Phase-change hydrogel microcapsule as well as preparation method and application thereof

Abstract

The invention relates to the technical field of phase change energy storage materials, and discloses a phase change hydrogel microcapsule as well as a preparation method and application thereof. The phase change hydrogel microcapsule comprises a hydrogel cross-linked network and a hydrophobic phase change material coated in the hydrogel cross-linked network, the raw materials of the hydrogel cross-linked network comprise an alginic acid material and water; the melting point of the hydrophobic phase change material is not higher than 90 DEG C. The phase-change hydrogel microcapsule forms a three-dimensional network structure through chemical crosslinking, the coated phase-change material is separated in the green and nontoxic hydrogel, leakage of the phase-change material caused by disturbance of an external environment is avoided, the coated phase-change material has good biocompatibility and environmental friendliness, and the phase-change hydrogel microcapsule has good application prospects. The harm of waste liquid pollution and heat energy leakage to the environment is avoided, and the problems of residual harm caused by falling of micro-nano powder in existing core-shell microspheres and phase change material leakage caused by shell layer breakage of the core-shell microspheres due to external disturbance are solved.

Description

Technical Field

[0001] The present application relates to the technical field of phase change energy storage materials, and in particular to a phase change hydrogel microcapsule and a preparation method and application thereof. Background Art

[0002] In phase change energy storage materials, the phase change process is inevitably accompanied by a change in volume. If this volume change is not effectively controlled or buffered, it will inevitably lead to increased stress in the packaging material, which can easily cause cracks or breakage, leading to failure. At the same time, compared to the solid state, the phase change material has stronger fluidity in the liquid phase and is easy to migrate out of the packaging material, thereby exacerbating the occurrence of leakage. In addition, after the liquid phase change material leaks, it quickly solidifies and releases heat, and the heat is transferred to the surrounding chemicals, which can easily cause a chain reaction, leading to increased maintenance costs, waste liquid pollution, and potential safety hazards. The problem of phase change material leakage has seriously restricted the performance and practical application promotion of phase change materials, making its application in energy storage and other fields a great challenge.

[0003] Traditional microencapsulation technology is one approach to addressing the leakage problem of phase-change materials. It forms a tough shell on the surface of the phase-change material to prevent leakage of the internal phase-change material. However, to ensure that heat exchange between the internal phase-change material and the outside world is not excessively affected by the encapsulation shell, microencapsulation technology requires multiple chemical synthesis and physical manipulation steps to control the shell thickness and overall size, resulting in a complex preparation process. Another viable approach is melt marble preparation, which utilizes surface tension to encapsulate the liquid phase-change material within tiny hydrophobic particles. This eliminates the need for complex chemical reaction steps and significantly reduces the complexity of the preparation process. Depending on the application needs, rolling, premixed melting, and high-speed cutting and stirring methods can be used to produce melt marbles with sub-centimeter, millimeter, or micron scales. However, because the formation of the surface shell of the melt marble is a purely physical process, its physical properties are significantly affected by dimensional changes. For melt marbles larger than a millimeter, the shell is easily deformed by repeated compression and collision, leading to leakage of the encapsulated material and the sticking of large batches of marbles.

[0004] Based on this, it is urgent to develop new technologies to effectively solve the technical problems of phase change material leakage. Summary of the Invention

[0005] The present application provides a phase change hydrogel microcapsule and a preparation method and application thereof, aiming to solve the technical problem of easy leakage of phase change materials in existing phase change energy storage materials.

[0006] In order to achieve the above objectives, this application adopts the following technical solutions.

[0007] In a first aspect of the present application, a phase change hydrogel microcapsule is provided, comprising a hydrogel cross-linked network and a hydrophobic phase change material coated inside the hydrogel cross-linked network;

[0008] The hydrogel cross-linked network is composed of alginate material and water;

[0009] The melting point of the hydrophobic phase change material is not higher than 90°C.

[0010] Preferably, the alginate material includes at least one of alginic acid, sodium alginate, potassium alginate or ammonium alginate;

[0011] The hydrophobic phase change material includes any one of a paraffin phase change material, a fatty acid ester phase change material, a polyethylene glycol phase change material or a liquid metal.

