CN111995895B

CN111995895B - Particulate material and use thereof

Info

Publication number: CN111995895B
Application number: CN202010893603.4A
Authority: CN
Inventors: 徐绍禹; 万容兵
Original assignee: Ningbo Ruiling New Energy Materials Research Institute Co ltd; Ningbo Ruiling New Energy Technology Co ltd
Current assignee: Ningbo Ruiling New Energy Materials Research Institute Co ltd; Ningbo Ruiling New Energy Technology Co ltd
Priority date: 2020-08-31
Filing date: 2020-08-31
Publication date: 2021-09-21
Anticipated expiration: 2040-08-31
Also published as: CN111995895A

Abstract

The invention relates to a particle material, which comprises an inner core, a first shell and a second shell, wherein the first shell and the second shell are sequentially coated on the surface of the inner core, the reflectivity of the material of the inner core in a wave band of 0.3-2.5 mu m is more than 75%, the emissivity of an atmospheric radiation window of 8-13 mu m is more than 0.9, and the materials of the inner core, the first shell and the second shell are different; the material of the first shell layer is silicon dioxide, and the material of the second shell layer is titanium dioxide, or the material of the first shell layer is titanium dioxide, and the material of the second shell layer is silicon dioxide. The invention also relates to the use of said particulate material in coatings, fibres and films. The particle material has excellent reflectivity in the whole wave band of 0.3-2.5 mu m and excellent emissivity in the atmospheric radiation window of 8-13 mu m, and products such as coatings, fibers, films and the like can have excellent solar reflectivity and emissivity by only using the particle material, so that the excellent cooling effect is achieved.

Description

Particulate material and use thereof

Technical Field

The invention relates to the technical field of refrigeration, in particular to a granular material and application thereof.

Background

When preparing products such as paint, fiber, film and the like with the cooling function, the filling materials such as titanium dioxide, ceramic beads, barium sulfate, zinc oxide, glass beads, silicon dioxide and the like are mainly used, and one or more of the filling materials are compounded according to a certain proportion. However, the product obtained by compounding is difficult to have high reflectivity in an ultraviolet band of 0.3-0.4 μm, a visible light band of 0.4-0.78 μm and an infrared band of 0.78-2.5 μm, and simultaneously cannot give consideration to high emissivity in a full band of 2.5-25 μm, especially low emissivity in an atmospheric radiation window band of 8-13 μm, so that the cooling effect of the product is poor.

Disclosure of Invention

In view of the above, there is a need to provide a particulate material with high emissivity in the 0.3 μm-2.5 μm full band reflectivity and 8 μm-13 μm atmospheric emission window and its use.

A particulate material comprising an inner core and first and second shells sequentially coated on the surface of the inner core, the material of the inner core having a reflectivity of greater than 75% at a wavelength band of 0.3 μm to 2.5 μm and an emissivity of greater than 0.9 at an atmospheric radiation window of 8 μm to 13 μm, the materials of the inner core, the first shell and the second shell being different;

the material of the first shell layer is silicon dioxide, and the material of the second shell layer is titanium dioxide, or the material of the first shell layer is titanium dioxide, and the material of the second shell layer is silicon dioxide.

In one embodiment, the material of the inner core has a reflectivity greater than 85% in the 0.3 μm-2.5 μm band and an emissivity greater than 0.94 in the 8 μm-13 μm atmospheric radiation window.

In one embodiment, the material of the inner core is selected from one of magnesium oxide, aluminum oxide and barium sulfate.

In one embodiment, the material of the inner core is alumina.

In one embodiment, the particle size of the inner core is 40% to 75% of the particle size of the particulate filler.

In one embodiment, the thickness of the first shell layer is 5% -18.75% of the particle size of the particulate filler, and the thickness of the second shell layer is 5% -18.75% of the particle size of the particulate filler.

In one embodiment, the particle size of the inner core is 0.8 μm to 1.2 μm, and the thicknesses of the first and second shell layers are independently selected from 0.1 μm to 0.3 μm.

