A cool pigment with high near-infrared reflectivity, and a preparation method and application thereof

Abstract

The application discloses a cold pigment with high near-infrared reflectivity and a preparation method and application thereof. (12‑x) Mn x O 19 , and x is selected from 0.1-1.0; the preparation method of the cold pigment is as follows: high-temperature solid-phase method is adopted, raw materials are uniformly mixed, and the cold pigment is prepared by calcining at 1500-1600 DEG C. The cold pigment has light brown color and excellent near-infrared reflectivity; in addition, the cold pigment also has very good acid and alkali resistance, high-temperature resistance and salt corrosion resistance, and long-term application stability in various complex environments is ensured.

Description

Technical Field

[0001] This invention belongs to the technical field of inorganic oxide pigments, and more specifically, relates to a cold pigment with high near-infrared reflectance, its preparation method, and its application. Background Technology

[0002] Against the backdrop of increasingly strained energy resources, effectively reducing energy consumption has become an urgent problem to be solved. Buildings and vehicles exposed to sunlight for extended periods often require cooling or insulation systems (such as air conditioning in the south and underfloor heating in the north) to maintain comfortable temperatures, which significantly increases energy consumption. Therefore, developing materials that can effectively reduce surface temperatures, especially "cold pigments" with high near-infrared reflectivity, is of great significance for achieving energy conservation and emission reduction.

[0003] Currently, white pigments are widely used in the coatings industry due to their high reflectivity. Among them, titanium dioxide (TiO2) is one of the best performing white pigments on the market, with advantages such as high whiteness, non-toxicity, stable physicochemical properties, and good acid and alkali resistance. Moreover, its reflectivity in the near-infrared region can reach about 85%.

[0004] However, despite the excellent energy-saving effects of white pigments, in certain specific scenarios, white coatings may have limitations such as being prone to getting dirty, difficult to maintain, and having a monotonous visual effect. In these cases, the market demand for non-white, especially dark-colored (such as brown) cool pigments with high near-infrared reflectivity is growing. However, there are few light brown inorganic pigments with excellent near-infrared reflectivity in the existing technology. Therefore, providing a dark-colored cool pigment with high near-infrared reflectivity to expand the application range of cool pigments and meet the diversified needs of the market has become an urgent technical problem to be solved. Summary of the Invention

[0005] In view of the aforementioned problems in the prior art, the primary objective of this invention is to provide a cold pigment with high near-infrared reflectivity.

[0006] A second objective of this invention is to provide a method for preparing the aforementioned cold pigment.

[0007] A third objective of this invention is to provide applications of the aforementioned cold pigments in the fields of construction, transportation, or outdoor equipment.

[0008] To achieve the above objectives, the present invention is implemented through the following technical solution: This invention claims protection for a cold pigment with high near-infrared reflectance, the cold pigment having the structural formula CaAl. (12-x) Mn x O 19 x is selected from 0.1-1.0 The cold pigment provided by this invention not only possesses excellent near-infrared reflectivity, surpassing existing commercial titanium dioxide, but also exhibits a unique light brown color, overcoming the limitations of existing white coatings such as poor stain resistance and difficulty in maintenance. Furthermore, the pigment provided by this invention has a specific structural formula CaAl. (12-x) Mn x O 19 The cold pigment exhibits minimal color variation within a pH range of 1-13 under salt corrosion conditions. It possesses excellent resistance to acids and alkalis, high temperatures, and salt corrosion, ensuring its long-term stability in various complex environments.

[0009] Preferably, x is selected from 0.1-0.4.

[0010] More preferably, x is selected from 0.1-0.2; under these preferred conditions, the prepared cold pigment has a higher near-infrared reflectance.

[0011] More preferably, x is selected from 0.38-0.42; under these preferred conditions, the prepared cold pigment has a higher near-infrared reflectance.

[0012] Preferably, the cold pigment of the present invention has high near-infrared reflectance in the 750-2500 nm wavelength range. More preferably, the cold pigment of the present invention has even higher near-infrared reflectance in the 2000-2500 nm wavelength range. Within this preferred near-infrared wavelength range, the cold pigment provided by the present invention exhibits superior infrared reflectance.

