Hydrogel preparation method with adjustable phase change temperature and hydrogel

Abstract

The invention belongs to the technical field of hydrogel materials, and relates to a phase change temperature adjustable hydrogel preparation method and a hydrogel, the method comprises the following steps: adding a polymer gel matrix into preheated deionized water, and fully stirring to form a uniform polymer solution; based on the preset phase change temperature of the target hydrogel material, the mass ratio of the sugar alcohol phase change substance to the polymer gel matrix is determined, and the mass ratio of the sugar alcohol phase change substance to the polymer gel matrix and the phase change temperature of the hydrogel material are in a continuous corresponding relation; adding a sugar alcohol phase change substance into the polymer solution according to a mass ratio, and stirring under a water bath condition to form a composite solution; injecting the composite solution into a mold, and vacuumizing to a target vacuum degree in stages to form a degassed gel precursor; standing and curing the gel precursor in a constant-temperature and constant-humidity environment to form an initial hydrogel material; the initial hydrogel material is subjected to freezing-unfreezing circulation treatment at a preset rate, and the target hydrogel material is obtained.

Description

Technical Field

[0001] The present application relates to the technical field of hydrogel materials, and in particular to a method for preparing a hydrogel with adjustable phase transition temperature and a hydrogel. Background Art

[0002] Cold storage materials are critical in many fields. Traditional materials (ice, dry ice, and saline solutions) have limitations: ice and dry ice undergo irreversible morphological changes during phase change, which can easily contaminate packaging and damage the structure, and the phase change temperature is fixed; although the saline solution can adjust the phase change temperature, it has poor stability and packaging problems. As a new type of cold storage material, hydrogel combines a unique physical structure with the energy storage characteristics of phase change materials. Its three-dimensional network can encapsulate phase change materials, and it remains solid during phase change without phase separation. It is stable in shape and leak-proof. It does not require high-strength packaging, is lightweight and portable, and can precisely control the phase change temperature.

[0003] However, although hydrogel cold storage materials improve the phase change stability by encapsulating phase change materials in a three-dimensional network, the existing technology still faces core defects such as poor mechanical properties (low toughness, insufficient tensile strength), limited phase change temperature adjustment range, and inability to synergistically optimize phase change and mechanical properties.

[0004] In summary, existing hydrogel materials have obvious defects in terms of limited phase change temperature control range and insufficient mechanical properties, making it difficult to meet the diverse performance and application requirements of cold storage materials in high-load scenarios. Summary of the invention

[0005] The embodiments of the present invention provide a method for preparing a hydrogel with adjustable phase transition temperature and a hydrogel, which at least solve the problems of limited phase transition temperature control range, insufficient mechanical properties and complex preparation process of existing hydrogel materials in the related art.

[0006] According to a first aspect of an embodiment of the present invention, there is provided a method for preparing a hydrogel with adjustable phase transition temperature, comprising:

[0007] Add the polymer gel matrix into preheated deionized water and stir thoroughly to form a uniform polymer solution;

[0008] Based on the preset phase transition temperature of the target hydrogel material, determining the mass ratio of the sugar alcohol phase change material to the polymer gel matrix, wherein the mass ratio of the sugar alcohol phase change material to the polymer gel matrix is ​​in a continuous corresponding relationship with the phase transition temperature of the hydrogel material;

[0009] Adding the sugar alcohol phase change material into the polymer solution according to the mass ratio, and stirring in a water bath to form a composite solution;

[0010] injecting the composite solution into a mold, and evacuating the mold in stages to a target vacuum degree to form a degassed gel precursor;

[0011] The gel precursor is allowed to stand and solidify in a constant temperature and humidity environment to form an initial hydrogel material;

[0012] The initial hydrogel material is subjected to a freeze-thaw cycle treatment at a predetermined rate to obtain the target hydrogel material.

[0013] According to an embodiment of the present invention, the polymer gel matrix is ​​one or more of carrageenan, gelatin, agarose, polyvinyl alcohol, sodium alginate, xanthan gum, guar gum or chitosan.

[0014] According to an embodiment of the present invention, the sugar alcohol phase change material is one or more of glucose, sucrose, trehalose, fructose, glycerol, propylene glycol, ethylene glycol or sorbitol.

[0015] According to an embodiment of the present invention, the mass fraction of the polymer gel matrix is ​​5% to 20%, and the preheating temperature of the deionized water is 40° C. to 85° C.;

[0016] The polymer gel matrix is ​​added into the preheated deionized water and stirred sufficiently to form a uniform polymer solution at a stirring speed of 500 rpm to 800 rpm and a stirring time of 1 to 2 hours.

[0017] According to an embodiment of the present invention, the mass fraction of the sugar alcohol phase change material is 1% to 30%, and the mass ratio of the sugar alcohol phase change material to the polymer gel matrix is ​​1 to 30:5 to 20.

[0018] According to an embodiment of the present invention, when the sugar alcohol phase change material is added to the polymer solution in the mass ratio and stirred in a water bath to form a composite solution, the water bath conditions are 25°C to 40°C, the stirring speed is 500rpm to 800rpm, and the stirring time is 1 hour to 2 hours.