[0012] Further preferably, the paraffin wax phase change material comprises a linear paraffin wax, a branched paraffin wax, or a mixture of a linear paraffin wax and a branched paraffin wax; wherein the linear paraffin wax has an even number of carbon atoms, ranging from 14 to 32; and the branched paraffin wax has a carbon atom range of 20 to 44;

[0013] The fatty acid ester phase change material includes at least one of a mono-fatty acid methyl ester, a long-chain fatty acid ester, a branched-chain fatty acid ester or a complex fatty acid ester having 12 to 20 carbon atoms;

[0014] The polyethylene glycol phase change material includes at least one of PEG2000, PEG4000, PEG6000, PEG8000, PEG10000 or PEG20000;

[0015] The liquid metal includes at least one of a gallium-indium alloy, an indium-tin alloy, or a gallium-indium-tin alloy.

[0016] In a second aspect of the present application, a method for preparing a phase-change hydrogel microcapsule is provided, comprising:

[0017] Dissolving an alginate material in deionized water to prepare a solution; adding a melt of a hydrophobic phase change material to the solution to obtain a mixed solution;

[0018] The mixed solution is subjected to ultrasonic treatment to obtain a phase change hydrogel emulsion;

[0019] shaping the phase-change hydrogel emulsion by gas phase solidification or freezing;

[0020] The shaped phase change hydrogel emulsion is mixed with a cross-linking agent solution and solidified to obtain a phase change hydrogel microcapsule.

[0021] Preferably, shaping the phase change hydrogel emulsion by gas phase coagulation is specifically: dripping the phase change hydrogel emulsion into a gas phase coagulation medium to shape it;

[0022] The medium for gas phase coagulation is at least one of air, nitrogen, oxygen or rare gas.

[0023] Further preferably, during the process of dripping and shaping the phase change hydrogel emulsion in the gas phase solidification medium, a super wettable mesh is used to cut, disperse or accumulate the phase change hydrogel emulsion;

[0024] The super-wetting mesh is a metal mesh loaded with micro-nano-scale super-hydrophilic particles or micro-nano-scale super-hydrophobic particles.

[0025] Preferably, the shaping of the phase change hydrogel emulsion by freezing is specifically as follows:

[0026] The phase-change hydrogel emulsion is cooled at a temperature of ≤4° C. to obtain a solidified phase-change hydrogel emulsion.

[0027] Preferably, the cross-linking agent solution comprises, by mass percentage:

[0028] 0.5% to 5% of a cationic crosslinking agent, 0.2% to 1% of a cationic surfactant, and the balance being water; and in the crosslinking agent solution, the content of the cationic surfactant is lower than the content of the cationic crosslinking agent;

[0029] and / or,

[0030] The cationic crosslinking agent is a metal ion with a valence of divalent or higher;

[0031] The cationic surfactant includes at least one of dodecyltrimethylammonium chloride, lauryltrimethylammonium chloride, octadecyltrimethylammonium chloride or dodecyldimethylbenzylammonium chloride.

[0032] Preferably, in the mixed solution, the mass content of the alginate material is 0.5% to 2wt%; the content of the hydrophobic phase change material is 1% to 5wt%, and the content of the hydrophobic phase change material in the mixed solution is greater than that of the alginate material.

[0033] The third aspect of the present application provides the use of the above-mentioned phase change hydrogel microcapsules or the phase change hydrogel microcapsules prepared by the above-mentioned preparation method in phase change energy storage materials.

[0034] Compared with the prior art, the present invention has the following advantages:

[0035] The phase change hydrogel microcapsules of the present application form a three-dimensional network structure through chemical cross-linking, which separates the encapsulated phase change material inside the green and non-toxic hydrogel, avoiding leakage of the phase change material caused by external environmental disturbances, so that the encapsulated phase change material has good biocompatibility and environmental friendliness, avoiding the harm to the environment caused by waste liquid pollution and heat leakage, and solving the residual hazards of the shedding of micro-nano powder in the existing core-shell microspheres, and the problem of phase change material leakage caused by the breakage of the core-shell microsphere shell due to external disturbances.

[0036] This application uses a super-wetting mesh to shape the phase change hydrogel according to actual application requirements before the phase change hydrogel and the cross-linking agent are solidified, so as to meet the stringent requirements of different working conditions for the appearance and morphology. Among them, the super-hydrophobic mesh can form a stable air cushion layer when the droplets come into contact through the synergistic effect of its unique micro-nano rough structure and low surface energy chemical modification, so that the droplets are suspended on the surface in a Cassie-Baxter state, thereby achieving efficient separation and manipulation of the droplets through physical cutting to obtain phase change hydrogels of different sizes. This application can adjust the geometric shape, appearance and size of the phase change hydrogel, is suitable for continuous large-scale production of phase change materials of non-nanomaterials, and can be combined with many mature processes. At the same time, the phase change hydrogel microcapsules do not use micro-nanoscale materials, can be decomposed by microorganisms in the natural environment, or can be quickly dissolved by adjusting the pH (such as acidic conditions), which is green and environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] To more clearly illustrate the technical solutions of the embodiments of this application, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some of the embodiments described in this application. For those skilled in the art, other drawings can be derived from these drawings without inventive effort.

