Method for manufacturing ultraviolet and visible solar radiation reflecting materials

Abstract

This invention provides a manufacturing method for a material that is highly flame-retardant, has low density, is easy to crush or pulverize, and exhibits high solar reflectance in the ultraviolet and visible wavelength ranges. [Solution] Rice husks are heated in the presence of air at any temperature in the range of 250°C to 400°C, and then heated again at 500°C.

Description

Technical Field

[0001] The present invention relates to reflection in the ultraviolet and visible light regions, and to materials that efficiently reflect wavelengths in the ultraviolet and visible regions.

Background Art

[0002] The wavelength of ultraviolet rays in sunlight reaching the ground is approximately 280 nm to 400 nm and has high energy. Due to the ultraviolet rays in sunlight, concrete and mortar crack, fade, and become choked, plastics such as those have a decrease in strength, become cloudy, and wood discolors, etc., causing great damage. Also, the wavelength of visible light in sunlight is approximately 400 to 830 nm, and in addition to having energy second only to ultraviolet rays, it also exhibits a heat effect together with wavelengths in the near-infrared region, and a high-temperature environment caused by being irradiated with summer sunlight may endanger life, etc., having a great impact on daily life and industrial activities.

[0003] In order to suppress the adverse effects of ultraviolet rays and visible light in sunlight, various measures against solar radiation are implemented for objects irradiated with sunlight both outdoors and indoors, and the use of reflection materials in the ultraviolet and visible regions is one of the major countermeasures.

[0004] Reflection materials include organic, metal, ceramic, etc. However, in order to be widely used outdoors, conditions such as high reflectivity, high flame retardancy, light weight, and ease of manufacturing are required. Organic materials are inferior in terms of flammability and reflectivity, while metal and ceramic materials are excellent in terms of reflectivity and flame retardancy and have been variously proposed. As reflection materials, Patent Document 1 presents oxides such as titanium, zirconium, aluminum, antimony, zinc, phosphorus, glass-based materials, and ceramics such as AL2O3, BeO, CaO. Patent Document 2 presents a mixture of slaked lime and barium carbonate, barium sulfate, and magnesium carbonate. Patent Document 3 presents a method using hollow silica.

[0005] However, the metal oxides such as titanium, as well as glass and ceramic materials described in Patent Document 1, have the drawback that their manufacturing is not easy because the minerals used as raw materials for these metals are hard, requiring strong physical force for crushing and pulverizing. Furthermore, the mixture with slaked lime described in Patent Document 2 has problems with reactivity when hydrated 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 mesopores in the outer shell of the silica, which limits the raw material silica 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 novel manufacturing method for a material that is highly flame-retardant, has low density, is easy to crush and pulverize, and has high solar reflectance in the ultraviolet and visible wavelength ranges. [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] One aspect of the present invention, which solves the above problems, is a method for producing an ultraviolet and visible solar radiation reflector, comprising heating rice husks in the presence of air at any temperature in the range of 250°C to 400°C, and then heating them again at 500°C.

[0010] Another aspect of the present invention relates to a method for producing an ultraviolet and visible solar radiation reflector, comprising heating rice husks in the presence of air at an arbitrary temperature in the range of 300°C to 400°C, and then heating them again at an arbitrary temperature in the range of 500°C to 650°C. [Effects of the Invention]

[0011] According to the present invention, a novel manufacturing method is available for a material that is highly flame-retardant, has low density, and is easy to crush or pulverize, while also having a high solar reflectance in the near-infrared wavelength range. [Modes for carrying out the invention]

[0012] The embodiments will be described in more detail below. These are examples of methods for realizing the technical concept of the present invention, and the technical concept of the present invention is not limited to those described below. The technical concept of the present invention can be modified in various ways within the technical scope defined by the claims described in the patent claims.

[0013] The ultraviolet and visible solar radiation reflecting material 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. One embodiment of the method for manufacturing the ultraviolet and visible solar radiation reflecting material of the present invention is to first heat the rice husks in the presence of air at any temperature in the range of 250°C to 400°C. The husks may be heated multiple times at different temperatures in the range of 250°C to 400°C. Next, they are heated at 500°C in the presence of air. After this, they are cooled to complete the process.