[0019] According to an embodiment of the present invention, the target vacuum degree is a vacuum degree less than or equal to 10Pa;

[0020] The composite solution is injected into a mold, and vacuumed to a target vacuum degree in stages to form a degassed gel precursor, comprising:

[0021] First, the pressure in the mold is reduced to 100 Pa by means of rapid vacuuming, and then the vacuum degree of the mold is brought to the target vacuum degree by means of slow pressure reduction.

[0022] According to an embodiment of the present invention, the constant temperature and humidity environment is 25° C. and 50% RH, and the static curing time is 24 hours.

[0023] According to an embodiment of the present invention, the number of freeze-thaw cycles is 3 to 5 times;

[0024] The step of subjecting the initial hydrogel material to freeze-thaw cycles at a predetermined rate to obtain the target hydrogel material includes:

[0025] Cooling the initial hydrogel material to -20°C at a rate of 0.5°C / min to 3°C / min and holding for 12 hours;

[0026] Heating the initial hydrogel material to 25°C at a rate of 0.5°C / min and holding for 12 hours.

[0027] According to a first aspect of an embodiment of the present invention, there is provided a hydrogel material, which is prepared by the method for preparing a hydrogel with adjustable phase transition temperature according to the first aspect.

[0028] Advantages of the embodiments of the present invention:

[0029] The method for preparing a hydrogel with adjustable phase transition temperature provided by the embodiments of the present invention can improve the comprehensive performance of the hydrogel while simplifying the preparation process. Specifically, first, by compounding a polymer gel matrix and a sugar alcohol-based phase change substance according to a preset mass ratio, precise control of the phase transition temperature in the range of -30°C to 0°C can be achieved, solving the defect that the phase transition temperature of traditional cold storage materials is fixed or non-adjustable; second, the staged vacuum pumping process can effectively eliminate the bubbles in the composite solution, and combined with static curing in a constant temperature and humidity environment, it ensures the uniformity and stability of the gel network structure, avoiding the decline in mechanical properties caused by internal defects; finally, through freeze-thaw cycles at a specific rate, promoting gel network reorganization and phase change substance crystallization can improve the mechanical properties of the material, enabling it to withstand repeated extrusion deformation during cold chain transportation. In addition, sugar alcohol substances have both phase change regulation and toughening functions, and in cooperation with the freeze-thaw process, while ensuring high phase change latent heat, the strengthening and toughening of the material and the optimization of the phase change performance are realized, overcoming the technical bottlenecks of traditional hydrogel cold storage materials such as easy cracking, phase separation, and supercooling phenomenon.

[0030] Details of one or more embodiments of the present invention are set forth in the following drawings and description to make other features, objects, and advantages of the present invention more comprehensible. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention, and those of ordinary skill in the art can also obtain other embodiments based on these drawings without creative efforts.

[0032] Figure 1 It is a flowchart of a preparation method of a hydrogel with adjustable phase transition temperature provided by an embodiment of the present invention.

[0033] Figure 2 It is a schematic diagram of the relationship between the phase transition temperature and the mass ratio of sugar alcohol phase change substances and polymer gel matrix provided by an embodiment of the present invention.

[0034] Figure 3 It is a schematic diagram of the performance test results of differential scanning calorimetry for Example 1 provided by an embodiment of the present invention.

[0035] Figure 4 It is a schematic diagram of the performance test results of differential scanning calorimetry for Example 2 provided by an embodiment of the present invention.

[0036] Figure 5 It is a schematic diagram of the mechanical property test results of Example 1 and Example 2 provided by an embodiment of the present invention. Detailed implementation manners

[0037] The embodiments of the present embodiment will be described in more detail below with reference to the accompanying drawings. Although some embodiments of the present embodiment are shown in the drawings, it should be understood that the present embodiment can be implemented in various forms and should not be construed as limited to the embodiments described herein. On the contrary, these embodiments are provided to more thoroughly and completely understand the present embodiment. It should be understood that the drawings and embodiments of the present embodiment are only for exemplary purposes and are not used to limit the protection scope of the present embodiment.

[0038] In the field of phase change energy storage materials, cold storage materials have attracted much attention due to their key role in scenarios such as cold chain transportation, medical cold storage, and electronic heat dissipation. Traditional cold storage materials such as ice, dry ice, and brine solutions have certain cold storage capabilities, but they have significant defects: the phase transition temperatures of ice and dry ice are fixed and cannot adapt to different temperature control requirements, and there are morphological changes during the phase transition process, which easily lead to packaging pollution or structural damage; although brine solution-based phase change materials can adjust the phase transition temperature by adjusting the solute ratio, they generally have supercooling phenomena and phase separation problems, and rely on high-strength encapsulation to prevent leakage, resulting in a decrease in cold storage density and a significant increase in cost. In recent years, hydrogel cold storage materials have become a research hotspot because their three-dimensional network structure can encapsulate phase change substances and maintain solid-state phase change characteristics, but the existing technology still faces severe challenges. Although the existing gel cold storage agents have improved the phase transition stability, they have not solved the core problem of poor mechanical properties of hydrogels - conventional hydrogels have low toughness and are easy to break, and cannot withstand repeated extrusion deformation during cold chain transportation, which severely restricts their practical applications. In addition, the existing technology has a limited phase transition temperature adjustment range, and there is a lack of effective means for synergistically optimizing the strengthening and phase change performance of materials, resulting in the difficulty of hydrogel cold storage materials to meet the requirements of high-load scenarios in terms of comprehensive performance.

