UV and visible solar radiation reflecting materials

Abstract

The present invention provides a material that has high solar reflectance in the ultraviolet and visible wavelength ranges, excellent flame retardancy, low density, and is easy to crush or pulverize during manufacturing. [Solution] Use calcined ash produced by heating rice husks.

Description

[Technical Field]

[0001] This invention relates to reflection in the ultraviolet and visible light regions, and more particularly to materials that efficiently reflect wavelengths in the ultraviolet and visible regions. [Background technology]

[0002] The ultraviolet (UV) radiation from sunlight that reaches the Earth's surface has wavelengths of approximately 280nm to 400nm and possesses high energy. UV radiation from sunlight causes significant damage to concrete and mortar, such as cracking, fading, and chalking; plastics experience a decrease in strength and clouding; and wood discolors. In addition, the visible wavelength range of sunlight is approximately 400 to 830nm, which has energy second only to UV radiation. Along with near-infrared wavelengths, it also exhibits thermal effects, and the high temperatures created by exposure to sunlight in summer can endanger lives, thus having a major impact on daily life and industrial activities.

[0003] To mitigate the harmful effects of ultraviolet and visible light from sunlight, various measures are taken to protect objects exposed to sunlight both indoors and outdoors, and the use of ultraviolet and visible light reflectors is one of the major countermeasures.

[0004] As reflective materials for the ultraviolet and visible regions, Patent Document 1 presents polymer-based materials such as polyester, polyamide, polyolefin, vinyl, polyetherketone, polysulfide, fluorine, and polycarbonate, as well as oxides such as titanium, zirconium, aluminum, antimony, zinc, and phosphorus, glass-based materials, and ceramics such as AL2O3, BeO, and CaO. Patent Document 2 presents a mixture of slaked lime and barium carbonate, barium sulfate, or magnesium carbonate. Patent Document 3 presents a method using hollow silica.

[0005] However, the polymer-based material described in Patent Document 1 has the drawback of low reflectivity and poor flame retardancy, while metal oxides such as titanium, glass, and ceramics have the drawback of requiring strong physical force for crushing and pulverizing due to the hardness of the raw materials, making them difficult to manufacture. Metal oxides such as titanium also have weight issues due to their high density. Furthermore, the mixture with slaked lime described in Patent Document 2 has problems with reactivity when absorbing moisture and safety for the skin because slaked lime exhibits strong alkalinity. The method using hollow silica described in Patent Document 3 has problems such as the need for the silica shell to have mesopores, and the fact that the raw material silica is limited to tetramethoxysilane and tetraethoxysilane. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2004-151271 [Patent Document 2] Patent No. 6980313 [Patent Document 3] Japanese Patent Publication No. 2011-122096 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] In view of the above issues, the present invention aims to provide a material that has high solar reflectance in the ultraviolet and visible wavelength ranges, excellent flame retardancy, low density, and is easy to crush or pulverize during manufacturing. [Means for solving the problem]

[0008] As a result of diligent research to solve the aforementioned problems, the present inventors have found that they can be solved by the following invention.

[0009] To solve the above problems, one aspect of the present invention is an ultraviolet and visible solar radiation reflector that contains the ash of calcined rice husks as an active ingredient.

[0010] Another aspect of the present invention is an ultraviolet and visible solar radiation reflecting material containing, as an active ingredient, calcined ash produced by heating rice husks at an arbitrary temperature within the range of 500°C or higher and 525°C or lower in the presence of air.

[0011] Another aspect of the present invention is a paint characterized by containing 1% by weight or more of an ultraviolet and visible solar radiation reflecting material containing, as an active ingredient, calcined ash of rice husks.

[0012] Still another aspect of the present invention is a paint characterized by containing 3% by weight or more of calcined ash having a size of 106 μm or less among ultraviolet and visible solar radiation reflecting materials containing, as an active ingredient, calcined ash of rice husks.