[0038] Figure 1 Optical micrographs of the phase change hydrogel microcapsules prepared in Example 1 and Example 2;

[0039] Figure 2 These are optical images of the phase-change hydrogel microcapsules prepared in Example 1 and Example 2;

[0040] Figure 3 This is an optical micrograph of a cross section of the phase change hydrogel of Example 1 after being heated to the melting point;

[0041] Figure 4 1 is a DSC thermal cycle diagram of the phase change hydrogel of Example 1;

[0042] Figure 5 This is a physical picture of the gallium indium tin alloy / sodium alginate phase change hydrogel prepared in Example 2-4;

[0043] Figure 6 This is a physical picture of the n-hexadecane / sodium alginate phase change hydrogel prepared in Example 5;

[0044] Figure 7 This is a physical picture of the gallium indium tin alloy / sodium alginate phase change hydrogel prepared in Example 6;

[0045] Figure 8 This is an optical micrograph of the columnar phase change hydrogel microcapsules prepared in Example 7;

[0046] Figure 9 This is an electron micrograph of the columnar phase change hydrogel microcapsules prepared in Example 7. DETAILED DESCRIPTION

[0047] The following will be combined with the accompanying drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0048] In the following description of this embodiment, the terms "include", "comprising", "having" and "containing" are open-ended terms, meaning including but not limited to.

[0049] In the following description of this embodiment, the term "and / or" is used to describe the association relationship between associated objects, indicating that three possible relationships exist. For example, A and / or B can represent: A exists alone, B exists alone, and both A and B exist. A and B can be singular or plural. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0050] In the following description of this embodiment, the term "at least one" refers to one or more, and "plurality" refers to two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can all represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0051] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The singular forms "a", "an" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise.

[0052] Those skilled in the art should understand that in the following description of the embodiments of the present application, the order of serial numbers does not mean the order of execution, some or all of the steps can be executed in parallel or sequentially, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0053] It will be understood by those skilled in the art that the numerical ranges in the examples of the present application are to be understood as specifically disclosing each intermediate value between the upper and lower limits of the range. Each smaller range between any intermediate value within a stated value or stated range and any other stated value or intermediate value within the stated range is also included in the present application. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

[0054] Unless otherwise indicated, the technical / scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which this application belongs. Although this application describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of this application. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In the event of any conflict with any incorporated document, the content of this specification shall prevail.

[0055] In a first aspect, the present application provides a phase-change hydrogel microcapsule, comprising a hydrogel cross-linked network and a hydrophobic phase-change material coated inside the hydrogel cross-linked network;

[0056] The hydrogel cross-linked network is composed of alginate material and water;

[0057] The melting point of the hydrophobic phase change material is not higher than 90°C.

[0058] In the present application, the alginate material includes at least one of alginic acid, sodium alginate, potassium alginate, or ammonium alginate. The hydrophobic phase change material is an intrinsically hydrophobic material that is insoluble in water in both the molten and solidified states; the hydrophobic phase change material includes any one of a paraffin phase change material, a fatty acid ester phase change material, a polyethylene glycol phase change material, or a liquid metal.

[0059] Specifically, the paraffin wax phase change material includes linear paraffin wax, branched paraffin wax or a mixture of linear paraffin wax and branched paraffin wax; wherein the linear paraffin wax has an even number of carbon atoms ranging from 14 to 32; the branched paraffin wax has a carbon atom range of 20 to 44.

[0060] The fatty acid ester phase change material includes at least one of a mono-fatty acid methyl ester, a long-chain fatty acid ester, a branched-chain fatty acid ester or a complex fatty acid ester having 12 to 20 carbon atoms;

[0061] The polyethylene glycol phase change material includes at least one of PEG2000, PEG4000, PEG6000, PEG8000, PEG10000 or PEG20000;

[0062] The liquid metal includes at least one of a gallium-indium alloy, an indium-tin alloy, or a gallium-indium-tin alloy.