[0039] In order to solve the problems of limited temperature control range, insufficient mechanical properties and complex preparation process of hydrogel materials in the prior art, the embodiments of the present invention optimize the composite process of polymer matrix and phase change material and freeze-thaw cycle treatment to achieve synergistic improvement of material toughening and phase change performance.

[0040] Figure 1 The present invention provides a flow chart of a method for preparing a hydrogel with adjustable phase transition temperature. Figure 1 As shown, the method includes the following steps.

[0041] Step S101, adding a polymer gel matrix into preheated deionized water, and stirring thoroughly to form a uniform polymer solution.

[0042] Step S102, based on the preset phase transition temperature of the target hydrogel material, the mass ratio of the sugar alcohol phase transition material to the polymer gel matrix is ​​determined, and the mass ratio of the sugar alcohol phase transition material to the polymer gel matrix is ​​in a continuous corresponding relationship with the phase transition temperature of the hydrogel material.

[0043] Step S103, adding the sugar alcohol phase change material into the polymer solution according to the mass ratio, and stirring in a water bath to form a composite solution.

[0044] Step S104, injecting the composite solution into the mold, and evacuating the mold in stages to a target vacuum degree to form a degassed gel precursor.

[0045] Step S105 , curing the gel precursor in a constant temperature and humidity environment to form an initial hydrogel material.

[0046] Step S106, subjecting the initial hydrogel material to a freeze-thaw cycle at a predetermined rate to obtain a target hydrogel material.

[0047] First, the polymer gel matrix is ​​added into preheated deionized water and stirred thoroughly to form a uniform polymer solution.

[0048] In this embodiment, before preparing the polymer solution, it is necessary to prepare the polymer gel matrix and preheat the deionized water.

[0049] When preparing the polymer gel matrix, one or more polymer gel matrices can be selected, such as carrageenan, gelatin, agarose, polyvinyl alcohol, sodium alginate, xanthan gum, guar gum or chitosan. These polymer materials have good gelling properties and biocompatibility and can form a three-dimensional network structure.

[0050] When preheating deionized water, the deionized water can be heated to 40°C to 85°C. The purpose of preheating the deionized water in this embodiment is to improve the dissolution rate and effect of the polymer gel matrix. Within the temperature range of 40°C to 85°C, the polymer gel matrix can dissolve rapidly to form a uniform solution. If the water temperature is too low, the dissolution rate of the polymer gel matrix will slow down, and incomplete dissolution may even occur, resulting in undissolved particles in the solution, which will affect the performance of the subsequent hydrogel. While if the water temperature is too high, it may damage the structure and performance of the polymer gel matrix. For example, it may cause partial degradation or denaturation of some polymer gel matrix, thus affecting its gel-forming performance and the encapsulation effect on the phase change material. Therefore, choosing a preheating temperature of 40°C to 85°C can not only ensure the full dissolution of the polymer gel matrix but also avoid damage to its structure and performance.

[0051] After preparing the polymer gel matrix and completing the preheating of the deionized water, the polymer gel matrix can be slowly added to the preheated deionized water. Slowly adding can prevent the polymer gel matrix from forming aggregates in water and ensure its uniform dispersion.

[0052] In this embodiment, the mass fraction of the polymer gel matrix is 5% to 20%. Here, the mass fraction of the polymer gel matrix refers to the percentage of the mass of the polymer gel matrix in the total mass of the entire preparation system. The polymer gel matrix is the basis for forming the three-dimensional network structure of the hydrogel. Reasonable control of its mass fraction is crucial for the performance of the hydrogel. When the mass fraction of the polymer gel matrix is lower than 5%, the formed network structure is relatively sparse, resulting in insufficient mechanical strength of the hydrogel, which is prone to cracking or deformation and cannot effectively encapsulate the phase change material, affecting the cold storage effect. While when the mass fraction is higher than 20%, the viscosity of the mixture is too large, which is not conducive to the uniform dispersion of the phase change material and subsequent processing operations, and will also increase the cost. Therefore, controlling the mass fraction of the polymer gel matrix at 5% to 20% can ensure good mechanical strength and encapsulation performance of the hydrogel while taking into account the feasibility and economy of processing.

[0053] Use a stirrer to stir at a speed of 500 rpm to 800 rpm for 1 hour to 2 hours until a uniform polymer solution is formed. The stirring process is to fully disperse and dissolve the polymer gel matrix in deionized water to form a uniform polymer solution. If the stirring speed is too low, it will lead to uneven dispersion of the polymer gel matrix, slow dissolution speed, and even local agglomeration may occur, affecting the uniformity of the solution and the performance of the subsequent hydrogel. While if the stirring speed is too high, it may introduce too many bubbles, resulting in bubble defects in the solution, affecting the mechanical strength and thermal conductivity of the hydrogel. When the stirring time is insufficient, the polymer gel matrix may not be completely dissolved, and there are undissolved particles in the solution; if the stirring time is too long, it will increase energy consumption and have limited effect on improving the solution quality. Therefore, controlling the stirring speed at 500 rpm to 800 rpm and the stirring time at 1 hour to 2 hours can avoid unnecessary energy waste and the generation of defects on the premise of ensuring the full dissolution of the polymer gel matrix and the uniformity of the solution.