[0014] Another method of production involves first heating the rice husks in the presence of air to any temperature in the range of 300°C to 400°C. This heating may be repeated multiple times at different temperatures within the range of 300°C to 400°C. Next, the husks are heated in the presence of air to any temperature in the range of 500°C to 650°C. After this, they are cooled to complete the process.

[0015] The heating times for temperatures within the 250°C to 400°C range, any temperature within the 300°C to 400°C range, and any temperature within the 500°C or 500°C to 650°C range vary depending on the amount of rice husks, heat conduction, and degree of contact with air. A larger amount of rice husks results in longer heating times. To shorten the heating time, it is best to ensure that heat is easily transferred to the rice husks and that they are exposed to air. Thinner layers of rice husks during heating result in shorter heating times. Heating of rice husks is carried out in a heating furnace, and both batch and continuous furnaces are possible. Heat sources include electric, gas, heavy oil, and fossil fuels such as kerosene; either method is acceptable as long as temperature control is possible.

[0016] For heating in the 250°C to 400°C and 300°C to 400°C ranges, the end of heating is indicated by the disappearance of brown rice husks. For heating in the 500°C and 500°C to 650°C ranges, the end of heating is indicated by the disappearance of black ash. 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 after burning. Oxygen can also be used instead of air.

[0017] The calcined ash produced by the method of the present invention all have high ultraviolet and visible solar radiation reflectances of 60% or more. The reflectance, which indicates the degree of effectiveness of ultraviolet and visible solar radiation reflection, is determined according to JIS K5602:2008, by setting the spectral reflectance of a standard white plate to 100% at wavelengths of 300 nm to 780 nm, using this as a reference, determining the spectral reflectance of each sample at each wavelength, multiplying it by a weighting coefficient that shows the distribution of spectral irradiance of standard sunlight, and taking a weighted average over wavelengths of 300 nm to 780 nm. The weighting coefficient is the irradiance obtained by integrating the spectral irradiance of standard sunlight, as defined in Table 1, Column 8 of ISO9845-1:1992, over wavelengths of 300 nm to 780 nm.

[0018] In addition, the calcined ash produced by the method of the present invention has a very high flame retardancy and a small density. When used as an ultraviolet and visible solar radiation reflector, it is easier to handle when powdered, and has excellent formability, coating properties, etc. The ash is brittle and can be easily crushed or pulverized to a size of several hundred micrometers or less using a mortar and a light force such as a pestle or an air current.

[0019] The ultraviolet and visible solar radiation reflector produced by the present invention can be used alone, but there is no problem in mixing and using it with other materials.

[0020] Examples are shown below to specifically explain the present invention, but this is merely for illustrative purposes and the present invention is not limited to these examples.

Example

[0021] (Manufacture 1 of ultraviolet and visible solar radiation reflector) 10 g of dried rice husks were added to each of two crucibles (outer diameter 72 mm × height 59 mm, internal volume 155 mL) and placed in a muffler furnace (HPM-1N, manufactured by AS ONE Corporation). As the first heating, heating was carried out at 200 °C, 250 °C, 300 °C, 350 °C, and 400 °C for 4 hours each. The temperature was raised from room temperature to the heating temperature at a rate of 20 °C / min. Next, each was heated to 500 °C at a rate of 20 °C / min and heated at 500 °C for 4 hours. All temperature increases and isothermal heating were carried out in the presence of air. Thereafter, natural cooling was performed to room temperature.

[0022] The rice husks had no black parts on the surface or deep inside, and all were whitened and ashed. When the ash from the two crucibles was collected and weighed, it was 5 g for all the initial heating temperatures from 200 °C to 400 °C. Each ash was ground manually with a light force for about 5 minutes using a mortar and a pestle.

[0023] (Measurement of ultraviolet and visible solar radiation reflectance) The ultraviolet and visible solar radiation reflectance of these calcined ashes was measured by the following method. The spectrophotometer was purple This system consists of a V-770 wide-field near-infrared spectrophotometer (manufactured by JASCO Corporation) and an integrating sphere unit for the photodetector (ISN-923, also manufactured by JASCO Corporation). Using the reflection of a standard white plate (registered trademark: Spectralon, manufactured by Labsphere Corporation) as the baseline, the sample was packed into a powder cell (PSH-002, also 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.

[0024] 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.