[0063] The phase change hydrogel microcapsules of the present application form a three-dimensional network structure through chemical cross-linking, which separates the encapsulated phase change material inside the green and non-toxic hydrogel, avoiding leakage of the phase change material caused by external environmental disturbances, so that the encapsulated phase change material has good biocompatibility and environmental friendliness, avoiding the harm to the environment caused by waste liquid pollution and heat leakage, and solving the residual hazards of the shedding of micro-nano powder in the existing core-shell microspheres, and the problem of phase change material leakage caused by the breakage of the core-shell microsphere shell due to external disturbances.

[0064] In a second aspect, the present application provides a method for preparing the above-mentioned phase change hydrogel microcapsules, comprising:

[0065] Dissolving an alginate material in deionized water to prepare a solution; adding a melt of a hydrophobic phase change material to the solution to obtain a mixed solution;

[0066] The mixed solution is subjected to ultrasonic treatment to obtain a phase change hydrogel emulsion;

[0067] shaping the phase-change hydrogel emulsion by gas phase solidification or freezing;

[0068] The shaped phase change hydrogel emulsion is mixed with a cross-linking agent solution and solidified to obtain a phase change hydrogel microcapsule.

[0069] In the present application, a hydrophobic phase change material is heated to a melting point to form a melt, which is then added to an aqueous solution of an alginic acid material to obtain a mixed solution. In the mixed solution, the mass content of the alginic acid material is preferably 0.5% to 2% by weight, and the content of the hydrophobic phase change material is preferably 1% to 5% by weight, and the content of the hydrophobic phase change material in the mixed solution is greater than the content of the alginic acid material.

[0070] In the present application, the mixed solution is ultrasonically treated by a cell disruptor or other ultrasonic equipment to emulsify the mixed solution to obtain a phase change hydrogel emulsion.

[0071] As an embodiment of the present application, a phase change hydrogel emulsion is dripped in an atmosphere of air, nitrogen, oxygen or a rare gas such as argon to form droplets; the droplets are poured into a coagulation bath and solidified under the action of a cationic crosslinker in the coagulation bath to obtain phase change hydrogel microcapsules.

[0072] As another embodiment of the present application, the phase change hydrogel emulsion is shaped by freezing treatment. Specifically, the phase change hydrogel emulsion is cooled at a temperature of ≤4°C to obtain a solidified phase change hydrogel emulsion, and then the solidified phase change hydrogel emulsion is immersed in a coagulation bath, where it is solidified under the action of a cationic crosslinker to obtain a phase change hydrogel microcapsule. In the present application, solidified phase change hydrogel emulsions of different shapes are obtained by injecting the phase change hydrogel emulsion into different freezing molds for cooling, such as spherical, rectangular, triangular or pentagonal freezing molds.

[0073] As a preferred embodiment of the present invention, a phase-change hydrogel emulsion is dripped into an atmosphere of air, nitrogen, oxygen, or a rare gas such as argon to form droplets. These droplets are then dispersed or accumulated through a superwettable mesh, and after changing their size, are dripped into a crosslinker solution, where they solidify under the action of a cationic crosslinker to form phase-change hydrogel microcapsules. The superwettable mesh is a metal mesh loaded with micro-nanoscale superhydrophilic particles or micro-nanoscale superhydrophobic particles, prepared by superwetting the metal mesh.

[0074] Specifically, the super-wetting net is loaded with micro-nano-level super-hydrophilic particles or micro-nano-level super-hydrophobic particles on the surface of the metal mesh by chemical etching, electrochemical deposition, surface modification or laser treatment for super-wetting modification. Wherein, the super-hydrophilic particles include silicon dioxide, carbon dioxide, zinc oxide, carbon nanotubes or nano-alumina; the super-hydrophobic particles include polytetrafluoroethylene, graphene oxide or polydimethylsiloxane, and or fluorinated silane-modified silicon dioxide, carbon dioxide, zinc oxide micro-nano particles. In the embodiment of the present application, the super-wetting net is a metal mesh loaded with nano super-hydrophilic silica or nano super-hydrophobic silica.

[0075] In this application, the cross-linking agent solution comprises, by mass percentage:

[0076] The content of the cationic crosslinking agent is 0.5% to 5%, the content of the cationic surfactant is 0.2% to 1%, and the balance is water. It should be noted that the content of the cationic surfactant in the crosslinking agent solution is lower than the content of the cationic crosslinking agent.