[0054] In practical applications, the step of preparing the polymer solution is the basis of the entire preparation process. After the polymer gel matrix is dissolved in preheated deionized water, a matrix with a three-dimensional network structure is formed, providing a basis for the subsequent encapsulation of the phase change material and the formation of the hydrogel. The control of the stirring speed and time is to ensure the full dissolution of the polymer gel matrix and avoid the presence of undissolved particles in the solution, which may affect the progress of the subsequent steps and the performance of the final hydrogel.

[0055] After the polymer solution is prepared, the mass ratio of the sugar alcohol-based phase change material to the polymer gel matrix can be determined based on the preset phase change temperature of the target hydrogel material. Among them, the mass ratio of the sugar alcohol-based phase change material to the polymer gel matrix has a continuous corresponding relationship with the phase change temperature of the hydrogel material.

[0056] In this embodiment, the preset phase change temperature of the target hydrogel material can be determined according to the application scenario and requirements of the target hydrogel material. For example, for the packaging and transportation of some temperature-sensitive products, it may be required that the hydrogel material undergoes a phase change at about -10°C.

[0057] The corresponding mass ratio can be determined according to the pre-established relationship between the phase change temperature and the mass ratio of the sugar alcohol-based phase change material and the polymer gel matrix. For example, when the preset phase change temperature is -30°C, the mass ratio of the sugar alcohol-based phase change material to the polymer gel matrix is 6:1.

[0058] Figure 2 It is a schematic diagram of the relationship between the phase change temperature, the sugar alcohol-based phase change material, and the mass ratio of the polymer gel matrix provided by the embodiment of the present invention.

[0059] As Figure 2As shown in the figure, the horizontal axis in the figure represents the mass ratio of the sugar alcohol-based phase change substance to the polymer gel matrix, and the vertical axis represents the corresponding phase change temperature. By adjusting this mass ratio, the phase change temperature of the hydrogel can be precisely controlled within the range of -30°C to 0°C. For example, when the mass ratio is 6:1, the phase change temperature is relatively low; when the mass ratio is 1:20, the phase change temperature is relatively high. This relationship provides a theoretical basis for preparing hydrogel materials with specific phase change temperatures.

[0060] Optionally, the mass fraction of the sugar alcohol-based phase change substance is 1% to 30%. The mass fraction of the sugar alcohol-based phase change substance refers to the percentage of the mass of the sugar alcohol-based phase change substance in the total mass of the entire preparation system. The sugar alcohol-based phase change substance is the main energy storage component of the hydrogel cold storage material, and the reasonable control of its mass fraction is crucial for the cold storage performance of the hydrogel. When the mass fraction of the sugar alcohol-based phase change substance is less than 1%, the phase change temperature of the hydrogel is relatively high, unable to meet the requirements for cold storage performance in application scenarios such as cold chain transportation. When the mass fraction is higher than 30%, there is too much sugar alcohol-based phase change substance, which may lead to uneven dispersion in the polymer matrix, affecting the mechanical properties and stability of the hydrogel, and also increasing costs. Therefore, controlling the mass fraction of the sugar alcohol-based phase change substance within 1% to 30% can ensure that the phase change temperature of the hydrogel is adjustable, with good cold storage performance, while taking into account its mechanical properties and economy.

[0061] The mass ratio of the sugar alcohol-based phase change substance to the polymer gel matrix can be 1 to 30:5 to 20. The mass ratio of the sugar alcohol-based phase change substance to the polymer gel matrix directly affects the phase change temperature and mechanical properties of the hydrogel. By adjusting this mass ratio, the phase change temperature of the hydrogel can be precisely controlled within the range of -30°C to 0°C to meet the requirements of different application scenarios. For example, when the mass ratio of the sugar alcohol-based phase change substance to the polymer gel matrix is 6:1, the phase change temperature is relatively low; when the mass ratio is 1:20, the phase change temperature is relatively high. At the same time, the polymer gel matrix can provide a stable three-dimensional network structure for the sugar alcohol-based phase change substance, preventing its leakage and improving the shape stability and mechanical strength of the hydrogel. Within the range of 1 to 30:5 to 20 for the mass ratio, it can ensure that the hydrogel has good phase change temperature regulation performance and sufficient mechanical strength and stability, enabling it to withstand repeated deformation and pressure in application scenarios such as cold chain transportation.

[0062] In this embodiment, the sugar alcohol-based phase change material can improve the elongation at break of the material. By adjusting the concentration of the sugar alcohol-based phase change material, not only can the phase change temperature of the material be regulated, but also the hydrogel can have stronger toughness and anti-deformation ability while maintaining good cold storage performance. This synergistic optimization of phase change temperature regulation and gel toughening solves the problems of poor mechanical properties, easy cracking or deformation of traditional hydrogel cold storage materials, and can ensure that it can withstand repeated deformations in practical applications, such as extrusion during cold chain transportation, etc., thereby extending the service life of the material and expanding its application range.

[0063] In this embodiment, a suitable sugar alcohol-based phase change material can be selected according to the target phase change temperature and performance requirements, such as one or more of glucose, sucrose, trehalose, fructose, glycerol, propylene glycol, ethylene glycol or sorbitol.

[0064] In practical applications, determining the mass ratio of the sugar alcohol-based phase change material to the polymer gel matrix is the key to achieving precise adjustment of the phase change temperature of the hydrogel material. The mass ratio of the sugar alcohol-based phase change material to the polymer gel matrix directly affects the phase change temperature of the hydrogel. By adjusting this mass ratio, the phase change temperature of the hydrogel can be precisely regulated within the range of -30°C to 0°C to meet the requirements of different application scenarios. At the same time, the selection of the sugar alcohol-based phase change material will also affect other properties of the hydrogel, such as mechanical strength, thermal stability and phase change latent heat, etc.