Effect of the Invention

[0013] According to the present invention, it is possible to provide a material having a high solar radiation reflectance in the wavelengths of the ultraviolet and visible regions, excellent flame retardancy, a small density, and being easy to crush and pulverize in production.

Mode for Carrying Out the Invention

[0014] Hereinafter, the embodiments will be described more specifically. This is an example of a method for embodying the technical idea of the present invention, and the technical idea of the present invention is not limited to the following. The technical idea of the present invention can be variously modified within the technical scope defined by the claims described in the claims.

[0015] The ultraviolet and visible solar radiation reflector of the present invention refers to a material that reflects electromagnetic waves with wavelengths of 300 nm to 780 nm. The rice husks of the present invention refer to the outer layer of rice husks. The ultraviolet and visible solar radiation reflector of the present invention is calcined ash produced by heating rice husks. It has been found that this calcined ash possesses ultraviolet and visible solar radiation reflectivity and can be used as an ultraviolet and visible solar radiation reflector. The calcined ash of the present invention is produced by heating in a range of approximately 500°C to 800°C. During production, heating the rice husks in the presence of air results in a higher ultraviolet and visible solar radiation reflectance of 50% or more, making it more effective as a reflector. The calcined ash produced in this case conforms to the L standard specified in the CIE standard. * a * b * L in the color system * The value is 70 or higher, and it exhibits a white color. Oxygen may be present instead of air.

[0016] The reflectance, which indicates the degree of effectiveness of ultraviolet and visible solar radiation reflection, is determined according to JIS K5602:2008. The spectral reflectance of a standard white plate is set to 100% at wavelengths of 300 nm to 780 nm. Using this as a reference, the spectral reflectance of each sample at each wavelength is determined, multiplied by a weighting coefficient that represents the distribution of spectral irradiance of the reference sunlight, and then weighted averaged over wavelengths of 300 nm to 780 nm. The weighting coefficient is the irradiance obtained by integrating the spectral irradiance of the reference sunlight, as defined in Table 1, Column 8 of ISO 9845-1:1992, over wavelengths of 300 nm to 780 nm.

[0017] Furthermore, the calcined ash produced by heating rice husks in the presence of air at any temperature within the range of 500°C to 525°C in this invention has particularly high reflectivity and is an effective component for use as an ultraviolet and visible solar radiation reflector, making it suitable. Heating of rice husks in the range of 500°C to 525°C is carried out in a heating furnace, and both batch furnaces and continuous furnaces are possible. Heat sources include electric, gas, heavy oil, and combustion types using fossil fuels such as kerosene, but electric is preferred because temperature control is easier. The heating time in the range of 500°C to 525°C varies depending on the amount of rice husks, heat conduction, and degree of contact with air, and the heating time increases as the amount of rice husks increases. To shorten the heating time, it is better to make it easier for heat to be transferred to the rice husks and for them to come into contact with air. The thinner the thickness of the stacked rice husks during heating, the shorter the heating time. The end of heating is indicated by the disappearance of black ash.

[0018] Use dried rice husks. When heating the rice husks, it is preferable to remove any stems or other parts mixed in with the husks before or after heating, as these will remain as black ash when burned.

[0019] When used as an ultraviolet and visible solar radiation reflector, powdering it makes handling easier and improves moldability and coating properties. The calcined ash is brittle and can be easily pulverized to a size of several hundred micrometers or less using a mortar and pestle with light force or airflow.

[0020] Furthermore, when using the calcined ash of the present invention as an ultraviolet or visible solar radiation reflector, it is acceptable to mix it with other reflective materials or components.