[0077] Wherein, the cationic crosslinking agent is a divalent or higher metal ion, such as Ca 2+ Mg 2+ 、Zn 2+ 、Sr 2+ 、Cu 2+ 、Al 3+ or Fe 3+At least one of; the present application introduces metal ions by adding corresponding water-soluble metal salts. The cationic surfactant includes at least one of dodecyltrimethylammonium chloride, dodecyltrimethylammonium chloride, octadecyltrimethylammonium chloride or dodecyldimethylbenzylammonium chloride.

[0078] This application uses a super-wetting mesh to shape the phase change hydrogel according to actual application requirements before the phase change hydrogel and the cross-linking agent are solidified, so as to meet the stringent requirements of different working conditions for the appearance and morphology. Among them, the super-hydrophobic mesh can form a stable air cushion layer when the droplets come into contact through the synergistic effect of its unique micro-nano rough structure and low surface energy chemical modification, so that the droplets are suspended on the surface in a Cassie-Baxter state, thereby achieving efficient separation and manipulation of the droplets through physical cutting to obtain phase change hydrogels of different sizes. This application can adjust the geometric shape, appearance and size of the phase change hydrogel, is suitable for continuous large-scale production of phase change materials of non-nanomaterials, and can be combined with many mature processes. At the same time, the phase change hydrogel microcapsules do not use micro-nanoscale materials, can be decomposed by microorganisms in the natural environment, or can be quickly dissolved by adjusting the pH (such as acidic conditions), which is green and environmentally friendly.

[0079] The phase-change hydrogel microcapsules of the present application have good stability, are not prone to leakage, are safe, and have good biocompatibility and environmental friendliness. They can be used to prepare phase-change energy storage materials.

[0080] The present application is further described below through specific examples.

[0081] Example 1

[0082] Add 2g of sodium alginate to 95g of deionized water and stir with a magnetic stirrer for 6 hours to obtain a sodium alginate aqueous solution. Heat the solution to a temperature above the melting point of n-hexadecane and keep the temperature constant. Heat 3g of n-hexadecane to its melting point and keep the temperature constant for 30 minutes to ensure that the n-hexadecane is completely liquid. Add the solution to the sodium alginate aqueous solution to obtain a mixed solution.

[0083] The mixed solution was placed in a cell disruptor and ultrasonicated for 5 minutes to obtain a n-hexadecane / sodium alginate emulsion.

[0084] 2 g of calcium chloride and 1 g of dodecyltrimethylammonium chloride were added to deionized water to prepare 100 g of a crosslinker solution, which served as a coagulation bath. The n-hexadecane / sodium alginate emulsion was vertically dripped into the coagulation bath from an appropriate height using a dropper to obtain a spherical n-hexadecane / sodium alginate phase change hydrogel.

[0085] Example 2

[0086] Add 2g of sodium alginate to 95g of deionized water and stir with a magnetic stirrer for 6h to obtain a sodium alginate aqueous solution. Heat the solution to a temperature above the melting point of the gallium-indium-tin alloy and keep it warm. Heat 3g of the gallium-indium-tin alloy to its melting point and keep it warm for 30min to ensure that it is completely liquid. Add the solution to the sodium alginate aqueous solution to obtain a mixed solution.

[0087] The mixed solution was placed in a cell disruptor and ultrasonicated for 5 minutes to obtain a gallium indium tin alloy / sodium alginate emulsion;

[0088] 2g of calcium chloride and 1g of dodecyltrimethylammonium chloride were added to deionized water to prepare 100g of crosslinker solution, which served as a coagulation bath. A dropper was used to vertically drop the gallium indium tin alloy / sodium alginate emulsion into the coagulation bath from an appropriate height to obtain a millimeter-scale spherical gallium indium tin alloy / sodium alginate phase change hydrogel.

[0089] Example 3

[0090] Add 2g of sodium alginate to 95g of deionized water and stir with a magnetic stirrer for 6h to obtain a sodium alginate aqueous solution. Heat the solution to a temperature above the melting point of the gallium-indium-tin alloy and keep it warm. Heat 3g of the gallium-indium-tin alloy to its melting point and keep it warm for 30min to ensure that it is completely liquid. Add the solution to the sodium alginate aqueous solution to obtain a mixed solution.

