Temperature increase preventive sheet, solar-exposed surface temperature increase preventing method, and coating

Abstract

To provide a sheet that prevents temperature increases on solar-exposed surfaces such as vehicle dashboards.SOLUTION: A sheet 1 for preventing solar-induced temperature increases comprises a sheet substrate 2, coated by an insulating layer 3 containing a specific proportion of soft hollow beads 4 and hard hollow beads 5 to preserve the flexibility of the sheet substrate, and then a reflective layer 6 containing a reflective material to achieve a solar reflectance at or above a predetermined value.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a high-temperature suppression sheet, a method for suppressing the high temperature of a solar irradiated surface, and a paint. [Background technology]

[0002] It is known that when sunlight shines on the inside of a parked car, the temperature inside the car rises. In particular, the dashboard of a car is prone to becoming very hot in a short period of time, raising the temperature inside the closed car.

[0003] On the other hand, there are few effective measures to suppress the temperature rise of solar radiation surfaces such as dashboards. For example, one measure is to keep the air conditioning in the car running, but it is not realistic to operate it this way all the time. One option is to use sunshades, but the general ones emphasize reflective function and have low insulation effect, and those that emphasize insulation have problems such as poor folding ability.

[0004] In this context, one type of vehicle interior material that is used in areas of the vehicle body exposed to sunlight is a nonwoven fabric made of a fiber body of a thermoplastic synthetic resin that contains an inorganic pigment that has infrared reflective properties (Patent Document 1).

[0005] This provides a nonwoven fabric that has a heat-shielding effect without increasing weight or impeding moldability, by using a fibrous body containing an inorganic pigment with infrared reflecting function, and a vehicle interior material using this nonwoven fabric.

[0006] However, according to Patent Document 1, a fibrous body of a thermoplastic synthetic resin containing an inorganic pigment having an infrared reflecting function is required, and the solar reflectance of the inorganic pigment must be adjusted within a predetermined range during the production of the fiber. In addition, since the fibrous body serves as the base material, there are problems such as the particle size in the crystal structure of the inorganic pigment being restricted by the specifications of the fiber. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2018-158627 A Summary of the Invention [Problem to be solved by the invention]

[0008] The problem to be solved by the present invention is to provide a sheet or the like that can prevent a solar irradiated surface from becoming hotter at low cost and simply.

[0009] The first invention is a sheet for suppressing high temperature caused by solar radiation, the sheet comprising an upper reflective layer and a lower insulating layer formed by painting on a sheet substrate, the reflective layer containing a reflective material so that the solar radiation reflectance is a predetermined value or more, and the insulating layer containing a predetermined ratio of soft hollow beads to hard hollow beads so that the flexibility of the sheet substrate is maintained. The second invention is a high temperature suppression sheet according to the first invention, characterized in that the reflective material forming the reflective layer is made of the same material as at least one of the hollow beads. The third invention is a high temperature suppression sheet according to the first or second invention, characterized in that the insulating layer is formed by a paint containing the hollow beads and the reflective material in the same coating film forming material. The fourth invention is a method for suppressing high temperature on a solar radiation surface, characterized in that the high temperature suppression sheet according to the first or second invention is applied to an area where a temperature rise due to solar radiation is expected to occur, to prevent a temperature rise in the area. The fifth invention is a paint for suppressing overheating in an area where a temperature rise due to solar radiation is expected by applying it to the area, the paint comprising a reflective material, hard hollow beads, and soft hollow beads, the reflective material being present in a content such that the solar reflectance is equal to or greater than a predetermined value, and the soft hollow beads being present in a content such that the flexibility of the application target is maintained. The sixth invention is a paint for suppressing overheating in an area where a temperature rise due to solar radiation is expected by applying it to the area, the paint comprising a reflective material, a pigment, hard hollow beads, and soft hollow beads, the reflective material and the pigment being present in a content such that the solar reflectance is within a predetermined range, and the soft hollow beads being present in a content such that the flexibility of the application target is maintained. The seventh invention is the paint according to the fifth or sixth invention, characterized in that the reflective material forming the reflective layer is made of the same material as at least one of the hollow beads. Effect of the Invention

