Portable renewable cooling hydrogel composite material as well as preparation method and application thereof

Abstract

The invention discloses a portable renewable cooling hydrogel composite material as well as a preparation method and application thereof. The portable renewable cooling hydrogel composite material comprises a three-dimensional network structure, porous solid particles and water, wherein the three-dimensional network structure is formed by cross-linking and curing macromolecules and an ionic cross-linking agent, and the porous solid particles are uniformly distributed in the three-dimensional network structure. The hydrogel composite material disclosed by the invention is beneficial to enhancing the diffuse reflection capability of sunlight, improving the optical reflectivity of the material and further improving the cooling performance, can be coated on a roof or other solid surfaces in situ without complex equipment during preparation, has good light reflectivity and evaporative cooling capability, can effectively reduce the surface temperature under sunlight, and is suitable for being used in the field of solar energy. The indoor cool feeling is kept; and after being dried, the composite material can be regenerated by spraying water, so that the composite material can be repeatedly used. The material is simple and convenient to prepare, low in cost and convenient to carry, and can be widely popularized in the fields of passive refrigeration, evaporative cooling, skin rehabilitation or building heat management and the like.

Description

Technical Field

[0001] This invention relates to a hydrogel material, specifically a portable renewable cooling hydrogel composite material, its preparation method, and its application, belonging to the technical field of gel materials and organic-inorganic composite materials. Background Technology

[0002] With the intensification of global climate change and the increase in energy consumption, the energy efficiency and environmental friendliness of buildings have become key considerations in modern building design, especially the thermal insulation effect of the roof, which is crucial for the temperature control and energy efficiency of buildings. Currently, common roof insulation materials on the market mainly include polyurethane foam, foam glass, and reflective coatings (CN217325879U, CN222500861U, CN118165590A). While these materials can provide insulation to some extent, they generally have many drawbacks. Most traditional insulation materials are composed of synthetic polymers or minerals, which may generate large amounts of carbon dioxide emissions during production and are difficult to degrade after disposal, burdening the environment. For example, polyurethane foam may produce harmful substances during production and disposal, which remain in the environment for a long time and are difficult to decompose. The performance of traditional insulation materials may also degrade over long-term use. For example, polyurethane foam is prone to aging under the influence of ultraviolet radiation and temperature changes, leading to a decrease in thermal insulation performance. Reflective coatings may lose their ability to reflect heat due to the accumulation of pollutants, thus affecting their thermal insulation effect.

[0003] In existing technologies, composite materials based on polymers and porous solid particles and their applications are relatively scarce, and most are concentrated in laboratory research with a lack of mature application examples. Particularly in the field of building roofing, existing technologies largely rely on non-degradable synthetic materials, and there is no widespread application of such composite materials in building roof insulation. Therefore, developing a novel composite material based on polymers and porous solid particles that can provide an environmentally friendly, efficient, and repairable insulation material has become an urgent technical problem to be solved. Summary of the Invention

[0004] The main objective of this invention is to provide a portable, renewable cooling hydrogel composite material and its preparation method, thereby overcoming the shortcomings of the prior art.

[0005] Another object of the present invention is to provide the application of the portable renewable cooling hydrogel composite material.

[0006] To achieve the aforementioned objectives, the technical solution adopted by this invention includes: A first aspect of the present invention provides a portable, renewable cooling hydrogel composite material, comprising: A three-dimensional network structure formed by cross-linking and curing of polymers and ionic cross-linking agents; Porous solid particles are uniformly distributed in the three-dimensional network structure; And water; The portable renewable cooling hydrogel composite material has a dense surface structure, and its solar reflectance is 0.65~0.85, infrared emissivity is 0.20~0.70, and elongation at break is 100%~400%.

[0007] A second aspect of this invention provides a method for preparing the portable, renewable cooling hydrogel composite material, comprising: Provides a mixed slurry containing polymers, water, and porous solid particles; The mixed slurry is applied to the surface of the substrate to form a coating, and then a solution containing an ionic crosslinking agent is applied to carry out an in-situ crosslinking reaction and curing to obtain a portable, renewable cooling hydrogel composite material.

[0008] A third aspect of the present invention provides the application of the portable renewable cooling hydrogel composite material in fields such as passive refrigeration, evaporative cooling, skin rehabilitation, or building thermal management.

[0009] Compared with the prior art, the advantages of the present invention include: 1) The present invention provides a method for preparing a portable renewable cooling hydrogel composite material. By using hydrogel as a functional unit to adjust the optical properties of traditional polymers and combining it with porous solid particles, the material exhibits a dense and rough surface structure after drying, thereby significantly improving the reflectivity of solar radiation and enhancing the radiative cooling effect of the material. This method has strong innovation in the fields of hydrogel functional materials and passive refrigeration technology and has high research and application value. 2) The portable renewable cooling hydrogel composite material provided by the present invention has the advantage of being portable and can be coated on the surface of different materials for cooling according to actual application needs. Its dense and rough surface structure not only gives it excellent solar reflectivity, but also has high infrared emissivity, which helps to achieve convenient and efficient cooling. 3) The radiative cooling mechanism and the evaporative cooling effect of the hydrogel itself are synergistically integrated in this invention and applied to the field of building roof insulation. Through the synergistic effect of the two mechanisms, the cooling performance is far superior to that of a single cooling mode. At the same time, it provides a new material solution and technical path for the promotion and application of passive cooling systems in the fields of building, transportation and energy. Attached Figure Description