[0013] Preferably, the average particle size of the cold pigment with high near-infrared reflectance is ≤5μm.

[0014] The present invention provides a method for preparing the above-mentioned cold pigment, which is as follows: using a high-temperature solid-state method, the raw materials are mixed evenly and then calcined at 1500-1600℃ to prepare a cold pigment with high near-infrared reflectivity.

[0015] This invention employs a high-temperature solid-state method, introducing trace amounts of manganese to replace aluminum sites, thereby optimizing the crystal structure of the material and preparing a CaAl material with a specific structural formula. (12-x) Mn x O 19 The cold pigment provided by this invention is non-toxic and is prepared using inexpensive raw materials commonly used in industry, combined with a simple and efficient high-temperature solid-state method. The entire preparation process does not produce any toxic or harmful substances, conforming to the concept of green environmental protection. Compared to titanium dioxide, this invention has advantages in raw material cost and production energy consumption, significantly reducing preparation costs.

[0016] Preferably, the preparation method of the cold pigment is as follows: calcium source, aluminum source and manganese source are mixed evenly according to stoichiometric ratio to obtain a mixture; the mixture is heated to 1500-1600℃ and calcined in air atmosphere to obtain a cold pigment with high near-infrared reflectivity.

[0017] Preferably, the calcination is carried out at 1500-1600℃ for 10-20 hours. More preferably, the calcination is carried out at 1500-1550℃ for 15-20 hours.

[0018] Preferably, the heating rate is 5-10℃ / min. More preferably, the heating rate is 5-6℃ / min.

[0019] Preferably, the average particle size of the mixture is 10-20 nm.

[0020] Preferably, the calcium source is selected from at least one of calcium oxide, calcium hydroxide, calcium carbonate, or calcium nitrate. More preferably, the calcium source is selected from calcium carbonate.

[0021] Preferably, the manganese source is selected from at least one of manganese dioxide, manganese oxide, manganese trioxide, manganese tetroxide, manganese acetate, or manganese nitrate. More preferably, the manganese source is selected from manganese trioxide.

[0022] Preferably, the method of uniformly mixing the calcium source, aluminum source and manganese source includes, but is not limited to, ball milling or grinding.

[0023] More preferably, a grinding aid may be added during the ball milling or grinding process. More preferably, the grinding aid includes, but is not limited to, anhydrous ethanol or deionized water.

[0024] More preferably, the ball milling or grinding time is 4-8 hours.

[0025] Preferably, the mixture further includes any of the following steps before calcination: (a) Drying: Dry the mixed slurry or powder at 80-100°C to remove moisture and grinding aids; (b) Precalcination: The dried mixture is precalcined at 800-1000℃ to promote the decomposition of calcium carbonate and the initial formation of oxides.

[0026] More preferably, the dried mixture is pre-calcined at 800-1000℃ for 2-4 hours.

[0027] Furthermore, this invention seeks protection for the application of the aforementioned cold pigment with high near-infrared reflectivity in the fields of construction, transportation, or outdoor equipment.

[0028] The cold pigment provided by this invention not only possesses excellent near-infrared reflectivity but also exhibits good resistance to acids and alkalis, high temperatures, and salt corrosion, ensuring its long-term application stability in various complex environments. As a novel light brown cold pigment, it fills the gap in the market for high-reflectivity non-white pigments. The cold pigment provided by this invention can be used as a functional colorant in coatings, inks, plastics, ceramics, and other fields. It is particularly suitable for scenarios requiring energy saving and cooling but where white pigments are unsuitable, such as building exteriors, transportation vehicles, outdoor equipment, and industrial equipment, providing more color options and energy-saving solutions, and has broad market application potential.

[0029] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a light brown, cold pigment, CaAl, with excellent near-infrared reflectance. (12-x) Mn x O 19 The cold pigment has excellent resistance to acids and alkalis, high temperatures, and salt corrosion, ensuring its long-term application stability in various complex environments. Attached Figure Description

[0030] Figure 1 CaAl prepared in Example 1 11.9 Mn 0.1 O 19 XRD pattern of cold pigment.

[0031] Figure 2 CaAl prepared in Example 2 11.8 Mn 0.2 O 19 XRD pattern of cold pigment.