[0010] In the present invention, since the high temperature suppression sheet having a reflective layer and a heat insulating layer is formed by painting, it is expected to be an inexpensive and simple sheet. In addition, in the present invention, since a predetermined ratio of soft hollow beads is contained in the hard hollow beads as the heat insulating layer, it is expected that the flexibility of the sheet is maintained, and it is easy to use the sheet according to a desired shape and to fold the sheet when not in use. In addition, in the present invention, since the reflective material and the heat insulating material are contained in the same coating film forming material, it is expected that the reflective layer and the heat insulating layer are formed by one application, and it is expected to be an inexpensive and simple sheet. In addition, since the present invention only requires covering the area where the temperature rise due to solar radiation is expected, it is expected to easily suppress the temperature rise of the solar radiation surface of the dashboard inside the car. In addition, in the present invention, since the coating film forming material contains a predetermined amount of pigment together with the reflective material and the heat insulating material, it is expected that the high temperature suppression function will be maintained even if the sheet is colored according to the application such as reducing reflected light. [Brief description of the drawings]

[0011] [Figure 1] This is an example of a substrate for a high temperature suppression sheet (the black part is the part where the heat insulating coating film is formed). [Diagram 2] 1 is a schematic cross-sectional image of a high temperature suppression sheet. [Diagram 3] This is a cross-sectional image of the coating film before it dries. [Figure 4] This is a cross-sectional image of the coating film after it has dried. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Example 1 Hereinafter, the present invention will be described in detail based on the embodiments.

[0013] <Sheet base material> Fig. 1 is a photograph of the surface of a cloth sheet used as a substrate 2 of a sheet 1 according to the present invention. The photograph shows a state in which a part of a white cloth sheet has been coated with a heat insulating paint (the black part at the bottom of the photograph is the part coated with the heat insulating paint). However, the material of the sheet is not limited to this, and it may be made of various resins or leather, paper, etc.

[0014] <Coating film> FIG. 2 is a schematic image of a cross section showing the internal structure of the sheet 1. The sheet 1 mainly consists of a sheet substrate 2, a heat insulating layer 3 (the heat insulating layer 3 mainly contains soft hollow beads 4 and hard hollow beads 5), and a reflective layer 6. FIG. 2 shows that there are multiple hollow bead materials in the coating film. In FIG. 2, the particle diameter of the hollow beads of each material is approximately the same for the sake of illustration, but in reality there is a range of particle diameters. In addition, although not shown in FIG. 2, a base conditioner for strengthening adhesion to the sheet substrate 2, a gloss finishing agent for the coating film surface, a coating agent for anti-fouling, etc. may be used in the coating film formation.

[0015] <Paint> In this embodiment, a water-based paint was used, but the paint for forming the coating film may be either water-based or solvent-based. For example, acrylic emulsion resin may be used, but urethane, silicone, fluorine-based components, or other components may be used as the main components.

[0016] <Hollow beads> The paint used in this embodiment contains acrylic hollow beads as the soft hollow beads 4 for forming the heat insulating layer 3, and hard hollow beads 5 (here, ceramic hollow beads) so that the coating film has a predetermined thickness. According to an enlarged photograph (omitted) of the inside of the coating film after the coating film has been formed, the part that forms the heat insulating layer 3 inside the coating film is adjacent to the acrylic hollow beads and the ceramic hollow beads, and although some of the soft acrylic hollow beads are deformed, each hollow bead is densely packed without cracking. The hollow beads are for forming the heat insulating layer 3, and the number of types of material is not limited.

[0017] The material of the hollow beads is not limited, but examples thereof include plastics such as acrylic, polystyrene, and polycarbonate, and elastomers such as rubber. These are examples of soft hollow beads. On the other hand, examples of hard hollow beads include ceramics, glass, and the like.