[0010] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0011] Figure 1 This is a SEM image of the portable renewable cooling hydrogel composite material obtained in Example 1 of the present invention; Figure 2 This is a SEM image of the portable renewable cooling hydrogel composite material obtained in Example 2 of the present invention; Figure 3 This is a SEM image of the portable renewable cooling hydrogel composite material obtained in Example 3 of the present invention; Figure 4 This is a SEM image of the portable renewable cooling hydrogel composite material obtained in Example 4 of the present invention; Figure 5 This is a SEM image of the portable renewable cooling hydrogel composite material obtained in Example 5 of the present invention; Figure 6 This is a SEM image of the portable renewable cooling hydrogel composite material obtained in Example 6 of the present invention; Figure 7 This is a SEM image of the portable renewable cooling hydrogel composite material obtained in Example 7 of the present invention; Figure 8 This is a diagram of the experimental setup used in Test Example 1 of the present invention; Figure 9 These are bar charts showing the highest cooling rates in Examples 1-7 and Comparative Examples 1-4 of the present invention. Detailed Implementation

[0012] To overcome the aforementioned problems, the application of natural materials in building insulation has gradually gained attention in recent years. Polymers can react with ionic crosslinking agents to form stable hydrogel structures. These hydrogels not only possess excellent biodegradability but also exhibit outstanding thermal insulation performance. Furthermore, porous solid particles, as lightweight and porous materials, have very low thermal conductivity, thus showing great potential in thermal insulation. Their low density and high surface area enable them to exhibit good thermal insulation performance in architectural coatings, especially in effectively reducing heat transfer at high temperatures. Combining polymers with porous solid particles to form composite materials can further improve the thermal insulation performance of coatings while retaining the environmental advantages of natural materials.

[0013] Given that there are currently no relevant technical solutions in the field of radiative cooling that directly apply hydrogels as functional units to building roof insulation, the inventors, after long-term research and repeated experiments, proposed the design concept and implementation path of this invention. Specifically, this invention uses a polymer hydrogel as a structural framework, disperses porous solid particles in different proportions and introduces them into a polymer hydrogel precursor system, and then achieves gelation through ionic crosslinking to prepare a portable, renewable cooling hydrogel material.

[0014] The following will further explain the technical solution, its implementation process, and its principles. However, it should be understood that within the scope of this invention, the above-mentioned technical features of this invention and the technical features specifically described below (in embodiments) can be combined with each other to form new or preferred technical solutions. Due to space limitations, they will not be described in detail here.

[0015] As one aspect of the technical solution of this invention, a portable renewable cooling hydrogel composite material includes: A three-dimensional network structure formed by cross-linking and curing of polymers and ionic cross-linking agents; Porous solid particles are uniformly distributed in the three-dimensional network structure; And water.

[0016] In some embodiments, the portable renewable cooling hydrogel composite material comprises a homogeneous composite consisting of a three-dimensional network structure of porous solid particles, water, ionic crosslinking agents, and polymers. Specifically, the portable renewable cooling hydrogel is composed of a three-dimensional network formed by polymers, silica particles dispersed in the polymer three-dimensional network, and ionic crosslinking agents.

[0017] In some embodiments, the portable renewable cooling hydrogel composite material has a dense surface structure with uniformly distributed particles, which helps to enhance the diffuse reflection of sunlight, improve the optical reflectivity of the material, and further improve the cooling performance.

[0018] In some embodiments, the portable renewable cooling hydrogel composite material has a solar reflectance of 0.65 to 0.85, an infrared emissivity of 0.20 to 0.70, and an elongation at break of 100% to 400%.

[0019] In some embodiments, based on the total dry weight of the portable renewable cooling hydrogel composite material, the polymer mass fraction is 1.5% to 3%, the porous solid particle mass fraction is 2.5% to 10%, and the ionic crosslinking agent mass fraction is 0.5% to 2%.

[0020] In some embodiments, the polymer may include one or more of sodium alginate, pectin, carrageenan, gelatin, cellulose, and gelatin, but is not limited thereto.

[0021] In some embodiments, the ionic crosslinking agent may include Ca... 2+ Crosslinking agents, Ba-containing 2+ Crosslinking agents, Al-containing 3+ It may be one or more of crosslinking agents, but is not limited to them.

[0022] In some preferred embodiments, the polymer is sodium alginate. Sodium alginate, as a natural polysaccharide, has broad application prospects in environmentally friendly coatings and gel materials due to its good biodegradability, non-toxicity, and biocompatibility. Sodium alginate can react with divalent metal ions (such as Ca²⁺). 2+ The reaction forms a stable hydrogel structure, which not only has excellent biodegradability but also performs well in thermal insulation.