[0021] The type of paint used in this invention is not particularly limited as long as the desired effect is achieved, but it can be used in various types of paints, such as water-based and oil-based paints. The solar reflecting material of this invention is preferably added to the paint in a crushed or powdered form for more uniform dispersion. Dispersants and binders may also be added as appropriate. The content of the ultraviolet and visible solar reflecting material used in the paint is 1% by weight or more from the viewpoint of ultraviolet and visible solar reflectance effect. On the other hand, when the reflecting material of this invention, which consists of particles of 106 μm or less after crushing, is added to the paint, the content is 3% by weight or more from the viewpoint of adhesion. The size of 106 μm or less in this invention refers to calcined ash that is small enough to pass through a sieve with a mesh size of 106 μm. Painting methods include brushes, rollers, and sprays. It can also be used in combination with other ultraviolet and visible solar reflecting materials and various components commonly used in paints.

[0022] The present invention can be used on structures such as houses, factories, and agricultural greenhouses that are exposed to sunlight outdoors, as well as on roofs, exterior walls, and interior walls of outdoor refrigerators and freezers, air conditioning outdoor units, storage tanks, and various other structures.

[0023] The present invention will be specifically described below with reference to examples, but these are merely illustrative and the present invention is not limited to these examples. [Examples]

[0024] (Manufacturing of UV and Visible Solar Radiation Reflective Materials 1) Four crucibles (72mm outer diameter x 59mm height, 155mL capacity) were each filled with 5g of dried rice husks and placed in a muffle furnace (HPM-1N, manufactured by AS ONE Corporation). The temperature was raised from room temperature at a rate of 20°C / min to 500°C, 525°C, 550°C, 600°C, and 650°C, and each temperature was heated for 2 hours. The temperature increase from room temperature and the 2-hour constant temperature heating were performed in the presence of air. Afterwards, the mixture was allowed to cool naturally to room temperature.

[0025] The rice husks had no black parts on the surface or inside, and were all white and ash-like. The ash from four crucibles was collected and weighed, and it was 5g at all heating temperatures. Each batch of ash was then ground using a mortar and pestle with light, manual force for about 5 minutes.

[0026] (Measurement of ultraviolet and visible solar reflectance) The ultraviolet and visible solar reflectance of these calcined ashes was measured using the following method. The spectrophotometer used was an ultraviolet-visible near-infrared spectrophotometer (V-770, manufactured by JASCO Corporation) with an integrating sphere unit for the light receiver (ISN-923, manufactured by JASCO Corporation). The reflection of a standard white plate (registered trademark: Spectralon, manufactured by Labsphere Corporation) was used as the baseline. The sample was packed into a powder cell (PSH-002, manufactured by JASCO Corporation) to a thickness of 3 mm or more, and the reflectance at wavelengths of 200 nm to 2500 nm was measured with a light incidence angle of 1° and a D65 lamp as the light source.

[0027] The solar reflectance in the ultraviolet and visible regions was calculated in accordance with JIS K5602:2008, using a solar transmittance / reflectance measurement program (manufactured by JASCO Corporation) installed on a personal computer controlling the ultraviolet-visible-near-infrared spectrophotometer. The calculation was performed by summing the products of the spectral reflectance and weight coefficient at each wavelength from 300 nm to 780 nm. A higher solar reflectance indicates a greater effect in reflecting ultraviolet and visible light.

[0028] As a result, the ultraviolet and visible solar reflectance of the calcined ash was 61% at a heating temperature of 500°C, 60% at 525°C, 58% at 550°C, 56% at 600°C, and 52% at 650°C. At heating temperatures of 500°C and 525°C, the ultraviolet and visible solar reflectance was high, exceeding 60%.

[0029] (Color evaluation) The above color evaluation of each type of calcined ash is based on the color system L. * a * b *The value was determined by measuring the reflectance with a spectrophotometer. The spectrophotometer was an ultraviolet-visible-near infrared spectrophotometer (V-770, manufactured by JASCO Corporation), attached with an integrating sphere unit for the light receiver (ISN-923 type, manufactured by JASCO Corporation). Using the reflectance of a standard white plate (registered trademark: Spectralon, manufactured by Labsphere) as the baseline, the sample was filled into a powder cell (PSH-002, manufactured by JASCO Corporation) to a thickness of 3 mm or more, and the reflectance at wavelengths from 360 nm to 830 nm was measured with an incident light angle of 1° and a D65 lamp as the light source. L * a * b * The value was calculated according to JIS Z8730:2002 using a color evaluation program (manufactured by JASCO Corporation) introduced into a personal computer that controls the ultraviolet-visible-near infrared spectrophotometer.