[0032] Figure 3 CaAl prepared in Example 3 11.7 Mn 0.3 O 19 XRD pattern of cold pigment.

[0033] Figure 4 CaAl prepared in Example 4 11.6 Mn 0.4 O 19 XRD pattern of cold pigment.

[0034] Figure 5 CaAl prepared in Example 5 11.2 Mn 0.8 O 19 XRD pattern of cold pigment.

[0035] Figure 6Near-infrared reflectance images of the cold pigments prepared in Examples 1-5, TiO2, and CaAlMnO4 prepared in Comparative Example 1.

[0036] Figure 7 The images show the appearance of the cold pigments prepared in Examples 1-5. Detailed Implementation

[0037] The present invention will be further described below with reference to the specification and specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in this technical field.

[0038] Example 1 CaAl 11.9 Mn 0.1 O 19 Preparation of cold pigments (1) Using an electronic balance, weigh the corresponding masses of raw materials CaCO3, Al2O3 and Mn2O3 according to the stoichiometric ratio Ca:Al:Mn = 1:11.9:0.1. Place the weighed raw materials in a mortar, add 5 mL of anhydrous ethanol as a grinding aid, and grind in a Michelin ball mill for 6 hours to obtain a mixture with an average particle size of 15 nm. Dry at 85 °C to remove moisture and grinding aid to obtain precursor powder.

[0039] (2) Place the dried precursor powder from step (1) into an alumina crucible and put it into a box-type high-temperature furnace. Under an air atmosphere, start from room temperature (25℃) and increase the temperature to 1500℃ at a rate of 5℃ / min. Calcinate in the furnace for 20 hours. After calcination, allow the furnace to cool naturally to room temperature. Crush, grind, and sieve the product to obtain a light brown powder with an average particle size of 4 micrometers, which is CaAl. 11.9 Mn 0.1 O 19 Cold pigments.

[0040] Figure 1 CaAl prepared in Example 1 11.9 Mn 0.1 O 19 XRD pattern of a cold pigment. (By...) Figure 1 It can be seen that the sample is a single phase and does not contain other impurities.

[0041] Example 2 CaAl 11.8 Mn 0.2 O 19 Preparation of cold pigments The difference between this embodiment and embodiment 1 is that in step (1), an electronic balance is used to weigh the corresponding mass of raw materials CaCO3, Al2O3 and Mn2O3 according to the stoichiometric ratio Ca:Al:Mn = 1:11.8:0.2.

[0042] Figure 2 CaAl prepared in Example 2 11.8 Mn 0.2 O 19 XRD pattern of a cold pigment. (By...) Figure 2 It can be seen that the sample is a single phase and does not contain other impurities.

[0043] Example 3 CaAl 11.7 Mn 0.3 O 19 Preparation of cold pigments The difference between this embodiment and embodiment 1 is that in step (1), an electronic balance is used to weigh the corresponding mass of raw materials CaCO3, Al2O3 and Mn2O3 according to the stoichiometric ratio Ca:Al:Mn = 1:11.7:0.3.

[0044] Figure 3 CaAl prepared in Example 3 11.7 Mn 0.3 O 19 XRD pattern of a cold pigment. (By...) Figure 3 It can be seen that the sample is a single phase and does not contain other impurities.

[0045] Example 4 CaAl 11.6 Mn 0.4 O 19 Preparation of cold pigments The difference between this embodiment and embodiment 1 is that in step (1), an electronic balance is used to weigh the corresponding mass of raw materials CaCO3, Al2O3 and Mn2O3 according to the stoichiometric ratio Ca:Al:Mn = 1:11.6:0.4.

[0046] Figure 4 CaAl prepared in Example 4 11.6 Mn 0.4 O 19 XRD pattern of a cold pigment. (By...) Figure 4 It can be seen that the sample is a single phase and does not contain other impurities.

[0047] Example 5 CaAl 11.2 Mn 0.8 O 19 Preparation of cold pigments The difference between this embodiment and embodiment 1 is that in step (1), an electronic balance is used to weigh the corresponding mass of raw materials CaCO3, Al2O3 and Mn2O3 according to the stoichiometric ratio Ca:Al:Mn = 1:11.2:0.8. Figure 5 CaAl prepared in Example 6 11.2 Mn 0.8 O 19 XRD pattern of a cold pigment. (By...) Figure 5 It can be seen that the sample is a single phase and does not contain other impurities.