[0023] In some embodiments, the porous solid particles may include one or more of silica particles, montmorillonite, diatomaceous earth, activated carbon microparticles, etc., but are not limited thereto.

[0024] In some preferred embodiments, the porous solid particles have a particle size of 50~100µm.

[0025] In some more preferred embodiments, the porous solid particles have a porosity of 80% to 90% and the pore size of the contained pores is 2 nm to 200 nm.

[0026] In some preferred embodiments, the silica particles comprise hydrophilic or hydrophobic silica aerogels.

[0027] In some embodiments, the contact angle between the portable renewable cooling hydrogel composite material and water is less than 90°.

[0028] In some embodiments, the elastic modulus of the portable renewable cooling hydrogel composite material is 0.03 MPa to 0.80 MPa.

[0029] In some embodiments, the water content of the portable renewable cooling hydrogel composite material is greater than 30 wt%.

[0030] In some embodiments, the portable renewable cooling hydrogel composite material is 5-15°C cooler than the ambient temperature under direct sunlight.

[0031] Furthermore, the portable renewable cooling hydrogel composite material can also be reused through repeated water absorption and loss.

[0032] In some preferred embodiments, the portable renewable cooling hydrogel composite material can undergo five or more cycles of repeated water absorption and loss.

[0033] As another aspect of the technical solution of this invention, it relates to a method for preparing a portable, renewable cooling hydrogel composite material, which includes: Provides a mixed slurry containing polymers, water, and porous solid particles; The mixed slurry is applied to the surface of the substrate to form a coating, and then a solution containing an ionic crosslinking agent is applied to carry out an in-situ crosslinking reaction and curing to obtain a portable, renewable cooling hydrogel composite material.

[0034] In some embodiments, the preparation method specifically includes: dissolving the polymer in water to form a polymer solution, and then mixing the porous solid particles with the polymer solution to obtain a mixed slurry.

[0035] The types of polymers and porous solid particles are as previously defined and will not be repeated here.

[0036] In some preferred embodiments, the mass ratio of the polymer to the porous solid particles is 1.5~3:2.5~10.

[0037] In some preferred embodiments, the polymer solution has a mass fraction of 1.5% to 3%.

[0038] In some preferred embodiments, the porous solid particles are mixed with the polymer solution by one or more of the following methods: magnetic stirring, high-speed mechanical stirring, ultrasonic dispersion, etc., preferably magnetic stirring, and the mixture is thoroughly and evenly mixed; wherein the magnetic stirring speed range is 800~2000 rpm, and the stirring time is 10~30 min.

[0039] In some preferred embodiments, the preparation method further includes: after uniformly mixing the porous solid particles with the polymer solution, a water-retaining agent may be added to the resulting mixed slurry, wherein the water-retaining agent includes, but is not limited to, sodium carboxymethyl cellulose.

[0040] In some embodiments, the mass fraction of the ionic crosslinking agent in the solution containing the ionic crosslinking agent is 0.5% to 2%. Specifically, the solution containing the ionic crosslinking agent is an aqueous solution with a concentration of 0.5% to 2%, and the crosslinking reaction time is controlled at 10 to 30 seconds. Compared to traditional chemical crosslinking agents, it is non-toxic, harmless, and environmentally friendly; based on in-situ crosslinking between ions, it can enhance the mechanical strength of the gel; during the crosslinking process, a denser and continuous three-dimensional network can be formed, improving water retention capacity and extending the cooling time during evaporation and cooling.

[0041] In some embodiments, the preparation method specifically includes: coating the mixed slurry onto the substrate surface to form a coating 0.5~5mm thick, then spraying the solution containing the ionic crosslinking agent, and allowing it to stand.

[0042] In some embodiments, the preparation method specifically includes: sequentially coating the mixed slurry and spraying a solution containing an ionic crosslinking agent by alternating layer-by-layer coating and crosslinking (coating a layer of the mixed slurry to form a thin layer, and lightly spraying the solution containing the ionic crosslinking agent onto the thin layer for crosslinking), repeating the coating and light spraying steps multiple times until the desired thickness is achieved.

[0043] In some preferred embodiments, the coating method includes scraping.

[0044] In some preferred embodiments, the spraying pressure is 0.1 MPa to 0.6 MPa.

[0045] In some preferred embodiments, the method for preparing the portable renewable cooling hydrogel composite material includes: Natural polymers are dissolved in deionized water to prepare a polymer solution with a mass fraction of 1.5% to 3%, which serves as an aqueous solution of natural polymer hydrogel precursor. Porous solid particles are added to a polymer solution and mixed evenly to obtain a mixed slurry; The mixed slurry is coated onto the substrate surface to form a coating of 0.5~5mm thickness. A solution containing an ionic crosslinking agent with a mass fraction of 0.5%~2% is sprayed for in-situ crosslinking. After standing, the portable renewable cooling hydrogel composite material is obtained.

[0046] As another aspect of the technical solution of the present invention, it also relates to a portable renewable cooling hydrogel composite material prepared by the aforementioned preparation method.

