A heat-insulating light-shielding plate with variable light transmittance and a method for manufacturing the same

Abstract

The application discloses a heat-insulating light-shielding plate with variable light transmittance and a preparation method thereof. The structure of the heat-insulating light-shielding plate is organic glass layer-aerogel layer-organic glass layer, wherein the aerogel layer is a sandwich structure, the inside of which is a first wet gel prepared from orthosilicate, and the outside of which is a second wet gel prepared from methyl triethoxysilane; and the aerogel layer and the organic glass layer are coated with methyl methacrylate. The application composites the aerogel and the organic glass, mutually supplements in the case of not affecting the respective performances, solves the problem that the heat insulation of the light-shielding plate is poor, and can adjust the light transmittance according to the environmental temperature, further assists heat insulation, and has a wide application prospect.

Description

Technical Field

[0001] This invention belongs to the technical field of heat-insulating and light-shielding panels, specifically relating to a heat-insulating and light-shielding panel with variable light transmittance and its preparation method. Background Technology

[0002] Acrylic glass, chemically known as polymethyl methacrylate (PMMA), is a polymer compound formed by the polymerization of methacrylates. It comes in four types: colorless transparent, colored transparent, pearlescent, and patterned acrylic glass, commonly known as acrylic, Zhongxuan acrylic, or acrylic glass. Acrylic glass possesses advantages such as good transparency, chemical stability, mechanical properties, weather resistance, ease of dyeing, ease of processing, and beautiful appearance, making it widely used in the construction industry, including for sunshades, ceilings, and lighting fixtures. However, existing acrylic glass has insufficient heat insulation performance when used for sunshade; if heat dissipation is poor, it can become quite stuffy.

[0003] Aerogels are a class of nanoporous materials with broad application prospects. They are lightweight, porous solid materials composed of a gel network and a gaseous medium, and are currently considered the best-performing thermal insulation materials. Silica aerogel is the most widely used and mature aerogel material, characterized by low density, low thermal conductivity, and high porosity. It is formed by using a silicon source through a sol-gel method, combined with a specific drying process, to replace the liquid phase in the gel with gas, resulting in a nanoporous amorphous solid material with a three-dimensional network structure. It is currently the best-performing thermal insulation material, as its fine nanonetwork structure effectively restricts heat transfer, making it widely used in thermal insulation applications. Furthermore, aerogels have extremely high porosity, allowing them to be repeatedly used to adsorb large amounts of liquid, and the presence of liquid affects the light transmittance of the aerogel.

[0004] However, aerogels are brittle and easily broken, while plexiglass has poor heat insulation properties. Therefore, the two can be combined to prepare new light-blocking materials, fully utilizing the strength and toughness of plexiglass and the excellent heat insulation properties of aerogel to synergistically enhance the performance of the light-blocking material. Simultaneously, aerogels have the characteristic of repeatedly adsorbing and releasing liquids, adjusting their own light transmittance, thereby further strengthening the light-blocking effect of the material. Therefore, it is necessary to develop a light-blocking panel that can adjust its light transmittance according to the intensity of sunlight, has good heat insulation effects, and can also address the problems of rapid heat loss and poor light transmittance in winter. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a heat-insulating and light-shielding panel with variable light transmittance and its preparation method. An aerogel with a sandwich structure is prepared and then composited with plexiglass to obtain a heat-insulating and light-shielding panel of plexiglass-aerogel-plexiglass. This process complements each other without affecting their respective performance, solving problems such as poor heat insulation and unchanged light transmittance due to environmental factors. It ensures excellent heat insulation performance during high summer temperatures while also addressing issues such as rapid heat loss and poor light transmittance in winter.

[0006] To achieve the above objectives, the present invention provides a heat-insulating and light-shielding panel with variable light transmittance. The structure of the heat-insulating and light-shielding panel is an plexiglass layer-aerogel layer-plexiglass layer; the thickness ratio of the plexiglass layer-aerogel layer-plexiglass layer is 1:2:1.

[0007] Preferably, the aerogel layer has a sandwich structure, with a first wet gel inside and a second wet gel outside; the thickness of the second wet gel is 1-3 mm.

[0008] More preferably, the first wet gel is composed of a first silicon source, water, an organic solvent and a catalyst; the second wet gel is composed of silane, water, an organic solvent and a catalyst.