[0025] As a result, the ultraviolet and visible solar reflectance of the calcined ash was 60% at an initial heating temperature of 200°C, 64% at 250°C, 64% at 300°C, 63% at 350°C, and 64% at 400°C. When the initial heating temperature was 250°C or higher, the ultraviolet and visible solar reflectance was high. [Examples]

[0026] (Manufacturing of UV and visible solar radiation reflecting materials 2) Two crucibles (72mm outer diameter x 59mm height, 155mL capacity) were each filled with 10g of dried rice husks and placed in a muffle furnace (HPM-1N, manufactured by AS ONE Corporation). For the initial heating, each crucible was heated at 250°C, 300°C, 350°C, 400°C, and 450°C for 4 hours. The temperature was increased from room temperature to the heating temperature at a rate of 20°C / min. Next, each crucible was heated to 550°C at a rate of 20°C / min and heated at 550°C for 4 hours. All heating and constant temperature heating were performed in the presence of air. Afterwards, the crucibles were allowed to cool naturally to room temperature.

[0027] The rice husks had no black parts on the surface or inside, and were all white and ash-like. The ash from two crucibles was collected and weighed, and all of them weighed 5g, depending on the initial heating temperature of 250°C to 450°C. Each batch of ash was then ground manually with a mortar and pestle using light force for about 5 minutes.

[0028] The ultraviolet and visible solar reflectance of these calcined ashes was measured. The measurement method was the same as that described in Example 1. As a result, the ultraviolet and visible solar reflectance of the calcined ash was 60% at an initial heating temperature of 250°C, 67% at 300°C, 63% at 350°C, 63% at 400°C, and 62% at 450°C. When the initial heating temperature was 300°C or higher, the ultraviolet and visible solar reflectance was high. [Examples]

[0029] (Manufacturing of UV and visible solar radiation reflecting materials 3) Two crucibles (72mm outer diameter x 59mm height, 155mL capacity) were each filled with 10g of dried rice husks and placed in a muffle furnace (HPM-1N, AS ONE Corporation). For the initial heating, each crucible was heated at 250°C, 300°C, 350°C, 400°C, and 500°C for 4 hours. The temperature was increased from room temperature to the initial heating temperature at a rate of 20°C / min. Next, each crucible was heated to 625°C at a rate of 20°C / min and heated at 625°C for 4 hours. All heating and constant temperature heating were performed in the presence of air. Afterwards, the crucibles were allowed to cool naturally to room temperature.

[0030] The rice husks had no black parts on the surface or inside, and were all white and ash-like. The ash from two crucibles was collected and weighed, and all of them weighed 5g, depending on the initial heating temperature of 250°C to 500°C. Each batch of ash was then ground using a mortar and pestle with light manual force for about 5 minutes.

[0031] The ultraviolet and visible solar reflectance of these calcined ashes was measured. The measurement method was the same as that described in Example 1. As a result, the ultraviolet and visible solar reflectance of the calcined ash was 61% at an initial heating temperature of 250°C, 66% at 300°C, 66% at 350°C, 63% at 400°C, and 61% at 500°C. The ultraviolet and visible solar reflectance of the calcined ash was high when the initial heating temperature was in the range of 300°C to 400°C. [Examples]

[0032] (Manufacturing of UV and visible solar radiation reflectors 4) Two crucibles (72mm outer diameter x 59mm height, 155mL capacity) were each filled with 10g of dried rice husks and placed in a muffle furnace (HPM-1N, manufactured by AS ONE Corporation). For the initial heating, the mixture was heated to 350°C for 4 hours. The temperature was increased from room temperature to 350°C at a rate of 20°C / min. Next, the temperature was increased to 650°C at a rate of 20°C / min and heated at 650°C for 4 hours. All heating and constant temperature heating were performed in the presence of air. Afterwards, the mixture was allowed to cool naturally to room temperature.

[0033] The rice husks had no black parts on the surface or inside, and were white and ash-like. The ash was collected from two crucibles and weighed, and it was 5g. This ash was then ground using a mortar and pestle with light manual force for about 5 minutes.

[0034] 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 66%. [Examples]

[0035] (Manufacturing of UV and visible solar radiation reflectors 5) Two crucibles (72mm outer diameter x 59mm height, 155mL capacity) were each filled with 10g of dried rice husks and placed in a muffle furnace (HPM-1N, manufactured by AS ONE Corporation). The first heating was performed at 300°C for 4 hours. The second heating was performed at 400°C for 4 hours, and finally at 500°C for 4 hours. The temperature was increased from room temperature to 300°C, and then to 400°C and 500°C at a rate of 20°C / min. All heating and constant temperature heating were performed in the presence of air. Afterwards, the mixture was allowed to cool naturally to room temperature.