[0047] The preparation method provided by this invention can effectively improve the solar reflectivity and infrared emissivity of hydrogel composite materials. The resulting hydrogel also possesses a certain tensile elongation at break and is convenient, readily applicable, and widely applicable for spray crosslinking. Regarding the cooling mechanism, this material achieves a synergistic effect of evaporative cooling and radiative cooling. Applying the portable, renewable cooling hydrogel composite material prepared according to the embodiments of this invention to outdoor environmental testing demonstrates a significant passive cooling effect under passive conditions.

[0048] Furthermore, the portable, renewable cooling hydrogel composite material prepared by this invention can be coated in situ onto rooftops or other solid surfaces without the need for complex equipment. It exhibits excellent light reflectivity and evaporative cooling capabilities, effectively reducing surface temperature under sunlight and maintaining a cool indoor environment. It also demonstrates good biocompatibility, as it can be regenerated by spraying water after drying, enabling repeated use. This material is simple to prepare, inexpensive, portable, and suitable for widespread application.

[0049] Another aspect of this invention provides the application of the portable renewable cooling hydrogel composite material. The excellent mechanical properties of this portable renewable cooling hydrogel enable its application in passive cooling (such as wearable cooling), evaporative cooling, skin rehabilitation (or skin repair), or building thermal management (such as passive building cooling), preferably in the field of building roof insulation, achieving efficient passive cooling applications through the reflection of sunlight and the evaporation of moisture.

[0050] Furthermore, the application includes: coating the portable renewable cooling hydrogel composite material onto the surface of a building roof, achieving passive cooling through the reflection of sunlight and the evaporation of moisture, thereby reducing the temperature by 5~15℃ during sunlight exposure.

[0051] Furthermore, when the portable renewable cooling hydrogel composite material is applied, it achieves passive cooling and refrigeration by relying on the high reflectivity of the hydrogel to sunlight and the high emission of mid-infrared light, combined with the evaporation of the gel moisture, through building roof insulation.

[0052] Furthermore, after the cooling effect of the hydrogel composite material weakens due to high-temperature drying, it is treated with water for 30 to 60 seconds to restore its cooling capacity.

[0053] In summary, this invention provides a simple and low-cost preparation method, successfully constructing a portable, renewable cooling hydrogel composite material with high solar reflectivity and high-to-medium infrared emissivity. This hydrogel composite material achieves a performance breakthrough based on traditional building cooling technologies by combining radiative cooling and evaporative cooling mechanisms, effectively solving the current technical bottlenecks in environmentally friendly building cooling. The hydrogel composite material prepared by this invention is characterized by high elasticity, low density, and easy processing. It can be flexibly prepared into different sizes and shapes according to application requirements. Its dense and rough surface structure endows it with excellent optical properties, possessing both ultra-high solar reflectivity and infrared emissivity. Through the synergistic effect of radiative cooling and evaporative cooling, this invention achieves the first application of this type of hydrogel composite material in the field of building roof insulation, and is suitable for various scenarios, including indoor and outdoor environments. It can significantly reduce the dependence of building cooling on energy and reduce carbon emissions, showing good prospects for widespread application.

[0054] The technical solution of the present invention will be further described in detail below with reference to several preferred embodiments and accompanying drawings. It should be understood that the embodiments are only used to illustrate some specific applications of the present invention, aiming to help understand the core idea of ​​the present invention, and do not constitute a limitation on the scope of protection of the present invention. Equivalent substitutions or modifications made by those skilled in the art based on the content of the present invention without creative effort should all be considered to fall within the scope of protection of the present invention. For experimental conditions not explicitly defined in the embodiments, unless otherwise specified, conventional methods or the instructions for relevant equipment and materials should be used.

[0055] Example 1

[0056] (1) Preparation of aqueous solution of polymer hydrogel precursor: 3g sodium alginate was added to 197ml deionized water and stirred for 1-2h until the sodium alginate was completely dissolved to obtain an aqueous solution of sodium alginate with a mass fraction of 1.5%; (2) Mixing of porous solid particles with sodium alginate solution: 0.5g of hydrophilic silica aerogel particles (Aladdin, type 380, particle size 7~40nm) were added to 20g of sodium alginate aqueous solution and stirred vigorously until uniformly dispersed. The stirring speed was 800rpm and the stirring time was 30min to obtain a mixed slurry. The mass fraction of silica aerogel particles was 2.4%. (3) Preparation of crosslinking agent: Take 1g of anhydrous calcium chloride and add it to 199ml of deionized water. Stir thoroughly to dissolve and obtain calcium chloride aqueous solution with a mass fraction of 0.5%; (4) Preparation of portable renewable cooling hydrogel composite material: The mixed slurry described in step (2) is uniformly coated on the solid surface, and the calcium chloride aqueous solution from step (3) is sprayed on. The mixture is allowed to stand for 10 seconds. This process is repeated three times. The spraying pressure is 0.1 MPa. Characterization shows that the hydrogel composite material is hydrophilic, with a surface contact angle of less than 90°. SEM images are shown below. Figure 1 The physical parameters of the portable renewable cooling hydrogel composite material prepared in this embodiment are shown in Table 1.