[0009] More preferably, the first silicon source is methyl orthosilicate and / or tetraethyl orthosilicate with a purity of 80-98% and a chloride ion content of <100ppm; the second silicon source is methyltriethoxysilane and / or polymethyltriethoxysilane with a purity of ≥85%.

[0010] Preferably, the plexiglass is any one of colorless transparent plexiglass, colored transparent plexiglass, and patterned plexiglass.

[0011] The present invention also provides a method for preparing a heat-insulating and light-shielding plate with variable light transmittance, comprising the following steps:

[0012] (1) Add water and organic solvent to the first silicon source, then add catalyst, and the reaction solidifies to obtain wet gel;

[0013] (2) Add water and organic solvent to the second silicon source, heat to complete the hydrolysis of the silicon source, then add catalyst to react and obtain hydrolysis-gel solution;

[0014] (3) Immerse the wet gel in the hydrolysis-gel solution and heat to solidify to form a gel with a sandwich structure;

[0015] (4) The gel with sandwiched layers is immersed in the extraction solution, and then heated and dried to obtain an aerogel;

[0016] (5) Coat the upper and lower surfaces of the aerogel with methyl methacrylate, and then coat the sides with semi-solidified plexiglass. After curing, a heat-insulating and light-shielding plate with variable light transmittance is obtained.

[0017] Preferably, the mass ratio of the first silicon source to water in step (1) is 1:0.2-0.4, and the mass ratio of the first silicon source to the organic solvent is 1:1-2.5.

[0018] Preferably, the mass ratio of the second silicon source to water in step (2) is 1:0.3-0.8, and the mass ratio of the second silicon source to the organic solvent is 1:0.8-1.5.

[0019] Preferably, the organic solvent in steps (1) and (2) is an alcohol solvent, and more preferably, the alcohol solvent is an ethanol solution with a purity ≥95%.

[0020] Preferably, the catalyst is an acidic catalyst and / or a basic catalyst.

[0021] More preferably, the acidic catalyst is one or more of oxalic acid, hydrochloric acid, and sulfuric acid; and the alkaline catalyst is one or more of sodium hydroxide, potassium hydroxide, urea, and ammonia.

[0022] Preferably, the extract in step (4) is anhydrous ethanol.

[0023] Preferably, the mass ratio of methyl methacrylate to aerogel in step (5) is 1:0.3-0.7.

[0024] Preferably, the hydrolysis temperature in step (2) is 45-65℃ and the heating time is 6-12h.

[0025] Preferably, the heating and solidification temperature in step (3) is 45-65℃ and the time is 1-3h.

[0026] Preferably, the heating extraction in step (4) is performed at a temperature of 45-65°C for 6-12 hours.

[0027] Preferably, the drying method described in step (4) is supercritical carbon dioxide drying, with drying conditions of 65-75℃, pressure of 14-16MPa, and drying time of 2-5h.

[0028] The beneficial effects of this invention are as follows:

[0029] 1. Using orthosilicate and methyltriethoxysilane as silicon sources, gels were prepared separately in the presence of water, organic solvent and catalyst. The wet gel prepared with orthosilicate as silicon source was embedded in the wet gel with methyltriethoxysilane as silicon source to obtain a sandwich aerogel. It has the characteristics of being hydrophobic on the outside and hydrophilic on the inside, which gives the aerogel layer a high thermal conductivity and excellent thermal insulation performance.

[0030] 2. Coating the surface of the aerogel layer with methyl methacrylate allows it to penetrate the pores of the outer second wet gel in the aerogel layer, but it will not penetrate the inner first wet gel, thus affecting the thermal insulation performance of the aerogel. During the process of laminating the aerogel with plexiglass after coating, methyl methacrylate reacts with the semi-polymerized plexiglass, enhancing the bonding force between the aerogel and the plexiglass and increasing the overall strength of the light-shielding plate. At the same time, the methyl methacrylate that penetrates the outer layer of the aerogel layer will react due to high temperature, changing the light transmittance of the aerogel.

[0031] 3. By embedding aerogel with plexiglass, the strength of plexiglass is used to solve the brittleness problem of aerogel and improve the overall strength of the light-shielding plate.