[0065] After determining the mass ratio of the sugar alcohol-based phase change material to the polymer gel matrix, the sugar alcohol-based phase change material can be added to the polymer solution according to the mass ratio and stirred to form a composite solution under water bath conditions.

[0066] In this embodiment, first, according to the determined mass ratio, accurately weigh the required sugar alcohol-based phase change material. Subsequently, the weighed sugar alcohol-based phase change material is slowly added to the polymer solution prepared in the above embodiment. Slowly adding can avoid the formation of aggregates of the phase change material in the solution and ensure its uniform dispersion.

[0067] In practical applications, the mixed solution of the sugar alcohol-based phase change material and the polymer solution can be placed under water bath conditions of 25°C to 40°C and stirred at a speed of 500 rpm to 800 rpm for 1 hour to 2 hours until a uniform composite solution is formed. The selection of the water bath temperature and stirring speed is to ensure that the sugar alcohol-based phase change material is fully dissolved and uniformly dispersed in the polymer solution.

[0068] The control of the water bath temperature can ensure that the sugar alcohol-based phase change material can be fully dissolved and evenly dispersed in the polymer solution. In the temperature range of 25°C to 40°C, the dissolution rate and solubility of the sugar alcohol-based phase change material are relatively ideal, which can effectively avoid the formation of aggregates or undissolved particles in the solution. If the water bath temperature is too low, the dissolution rate of the sugar alcohol-based phase change material will slow down, and even incomplete dissolution may occur, affecting the uniformity of the solution and the performance of the subsequent hydrogel. While too high water bath temperature may cause degradation or denaturation of the sugar alcohol-based phase change material, destroying its phase change performance, and also increasing energy consumption. Therefore, choosing the water bath condition of 25°C to 40°C can not only ensure the full dissolution and uniform dispersion of the sugar alcohol-based phase change material, but also avoid the damage of its performance.

[0069] After the composite solution is prepared, the composite solution can be injected into a mold and evacuated to the target vacuum degree in stages to form a degassed gel precursor.

[0070] In this embodiment, before preparing the gel precursor, a mold needs to be prepared first. Specifically, a mold with appropriate size and shape can be selected according to specific implementation needs, and its cleanliness and dryness are ensured. Subsequently, the composite solution is quickly injected into the mold to prevent the solution from being exposed to the air for too long and avoid water evaporation or contamination.

[0071] Then the mold is evacuated in stages. Specifically, the mold filled with the composite solution can be transferred to a vacuum drying oven, quickly evacuated to 100 Pa first, and then slowly depressurized to the target vacuum degree, and the target vacuum degree is a vacuum degree less than or equal to 10 Pa.

[0072] In this embodiment, the method of evacuating in stages is used to remove the bubbles in the composite solution, which can prevent the bubbles from affecting the mechanical properties and heat conduction properties of the hydrogel during the subsequent curing process. Evacuating in stages can effectively avoid the generation of new bubbles during the evacuation process of the solution and ensure that the bubbles in the solution are completely removed. The formed gel precursor has a uniform internal structure, providing a good foundation for the subsequent curing and freeze-thaw cycle treatment.

[0073] Subsequently, the gel precursor is left to cure in a constant temperature and humidity environment to form an initial hydrogel material.

[0074] In this embodiment, when setting up a constant temperature and humidity environment, the mold containing the gel precursor can be placed in a constant temperature and humidity chamber with a temperature of 25°C and a relative humidity of 50%RH. Such environmental conditions are conducive to the full cross-linking of polymer segments and the formation of a hydrogel network structure. Specifically, a temperature of 25°C is the ideal cross-linking and curing temperature for many polymer gel matrices. At this temperature, the polymer segments have appropriate activity and can be fully cross-linked to form a stable three-dimensional network structure. A humidity of 50%RH ensures that there is an appropriate amount of moisture in the environment, which will neither cause the hydrogel to lose water too quickly due to excessive dryness and affect the formation of the network structure, nor cause too much moisture due to too high humidity and lead to a loose gel structure. Such environmental conditions help the interaction between polymer segments, promote their orderly arrangement and cross-linking, thereby improving the mechanical properties and shape stability of the hydrogel.

[0075] Leave it standing in the constant temperature and humidity environment for 24 hours to allow the polymer segments to be fully cross-linked and form an initial hydrogel material with a three-dimensional network structure. The selection of the standing time is to ensure that the polymer segments have enough time to cross-link and form a stable network structure.

[0076] In this embodiment, in the constant temperature and humidity environment, the polymer segments undergo a cross-linking reaction under appropriate temperature and humidity conditions to form a stable three-dimensional network structure. This network structure not only endows the hydrogel with good mechanical properties but also can effectively encapsulate the phase change material and prevent its leakage. The standing and curing time and environmental conditions have an important impact on the final properties of the hydrogel. Too short a time or inappropriate environment will result in an imperfect network structure and affect the performance of the hydrogel.

[0077] Finally, the initial hydrogel material is subjected to freeze-thaw cycling at a predetermined rate to obtain the target hydrogel material.