In the particle material, the reflectivity of the particle material in an ultraviolet band of 0.3-0.4 mu m and a visible light band of 0.4-0.78 mu m can be effectively improved by the first shell layer and the second shell layer which are wrapped on the surface of the inner core, so that the reflectivity of the particle material in a whole band of 0.3-2.5 mu m is more than or equal to 82%, meanwhile, the emissivity of the particle material in a whole band of 2.5-25 mu m is more than or equal to 0.93, and especially the emissivity of an atmospheric radiation window band of 8-13 mu m is more than or equal to 0.92. Therefore, products such as coatings, fibers, films and the like can have excellent solar reflectivity and emissivity only by using the particle material, and further, the excellent cooling effect is achieved.

In addition, the particle material is insoluble in water, resistant to acid, alkali and aging, can be used at a temperature below 1600 ℃, has good stability, and can meet the preparation requirements and the use requirements of products such as coatings, fibers, films and the like.

Use of a particulate material as described above in a coating.

Use of a particulate material as described above in a fibre.

Use of a particulate material as described above in a film.

The granular material of the invention is used in products such as paint, fiber, film and the like, so that the products have excellent reflectivity in the whole wave band of 0.3-2.5 mu m, excellent emissivity in the whole wave band of 2.5-25 mu m, and especially excellent emissivity in the atmospheric radiation window wave band of 8-13 mu m, and other fillers are not required to be compounded, thus greatly simplifying the production and construction processes of the products such as paint, fiber, film, ceramic and the like, improving the efficiency and reducing the cost.

Drawings

FIG. 1 is a schematic structural view of a particulate material of the present invention;

FIG. 2 is a graph showing the particle size distribution of the particulate material prepared in example 1 of the present invention;

FIG. 3 is a graph showing the reflectance of the granular material prepared in example 1 of the present invention;

FIG. 4 is a graph of the emissivity of a particulate material prepared in example 1 of the present invention;

FIG. 5 is a graph showing the reflectance of a coating layer prepared in application example 1 of the present invention;

fig. 6 is a reflectance graph of the fabric prepared in application example 2 of the present invention.

In the figure: 10. a kernel; 20; a first shell layer; 30. and a second shell layer.

Detailed Description

The particulate material provided by the present invention and its use will be further described below.

As shown in fig. 1, the particulate material provided by the present invention is a core-shell structure, and includes an inner core 10 and a first shell 20 and a second shell 30 sequentially coated on a surface of the inner core 10, wherein a reflectivity of a material of the inner core 10 in a wavelength band of 0.3 μm to 2.5 μm is greater than 75%, an emissivity in an atmospheric radiation window of 8 μm to 13 μm is greater than 0.9, and materials of the inner core 10, the first shell 20, and the second shell 30 are different.

The material of the first shell layer 20 is silicon dioxide, and the material of the second shell layer 30 is titanium dioxide, or the material of the first shell layer 20 is titanium dioxide, and the material of the second shell layer 30 is silicon dioxide.

In the inorganic material, the solar reflectance of the silicon dioxide material in an ultraviolet band of 0.3-0.4 μm can reach 97.8%, and the solar reflectance is more than 90% in a visible light band of 0.4-0.78 μm and an infrared band of 0.78-2.5 μm; the sunlight reflectivity of the titanium dioxide material in a visible light waveband of 0.4-0.78 mu m can reach 98.8%, and the sunlight reflectivity of the titanium dioxide material in an ultraviolet waveband of 0.3-0.4 mu m and an infrared waveband of 0.78-2.5 mu m is more than 90%.

Meanwhile, the emissivity of the silicon dioxide material in the whole wave band of 2.5-25 μm can reach 0.936, and the emissivity in the atmospheric radiation window wave band of 8-13 μm can reach 0.928; the emissivity of the titanium dioxide material in the whole wave band of 2.5-25 μm can reach 0.925, and the emissivity in the atmospheric radiation window wave band of 8-13 μm can reach 0.972.