[0091] The mixed solution was placed in a cell disruptor and ultrasonicated for 5 minutes to obtain a gallium indium tin alloy / sodium alginate emulsion;

[0092] Add 2g of calcium chloride and 1g of dodecyltrimethylammonium chloride to deionized water to prepare 100g of crosslinker solution as a coagulation bath;

[0093] A dropper is used to vertically drop the gallium indium tin alloy / sodium alginate emulsion into the coagulation bath from an appropriate height. During the dripping process, the droplets are dispersed with a superhydrophobic metal mesh to obtain micron-sized spherical gallium indium tin alloy / sodium alginate phase change hydrogel.

[0094] Example 4

[0095] Add 2g of sodium alginate to 95g of deionized water and stir with a magnetic stirrer for 6h to obtain a sodium alginate aqueous solution. Heat the solution to a temperature above the melting point of the gallium-indium-tin alloy and keep it warm. Heat 3g of the gallium-indium-tin alloy to its melting point and keep it warm for 30min to ensure that it is completely liquid. Add the solution to the sodium alginate aqueous solution to obtain a mixed solution.

[0096] The mixed solution was placed in a cell disruptor and ultrasonicated for 5 minutes to obtain a gallium indium tin alloy / sodium alginate emulsion;

[0097] 2g of calcium chloride and 1g of dodecyltrimethylammonium chloride were added to deionized water to prepare 100g of crosslinker solution, which served as a coagulation bath. A dropper was used to vertically drip the gallium indium tin alloy / sodium alginate emulsion into the coagulation bath from an appropriate height. During the dripping process, a Janus-structured hydrophobic metal mesh was used to accumulate the liquid, resulting in a sub-centimeter-scale spherical gallium indium tin alloy / sodium alginate phase change hydrogel.

[0098] Example 5

[0099] Add 2g of sodium alginate to 95g of deionized water and stir with a magnetic stirrer for 6h to obtain a sodium alginate aqueous solution, which is then heated to above the melting point of n-hexadecane and kept warm. Heat 3g of n-hexadecane to its melting point and keep warm for 30min to ensure that all the n-hexadecane is liquid, then add it to the sodium alginate aqueous solution to obtain a mixed solution.

[0100] The mixed solution was placed in a cell disruptor and ultrasonicated for 5 minutes to obtain a n-hexadecane / sodium alginate emulsion; the n-hexadecane / sodium alginate emulsion was injected into a mold and placed at below 4° C. for 1 hour to obtain a solidified n-hexadecane / sodium alginate emulsion.

[0101] Add 2g of calcium chloride and 1g of dodecyltrimethylammonium chloride to deionized water to prepare a 100g crosslinker solution as a coagulation bath, which is then cooled to 4°C. The solidified n-hexadecane / sodium alginate emulsion is quickly placed into the coagulation bath to form the n-hexadecane / sodium alginate phase-change hydrogel. Using molds of varying shapes allows for the production of different n-hexadecane / sodium alginate phase-change hydrogels.

[0102] Example 6

[0103] Add 2g of sodium alginate to 95g of deionized water and stir with a magnetic stirrer for 6h to obtain a sodium alginate aqueous solution. Heat the solution to a temperature above the melting point of the gallium indium tin alloy and keep it warm. Heat 3g of the gallium indium tin alloy to its melting point and keep it warm for 30min to ensure that the gallium indium tin alloy is completely liquid. Add the mixture to the sodium alginate aqueous solution to obtain a mixed solution.

[0104] The mixed solution was placed in a cell disruptor and ultrasonicated for 5 minutes to obtain a gallium indium tin alloy / sodium alginate emulsion; the gallium indium tin alloy / sodium alginate emulsion was injected into a mold and placed below 4° C. for 1 hour to obtain a solidified gallium indium tin alloy / sodium alginate emulsion.

[0105] Add 2g of calcium chloride and 1g of dodecyltrimethylammonium chloride to deionized water to prepare a 100g crosslinker solution as a coagulation bath, which is then cooled to 4°C. The solidified gallium indium tin alloy / sodium alginate emulsion is quickly placed into the coagulation bath to form a gallium indium tin alloy / sodium alginate phase-change hydrogel. Using molds of varying shapes allows for the production of different gallium indium tin alloy / sodium alginate phase-change hydrogel shapes.