[0018] The particle size of the hollow beads of each material in this embodiment is mostly on the order of several tens of μm. Specifically, excluding those with a very small particle size of 1 μm or less, most of the hollow beads of each material have particle sizes of about 80 μm, about 60 μm, and about 50 μm, with a weight ratio of about 5:3:2. In addition, the volume of the hollow part of the hollow beads is generally 80% or more.

[0019] <Reflective materials and reflectance> The reflective material may be any material that can achieve a predetermined reflectance. The reflectance of the reflective layer 6 formed by the reflective material is a guideline that the temperature rise of the solar radiation surface that is the target of the high temperature suppression can be reduced. More specifically, the reflectance is about 90% in the entire wavelength range of 300 to 2500 nm as specified in JISK5602:2008. However, it is not limited to this. In this embodiment, fine powder 7 produced by crushing ceramic hollow beads during the manufacturing process was used as the reflective material. This reflective material floats to the surface of the coating film during the drying process of the coating film, forming the reflective layer 6. Other reflective materials such as titanium oxide, zinc oxide, tin oxide, and glass may also be used.

[0020] <Painting> The coating (applying) process includes a step of removing dirt from the sheet substrate 2 and a step of applying paint to a film thickness of about 200 μm (when dry) with a roller brush. In this embodiment, a coating film of about 200 μm was formed by one application. However, the coating method is not limited thereto. For example, spraying may be used.

[0021] <Coating film formation> Figure 3 is a cross-sectional image of the coating film before drying. In Figure 2, the particle size of each bead is uniform, but in reality, the coating film forming material contains beads of various particle sizes as shown in Figure 3. Before drying, the soft hollow beads 4, hard hollow beads 5, and fine powder 7 that forms the reflective material 6 are dispersed with some space between them. The coating film changes to the state shown in Figure 4 when it dries. Figure 4 is a cross-sectional image of the coating film after drying, that is, the heat insulating layer 3. The beads become denser, and the fine powder 7 forms a reflective layer 6 on the surface of the coating film. The degree of density of the beads 4, 5 and fine powder 7 shown in Figures 3 and 4 varies depending on the amount of each used.

[0022] <High temperature suppression test> The effectiveness confirmation test of Sheet 1 was as follows. The test was carried out in autumn (on a sunny day). Target for suppressing high temperatures: Dashboard in a regular passenger car Conditions: Car engine is off (air conditioner is off), sunlight is shining on the car dashboard Confirmation point 1: Difference in the effect of suppressing temperature rise inside the car when the dashboard is covered with Sheet 1 and when it is not Check point 2: Effects of coloring of sheet coating (white pigment / black pigment) Test time: Approximately 30 minutes each Evaluation method: Sensory evaluation based on sensation (3-level evaluation: "normal", "slightly hot", "very hot")

[0023] <Result> The results of the comparison of perceived temperature are as follows: When the dashboard was not covered by Sheet 1, the temperature went from normal to extremely hot. When the dashboard was covered with white-colored Sheet 1, the temperature went from normal to slightly hot.

[0024] The results of confirming the effects of paint film coloring are as follows: In the case of the white pigment, the temperature increased and the sensation of being slightly hot continued. In the case of black pigments, the temperature increased and the sensation of being slightly hot continued.

[0025] <Consideration> It was confirmed that when sunlight shines onto the dashboard of a car, the presence or absence of Sheet 1 causes a significant difference in the perceived temperature within a short period of time. Since the areas where the temperature is expected to rise due to sunlight are the areas directly exposed to sunlight, shading these areas will suppress the temperature rise through shading and insulation of the dashboard and other solar radiation surfaces, and thus is suggested to be effective in suppressing the rise in the perceived temperature inside the car.

[0026] The sheet 1 according to the present invention has a heat insulating layer 3 and a reflective layer 6 on a sheet substrate 2. The reflective layer 6, which is the surface layer of the sheet 1, is one of the factors that contribute to suppressing the rise in temperature inside the vehicle through shading the solar radiation surface of the dashboard and insulating it. In this embodiment, the reflective layer 6 is formed from fine powder 7 generated during the manufacturing process of the ceramic hollow beads.

