat was also calculated using the Stefan-Boltzmann equation. The prepared metal plates were also bent to check for cracks, peeling, etc. in the coating film, to evaluate their flexibility.

[0043] Table 3 shows the results for metal plates coated with the paints of Examples 1 to 12 and Comparative Examples 1 to 7. It can be seen from Table 3 that the paints of the present invention are excellent in emissivity and flexibility. In addition, in the formulation parts of Table 3, unless otherwise specified, the units are given in parts by mass. Table 3 gives the mass ratio of aluminum powder to 100 parts by mass of vehicle, and also gives the mass ratio of solids and volatile components. These ratios enable the paints of the present application to form coating films that have a high thermal radiation reduction effect and excellent flexibility.

[0044] TIFF0007665262000004.tif254147 [Industrial Applicability]

[0045] The coating material according to the present invention is useful because it can more reliably suppress the amount of heat entering the room by using the coating material according to the present invention. In addition, the coating material according to the present invention is useful because it can produce a coated metal plate that is easy to process due to its excellent flexibility. [Explanation of symbols]

[0046] 1. Prototype heating box 2. Wooden plywood 3. Painted metal plate 4 Heat Lamps

Claims

1. A paint for coating a metal substrate, The present invention includes a vehicle, an aluminum powder, a solvent, and an anti-settling agent, the vehicle is 100 parts by mass, the aluminum powder is 48.1 to 60.2 parts by mass, and the anti-settling agent is 6.9 to 27.8 parts by mass; The paint is characterized in that the volatile components are 71.36% to 82.16% by mass.

2. A method for producing a coating composition comprising: a vehicle; aluminum powder; a solvent; and an anti-settling agent; the vehicle is 100 parts by mass, the aluminum powder is 48.1 to 60.2 parts by mass, and the anti-settling agent is 6.9 to 27.8 parts by mass; A method for producing a coated metal sheet, comprising applying a coating material having a volatile component content of 71.36% to 82.16% by mass, A coating step of coating the paint on a back surface of the metal substrate, which is a side that is not exposed to solar radiation; and a coating film forming step of drying the paint on the metal substrate to which the paint has been applied to form a coating film.

3. The method for manufacturing a painted metal plate as described in claim 2, characterized in that in the coating film forming process, a coating film having a thickness of 1.8 to 2.9 μm and an emissivity of 0.15 to 0.29 is formed.

4. The method for producing a coated metal sheet according to claim 2 or 3, characterized in that the amount of the paint applied in the coating step is 13.0 to 13.9 parts by mass per m 2 .

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