[0057] Example 2 (1) Preparation of aqueous solution of polymer hydrogel precursor: 4g of pectin was added to 196ml of deionized water and stirred for 1-2h until the pectin was completely dissolved to obtain a pectin aqueous solution with a pectin mass fraction of 2%; (2) Mixing of porous solid particles with pectin solution: 2.3g of hydrophobic silica aerogel particles (purchased from Shenzhen Yidahui Co., Ltd., with an average particle diameter of 15µm) were added to 20g of pectin aqueous solution and stirred vigorously until evenly dispersed. The stirring speed was 800rpm and the stirring time was 30min to obtain a mixed slurry, wherein the mass fraction of silica particles was 10%. (3) Preparation of crosslinking agent: Take 2g of anhydrous barium chloride and add it to 198ml of deionized water. Stir thoroughly to dissolve and obtain barium chloride aqueous solution. The mass fraction of barium chloride is 1%. (4) Preparation of portable renewable cooling hydrogel composite material: The mixed slurry described in step (2) was uniformly coated on the solid surface, and the barium chloride aqueous solution from step (3) was sprayed on. The mixture was allowed to stand for 20 seconds. The spraying pressure was 0.3 MPa. The above steps were repeated three times. Characterization showed that the hydrogel composite material was hydrophilic, with a surface contact angle of less than 90°. SEM images are shown below. Figure 2 The physical parameters of the portable renewable cooling hydrogel composite material prepared in this embodiment are shown in Table 1.

[0058] Example 3 (1) Preparation of aqueous solution of polymer hydrogel precursor: 4g of carrageenan was added to 196ml of deionized water and stirred for 1-2h until the carrageenan was completely dissolved to obtain an aqueous solution of carrageenan with a mass fraction of 2%; (2) Mixing of porous solid particles with carrageenan solution: 1g of hydrophilic montmorillonite particles were added to 20g of carrageenan aqueous solution and stirred vigorously until evenly dispersed. The stirring speed was 200rpm and the stirring time was 10min to obtain a mixed slurry, wherein the mass fraction of montmorillonite particles was 5%; (3) Preparation of crosslinking agent: Take 4g of anhydrous aluminum chloride and add it to 196ml of deionized water. Stir thoroughly to dissolve and obtain an aqueous solution of aluminum chloride with a mass fraction of 2%. (4) Preparation of portable renewable cooling hydrogel composite material: The mixed slurry described in step (2) was uniformly coated on the solid surface, and the aluminum chloride aqueous solution from step (3) was sprayed on. The mixture was allowed to stand for 30 seconds. The spraying pressure was 0.6 MPa. The above steps were repeated three times. Characterization showed that the hydrogel composite material was hydrophilic, with a surface contact angle of less than 90°. SEM images are shown below. Figure 3 The physical parameters of the portable renewable cooling hydrogel composite material prepared in this embodiment are shown in Table 1.

[0059] Example 4 (1) Preparation of aqueous solution of polymer hydrogel precursor: 4g of gelatin was added to 196ml of deionized water and stirred for 1-2h until the gelatin was completely dissolved to obtain an aqueous solution of gelatin with a mass fraction of 2%; (2) Mixing of porous solid particles with gelatin solution: 1.5g of hydrophilic diatomaceous earth particles were added to 20g of gelatin aqueous solution and stirred vigorously until evenly dispersed. The stirring speed was 800rpm and the stirring time was 30min to obtain a mixed slurry, wherein the mass fraction of hydrophilic diatomaceous earth particles was 7%; (3) Preparation of crosslinking agent: Take 2g of anhydrous calcium chloride and add it to 198ml of deionized water. Stir thoroughly to dissolve and obtain calcium chloride aqueous solution. The mass fraction of calcium chloride is 1%. (4) Preparation of portable renewable cooling hydrogel composite material: The mixed slurry described in step (2) was uniformly coated on the solid surface, and the calcium chloride aqueous solution from step (3) was sprayed on. The mixture was allowed to stand for 20 seconds. The spraying pressure was 0.2 MPa. The above steps were repeated three times. Characterization showed that the hydrogel composite material was hydrophilic, with a surface contact angle of less than 90°. SEM images are shown below. Figure 4 The physical parameters of the portable renewable cooling hydrogel composite material prepared in this embodiment are shown in Table 1.