[0027] By being contained in advance in the coating film-forming material together with the hollow beads, the fine powder 7 rises to the surface of the coating film during the drying process and forms the reflective layer 6. This is an effect discovered by the inventors of the present invention. It is suggested that the fine powder 7 having a smaller particle size (for example, a particle size of 1 μm or less) is more susceptible to the influence of moisture that moves out of the coating film during the drying process and is more likely to be pushed out to the coating film surface.

[0028] In this embodiment, the fine powder 7 forming the reflective layer 6 is derived from ceramic hollow beads, but the present invention is not limited to this. For example, it may be derived from glass hollow beads, or the fine powder 7 may be made of a resin used for soft hollow beads. In this case, the reflective layer 6 is also formed during the drying process of the coating. In other words, the reflectance of the reflective layer 6 formed can be adjusted by adjusting the amount of the fine powder 7 used. The fine powder 7 may also be made of a plurality of materials.

[0029] The reflective layer 6 thus formed reflects sunlight. The smaller the particle size of the fine powder 7 and the more used, the higher the reflectance of the reflective layer 6. A predetermined amount of the fine powder 7 can achieve a reflectance of about 90% over the entire wavelength range of 300 to 2500 nm as specified by JIS K5602:2008. In this way, the reflective layer 6 suppresses the temperature rise of the solar radiation surface of the dashboard due to sunlight. In addition, since the fine powder 7 is fragments of hollow beads that constitute the heat insulating layer 3, there is no need to apply a separate reflective material, and the process of forming a reflective layer by application is also unnecessary.

[0030] Next, the heat insulating layer 3, which is the layer below the reflective layer 6, can be cited as a factor that contributed to suppressing the temperature rise of the sun-irradiated surface of the dashboard. The heat insulating layer 3 blocks the heat of sunlight that could not be reflected by the reflective layer 6. In this embodiment, the heat insulating layer 3 was formed by two types of hollow beads: acrylic hollow beads (soft hollow beads 4) and ceramic hollow beads (hard hollow beads 5). Thus, the combined effects of using the soft hollow beads 4 and the hard hollow beads 5 mainly include the following two points.

[0031] The first point is that a dense hollow structure without cracks is formed in the hollow beads. In this embodiment, the same amount of acrylic hollow beads and ceramic hollow beads are used, and they are almost evenly dispersed. In addition, the acrylic hollow beads adjacent to the ceramic hollow beads may be slightly distorted by the ceramic hollow beads, but since they have a certain degree of elasticity, they do not crack and maintain a dense state with the adjacent beads. The dense hollow structure formed in this way improves the thermal insulation.

[0032] The second point is that the thickness of the coating film can be made larger to a certain extent than that of a general coating film. The dense hollow bead structure allows for a coating film thickness of at least several hundred μm, and it has been confirmed that the coating film will not deform for more than a year even outdoors after it has been formed. For example, if the heat insulating layer 3 is formed only with acrylic hollow beads, it is difficult to achieve the same quality and thickness as in this embodiment. In addition, if the heat insulating layer 3 is formed only with ceramic hollow beads, the coating film will crack and the heat insulating effect will decrease.

[0033] However, there is no denying that there is only one type of hollow beads. This is because the required heat insulating performance differs depending on the situation. Also, since the sheet 1 is used for objects of various shapes such as dashboards, and is folded and stored when not in use, the role played by the soft hollow beads 4 is large. This is because it is expected that cloth or other flexible materials will be used as the sheet base material 2, and if the flexibility of the sheet 1 is lost after the coating film is formed, convenience will decrease.

[0034] In addition, in this embodiment, no significant difference in sensible temperature was confirmed between white and black pigments. Generally, black pigments are rarely used as light-shielding paints. This is because black pigments reduce reflectance. However, in this embodiment, there was no significant difference in sensible temperature between white and black pigments, suggesting that the high temperature suppression function is not lost even by blackening. In addition, it is suggested that other arbitrary colorings such as red, green, blue, and dark colors such as brown, navy blue, purple, and gray will have the same effect.