Therefore, when the surface of the inner core 20 is coated with the silicon dioxide shell layer and the titanium dioxide shell layer, the reflectivity of the particle material in the ultraviolet band of 0.3-0.4 μm and the visible light band of 0.4-0.78 μm can be effectively improved, the reflectivity of the particle material in the whole band of 0.3-2.5 μm is more than or equal to 82%, meanwhile, the emissivity of the particle material in the whole band of 2.5-25 μm is more than or equal to 0.93, and especially the emissivity of the particle material in the atmospheric radiation window band of 8-13 μm is more than or equal to 0.92. Therefore, products such as coatings, fibers, films and the like can have excellent solar reflectivity and emissivity only by using the particle material, and further, the excellent cooling effect is achieved.

It should be noted that the surface of the core 10 may be coated with the titanium dioxide shell layer first and then with the silicon dioxide shell layer, or may be coated with the silicon dioxide shell layer first and then with the titanium dioxide shell layer, and therefore, the materials of the first shell layer 20 and the second shell layer 30 are not limited to be selected, and are independently selected from silicon dioxide or titanium dioxide, but may not be the same.

In order to further increase the reflectivity of the particulate material in the whole wavelength band between 0.3 μm and 2.5 μm and the emissivity in the whole wavelength band between 2.5 μm and 25 μm, in particular in the atmospheric radiation window band between 8 μm and 13 μm, the reflectivity of the material of the inner core 10 in the 0.3 μm to 2.5 μm wavelength band is preferably greater than 80% and the emissivity in the atmospheric radiation window between 8 μm and 13 μm is preferably greater than 0.93.

For example, the material of the inner core 10 is selected from one of magnesium oxide, aluminum oxide, barium sulfate and glass beads, so that the reflectivity of the granular material in the whole wave band of 0.3-2.5 μm is more than or equal to 85%, and the emissivity of the granular material in the whole wave band of 2.5-25 μm is more than or equal to 0.93, especially the emissivity of the granular material in the atmospheric radiation window wave band of 8-13 μm is more than or equal to 0.93.

In order to further increase the reflectivity of the particulate material in the whole wavelength band between 0.3 μm and 2.5 μm and the emissivity in the whole wavelength band between 2.5 μm and 25 μm, in particular in the atmospheric emission window band between 8 μm and 13 μm, the reflectivity of the material of the inner core 10 in the wavelength band between 0.3 μm and 2.5 μm is preferably greater than 85% and the emissivity in the atmospheric emission window between 8 μm and 13 μm is preferably greater than 0.94.

For example, the material of the inner core 10 is selected from one of magnesium oxide, aluminum oxide and barium sulfate, so that the reflectivity of the granular material in the whole wave band of 0.3-2.5 μm is more than or equal to 89%, and the emissivity of the granular material in the whole wave band of 2.5-25 μm is more than or equal to 0.93, especially the emissivity in the atmospheric radiation window wave band of 8-13 μm is more than or equal to 0.94.

Wherein, the reflectivity of the aluminum oxide in the ultraviolet band of 0.3-0.4 μm can reach 92.3%, the reflectivity in the visible light band of 0.4-0.78 μm can reach 93.6%, the reflectivity in the infrared band of 0.78-2.5 μm can reach 92.2%, the reflectivity in the whole band of 0.3-2.5 μm can reach 92.8%, and the emissivity of the aluminum oxide in the whole band of 2.5-25 μm can reach 0.952, especially the emissivity in the atmospheric radiation window band of 8-13 μm can reach 0.976.

Therefore, the material of the inner core 10 is further preferably alumina, so that the reflectivity of the particle material in the whole wave band of 0.3-2.5 μm is more than or equal to 93%, and the emissivity of the particle material in the whole wave band of 2.5-25 μm is more than or equal to 0.93, especially the emissivity of the particle material in the atmospheric radiation window wave band of 8-13 μm is more than or equal to 0.94, and the particle material has excellent solar reflectivity and atmospheric radiation window emissivity.