[0060] Example 5 (1) Preparation of aqueous solution of polymer hydrogel precursor: Take 4g of cellulose (methylcellulose supplied by TCI (Shanghai) Chemical Industry Development Co., Ltd., with a viscosity of 7000~10000 mPa·s) and add it to 196ml of deionized water. Stir for 1~2h until the cellulose is completely dissolved to obtain an aqueous solution of cellulose with a mass fraction of 2%. (2) Mixing of porous solid particles with cellulose solution: 2g of hydrophilic activated carbon particles were added to 20g of cellulose aqueous solution and stirred vigorously until evenly dispersed. The stirring speed was 2000rpm and the stirring time was 10min to obtain a mixed slurry, wherein the mass fraction of hydrophilic activated carbon particles was 9%; (3) Preparation of crosslinking agent: Take 2g of anhydrous barium chloride and add it to 198ml of deionized water. Stir thoroughly to dissolve and obtain barium chloride aqueous solution. The mass fraction of barium chloride is 1%. (4) Preparation of portable renewable cooling hydrogel composite material: The mixed slurry described in step (2) above is uniformly coated on the solid surface, and the barium chloride aqueous solution in step (3) is sprayed on, and left to stand for 20 seconds. The spraying pressure is 0.2 MPa. The above steps are repeated three times. Characterization shows that the hydrogel composite material is hydrophilic, with a surface contact angle of less than 90°. SEM images are shown below. Figure 5 The physical parameters of the portable renewable cooling hydrogel composite material prepared in this embodiment are shown in Table 1.

[0061] Example 6 (1) Preparation of aqueous solution of polymer hydrogel precursor: Take 4g of gelatin and add it to 196ml of deionized water. Stir for 1~2h until the gelatin is completely dissolved to obtain an aqueous solution of gelatin with a mass fraction of 2%; (2) Mixing of porous solid particles with gelatin solution: 1.5g of hydrophilic silica aerogel particles (purchased from Aladdin, type 380, particle size 7~40 nm) and 0.2g of hydrophobic silica aerogel particles (purchased from Shenzhen Yidahui Co., Ltd., average particle diameter 15µm) were added to 20g of gelatin aqueous solution and stirred vigorously until evenly dispersed. The stirring speed was 800 rpm and the stirring time was 30 min to obtain a mixed slurry, wherein the mass fraction of hydrophilic silica aerogel particles and hydrophobic silica aerogel particles was 8%; (3) Preparation of crosslinking agent: Take 2g of anhydrous aluminum chloride and add it to 198ml of deionized water. Stir thoroughly to dissolve and obtain an aqueous solution of aluminum chloride. The mass fraction of aluminum chloride is 1%. (4) Preparation of portable renewable cooling hydrogel composite material: The mixed slurry described in step (2) was uniformly coated on the solid surface, and the aluminum chloride aqueous solution from step (3) was sprayed on. The mixture was allowed to stand for 20 seconds. The spraying pressure was 0.4 MPa. The above steps were repeated three times. Characterization showed that the hydrogel composite material was hydrophilic, with a surface contact angle of less than 90°. SEM images are shown below. Figure 6 The physical parameters of the portable renewable cooling hydrogel composite material prepared in this embodiment are shown in Table 1.

[0062] Example 7 (1) Preparation of aqueous solution of polymer hydrogel precursor: 6g sodium alginate was added to 194ml deionized water and stirred for 1-2h until sodium alginate was completely dissolved to obtain sodium alginate aqueous solution with a mass fraction of 3%; (2) Preparation of water-retaining agent: Take 2 grams of sodium carboxymethyl cellulose, add it to 198 ml of deionized water, and stir until the sodium carboxymethyl cellulose is completely dissolved; (3) Mixing water-retaining agent with sodium alginate solution: Take 50g of sodium alginate aqueous solution from step (1) above and 50g of the solution obtained in step (2) above, and mix them evenly; (4) Mixing of porous solid particles with the solution obtained in step (3): 1.5g of hydrophilic silica aerogel particles (purchased from Aladdin, type 380, particle size 7~40nm) and 0.2g of hydrophobic silica aerogel particles (purchased from Shenzhen Yidahui Co., Ltd., average particle diameter 15µm) were added to 20g of the solution obtained in step (3), and stirred vigorously until evenly dispersed. The stirring speed was 2000rpm and the stirring time was 10min to obtain a mixed slurry, wherein the mass fraction of hydrophilic silica aerogel particles and hydrophobic silica aerogel particles was 9%; (5) Preparation of crosslinking agent: Take 2g of anhydrous calcium chloride and add it to 198ml of deionized water. Stir thoroughly to dissolve and obtain calcium chloride aqueous solution. The mass fraction of calcium chloride is 1%. (6) Preparation of portable renewable cooling hydrogel composite material: The mixed slurry described in step (4) above is uniformly coated on the solid surface, and the calcium chloride aqueous solution in step (5) is sprayed on, and left to stand for 20 seconds. The spraying pressure is 0.3 MPa. The above steps are repeated three times. Characterization shows that the hydrogel composite material is hydrophilic, with a surface contact angle of less than 90°. SEM images are shown below. Figure 7 The physical parameters of the portable renewable cooling hydrogel composite material prepared in this embodiment are shown in Table 1.

[0063] Test Example 1

[0064] The inventors of this case also conducted performance tests on the hydrogels obtained in the above embodiments.

[0065] Figure 8 A diagram of the experimental setup used in the test is shown. Figure 9 The bar charts showing the highest temperature drop of Examples 1-7 and Comparative Examples 1-4 are shown.