[0048] Comparative Example 1: Preparation of CaAlMnO4 The difference between this comparative example and Example 1 is that in step (1), an electronic balance is used to weigh the corresponding mass of raw materials CaCO3, Al2O3 and Mn2O3 according to the stoichiometric ratio Ca:Al:Mn = 1:1:1.

[0049] Test Example 1 (1) Test subject: CaAl prepared in Example 2 11.8 Mn 0.2 O 19 Cold pigments.

[0050] (2) Test method: Using a spectrophotometer, place a 0.5000g sample flat on a glass plate, then place the spectrophotometer above the sample and measure the L, a, and b values ​​of the sample before and after treatment. Calculate the ΔE value using the following formula: ΔE = When ΔE > 5, it indicates that the color change of the sample can be observed with the naked eye, suggesting poor sample stability.

[0051] (3) Table 1 shows the CaAl prepared in Example 2. 11.8 Mn 0.2 O 19 Cold pigments and their chromaticity values ​​after treatment with acid, alkali and seawater.

[0052] Table 1

[0053] Table 1 shows the CaAl prepared according to the present invention. 11.8 Mn 0.2 O 19 Colorimetric value changes under different conditions. After soaking in H2SO4 (pH=3), HCl (pH=3), and NaOH (pH=12) and sonicating for 15 min, the colorimetric value of the material did not change much. After soaking in seawater for 24 h, there was a slight change in color difference, with colorimetric value change ΔE≤2.5.

[0054] Test Example 2 (1) Test subject: CaAlMnO4 prepared in Comparative Example 1.

[0055] (2) Test method: Refer to the test method of test example 1.

[0056] (3) Table 2 shows the color values ​​of CaAlMnO4 prepared in Comparative Example 1 and its samples after acid, alkali and seawater treatment.

[0057] Table 2

[0058] As shown in Table 2, the CaAlMnO4 prepared in Comparative Example 1 showed significant changes in colorimetric values ​​after immersion in H2SO4 (pH=3), HCl (pH=3), and NaOH (pH=12) followed by sonication for 15 min, with colorimetric changes ΔE ≥ 5 for each. After immersion in seawater for 24 h, the colorimetric changes were even greater, with ΔE exceeding 8. The results were inferior to the CaAl prepared in this invention. 11.8 Mn 0.2 O 19 Cold pigments.

[0059] Test Example 3 (1) Test objects: cold pigments prepared in Examples 1-5, TiO2, and CaAlMnO4 prepared in Comparative Example 1.

[0060] (2) Test method: UV-Vis-NIR spectrophotometer with integrating sphere accessory. Diffuse reflectance test mode is selected. Specular reflection components are excluded through the trap, which is often used to analyze rough surfaces or powder samples. The powder is placed in the integrating sphere, and its reflectance is measured by diffuse reflectance, with barium sulfate as the reference.

[0061] (3) Test results Figure 6 The near-infrared reflectance spectra of the cold pigments prepared in Examples 1-5, TiO2, and CaAlMnO4 prepared in Comparative Example 1 are shown in Table 3. Table 3 shows the reflectance of the cold pigments prepared in Examples 1-5, TiO2, and CaAlMnO4 prepared in Comparative Example 1 at a wavelength of 2250 nm.

[0062] Table 3

[0063] like Figure 6As shown in Table 3, when the wavelength is 2250 nm, the near-infrared reflectance of the cold pigment prepared in the embodiments of the present invention is ≥88.3%. More preferably, the near-infrared reflectance is ≥99.7%. More preferably, the near-infrared reflectance is 109.1%.

[0064] The cold pigments prepared in the embodiments of the present invention exhibit significantly superior near-infrared reflectance compared to existing TiO2 and the materials prepared in Comparative Example 1 at wavelengths of 2000-2500 nm.