[0036] The rice husks had no black parts on the surface or inside, and were white and ash-like. The ash was collected from two crucibles and weighed, and it was 5g. This ash was then ground using a mortar and pestle with light manual force for about 5 minutes.

[0037] 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 62%. [Examples]

[0038] (Manufacturing of UV and visible solar radiation reflectors 6) 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.). For the initial heating, the furnace was heated to 350°C for 6 hours. The temperature was increased from room temperature to 350°C at a rate of 20°C / min. Subsequently, the temperature was increased to 600°C at a rate of 20°C / min and heated at 600°C for 6 hours. All heating and constant temperature heating were carried out in the presence of air. Afterwards, the furnace was allowed to cool naturally to room temperature.

[0039] The rice husks had no black parts on the surface or inside, and were white and ash-like. The ash collected from three evaporation dishes was weighed and found to be 30g. This ash was ground using a mortar and pestle with light manual force for about 15 minutes. The manufacturing process described here was repeated twice to obtain a total of 60g of ash.

[0040] (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 64%.

[0041] (Color evaluation) The above color evaluation of calcined ash is based on the color system L. * a * b * The value was determined by measuring the reflectance using a spectrophotometer. The spectrophotometer 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 whiteboard (registered trademark: Spectralon, manufactured by Labsphere Corporation) was used as the baseline, and the sample was packed into a powder cell (PSH-002, manufactured by JASCO Corporation) to a thickness of 3 mm or more. The reflectance at wavelengths of 360 nm to 830 nm was measured with a light incidence angle of 1° and a D65 lamp as the light source. The Lab value was calculated in accordance with JIS Z8730:2002, using a color evaluation program (manufactured by JASCO Corporation) installed on a personal computer controlling the ultraviolet-visible-near-infrared spectrophotometer. As a result, L * ga 79, a * 3.1, b * The value was 1.7.

[0042] (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 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.

[0043] (Sifting) When the above calcined ash was sorted by size using stainless steel test sieves with mesh openings of 250 μm and 106 μm, ash larger than 250 μm accounted for 13% by weight, ash between 106 μm and 250 μm accounted for 24% by weight, and ash smaller than 106 μm accounted for 63% by weight.

[0044] (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]

[0045] (Comparative study 1) 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 was added to one crucible (outer diameter 72 mm x height 59 mm, internal volume 155 mL) and placed in a muffle furnace (HPM-1N, AS ONE Corporation). The temperature was raised from room temperature at a rate of 20 °C / min to 300 °C, and then heated at 300 °C for 2 hours. The temperature increase from room temperature to 300 °C and the heating at 300 °C for 2 hours were performed in the presence of air. After that, it was allowed to cool naturally to room temperature. The surface of the rice husks was entirely black. This ash was ground in a mortar.

[0046] The ultraviolet and visible solar reflectance of these two comparative samples was 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 41%, while that of burnt ash heated at 300°C was 12%. [Examples]

[0047] (Comparative study 2) As a separate comparative test, 5g of dried rice husks was added to each of four crucibles (outer diameter 72mm x height 59mm, capacity 155mL) and placed in a muffle furnace (HPM-1N, manufactured by AS ONE Corporation). The temperature was increased from room temperature at a rate of 20°C / min to 500°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. The rice husks had no black parts on the surface or in the depths, and were all white and ash-like. Each ash was then ground manually with light force using a mortar and pestle for about 5 minutes.

[0048] The ultraviolet and visible solar reflectance of these ashes 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% at 500°C, 58% at 550°C, 56% at 600°C, and 52% at 650°C. [Industrial applicability]

[0049] 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 method for producing an ultraviolet and visible solar radiation reflector, comprising heating rice husks in the presence of air at any temperature in the range of 250°C to 400°C, and then heating them again at 500°C.

2. A method for producing an ultraviolet and visible solar radiation reflector, comprising heating rice husks in the presence of air at an arbitrary temperature in the range of 300°C to 400°C, and then heating them again at an arbitrary temperature in the range of 500°C to 650°C.