[0066] Table 1. Physical property parameters of portable renewable cooling hydrogel composite materials obtained in Examples 1-7 project Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Modulus (MPa) 0.030 0.068 0.202 0.266 0.136 0.528 0.800 Elongation at break 120% 230% 380% 310% 180% 100% 400% Reflectivity (%) 0.65 0.68 0.66 0.70 0.72 0.74 0.85 Emission rate (%) 0.22 0.68 0.55 0.32 0.27 0.35 0.61 Moisture content (%) 96 88 95 90 88 90 90 Compare with Example 1 (1) Preparation of aqueous solution of polymer hydrogel precursor: 0.2g sodium alginate was added to 198ml deionized water and stirred for 1-2h until the sodium alginate was completely dissolved to obtain an aqueous solution of sodium alginate with a mass fraction of 0.2%; (2) Mixing of porous solid particles with sodium alginate solution: Add 1.5g of hydrophilic silica aerogel particles to 20g of the solution obtained in step (1), stir vigorously until evenly dispersed, stir at 800 rpm for 30 min to obtain a mixed slurry; (3) Preparation of crosslinking agent: Take 2g of anhydrous calcium chloride, add it to 198ml of deionized water, stir thoroughly to dissolve, and obtain calcium chloride aqueous solution; (4) Preparation of portable renewable cooling hydrogel: The mixed slurry described in step (2) is uniformly coated on the solid surface, the crosslinking agent described in (3) is sprayed on, and left to stand for a few seconds. Repeat the above steps three times.

[0067] In this comparative example, the mass fraction of sodium alginate is 0.2%, which is lower than the concentration of polymer in Example 1. The low concentration will result in insufficient cross-linking points, making it difficult to gel completely, leading to sample structure collapse or local gelation, which will affect the evaporation rate and result in insufficient continuous cooling effect.

[0068] Compare with Example 2 (1) Preparation of aqueous solution of natural polymer hydrogel precursor: Take 8g of pectin and add it to 192ml of deionized water. Stir for 1-2h until the pectin is completely dissolved to obtain a pectin aqueous solution with a pectin mass fraction of 4%. (2) Mixing of porous solid particles with pectin solution: Add 1.5g of hydrophilic montmorillonite particles and 0.2g of hydrophobic montmorillonite particles to 20g of the solution obtained in step (1), stir vigorously until evenly dispersed, the stirring speed is 1000rpm, the stirring time is 10min, and a mixed slurry is obtained. (3) Preparation of crosslinking agent: Take 2g of anhydrous barium chloride, add it to 198ml of deionized water, stir thoroughly to dissolve, and obtain barium chloride aqueous solution; (4) Preparation of portable renewable cooling hydrogel: The mixed slurry described in step (2) is uniformly coated on the solid surface, the crosslinking agent described in (3) is sprayed on, and left to stand for 20 seconds. Repeat the above steps three times.

[0069] In this comparative example, the pectin mass fraction is 4%, which is higher than the polymer concentration in Example 2. The high concentration leads to a denser cross-linked network and smaller pore structure, resulting in greater resistance to water migration, limited sample evaporation, and insufficient cooling effect.

[0070] Compare with Example 3 (1) Preparation of aqueous solution of natural polymer hydrogel precursor: 4g of carrageenan was added to 196ml of deionized water and stirred for 1-2h until the carrageenan was completely dissolved to obtain an aqueous solution of carrageenan with a mass fraction of 2%; (2) Preparation of crosslinking agent: Take 2g of anhydrous aluminum chloride, add it to 198ml of deionized water, stir thoroughly to dissolve, and obtain an aqueous solution of aluminum chloride; (3) Preparation of portable renewable cooling hydrogel: The carrageenan aqueous solution described in step (1) is uniformly coated on the solid surface, the crosslinking agent described in step (2) is sprayed on, and left to stand for 10 seconds. Repeat the above steps three times.

[0071] Compare with Example 4 (1) Preparation of aqueous solution of natural polymer hydrogel precursor: Take 2g of gelatin and add it to 198ml of deionized water. Stir for 1-2 hours until the gelatin is completely dissolved to obtain a gelatin aqueous solution with a mass fraction of 1%; (2) Preparation of crosslinking agent: Take 2g of anhydrous calcium chloride, add it to 198ml of deionized water, stir thoroughly to dissolve, and obtain calcium chloride aqueous solution; (3) Preparation of portable renewable cooling hydrogel: The gelatin aqueous solution described in step (1) is uniformly coated on the solid surface, the crosslinking agent described in step (2) is sprayed on, and left to stand for 20 seconds. Repeat the above steps three times.

[0072] Compared to the above embodiments, Comparative Examples 3 and 4 did not include porous solid particles, resulting in samples with excessively high transparency and a lack of diffuse reflection capability of sunlight. This reduced the optical reflectivity of the material and further affected the cooling performance, resulting in insufficient cooling effect.

[0073] In addition, the inventors of this case also conducted relevant experiments based on the aforementioned embodiments, referring to other raw materials, process steps and process conditions described in this specification, and all of them achieved relatively ideal results.