[0032] 4. Without affecting the performance of the light-shielding panel, this invention solves the problems of poor heat insulation performance in summer and rapid heat loss and poor light transmission performance in winter. It enables the light-shielding panel to change its light transmittance according to changes in ambient temperature, and has broad application prospects. Detailed Implementation

[0033] The technical solution of the present invention will be further explained and described below with reference to specific embodiments. It is worth noting that the following embodiments are only preferred embodiments of the present invention and should not be construed as limiting the present invention. The scope of protection of the present invention should be determined by the contents of the claims. Modifications and substitutions made by those skilled in the art to the technical solution of the present invention without creative effort all fall within the scope of protection of the present invention.

[0034] Example 1

[0035] (1) Add 30 parts of deionized water to 100 parts of tetraethyl orthosilicate (purity is 99%) and stir to dilute. Then add 200 parts of ethanol solution (purity is 95%) and stir to hydrolyze. After hydrolysis, add 2 parts of sodium hydroxide to form a wet gel with a thickness of 2 mm.

[0036] (2) Add 50 parts of deionized water to 100 parts of methyltriethoxysilane (purity is 98%) and stir to dilute. Then heat to 60°C and add 100 parts of ethanol solution (purity is ≥95%). After hydrolysis for 8 hours, add 2 parts of sodium hydroxide and stir evenly to obtain hydrolysis-gel solution.

[0037] (3) Inject the hydrolyzed-gel liquid into the mold, and immerse the wet gel prepared in step (1) into it before gelation as the first wet gel layer, and ensure that there is a 1.5 mm thick liquid around the first wet gel layer. After heating to 45-60℃ and keeping warm for 1-4 hours, a wet gel with a sandwich structure is obtained, that is, the thickness of the second wet gel layer located on the outer layer is 1.5 mm.

[0038] (4) The wet gel with sandwich structure is immersed in anhydrous ethanol solution at 60°C for 12 hours for extraction. During this period, the anhydrous ethanol is circulated 3 times (the ethanol is completely discharged and then added again) to complete the extraction of water and the aging of the gel. Then, the aerogel layer with a thickness of 5 mm is obtained by supercritical carbon dioxide drying. The drying temperature of supercritical carbon dioxide drying is 60-80°C, the pressure is 12-15 MPa, and the time is 4-6 hours.

[0039] (5) Weigh the aerogel layer, and then coat the upper and lower surfaces of the aerogel layer with methyl methacrylate at a mass ratio of 1:0.5; then coat the semi-solid semi-polymethyl methacrylate, and after it solidifies, obtain a heat insulation and light-shielding plate with an overall thickness of 10 mm. The structure is plexiglass layer-aerogel layer-plexiglass layer.

[0040] Example 2

[0041] The method and steps are the same as in Example 1, except that the thickness of the wet gel in step (1) is changed to 3 mm, and the thickness of the second wet gel layer in step (3) is changed to 1 mm, so that the heat insulation and light shielding plate is prepared, with the structure of organic glass layer-aerogel layer-organic glass layer.

[0042] Example 3

[0043] The method and steps are the same as in Example 1, except that the thickness of the wet gel in step (1) is changed to 1 mm, and the thickness of the second wet gel layer in step (3) is changed to 1 mm, so that a heat insulation and light shield with an overall thickness of 10 mm is prepared, and the structure is an organic glass layer-aerogel layer-organic glass layer.

[0044] Example 4

[0045] The method and steps are the same as in Example 1, except that the thickness of the wet gel in step (1) is changed to 3 mm, and the thickness of the second wet gel layer in step (3) is changed to 2 mm, so that a heat insulation and light shield with an overall thickness of 10 mm is prepared, and the structure is an organic glass layer-aerogel layer-organic glass layer.

[0046] Example 5

[0047] The method and steps are the same as in Example 1, except that the number of cycles of anhydrous ethanol in step (4) is changed to 6 times to prepare a light shield with a structure of organic glass layer-aerogel layer-organic glass layer.

[0048] Comparative Example 1

[0049] (1) Add 30 parts of deionized water to 100 parts of tetraethyl orthosilicate (purity is 99%) and stir to dilute. Then add 200 parts of ethanol solution (purity is 95%) and stir to hydrolyze. After hydrolysis, add an alkaline catalyst to form a wet gel with a thickness of 5 mm.