[0078] In this embodiment, the freeze-thaw cycling includes a freezing process and a thawing process. Among them:

[0079] During the freezing process, the initial hydrogel material can be cooled to -20°C at a rate of 0.5°C / min to 3°C / min and kept at this temperature for 12 hours. Rapid cooling can cause the phase change material to crystallize rapidly, release the latent heat of crystallization, and at the same time, the gel network structure shrinks.

[0080] During the thawing process, the hydrogel material can be heated to 25°C at a rate of 0.5°C / min and kept at this temperature for 12 hours. Slow heating can promote the re-expansion and reorganization of the gel network, making the network structure more compact.

[0081] Repeat the above freezing and thawing processes 3 to 5 times to obtain the target hydrogel material. Multiple cycling processes can further optimize the gel network structure and improve the toughness and cold storage performance of the hydrogel.

[0082] In this embodiment, the freeze-thaw cycle treatment optimizes the gel network structure by simulating the crystallization and melting processes during the phase change. During the freezing process, the phase change material crystallizes and releases heat, while the gel network shrinks; during the thawing process, the phase change material melts and absorbs heat, and the gel network expands again. After multiple cycles, the binding between the molecular chain segments of the gel network becomes tighter, and the mechanical properties and cold storage performance of the hydrogel are significantly improved. The selection of the number of cycles and the rate of temperature change is to balance the treatment effect and treatment time to ensure the best performance improvement within a limited time.

[0083] Based on the above embodiments, the polymer gel matrix is one or more of carrageenan, gelatin, agarose, polyvinyl alcohol, sodium alginate, xanthan gum, guar gum, or chitosan. The above polymer gel matrices can all be quickly dissolved in preheated deionized water to form a homogeneous solution with a three-dimensional network structure.

[0084] When preparing the hydrogel with adjustable phase change temperature, a polymer gel matrix (such as carrageenan, gelatin, agarose, polyvinyl alcohol, sodium alginate, xanthan gum, guar gum, chitosan, or a combination thereof) is used as the core material, and a three-dimensional network structure is constructed through a standardized process. Different matrices can endow the material with different characteristics: natural matrices (carrageenan / gelatin) have both low cost and biocompatibility; agarose and polyvinyl alcohol can strengthen thermal stability and mechanical strength respectively; sodium alginate and chitosan can improve degradability and antibacterial properties; xanthan gum / guar gum can enhance system stability and thickening effect. Through composite matrices (such as carrageenan-gelatin or agarose-polyvinyl alcohol combinations), the performance can be synergistically optimized to meet diverse requirements such as medical packaging (biological safety), cold chain transportation (temperature tolerance), or industrial products (chemical stability), realizing the efficient encapsulation and leakage prevention of the phase change material.

[0085] Similarly, as described in the above embodiments, the sugar alcohol-based phase change material is one or more of glucose, sucrose, trehalose, fructose, glycerol, propylene glycol, ethylene glycol, or sorbitol.

[0086] When preparing a hydrogel with adjustable phase transition temperature, sugar alcohols (such as trehalose, sucrose, glucose, fructose, glycerol, propylene glycol, ethylene glycol, sorbitol or a combination thereof) are used as the core phase change components. By compounding with different polymer gel matrices (such as carrageenan, gelatin, agarose, etc.) at different mass ratios, precise regulation of the phase change performance is achieved. Different sugar alcohols can endow the material with different characteristics: trehalose / sorbitol enhances biocompatibility, sucrose optimizes cost-effectiveness, glycerol / ethylene glycol enhances chemical stability, and a composite system (such as a trehalose-sucrose combination) can synergistically improve the phase change latent heat and temperature regulation accuracy (±1°C). By adjusting the sugar alcohol ratio and the freezing rate (0.5 - 3°C / min), the material has better cold storage capacity and mechanical strength in the cold chain transportation scenario and can withstand repeated deformation. Through modular parameter adjustment, it can meet the diverse needs of the pharmaceutical cold chain (biocompatibility), industrial temperature control (chemical resistance), and food transportation (cost efficiency).

[0087] The following will illustrate the preparation method of the hydrogel with adjustable phase transition temperature provided by the embodiments of the present invention in conjunction with specific embodiments.

[0088] Example 1: Preparation of a carrageenan-trehalose system hydrogel material

[0089] The raw material ratio of this example includes: carrageenan: 10%; trehalose: 15%; deionized water: 75%.

[0090] Preparation steps:

[0091] Step 1: Slowly add 10 g of carrageenan powder to 75 mL of deionized water preheated to 40°C. Use a stirrer to stir at a speed of 600 rpm for 60 minutes to ensure that the carrageenan is completely dissolved to form a homogeneous polymer solution.

[0092] Step 2: Slowly add 15 g of trehalose to the above carrageenan solution at a mass ratio of 1.5:1 (trehalose: carrageenan).

[0093] Under the water bath condition of 40°C, stir at a speed of 600 rpm for 60 minutes to uniformly disperse the trehalose in the carrageenan solution.

[0094] Step 3: Quickly inject the obtained carrageenan-trehalose composite solution into a pre-prepared mold, and then transfer the mold to a vacuum drying oven.

[0095] Set the vacuum degree of the vacuum drying oven ≤ 10 Pa. First, quickly pump it to 100 Pa, and then slowly reduce the pressure to the target vacuum degree to avoid foam formation.