[0030] As a result, the calcined ash at a heating temperature of 500 °C had L * of 78, a * of 1.9, b * of 3.8, and at 525 °C, L * was 77, a * was 1.5, b * was 3.5, and at 550 °C, L * was 76, a * was 1.7, b * was 2.4, and at 600 °C, L * was 75, a * was 1.5, b * was 2.0, and at 650 °C, L * was 73, a * was 1.4, b * was 0.6.

Example

[0031] (Comparative Test) As a comparative sample, dried rice husks were ground in a continuous mill (MF10 Basic, IKA Corporation) without calcination, and powder smaller than 500 μm was collected using a sieve. As another comparative sample, 5 g of dried rice husks were added to each crucible (outer diameter 72 mm x height 59 mm, capacity 155 mL) and placed in a muffle furnace (HPM-1N, AS ONE Corporation). The temperature was raised from room temperature to 300°C at a rate of 20°C / min and heated at 300°C for 2 hours. The temperature increase from room temperature to 300°C and the heating at 300°C were performed in the presence of air. Afterwards, it was allowed to cool naturally to room temperature. The rice husks were entirely black. This ash was ground in a mortar.

[0032] The ultraviolet and visible solar reflectance and color system L of these two comparative samples * a * b * The values ​​were measured. The measurement method was the same as that described in Example 1. As a result, the ultraviolet and visible solar reflectance of unburnt rice husks was 52%, L * ga 64, a * 1.3, b * The value is 11, and the ultraviolet and visible solar reflectance of the calcined ash at a heating temperature of 300°C is 12%, L * 34, a * 0.8, b * The value was 1.0. [Examples]

[0033] (Manufacturing of UV and visible solar radiation reflecting materials 2) Three porcelain evaporating dishes (150mm outer diameter x 42mm height, 400mL capacity) were each filled with 40g of dried rice husks and placed in an electric furnace (F0610, manufactured by Yamato Scientific Co., Ltd.). The temperature was raised from room temperature to 500°C at a rate of 20°C / min, and then heated at 500°C for 6 hours. The temperature increase from room temperature to 500°C and the heating at 500°C were performed in the presence of air. Afterwards, the furnace was allowed to cool naturally to room temperature.

[0034] The rice husks had no black parts on the surface or inside, and were all white and ash-like. The ash was collected from three evaporation dishes and weighed 30g. This ash was placed in a mortar and ground with a pestle using light manual force for about 15 minutes. The manufacturing process described here was repeated twice to obtain a total of 60g of ash.

[0035] (UV and visible solar reflectance) The ultraviolet and visible solar reflectance of this calcined ash was measured. The measurement method was the same as that described in Example 1. As a result, the ultraviolet and visible solar reflectance was 61%.

[0036] (Color evaluation) Color system L of the above calcined ash * a * b * The value was measured. The measurement method was the same as the method described in Example 1. As a result, L * ga 77, a * 1.9, b * The value was 3.8.