[0050] (2) The wet gel was immersed in anhydrous ethanol solution at 60°C for 12 hours for extraction. During this period, the soaking solution was circulated 3 times (the ethanol was completely drained and then added again) to complete the extraction of water and the aging of the gel. Then, supercritical carbon dioxide drying was used to obtain a 5 mm thick aerogel layer. The supercritical carbon dioxide drying temperature was 60°C, the pressure was 14 MPa, and the time was 5 hours.

[0051] (3) Weigh the aerogel layer, and then coat the upper and lower surfaces of the aerogel layer with methyl methacrylate at a mass ratio of 1:0.5; then coat the semi-solid semi-polymethyl methacrylate, and after it solidifies, obtain a light shield with an overall thickness of 10 mm, the structure of which is plexiglass layer-aerogel layer-plexiglass layer.

[0052] Comparative Example 2

[0053] (1) Add 50 parts of deionized water to 100 parts of methyltriethoxysilane (purity is 98%) and stir to dilute. Then heat to 60°C and add 100 parts of ethanol solution (purity is 95%). After hydrolysis for 8 hours, add alkaline catalyst and stir evenly to solidify and form a wet gel with a thickness of 5 mm.

[0054] (2) The wet gel was immersed in anhydrous ethanol solution at 60°C for 12 hours for extraction. During this period, the soaking solution was circulated 3 times (the ethanol was completely drained and then added again) to complete the extraction of water and the aging of the gel. Then, supercritical carbon dioxide drying was used to obtain a 5 mm thick aerogel layer. The supercritical carbon dioxide drying temperature was 60°C, the pressure was 14 MPa, and the time was 5 hours.

[0055] (3) Weigh the aerogel layer, and then coat the upper and lower surfaces of the aerogel layer with methyl methacrylate at a mass ratio of 1:0.5; then coat the semi-solid semi-polymethyl methacrylate, and after it solidifies, obtain a light shield with an overall thickness of 10 mm, the structure of which is plexiglass layer-aerogel layer-plexiglass layer.

[0056] Comparative Example 3

[0057] The method and steps are the same as in Example 1, except that in step (5), methyl methacrylate is not uniformly coated on the upper and lower surfaces of the aerogel layer to prepare a light shield with a structure of plexiglass layer-aerogel layer-plexiglass layer.

[0058] Comparative Example 4

[0059] The method and steps are the same as in Example 1, except that anhydrous ethanol is not used for soaking and extraction in step (4) to prepare a light shield with a structure of organic glass layer-aerogel layer-organic glass layer.

[0060] Comparative Example 5

[0061] The method and steps are the same as in Example 1, except that the semi-polymethyl methacrylate in step (5) is replaced with methyl methacrylate with added catalyst, wherein the catalyst is an alkaline reagent, and a light shield is prepared with an organic glass layer-aerogel layer-organic glass layer.

[0062] Comparative Example 6

[0063] The method and steps are the same as in Example 1, wherein a 2.5 mm thick organic glass plate is physically attached to both sides of the 5 mm thick aerogel layer obtained in step (4) to form a light-shielding plate with an overall thickness of 10 mm. The structure is organic glass layer-aerogel layer-organic glass layer.

[0064] The light-shielding plates prepared in the above examples and comparative examples were tested for thermal conductivity using a flat plate heat flow meter, their light transmittance was visually assessed, and the bonding strength between the gel and the plexiglass was tested using the Lapa method. The results are shown in the table below:

[0065]

[0066] The results showed that, compared with Example 1, when only tetraethyl orthosilicate was used to prepare a wet gel as an aerogel layer (Comparative Example 1), and then it was combined with plexiglass to form a light-shielding plate, the thermal conductivity of the light-shielding plate was significantly reduced, and the strength and bonding force with plexiglass also showed a downward trend; while when only methyltriethoxysilane was used to prepare a wet gel as an aerogel layer (Comparative Example 2), the heat insulation performance of the light-shielding plate decreased, and the high-temperature light transmittance was even worse.