[0096] Step 4: After vacuum treatment, it is left to cure for 24 hours in a thermostatic and humidified chamber at 25°C and a relative humidity of 50% RH, allowing the polymer segments to crosslink sufficiently to form a stable three-dimensional network structure.

[0097] Step 5: Take out the cured hydrogel sample from the mold and place it in a freeze-thaw cycling device.

[0098] Lower the temperature to -20°C at a rate of 0.5°C / min and hold at this temperature for 12 hours to ensure that the phase change substance trehalose is completely crystallized.

[0099] Raise the temperature to 25°C at a rate of 0.5°C / min and hold at this temperature for 12 hours to promote the reorganization of the gel network. This process is carried out for 3 complete cycles. The freeze-thaw cycling treatment is a key step in enhancing the performance of the hydrogel. By simulating the crystallization and melting processes during the phase change, the gel network structure is optimized.

[0100] Figure 3 It is a schematic diagram of the performance test results of differential scanning calorimetry for Example 1 provided in the embodiments of the present invention.

[0101] As Figure 3 shown, the phase transition temperature measured by differential scanning calorimetry (DSC) for the above Example 1 is -8.30°C. This temperature is within the adjustable range of -30°C to 0°C, meeting the regulation target of the phase transition temperature of the present invention and being able to meet the packaging and transportation requirements of temperature-sensitive products.

[0102] The latent heat of phase transition value measured by differential scanning calorimetry (DSC) for the above Example 1 is 167.1 J / g. A higher latent heat of phase transition value means that this hydrogel cold storage material can absorb or release a large amount of heat during the phase change process, has good cold storage capacity, and can effectively maintain a low-temperature environment in practical applications.

[0103] Example 2: Preparation of a gelatin and sucrose-based hydrogel material

[0104] The raw material ratio of this example includes: gelatin: 10%; sucrose: 2%; deionized water: 88%.

[0105] Preparation steps:

[0106] Step 1: Slowly add 10 g of gelatin powder to 88 mL of deionized water preheated to 40°C.

[0107] Use a stirrer to stir at a speed of 600 rpm for 60 minutes to ensure that the gelatin is completely dissolved to form a homogeneous polymer solution.

[0108] Step 2: Slowly add 2 g of sucrose to the above gelatin solution according to a mass ratio of 1:5 (sucrose: gelatin).

[0109] Under the condition of a water bath at 40 °C, stir at a speed of 600 rpm for 60 minutes to uniformly disperse sucrose in the gelatin matrix.

[0110] Step 3: Quickly inject the obtained gelatin-sucrose composite solution into a pre-prepared mold, and then transfer the mold into a vacuum drying oven.

[0111] Set the vacuum degree of the vacuum drying oven ≤ 10 Pa. First, quickly pump it down to 100 Pa, and then slowly reduce the pressure to the target vacuum degree to avoid foam formation. The main purpose of the vacuum treatment is to remove the bubbles in the solution and prevent the existence of bubbles from affecting the mechanical properties and heat conduction properties of the hydrogel.

[0112] Step 4: After the vacuum treatment, leave it to cure in a constant temperature and humidity box at 25 °C and a relative humidity of 50% RH for 24 hours to fully crosslink the polymer segments and form a stable three-dimensional network structure.

[0113] Step 5: Take out the cured hydrogel sample from the mold and put it into a freeze-thaw cycling device.

[0114] Lower the temperature to -20 °C at a rate of 0.5 °C / min and keep it at this temperature for 12 hours to ensure that the phase change substance sucrose is completely crystallized.

[0115] Raise the temperature to 25 °C at a rate of 0.5 °C / min and keep it at this temperature for 12 hours to promote the reorganization of the gel network. This process is carried out for 3 complete cycles. The freeze-thaw cycling treatment is a key step to improve the performance of the hydrogel. By simulating the crystallization and melting processes during the phase change, the gel network structure is optimized.

[0116] Figure 4 It is a schematic diagram of the performance test results of differential scanning calorimetry for Example 2 provided by the embodiments of the present invention.

[0117] As Figure 4 shown, the phase change temperature measured by differential scanning calorimetry (DSC) for the above Example 2 is -2.74 °C. This temperature is within the adjustable range of -30 °C to 0 °C, meeting the regulation target of the phase change temperature of the present invention and being able to meet the packaging and transportation requirements of temperature-sensitive products.

[0118] The latent heat of phase change value measured by differential scanning calorimetry (DSC) for the above Example 2 is 297.8 J / g. A higher latent heat of phase change value means that this hydrogel cold storage material can absorb or release a large amount of heat during the phase change process, has good cold storage capacity, and can effectively maintain a low-temperature environment in practical applications.

[0119] Figure 5Schematic diagram of the mechanical property test results of Example 1 and Example 2 provided by the embodiments of the present invention.

[0120] As Figure 5 shown, the tensile strength of the hydrogel in Example 1 above is 2.9 MPa. This indicates that the hydrogel material has good mechanical strength and can withstand external forces such as extrusion during transportation without deformation or rupture, ensuring its stability and reliability in application scenarios such as cold chain transportation.

[0121] The tensile strength of the hydrogel in Example 2 above is 1.0 MPa. This indicates that the hydrogel material also has a certain mechanical strength and can withstand a certain amount of external force during transportation. Although its tensile strength is relatively low, it can still meet the cold chain transportation requirements of some lightweight products.