[0074] It should be noted that the above embodiments are only used to illustrate the technical concept and main features of the present invention, and are intended to enable those skilled in the art to understand and implement the present invention. They do not constitute a limitation on the scope of protection of the present invention. All equivalent substitutions, improvements or modifications made within the basic concept and essential spirit of the present invention should be considered to fall within the scope of protection of the present invention.

Claims

1. A portable, renewable cooling hydrogel composite material, characterized in that, include: A three-dimensional network structure formed by cross-linking and curing of polymers and ionic cross-linking agents; Porous solid particles are uniformly distributed in the three-dimensional network structure; And water; The portable renewable cooling hydrogel composite material has a dense surface structure, and its solar reflectance is 0.65~0.85, infrared emissivity is 0.20~0.70, and elongation at break is 100%~400%.

2. The portable renewable cooling hydrogel composite material according to claim 1, characterized in that: Based on the total dry weight of the portable renewable cooling hydrogel composite material, the mass fraction of polymer is 1.5%~3%, the mass fraction of porous solid particles is 2.5%~10%, and the mass fraction of ionic crosslinking agent is 0.5%~2%. And / or, the portable renewable cooling hydrogel composite material comprises a homogeneous composite consisting of a three-dimensional network structure of porous solid particles, water, ionic crosslinking agents and polymers.

3. The portable renewable cooling hydrogel composite material according to claim 1, characterized in that: The polymer includes one or more of sodium alginate, pectin, carrageenan, gelatin, cellulose, and gelatin. And / or, the ionic crosslinking agent includes Ca-containing... 2+ Crosslinking agents, Ba-containing 2+ Crosslinking agents, Al-containing 3+ One or more combinations of crosslinking agents; And / or, the porous solid particles include one or more combinations of silica particles, montmorillonite, diatomaceous earth, and activated carbon particles; Preferably, the porous solid particles have a particle size of 50~100µm; Preferably, the porous solid particles have a porosity of 80% to 90% and the pore size of the contained pores is 2 nm to 200 nm; Preferably, the silica particles comprise hydrophilic or hydrophobic silica aerogels.

4. The portable renewable cooling hydrogel composite material according to claim 1, characterized in that: The portable renewable cooling hydrogel composite material has a contact angle with water of less than 90°; And / or, the elastic modulus of the portable renewable cooling hydrogel composite material is 0.03 MPa to 0.80 MPa; And / or, the water content of the portable renewable cooling hydrogel composite material is greater than 30 wt%; And / or, the portable renewable cooling hydrogel composite material is 5-15°C cooler than the ambient temperature under direct sunlight.

5. The method for preparing the portable renewable cooling hydrogel composite material according to any one of claims 1 to 4, characterized in that, include: Provides a mixed slurry containing polymers, water, and porous solid particles; The mixed slurry is applied to the surface of the substrate to form a coating, and then a solution containing an ionic crosslinking agent is applied to carry out an in-situ crosslinking reaction and curing to obtain a portable, renewable cooling hydrogel composite material.

6. The preparation method according to claim 5, characterized in that, include: The polymer is dissolved in water to form a polymer solution, and then the porous solid particles are mixed evenly with the polymer solution to obtain a mixed slurry. Preferably, the polymer solution has a mass fraction of 1.5% to 3%; Preferably, the mass ratio of the polymer to the porous solid particles is 1.5~3:2.5~10; Preferably, the method of mixing the porous solid particles with the polymer solution includes one or more combinations of magnetic stirring, high-speed mechanical stirring, and ultrasonic dispersion, and is particularly preferred to be magnetic stirring, wherein the magnetic stirring speed is 800~2000 rpm and the time is 10~30 min; Preferably, the preparation method further includes adding a water-retaining agent to the mixed slurry, and more preferably, the water-retaining agent includes sodium carboxymethyl cellulose.

7. The preparation method according to claim 5, characterized in that: The solution containing the ionic crosslinking agent has a mass fraction of 0.5% to 2% for the ionic crosslinking agent. And / or, the preparation method includes: coating the mixed slurry onto the substrate surface to form a coating 0.5~5mm thick, then spraying the solution containing the ionic crosslinking agent, and allowing it to stand.

8. The preparation method according to claim 7, characterized in that: include: The mixture is coated and sprayed with a solution containing an ionic crosslinking agent in sequence using an alternating layer-by-layer coating method. The coating and light spraying steps are repeated multiple times until the required thickness is achieved. And / or, the coating method includes scraping; And / or, the spraying pressure is 0.1 MPa to 0.6 MPa; And / or, the crosslinking reaction takes 10s to 30s.

9. The application of the portable renewable cooling hydrogel composite material according to any one of claims 1 to 4 in the fields of passive refrigeration, evaporative cooling, skin rehabilitation or building thermal management, preferably in the field of building roof insulation.

10. The application according to claim 9, characterized in that, include: The portable renewable cooling hydrogel composite material is coated on the surface of a building roof. Through the reflection of sunlight and the evaporation of water, passive cooling is achieved, resulting in a temperature reduction of 5~15℃ during sunlight.

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