In the particle material, the particle size of the inner core 10 or the thickness of any shell is too large or too small, so that the full-band reflectivity and the full-band emissivity of the particle material are biased to show the full-band reflectivity and the atmospheric radiation window emissivity of the material of the inner core 10 or any shell, and the composite reflectivity and emissivity effect of the material cannot be better shown.

In order to enable the interaction of the inner core 10, the first shell 20 and the second shell 30, and to enable the particulate material to exhibit excellent all-band reflectivity and atmospheric radiation window emissivity, the particle size of the inner core 10 is 40% -75% of the particle size of the particulate filler, the thickness of the first shell 20 is 5% -18.75% of the particle size of the particulate filler, and the thickness of the second shell 30 is 5% -18.75% of the particle size of the particulate filler.

In one or more embodiments, the shape of the core 10 is not limited, including spherical, ellipsoidal, rod-like, and the like, and is preferably spherical. Further, the first shell layer 20 and the second shell layer 30 are sequentially and uniformly coated on the surface of the inner core 10 to obtain a spherical particle material.

In one or more embodiments, the particle size of the inner core 10 is preferably 0.8 μm to 1.2 μm, and the thicknesses of the first and

second shell layers

20 and 30 are independently selected from 0.1 μm to 0.3 μm. Thus, the particle size of the particulate material is controlled to be in the range of 1.2 μm to 2.4 μm, enabling better dispersion in use.

The particle size of the core 10 and the particle size of the particulate material are both the center particle size D50.

In the particulate material of the present invention, the first shell 20 and the second shell 30 may be coated on the surface of the core 10 in sequence by a chemical method, and the materials of the first shell 20 and the second shell 30 are independently selected from silica or titania, so that the silica coating and the titania coating may be performed by the same chemical method and the same method.

Wherein, when coating the silica shell, a first mixture including the core 10 or the core 10 coated with the titania shell is providedA liquid mixture and Na-containing₂SiO₃And (3) waiting for the silicon precursor solution, mixing the first mixed solution with the silicon precursor solution, maintaining the pH value at 10-12, reacting at 60-75 ℃, adjusting the pH value to 7 after the reaction is finished, and drying to obtain the inner core 10 coated with the silicon dioxide shell layer or obtain the granular material.

When the shell layer of titanium dioxide is coated, a second mixed solution including the core 10 or the core 10 coated with the shell layer of silicon dioxide and a solution containing Ti (SO) is provided₄)₂And (2) waiting for the titanium precursor solution, mixing the second mixed solution, the titanium precursor solution and a surfactant solution such as sodium dodecyl sulfate, adjusting the pH to 2.5-3 by ammonia water and the like, reacting at 70-80 ℃, filtering a reactant after the reaction is finished, and washing, drying and calcining to obtain the core 10 coated with the titanium dioxide shell layer or obtain the granular material.

The granular material can be used as a filler to obtain a product with a cooling function.

The granular material according to the invention can be used in coatings to obtain coated articles having a cooling function.

The particulate material according to the invention can be applied in fibres to obtain a fibrous product with a cooling function.

The granular material according to the invention can be applied in films to obtain film products with a cooling function.

When the particle material is used in products such as coatings, fibers, films and the like, the products can have excellent reflectivity at the whole wave band of 0.3-2.5 mu m and excellent emissivity at the whole wave band of 2.5-25 mu m without compounding other fillers, and especially have excellent emissivity at the atmospheric radiation window wave band of 8-13 mu m, so that the production and construction processes of the products such as coatings, fibers, films and the like can be greatly simplified, the efficiency is improved, and the cost is reduced.

Hereinafter, the particulate material and its use will be further described by the following specific examples.