[0067] Compared with Example 1, when the thickness ratio of the first wet gel layer to the second wet gel was changed from 2:1.5 to 3:1 (Example 2), the thermal conductivity of the heat-insulating and light-shielding board decreased, while other properties did not change significantly. When the thickness ratio of the first wet gel layer to the second wet gel was changed to 1:1 (Example 3), the thermal conductivity and strength of the heat-insulating and light-shielding board increased significantly. When the thickness ratio was changed to 3:2 (Example 4), the heat insulation performance of the heat-insulating and light-shielding board improved, while the strength decreased significantly, indicating that the intermediate aerogel layer has excellent heat insulation effect and that the increased thickness of the plexiglass increases the strength.

[0068] Compared to Example 1, when methyl methacrylate coating was not used (Comparative Example 3), the thermal conductivity of the light-shielding plate was significantly reduced, the strength and adhesion decreased, while the high-temperature light transmittance increased, indicating that methyl methacrylate helps to improve the adhesion of the sandwich light-shielding plate.

[0069] Compared with Example 1, after replacing semi-polymethyl methacrylate with methyl methacrylate with added catalyst (Comparative Example 5), the thermal conductivity, strength and bonding force of the light-shielding plate increased, but the high-temperature light transmittance decreased significantly, making it unsuitable as a light-shielding plate.

[0070] When plexiglass is directly attached to both sides of the aerogel (Comparative Example 6), the thermal conductivity and bonding strength of the resulting light-shielding plate are significantly reduced, resulting in poor heat insulation performance.

Claims

1. A method for preparing a heat-insulating and light-shielding plate with variable light transmittance, characterized in that: Includes the following steps: (1) Add water and organic solvent to the first silicon source, then add catalyst, and the reaction solidifies to obtain wet gel; (2) Add water and organic solvent to the second silicon source, heat up and add catalyst to obtain hydrolysis-gel solution; (3) Immerse the wet gel in the hydrolysis-gel solution to form a gel with a sandwich structure; (4) The gel with sandwiched layers is immersed in the extraction solution, and then heated and dried to obtain an aerogel; (5) Coat the surface of the aerogel with methyl methacrylate, and then coat the sides with semi-solidified plexiglass, and cure to obtain a heat-insulating and light-shielding board with variable light transmittance. The structure of the heat-insulating and light-shielding panel is an organic glass layer-aerogel layer-organic glass layer; the thickness ratio of the organic glass layer-aerogel layer-organic glass layer is 1:2:

1.

2. The method for preparing a heat-insulating and light-shielding plate with variable light transmittance according to claim 1, characterized in that: The aerogel layer has a sandwich structure, with a first wet gel inside and a second wet gel on the outside.

3. The method for preparing a heat-insulating and light-shielding plate with variable light transmittance according to claim 2, characterized in that: The first wet gel is composed of a first silicon source, water, an organic solvent, and a catalyst; the second wet gel is composed of silane, water, an organic solvent, and a catalyst.

4. The method for preparing a heat-insulating and light-shielding plate with variable light transmittance according to claim 3, characterized in that: The first silicon source is methyl orthosilicate and / or tetraethyl orthosilicate; the second silicon source is methyltriethoxysilane.

5. The method for preparing a heat-insulating and light-shielding plate with variable light transmittance according to claim 1, characterized in that: The mass ratio of the first silicon source to water in step (1) is 1:0.2-0.4, and the mass ratio of the first silicon source to the organic solvent is 1:1-2.

5.

6. The method for preparing a heat-insulating and light-shielding plate with variable light transmittance according to claim 1, characterized in that: The mass ratio of the second silicon source to water in step (2) is 1:0.3-0.8, and the mass ratio of the second silicon source to the organic solvent is 1:0.8-1.

5.

7. The method for preparing a heat-insulating and light-shielding plate with variable light transmittance according to claim 1, characterized in that: The organic solvent in steps (1) and (2) is an alcohol solvent, and the catalyst is an acidic catalyst and / or a basic catalyst; the extract in step (4) is anhydrous ethanol.

8. The method for preparing a heat-insulating and light-shielding plate with variable light transmittance according to claim 7, characterized in that: The acidic catalyst is one or more of oxalic acid, hydrochloric acid, and sulfuric acid; the alkaline catalyst is one or more of sodium hydroxide, potassium hydroxide, urea, and ammonia.

9. The method for preparing a heat-insulating and light-shielding plate with variable light transmittance according to claim 1, characterized in that: The mass ratio of methyl methacrylate to aerogel in step (5) is 1:1.

Images