[0035] Thus, in this embodiment, it was confirmed that the combination of the heat insulating layer 3 and the reflective layer 6 mitigates the temperature rise caused by coloring. A white-based color coating film has a high reflectance and is generally said to have a large effect of suppressing high temperatures, but on the other hand, there are problems such as reflected light hitting people outside the vehicle. It is suggested that the combination of the heat insulating layer 3 and the reflective layer 6 suppresses the temperature rise inside the vehicle while mitigating the glare caused by reflected light through coloring.

[0036] Example 2 Considerations and verification results of useful embodiments of the present invention are described below.

[0037] The balance between the reflective and insulating functions varies depending on the purpose. For example, if the emphasis is on shading, a reflectance of 90% or more is desirable. In this case, the reflective layer 6 plays a major role in suppressing the rise in temperature of the solar radiation surface, such as the dashboard. A larger amount of reflective material 7 is used to form the reflective layer 6, while a smaller amount of insulating material is used to form the insulating layer 3.

[0038] On the other hand, when it is desired to reduce glare due to reflected sunlight or when the design of the sheet 1 is important, the amount of reflective material 7 used to form the reflective layer 6 will be reduced. Furthermore, when the sheet 1 is colored black or other colors, it is easier to absorb sunlight, and the reflectance will be lower accordingly. The reflectance may be set to 40% to 80%. In this case, the role of the heat insulating layer 3 becomes important. That is, the role of the heat insulating layer 3 becomes greater, as it minimizes heat storage due to absorption of sunlight on the surface layer of the sheet and suppresses the temperature increase. In this case, the density of the heat insulating material becomes particularly important.

[0039] For example, there is the heat insulating layer 3 formed by a paint in which soft hollow beads 4 and hard hollow beads 5 are used in a 1:1 ratio as in Example 1. Before the coating film is formed, the soft hollow beads 4 and the hard hollow beads 5 are positioned with ample space between them, but as the coating film dries, the gaps between the respective hollow beads become narrower and the density increases.

[0040] However, if the ratio of hard hollow beads 5 to soft hollow beads 4 is large, the hard hollow beads 5 come into contact with each other more frequently, making them more likely to crack. Therefore, when hard hollow beads 5 are used, it is necessary to select a material that is resistant to cracking and to set the ratio of soft hollow beads 4 so that it is not too low.

[0041] Furthermore, when the target to be coated, such as the sheet substrate 2, is soft, the flexibility decreases as the ratio of the hard hollow beads 5 increases. As for the ratio of the soft hollow beads 4 to the hard hollow beads 5, a 1:1 ratio is applicable to many targets (such as resin materials and paper materials) such as general sunshade substrates.

[0042] In addition, by using hollow beads of different particle sizes (for example, hollow beads with a particle size of several tens of μm and hollow beads with a particle size of several μm), the small hollow beads fill the gaps between the large hollow beads, increasing the density when the coating film dries. The heat insulating layer 3 with the hollow beads densely formed in this way has enhanced heat insulating function, retaining heat from sunlight on the surface layer of the sheet and suppressing the temperature rise of the sun-irradiated surface.

[0043] In Example 1, the ceramic fine powder 7 naturally forms a reflective layer 6 on the sheet surface during the coating film formation process. In order for the reflective layer 6 to be naturally formed during the coating film formation process, the particle size must be such that it can move between the hollow beads. For example, the particle size of the reflective material is assumed to be less than 1 μm.

[0044] In Example 1, ceramic was used as the reflective material, but any material may be used as long as the reflective layer 6 is naturally formed during the coating film formation process. It is suggested that the ceramic fine powder 7 is pushed out to the coating film surface with the movement of moisture in the coating film forming material during the coating film formation process, forming the reflective layer 6.