[0065] (4) The colorimetric values ​​of the cold pigments prepared in Examples 1-5 were tested. The test method was as follows: using a spectrophotometer, 0.5000g of sample was placed flat on a glass plate, and then the spectrophotometer was placed above the sample to measure the L, a, and b values ​​of the sample before and after treatment. The value of C* can be calculated according to the formula C* = (a2+ b2)^(1 / 2), and H* is measured using the formula H* = tan-1(b* / a*). The test results are shown in Table 3 below.

[0066] In the CIE L*, a*, b*, C*, H* color space, these five parameters together provide a precise quantitative description of color: L* (Lightness): Characterizes the lightness or darkness of a color, ranging from 0 (pure black) to 100 (pure white). a* (Red-Green axis): Characterizes the color's bias on the red-green axis. Positive values ​​represent a reddish bias, and negative values ​​represent a greenish bias. b* (Yellow-Blue axis): Characterizes the color's bias on the yellow-blue axis. Positive values ​​represent a yellowish bias, and negative values ​​represent a bluish bias. C* (Chroma): Characterizes the vividness or purity of a color, calculated by taking the square root of the sum of the squares of a* and b*. A larger value indicates a more saturated and richer color. H* (Hue angle): Characterizes the basic color category (e.g., red, yellow, green, blue), reflected by the rotation angle H* on the color plane. 0° represents pure red, and 90° represents pure yellow. The brown color of a pigment is determined by its chromaticity coordinates. Positive a* and a large positive b* value give the material a hue H* between red and yellow. When the hue H* value is stable between 64° and 72°, the material appears brown visually.

[0067] Table 4

[0068] As shown in Table 4, the hue H* value of the material prepared in the embodiments of the present invention is between 64° and 72°, indicating that the material appears brown visually.

[0069] Figure 7The images show the appearance of the cold pigments prepared in Examples 1-5; where a corresponds to the cold pigment prepared in Example 1; b corresponds to the cold pigment prepared in Example 2; c corresponds to the cold pigment prepared in Example 3; d corresponds to the cold pigment prepared in Example 4; and e corresponds to the cold pigment prepared in Example 5. Figure 7 It is known that the cold pigments prepared in Examples 1-5 of the present invention are brown.

[0070] The foregoing examples are merely illustrative, used to explain some features of the method described in this invention. The appended claims are intended to claim the broadest possible scope, and the embodiments presented herein are demonstrated by the applicant's actual experimental results. Therefore, the applicant intends that the appended claims are not limited by the selection of examples illustrating the features of the invention. Some numerical ranges used in the claims also include sub-ranges within them, and variations within these ranges should also be interpreted as being covered by the appended claims where possible.

Claims

1. A cold pigment with high near-infrared reflectance, characterized in that, The structure of the cold pigment is CaAl (12-x) Mn x O 19 x is selected from 0.1-1.

0.

2. The cold pigment according to claim 1, characterized in that, x is selected from 0.1 to 0.

4.

3. The method for preparing the cold pigment according to claim 1 or 2, characterized in that, The preparation method of the cold pigment is as follows: using a high-temperature solid-state method, the raw materials are mixed evenly and then calcined at 1500-1600℃ to prepare a cold pigment with high near-infrared reflectivity.

4. The preparation method according to claim 3, characterized in that, The method for preparing the cold pigment is as follows: calcium source, aluminum source and manganese source are mixed evenly according to stoichiometric ratio to obtain a mixture; the mixture is calcined at 1500-1600℃ in an air atmosphere to obtain a cold pigment with high near-infrared reflectivity.

5. The preparation method according to claim 4, characterized in that, Calcination at 1500-1600℃ for 10-20 hours.

6. The preparation method according to claim 4, characterized in that, The heating rate is 5-10℃ / min.

7. The preparation method according to claim 4, characterized in that, The average particle size of the mixture is 10-20 nm.

8. The preparation method according to claim 4, characterized in that, The calcium source is selected from at least one of calcium oxide, calcium hydroxide, calcium carbonate, or calcium nitrate.

9. The preparation method according to claim 4, characterized in that, The manganese source is selected from at least one of manganese dioxide, manganese oxide, manganese trioxide, manganese tetroxide, manganese acetate, or manganese nitrate.

10. The use of the cold pigment according to any one of claims 1 or 2 in the fields of construction, transportation or outdoor equipment.

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