[0122] Through reasonable raw material ratios and preparation processes, Example 1 and Example 2 above successfully prepared a hydrogel cold storage material. This material not only has excellent cold storage properties, such as adjustable phase change temperature and large phase change latent heat, but also has certain mechanical properties and anti-leakage capabilities, meeting the requirements for cold storage materials in fields such as cold chain transportation. Its preparation process is simple, easy to operate, and low in cost, with good application prospects and market competitiveness.

[0123] It should be noted that the term "including" and its variations used in the embodiments of the present invention are open-ended, that is, "including but not limited to". The term "based on" is "at least partially based on". The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments". The modifications of "one" and "multiple" mentioned in the embodiments of the present invention are illustrative rather than restrictive, and those skilled in the art should understand that unless clearly stated otherwise in the context, it should be understood as "one or more".

[0124] The various steps recorded in the method implementation manners provided by the embodiments of the present invention can be executed in different orders and / or in parallel. In addition, the method implementation manners may include additional steps and / or omit the steps shown. The protection scope of the present invention is not limited in this regard.

[0125] As used in this specification, the term "embodiment" means that the specific features, structures, or characteristics described in connection with an embodiment may be included in at least one embodiment of the present invention. The phrase appears in various positions in the specification and does not necessarily mean the same embodiment, nor does it mean independence or alternative to other embodiments that are mutually exclusive. The various embodiments in this specification are described in a related manner, and the same or similar parts between the embodiments are cross-referenced. In particular, for device, equipment, and system embodiments, since they are basically similar to method embodiments, the description is relatively simple, and the relevant parts refer to the partial description of the method embodiments.

[0126] The above-described embodiments merely represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of patent protection. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all fall within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the appended claims.

Claims

1. A method for preparing a hydrogel with adjustable phase transition temperature, characterized in that: include: Add the polymer gel matrix into preheated deionized water and stir thoroughly to form a uniform polymer solution; Based on the preset phase transition temperature of the target hydrogel material, determining the mass ratio of the sugar alcohol phase change material to the polymer gel matrix, wherein the mass ratio of the sugar alcohol phase change material to the polymer gel matrix is ​​in a continuous corresponding relationship with the phase transition temperature of the hydrogel material; Adding the sugar alcohol phase change material into the polymer solution according to the mass ratio, and stirring in a water bath to form a composite solution; injecting the composite solution into a mold, and evacuating the mold in stages to a target vacuum degree to form a degassed gel precursor; The gel precursor is allowed to stand and solidify in a constant temperature and humidity environment to form an initial hydrogel material; The initial hydrogel material is subjected to a freeze-thaw cycle treatment at a predetermined rate to obtain the target hydrogel material.

2. The method for preparing a hydrogel according to claim 1, characterized in that: The polymer gel matrix is ​​one or more of carrageenan, gelatin, agarose, polyvinyl alcohol, sodium alginate, xanthan gum, guar gum or chitosan.

3. The method for preparing a hydrogel according to claim 1, characterized in that: The sugar alcohol phase change material is one or more of glucose, sucrose, trehalose, fructose, glycerol, propylene glycol, ethylene glycol or sorbitol.

4. The method for preparing a hydrogel according to claim 1, characterized in that: The mass fraction of the polymer gel matrix is ​​5% to 20%, and the preheating temperature of the deionized water is 40° C. to 85° C.; The polymer gel matrix is ​​added into preheated deionized water and stirred sufficiently to form a uniform polymer solution at a stirring speed of 500 rpm to 800 rpm and a stirring time of 1 to 2 hours.

5. The method for preparing a hydrogel according to claim 1, characterized in that: The mass fraction of the sugar alcohol phase change material is 1% to 30%, and the mass ratio of the sugar alcohol phase change material to the polymer gel matrix is ​​1-30:5-20.

6. The method for preparing a hydrogel according to claim 1, wherein: The sugar alcohol phase change material is added to the polymer solution according to the mass ratio, and stirred in a water bath to form a composite solution. The water bath condition is 25° C. to 40° C., the stirring speed is 500 rpm to 800 rpm, and the stirring time is 1 hour to 2 hours.

7. The method for preparing a hydrogel according to claim 1, wherein: The target vacuum degree is a vacuum degree less than or equal to 10 Pa; The composite solution is injected into a mold, and vacuumed to a target vacuum degree in stages to form a degassed gel precursor, comprising: First, the pressure in the mold is reduced to 100 Pa by rapid vacuuming, and then the vacuum degree of the mold is slowly reduced to reach the target vacuum degree.

8. The method for preparing a hydrogel according to claim 1, characterized in that: The constant temperature and humidity environment is 25° C. and 50% RH, and the static curing time is 24 hours.

9. The method for preparing a hydrogel according to claim 1, characterized in that: The number of freeze-thaw cycle treatments is 3 to 5 times; The method of subjecting the initial hydrogel material to a freeze-thaw cycle at a predetermined rate to obtain the target hydrogel material comprises: Cooling the initial hydrogel material to -20°C at a rate of 0.5°C / min to 3°C / min and keeping the temperature for 12 hours; The initial hydrogel material was heated to 25°C at a rate of 0.5°C / min and kept at this temperature for 12 hours.

10. A hydrogel material, wherein the hydrogel material is prepared according to the method for preparing a hydrogel with adjustable phase transition temperature according to any one of claims 1 to 9.

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