[0106] Example 7

[0107] Add 2g of sodium alginate to 95g of deionized water and stir with a magnetic stirrer for 6h to obtain a sodium alginate aqueous solution. Heat the solution to a temperature above the melting point of n-eicosane and keep the temperature constant. Heat 3g of n-eicosane to the melting point and keep the temperature constant for 30min to ensure that the n-eicosane is completely liquid. Add the solution to the sodium alginate aqueous solution to obtain a mixed solution.

[0108] The mixed solution was placed in a cell disruptor and sonicated for 5 min to obtain an n-eicosane / sodium alginate emulsion;

[0109] Add 2g of calcium chloride and 1g of dodecyltrimethylammonium chloride to deionized water to prepare 100g of crosslinker solution;

[0110] The crosslinker solution is dispersed using a superhydrophobic metal mesh and then dropped into the n-eicosane / sodium alginate emulsion. The cationic crosslinker is pulled out of the coagulation bath using pointed tweezers to obtain columnar phase change hydrogel microcapsules.

[0111] The morphology and performance evaluation of the phase change hydrogel microcapsules prepared in Examples 1 and 2 of the present application were performed as follows:

[0112] The optical micrographs of the phase change hydrogel microcapsules prepared in Example 1 and Example 2 are as follows: Figure 1 As shown. Among them, Figure 1 Figure (a) is an optical micrograph of the n-hexadecane / sodium alginate phase change hydrogel of Example 1. Figure 1 Figure (b) is an optical micrograph of the gallium indium tin alloy / sodium alginate phase change hydrogel of Example 2. The optical images of the phase change hydrogel microcapsules prepared in Example 1 and Example 2 are shown in Figure 3. Figure 2 Shown in the left and right pictures.

[0113] from Figure 1 and Figure 2 It can be seen that both the n-hexadecane / sodium alginate phase change hydrogel and the gallium indium tin alloy / sodium alginate phase change hydrogel are spherical, and their sizes are in the micron order.

[0114] The n-hexadecane / sodium alginate phase change hydrogel prepared in Example 1 was heated to above the melting point and then cut and observed using an optical microscope. The optical micrograph of the cross section is shown in FIG. Figure 3 As shown, microcapsule structures can be observed encapsulating the molten phase change emulsion.

[0115] The n-hexadecane / sodium alginate phase change hydrogel prepared in Example 1 was dried in a low-temperature oven at a temperature below 50° C., and the energy storage effect of the dried phase change hydrogel was determined using a differential scanning calorimeter. Figure 4 As shown. Figure 4It can be seen that the DSC curve of the prepared phase change hydrogel is stable during the heat absorption and heat release process, and there will be no demulsification and stratification phenomenon that affects the energy storage effect.

[0116] The actual picture of the gallium indium tin alloy / sodium alginate phase change hydrogel prepared in Example 2-4 is as follows: Figure 5 As shown. Among them, Figure 5 The middle left picture shows the sub-centimeter-scale spherical gallium indium tin alloy / sodium alginate phase change hydrogel prepared in Example 4. Figure 5 The middle picture shows the millimeter-scale spherical gallium indium tin alloy / sodium alginate phase change hydrogel prepared in Example 2. Figure 5 The middle right picture shows the micron-sized spherical gallium indium tin alloy / sodium alginate phase change hydrogel prepared in Example 3. Figure 5 It can be seen that through the physical cutting or aggregation of the superhydrophobic network, efficient separation and manipulation of droplets can be achieved to obtain phase change hydrogels of different sizes.

[0117] The actual pictures of the n-hexadecane / sodium alginate phase change hydrogel prepared in Example 5 and the gallium indium tin alloy / sodium alginate phase change hydrogel prepared in Example 6 are shown in FIG. Figure 6 and Figure 7 As shown. Figure 6 and Figure 7 It can be seen that the n-hexadecane / sodium alginate phase change hydrogel and the gallium indium tin alloy / sodium alginate phase change hydrogel can be processed into various shapes to meet the needs of actual use.

[0118] The optical micrograph of the columnar phase change hydrogel microcapsules prepared in Example 7 is as follows: Figure 8 As shown. Figure 8 It can be seen that the columnar phase change hydrogel microcapsules present a regular columnar shape.

[0119] The electron micrograph of the columnar phase change hydrogel microcapsules prepared in Example 7 is as follows: Figure 9 As shown. Figure 9 It can be seen that the microscopic morphology of the columnar n-hexadecane / sodium alginate phase change hydrogel has a honeycomb vesicle structure and a stable structure in the molten state, which can prevent the phase change material from leaking in large quantities due to cutting, collision, and swelling.