Example 1

Dispersing alumina powder into mass percent in a stirring cylinder20% of slurry, adding 1% of sodium acrylate dispersant by mass percentage during dispersion, dispersing for 2 hours at the rotating speed of 1500rpm, transferring to a grinder, grinding to the fineness of less than 10 mu m, and filtering the slurry by using a 300-mesh gauze. Adding 30kg of filtered slurry into a 100L reaction kettle, heating to 70 ℃, adjusting the pH value to 11 by using 5% sulfuric acid, and slowly dropwise adding 25% by mass of Na into the reaction kettle₂SiO₃And (3) dripping hydrochloric acid with the mass percentage of 5% into the solution 38kg, keeping the pH of the solution stable, reacting, adjusting the pH to 7 after the reaction is finished, continuing stirring for reacting for 3 hours, precipitating and filtering reactants, and drying in an oven at 120 ℃ for 5 hours to obtain the alumina particles with the surfaces coated with the silica shells.

Dispersing the alumina particles coated with the silica shell layer into 20 mass percent of slurry in a stirring cylinder, adding 1 mass percent of propionic acid sodium salt dispersing agent during dispersion, dispersing at high speed for 2h at the rotating speed of 1500rpm, transferring to a grinder, grinding to the fineness of less than 10 mu m, and filtering the slurry by using a 300-mesh gauze. Adding 10kg of filtered slurry and 3L of 4% sodium dodecyl sulfate solution into a 100L reaction kettle, stirring and dispersing, heating to 75 ℃, then adjusting the pH value to 3 by using ammonia water, and slowly dropwise adding 50kg of Ti (SO) with the mass percent of 15% into the reaction kettle₄)₂And simultaneously dropwise adding ammonia water to maintain the pH of the solution stable. After the reaction, the reaction was filtered, washed with water and dried in an oven at 150 ℃ for 1 h. Then calcining for 1h at 900 ℃, crushing the obtained product in a jet mill, adjusting the air pressure to be 0.8MPa, the air flow velocity to be 2 Mach and the feeding speed to be 2kg/min, and collecting the particle material which takes alumina as an inner core and is coated with a silicon dioxide shell layer and a titanium dioxide shell layer on the surface in sequence.

As shown in FIG. 2, the particle size of the particulate material obtained in this example was 1.4. mu.m, wherein the particle size of the alumina core was 1 μm, the thickness of the silica shell was 0.1. mu.m, and the thickness of the titania shell was 0.1. mu.m.

As shown in FIG. 3, in order to obtain a reflectance curve of the prepared particulate material in the 0.3 μm-2.5 μm wavelength band, it can be seen from FIG. 3 that the average reflectance of the particulate material in the 0.3 μm-0.4 μm ultraviolet wavelength band is 95.1%, the average reflectance in the 0.4 μm-0.78 μm visible wavelength band is 97.2%, the average reflectance in the 0.78 μm-2.5 μm near infrared wavelength band is 92.1%, and the average reflectance in the 0.3 μm-2.5 μm full wavelength band is 96.8%.

As shown in FIG. 4, in order to obtain an emission curve of the particulate material in the 2.5 μm-25 μm band, it can be seen from FIG. 4 that the average emissivity of the particulate material in the 8 μm-13 μm atmospheric radiation window band is 0.96, and the average emissivity in the 2.5 μm-25 μm band is 0.94.

Example 2

Example 2 is different from example 1 in that the particle size of the alumina core and the thickness of the titania shell layer in example 2 are different from those in example 1.

Wherein the grain diameter of the alumina core is 0.8 μm, and the thickness of the titanium dioxide shell layer is 0.2 μm.

Example 3

Example 3 differs from example 1 in that the particle size of the particulate material and the particle size of the alumina core in example 3 are different from those in example 1.

The particle size of the particulate material obtained in this example was 1.2 μm, with the particle size of the alumina core being 0.8 μm.

Example 4

Example 4 is different from example 1 in that the particle size of the particulate material, the particle size of the alumina core, the thickness of the silica shell layer and the thickness of the titania shell layer in example 4 are different from those in example 1.

The particle size of the particulate material obtained in this example was 2.4 μm, with the alumina core having a particle size of 1.2 μm, the silica shell having a thickness of 0.3 μm and the titania shell having a thickness of 0.3 μm.