[0045] Examples of fine powder 7 made of other materials include titanium oxide, zinc oxide, tin oxide, glass, etc., and it is suggested that the use of such fine powder 7 in a coating film forming material will form a reflective layer 6. The same applies to fine powder 7 made of the above-mentioned resins that are also used for soft hollow beads 4, etc. The same applies to the case where there are multiple types of fine powder 7.

[0046] The reflective layer 6 may be formed separately after the coating film is formed. For example, after the coating film according to Example 1 is formed, ceramic fine powder 7 may be additionally applied to the upper surface of the coating film. This is an example of reinforcement when the desired reflectance is not obtained by forming the coating film. Also, photocatalytic fine powder 7 such as titanium oxide may be additionally applied. This is an example of imparting a function according to a purpose, such as an antifouling function.

[0047] The sheet substrate 2 may also be a sticker with an adhesive applied on one side. For example, the sheet substrate 2 may be a high-temperature suppression sheet with a paint applied to the surface of the sticker and equipped with a heat insulating layer 3 and a reflective layer 6. In this case, the sheet is attached to an area where it is desired to prevent the area from becoming hot due to sunlight, with the adhesive applied side.

[0048] Also, a paint containing a predetermined reflective material and a heat insulating material in the coating film forming material may be applied to a portion where it is desired to prevent the temperature from increasing due to sunlight (a region where the temperature is expected to increase due to solar radiation). In this way, the form in which a sticker with a coating film formed in advance is attached, the above-mentioned paint, and the method of suppressing the temperature increase using the above-mentioned paint are all within the scope of the present invention. [Industrial Applicability]

[0049] The present invention can be used as a method applicable to areas where a temperature rise due to solar radiation is expected, such as the dashboard of a vehicle interior. The present invention can also be used to manufacture an inexpensive sheet that can easily form a heat insulating layer 3 and a reflective layer 6. The present invention can also be used as a paint that can be applied to areas where a temperature rise due to solar radiation is expected. [Explanation of symbols]

[0050] 1 sheet 2 Sheet substrate 3. Insulation layer 4. Soft hollow beads 5. Hard Hollow Beads 6 reflective layer 7 Fine powder

Claims

1. A sheet for suppressing high temperatures caused by solar radiation, The sheet includes an upper reflective layer and a lower heat insulating layer formed by painting on a sheet base material, The reflective layer contains a reflective material so that the solar reflectance is equal to or greater than a predetermined value, The heat insulating layer comprises hard hollow beads and soft hollow beads at a predetermined ratio so that the flexibility of the sheet base material is maintained.

2. 2. The high temperature suppressing sheet according to claim 1, wherein the reflective material forming the reflective layer is made of the same material as at least one of the hollow beads.

3. 3. The high temperature suppressing sheet according to claim 1, wherein the heat insulating layer is formed by a paint containing the hollow beads and the reflective material in the same coating film forming material.

4. A method for suppressing an increase in temperature of a solar radiation surface, comprising: A method for suppressing an increase in temperature of a solar irradiated surface, comprising covering an area where a temperature increase due to solar radiation is expected with the high-temperature suppression sheet according to claim 1 or 2 to prevent a temperature increase in said area.

5. A paint for suppressing an increase in temperature in an area where a temperature rise due to solar radiation is expected, comprising: The present invention includes a reflector, hard hollow beads, and soft hollow beads, The content of the reflective material is such that the solar reflectance is equal to or greater than a predetermined value, The coating material is characterized in that the content of the soft hollow beads is such that the flexibility of the coating object is maintained.

6. A paint for suppressing an increase in temperature in an area where a temperature rise due to solar radiation is expected, comprising: The present invention includes a reflector, a pigment, hard hollow beads, and soft hollow beads, The content of the reflective material and the pigment is such that the solar reflectance falls within a predetermined range, The coating material is characterized in that the content of the soft hollow beads is such that the flexibility of the coating object is maintained.

7. 7. The coating material according to claim 5, wherein the reflective layer is made of the same material as at least one of the hollow beads.

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