[0120] Although this specification has been used to fully describe the present application using general descriptions and specific embodiments, it is obvious to those skilled in the art that modifications or improvements may be made based on the present application. Therefore, such modifications or improvements made without departing from the spirit of the present application are within the scope of protection claimed in this application.

Claims

1. A phase change hydrogel microcapsule, characterized in that: It includes a hydrogel cross-linked network and a hydrophobic phase change material coated inside the hydrogel cross-linked network; The raw materials of the hydrogel cross-linked network include alginate material and water; The melting point of the hydrophobic phase change material is not higher than 90°C.

2. The phase change hydrogel microcapsule according to claim 1, characterized in that: The alginate material includes at least one of alginic acid, sodium alginate, potassium alginate or ammonium alginate; The hydrophobic phase change material includes any one of a paraffin phase change material, a fatty acid ester phase change material, a polyethylene glycol phase change material or a liquid metal.

3. The phase change hydrogel microcapsule according to claim 2, characterized in that: The paraffin wax phase change material includes straight-chain paraffin wax, branched-chain paraffin wax, or a mixture of straight-chain paraffin wax and branched-chain paraffin wax; wherein the carbon atoms of the straight-chain paraffin wax are an even number ranging from 14 to 32; the carbon atoms of the branched-chain paraffin wax range from 20 to 44; The fatty acid ester phase change material includes at least one of a mono-fatty acid methyl ester, a long-chain fatty acid ester, a branched-chain fatty acid ester or a complex fatty acid ester having 12 to 20 carbon atoms; The polyethylene glycol phase change material includes at least one of PEG2000, PEG4000, PEG6000, PEG8000, PEG10000 or PEG20000; The liquid metal includes at least one of a gallium-indium alloy, an indium-tin alloy, or a gallium-indium-tin alloy.

4. The method for preparing the phase change hydrogel microcapsule according to claim 1, characterized in that: include: Dissolve the alginate material in deionized water to prepare a solution; adding a melt of a hydrophobic phase change material into the solution to obtain a mixed solution; The mixed solution is subjected to ultrasonic treatment to obtain a phase change hydrogel emulsion; shaping the phase-change hydrogel emulsion by gas phase solidification or freezing; The shaped phase change hydrogel emulsion is mixed with a cross-linking agent solution and solidified to obtain a phase change hydrogel microcapsule.

5. The preparation method according to claim 4, characterized in that The shaping of the phase change hydrogel emulsion by gas phase coagulation is specifically as follows: dripping the phase change hydrogel emulsion into a gas phase coagulation medium to shape it; The medium for gas phase coagulation is at least one of air, nitrogen, oxygen or rare gas.

6. The preparation method according to claim 5, characterized in that During the process of dripping and shaping the phase change hydrogel emulsion in a gas-phase solidified medium, a super-wettable mesh is used to cut, disperse or accumulate the phase change hydrogel emulsion; The super-wetting mesh is a metal mesh loaded with micro-nano-scale super-hydrophilic particles or micro-nano-scale super-hydrophobic particles.

7. The preparation method according to claim 4, characterized in that The shaping of the phase change hydrogel emulsion by freezing is specifically as follows: The phase-change hydrogel emulsion is cooled at a temperature of ≤4° C. to obtain a solidified phase-change hydrogel emulsion.

8. The preparation method according to claim 4, characterized in that The cross-linking agent solution comprises, by mass percentage: 0.5% to 5% of a cationic crosslinking agent, 0.2% to 1% of a cationic surfactant, and the balance being water; and in the crosslinking agent solution, the content of the cationic surfactant is lower than the content of the cationic crosslinking agent; and / or, The cationic crosslinking agent is a metal ion with a valence of divalent or higher; The cationic surfactant includes at least one of dodecyltrimethylammonium chloride, lauryltrimethylammonium chloride, octadecyltrimethylammonium chloride or dodecyldimethylbenzylammonium chloride.

9. The preparation method according to claim 4, characterized in that In the mixed solution, the mass content of the alginate material is 0.5% to 2wt%; the content of the hydrophobic phase change material is 1% to 5wt%, and the content of the hydrophobic phase change material in the mixed solution is greater than that of the alginate material.

10. Use of the phase-change hydrogel microcapsule according to any one of claims 1 to 3 or the phase-change hydrogel microcapsule prepared by the preparation method according to any one of claims 4 to 9 in phase-change energy storage materials.

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