Example 5

Example 5 is different from example 1 in that the particle diameter and the thickness of the particle diameter of the alumina core in example 5 are different from those in example 1.

The particle size of the particulate material obtained in this example was 1.6 μm, with the particle size of the alumina core being 1.2 μm.

Example 6

Example 6 is different from example 1 in that the particle size of the particulate material, the particle size of the alumina core, the thickness of the silica shell layer and the thickness of the titania shell layer in example 6 are different from those in example 1.

The particle size of the particulate material obtained in this example was 2.0 μm, with the alumina core having a particle size of 1.2 μm, the silica shell having a thickness of 0.2 μm, and the titania shell having a thickness of 0.2 μm.

Example 7

Example 7 differs from example 1 in that the titanium dioxide shell layer is coated first and then the silica shell layer is coated.

The particle size of the particulate material obtained in this example was 1.4 μm, with the alumina core having a particle size of 1.0 μm, the titania shell having a thickness of 0.1 μm, and the silica shell having a thickness of 0.1 μm.

Example 8

Example 8 differs from example 2 in that the titanium dioxide shell is coated first and then the silicon dioxide shell is coated.

The particle size of the particulate material obtained in this example was 1.4 μm, with the alumina core having a particle size of 0.8 μm, the titania shell having a thickness of 0.2 μm, and the silica shell having a thickness of 0.1 μm.

Example 9

Example 9 differs from example 1 in that the material of the core is magnesium oxide.

The particle size of the particulate material obtained in this example was 1.4 μm, with the particle size of the magnesia core being 1.0 μm, the thickness of the titania shell being 0.1 μm, and the thickness of the silica shell being 0.1 μm.

Example 10

Example 10 differs from example 1 in that the material of the inner core is barium sulfate.

The particle size of the particulate material obtained in this example was 1.4 μm, with the barium sulfate core having a particle size of 1.0 μm, the titanium dioxide shell having a thickness of 0.1 μm, and the silicon dioxide shell having a thickness of 0.1 μm.

Example 11

Example 11 differs from example 1 in that the material of the core is glass beads.

The particle size of the particulate material obtained in this example was 1.4 μm, wherein the particle size of the glass bead core was 1 μm, the thickness of the titanium dioxide shell layer was 0.1 μm, and the thickness of the silicon dioxide shell layer was 0.1 μm.

Example 12

Example 12 differs from example 1 in that the material of the inner core is heavy calcium powder.

The particle size of the particulate material obtained in this example was 1.4 μm, with the coarse whiting powder core having a particle size of 1.0 μm, the titanium dioxide shell having a thickness of 0.1 μm, and the silicon dioxide shell having a thickness of 0.1 μm.

Comparative example 1

The difference between the comparative example 1 and the example 1 is that the material of the inner core is silicon dioxide, and the outer shell of the aluminum oxide is coated first, and then the outer shell of the titanium dioxide is coated.

Comparative example 2

The difference between the comparative example 2 and the example 1 is that the material of the inner core is titanium dioxide, and the outer shell of the alumina is coated firstly, and then the outer shell of the silica is coated.

Comparative example 3

The difference between the comparative example 3 and the example 1 is that the material of the inner core is titanium dioxide, and the inner core is coated with a silica shell layer and then coated with an alumina shell layer.

The particulate materials of examples 1 to 12 and comparative examples 1 to 3 were subjected to solar reflectance and emissivity tests, and the results are shown in tables 1 and 2.

TABLE 1

TABLE 2

Application example 1

TABLE 3

Raw materials	Mass percent
		Acrylic resin	45％
Particulate material of example 1	35％
		Wetting dispersant CF10	2％
Fiber bundle HBR250	1％
		Defoaming agent BYK024	0.50％
Film-forming aid CS12	3％
		Thickener RM2020	2％
Bactericide CMC	0.60％
		Water (W)	11％

The coating was formulated according to the formulation in Table 3 and formed into a coating having a thickness of 100 μm. The coating was subjected to performance testing and the results are shown in fig. 5, with specific data in table 4.