[0037] (Specific heat capacity) The specific heat capacity of the calcined ash described above was determined by differential scanning calorimetry (DSC). A Rigaku DSC8230 differential scanning calorimeter was used, and Rigaku Thermo Plus2 series software was used for data processing. Approximately 10 mg of calcined ash was accurately weighed into a 5 mm diameter aluminum container, an aluminum lid was placed over it, and it was compressed and sealed tightly using a special jig. An empty container was placed in one of the two container holders as a control, and the temperature was increased from room temperature to 30°C at a rate of 5°C / min, held at 30°C for 5 minutes, and then increased to 90°C at a rate of 5°C / min, and the heat flux value (mW) was measured. The empty container was measured in the same manner, and this value was used as the baseline. Approximately 10 mg of α-alumina (Rigaku Corporation) was accurately weighed as a standard substance and measured in the same manner. The specific heat capacity of the calcined ash was calculated by multiplying the ratio of the difference in heat flux values ​​between the calcined ash, the standard substance, and the baseline at 86.9°C by the specific heat capacity value of α-alumina at 86.9°C, which is 0.887 J / g·°C. As a result, the specific heat capacity of the calcined ash at 86.9°C was 1.3 J / g·°C.

[0038] (Sifting) When the above calcined ash was separated by size using stainless steel test sieves with mesh openings of 250 μm and 106 μm, ash larger than 250 μm accounted for 5% by weight, ash between 106 μm and 250 μm accounted for 16% by weight, and ash smaller than 106 μm accounted for 79% by weight.

[0039] (Bulk density) 20 g of the sieved ash, with a size of 106 μm or less, was accurately weighed, placed in a glass graduated cylinder, and tapped. The volume was measured, and the bulk density was calculated to be 0.67 g / mL. [Examples]

[0040] (Paint containing UV and visible solar radiation reflectors 1) 20g of water-based wood protective paint (product name: synthetic resin paint, color: transparent, manufactured by Kanpe Hapio Co., Ltd.) was mixed with the calcined ash prepared in Example 3 in amounts of 1%, 2.5%, and 5% by weight, and thoroughly stirred with chopsticks. Each of these paints was applied once to a cedar board with a brush and allowed to air dry at room temperature overnight.

[0041] At all concentrations, the surface of the board was white, the color of the calcined ash, and an amount of the ash was applied that exhibited ultraviolet and visible solar radiation reflection. When the painted board was tapped on a table, the calcined ash did not peel off at any concentration. Furthermore, when cool air from a hairdryer was applied to the same board surface from a distance of 10 cm for 3 minutes, the calcined ash did not peel off. [Examples]

[0042] (Paint containing UV and visible solar radiation reflectors 2) To 20g of water-based wood protective coating (product name: synthetic resin coating, color: transparent, manufactured by Kanpe Hapio Co., Ltd.), calcined ash prepared in Example 3 above and passed through a sieve with a mesh size of 106 μm was added in amounts of 1%, 2%, 3%, 5%, 10%, and 20% by weight, and the mixture was thoroughly stirred with chopsticks. This coating was applied once to each cedar board with a brush and air-dried overnight at room temperature.

[0043] When 1% and 2% by weight of calcined ash were added to the surface of the board, the thickness of the calcined ash was very thin and insufficient to exhibit ultraviolet and visible solar radiation reflection. With paint containing 3% or more by weight of calcined ash, an amount sufficient to exhibit ultraviolet and visible solar radiation reflection was attached to the surface of the board. When boards coated with paint containing 3% or more by weight of calcined ash were tapped on a table, the calcined ash did not peel off at any concentration. Furthermore, when cold air from a hairdryer was applied to the surface of the same board from a distance of 10 cm for 3 minutes, the calcined ash did not peel off. [Industrial applicability]

[0044] The present invention is useful, for example, in the field of materials for providing light degradation suppression and heat shielding properties to buildings and structures.

Claims

1. A material that reflects ultraviolet and visible solar radiation, with the ash of burnt rice husks as an active ingredient.

2. An ultraviolet and visible solar radiation reflector whose active ingredient is calcined ash produced by heating rice husks in the presence of air at any temperature in the range of 500°C to 525°C.

3. A paint characterized by containing 1% by weight or more of the ultraviolet and visible solar radiation reflecting material described in claim 1.

4. A paint characterized by containing 3% by weight or more of calcined ash having a size of 106 μm or less, among the ultraviolet and visible solar radiation reflecting materials described in claim 1.