TABLE 4

Application comparative example 1

Comparative application example 1 differs from application example 1 in that the particulate material is replaced with alumina particles, silica particles and titanium dioxide particles, wherein the mass percentages of the alumina particles, silica particles and titanium dioxide particles in the coating material are 15%, 5% and 15%, respectively.

The coating material of practical example 1 was formed into a coating layer having a thickness of 100 μm by the method of practical example 1, and the coating layer was subjected to the performance test by the same method, and the specific data are shown in Table 5.

TABLE 5

Application example 2

The PET fiber with the fiber grade is adopted, 10% of the granular material in the embodiment 1 is added into the PET, the granular material is uniformly dispersed in the resin by granulation through a granulator, 25kV voltage is adopted, the spinning temperature of 260 ℃ is adopted for electrostatic spinning, the environment temperature is controlled to be 70 ℃, and the PET fiber with the diameter of about 1 mu m is obtained.

The 150D yarn is made by adopting a plurality of strands of weaving, the warp and weft of the cloth are interwoven by adopting 150D silk plain weave, the density is 21 x 33, and the width is 150 cm. The thickness of the prepared cloth is about 90 μm.

The fabric was subjected to a performance test, the results are shown in fig. 6, and the specific data are shown in table 6.

TABLE 6

Comparative application example 2

Application comparative example 2 differs from application example 2 in that the particulate material is replaced with alumina particles, silica particles and titania particles, wherein the mass percentages of the addition of the alumina particles, silica particles and titania particles are 4%, 2% and 4%, respectively.

The fabric using comparative example 2 was subjected to the same performance test, and the specific data are shown in table 7.

TABLE 7

Application example 3

The granular material of example 1 was added to PET in an amount of 5% by mass, and the mixture was granulated by a granulator, and the granular material was uniformly dispersed in PET, followed by melt casting to obtain a film having a thickness of about 100 μm.

The films were tested for properties and the data are shown in table 8.

TABLE 8

Comparative application example 3

Comparative application example 3 differs from application example 3 in that the particulate material is replaced with alumina particles, silica particles and titania particles, wherein the mass percentages of the alumina particles, silica particles and titania particles are 2%, 1% and 2%, respectively.

The film of practical comparative example 3 was formed into a coating layer having a thickness of 100 μm by the method of practical example 3, and the film was subjected to the performance test by the same method, and the specific data are shown in Table 9.

TABLE 9

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims

1. A particulate material comprising an inner core and first and second shells sequentially coated on the surface of the inner core, the material of the inner core having a reflectivity of greater than 75% at a wavelength band of 0.3 μm to 2.5 μm and an emissivity of greater than 0.9 at an atmospheric radiation window of 8 μm to 13 μm, the materials of the inner core, the first shell and the second shell being different;

2. A particulate material according to claim 1 wherein the material of the inner core has a reflectivity of greater than 85% in the 0.3 to 2.5 μm wavelength band and an emissivity of greater than 0.94 in the 8 to 13 μm atmospheric radiation window.

3. The particulate material of claim 2, wherein the material of the inner core is selected from one of magnesium oxide, aluminum oxide, and barium sulfate.

4. A particulate material as claimed in claim 3 wherein the material of the core is alumina.

5. A particulate material as claimed in any one of claims 1 to 4 wherein the particle size of the inner core is in the range 40% to 75% of the particle size of the particulate material.

6. The particulate material of claim 5 wherein the first shell has a thickness of 5% to 18.75% of the particle size of the particulate material and the second shell has a thickness of 5% to 18.75% of the particle size of the particulate material.

7. The particulate material of claim 6 wherein the particle size of the inner core is 0.8 μm to 1.2 μm and the thickness of the first and second shell layers is independently selected from 0.1 μm to 0.3 μm.

8. Use of a particulate material as claimed in any one of claims 1 to 7 in a coating.

9. Use of a particulate material as claimed in any one of claims 1 to 7 in a fibre.

10. Use of a particulate material as claimed in any one of claims 1 to 7 in a film.