Hydrated salt phase change microcapsule and preparation method thereof

Abstract

The invention discloses a hydrated salt phase change microcapsule and a preparation method thereof.The hydrated salt phase change microcapsule is composed of a nucleating agent modified hydrated salt phase change core material and a polymer / heat conduction material hybrid shell layer, and the phase change microcapsule is prepared by the steps that firstly, the nucleating agent modified low-supercooling-degree inorganic hydrated salt phase change core material is prepared through a melt blending method; then inducing monomer polymerization on an oil-water interface through a W / O inverse emulsion template method to form a polymer shell layer, and finally introducing the modified heat-conducting material into the polymer shell layer to construct a high-heat-conducting shell layer. The phase change microcapsule prepared by the invention has a coating rate higher than 80%, a supercooling degree lower than 3 DEG C, an apparent heat-conducting property greater than 1 W / (m.K), controllable particle size distribution (5-70 [mu] m), excellent encapsulation performance and cycling stability, and has a wide application prospect in the field of heat storage.

Description

Technical Field

[0001] The present invention belongs to the technical field of phase change materials and phase change microcapsules, and relates to a hydrated salt phase change microcapsule and a preparation method thereof. Background Art

[0002] With the increasingly severe energy crisis and environmental problems, the efficient storage and management of thermal energy have become an important research topic. Phase change materials are widely used in the fields of thermal energy storage, temperature control systems, and energy-saving buildings because they can absorb or release a large amount of latent heat during the phase change process. As a typical inorganic phase change material, inorganic hydrated salts have become one of the research hotspots due to their high phase change latent heat, low price, and good environmental friendliness. However, inorganic hydrated salt phase change materials face a series of problems in practical applications. In a humid and hot environment, inorganic hydrated salts are prone to component loss and morphological distortion due to their high solubility and hygroscopic properties, resulting in a significant decline in the heat storage density; during the phase change process, inorganic hydrated salts are prone to phase separation, seriously affecting their thermal cycling performance; in the molten state, the low-viscosity fluid characteristics of inorganic hydrated salts make them prone to leakage, further restricting the application range. Research shows that if inorganic hydrated salts are confined in a microscale space and the microspace confinement effect is utilized, not only can the hygroscopic characteristics of inorganic hydrated salts be significantly inhibited, but also the occurrence of phase separation can be effectively prevented. At the same time, the physical barrier formed by the microencapsulation structure can effectively prevent the leakage of inorganic hydrated salts, thereby improving their service performance. For example, Chinese patent application with publication number CN118530697A discloses a LiNO3•3H2O / modified diatomite-based composite phase change material and its preparation method and application. This application uses LiNO3•3H2O as the phase change material and modified diatomite as the porous framework, and prepares the LiNO3•3H2O / modified diatomite-based composite phase change material by vacuum impregnation, significantly improving the shape stability and thermal cycling stability of LiNO3·3H2O. However, the high mass ratio of the modified diatomite framework seriously reduces the enthalpy value of the composite phase change material, and although the traditional porous material adsorption method can partially improve the encapsulation effect of the phase change material, due to its broad pore size distribution and weak interfacial binding force, it is difficult to meet the long-term stable use requirements. Further research shows that by constructing a submicron-thin shell structure through the microencapsulation process, not only can more efficient encapsulation of the phase change material be achieved, but also the loading rate of the core material of the phase change material can be significantly improved. For example, Chinese patent application with publication number CN117567992A discloses a preparation method of a core-shell type silica / inorganic phase change material microcapsule. This patent application uses sodium acetate trihydrate as the core and silica as the shell, and prepares the sodium acetate trihydrate-based phase change microcapsule by the sol-gel method. The obtained phase change microcapsule has high thermal cycling stability.

[0003] However, the inherent high supercooling characteristics of inorganic hydrated salts still lead to a significant time lag effect in the release of their phase change enthalpy. Under rapid thermal cycling conditions, there will be a large loss in the utilization rate of the latent heat of phase change. This thermal response hysteresis and phase change failure together exacerbate the deterioration of the cycling performance of inorganic hydrated salts. Research has found that by introducing nanoscale nucleating agents, high-density nucleation sites can be constructed in the inorganic hydrated salt phase change system, reducing its heterogeneous nucleation activation energy by 40% - 60%, thus significantly improving its nucleation ability and maintaining stable nucleation performance after multiple thermal cycles. For example, Chinese Patent Application with Publication No. CN112175582A discloses a eutectic phase change material of oxalic acid dihydrate / vanadium salt and its preparation method. This patent uses the eutectic of oxalic acid dihydrate / vanadium salt as the phase change main body and uses boric acid, strontium chloride hexahydrate, and nickel sulfate hexahydrate as nucleating agents to prepare a composite phase change material, and the supercooling degree of the obtained composite phase change material is lower than 2.5 °C.

[0004] In addition, during the preparation of inorganic hydrated salt phase change microcapsules, emulsification difficulties lead to a low coating rate, resulting in limited improvement in the enthalpy value of the material. At the same time, the low thermal conductivity of inorganic hydrated salts severely limits the heat transfer and regulation efficiency. Therefore, improving the coating rate of inorganic hydrated salt phase change microcapsules, enhancing the thermal conductivity, and improving the thermal cycling stability are still important research directions at present. Summary of the Invention

[0005] Aiming at the problems existing in the prior art, the present invention provides a hydrated salt phase change microcapsule and its preparation method, so as to solve the technical problems of easy phase separation, large supercooling degree, easy leakage, poor cycling stability, and low thermal conductivity of hydrated salt phase change materials in the prior art during use.

[0006] The present invention is realized through the following technical solutions: A hydrated salt phase change microcapsule, comprising a core layer and a shell layer; The core layer comprises a nucleating agent and an inorganic hydrated salt phase change material, and the shell layer is a polymer layer formed by the reaction of a water-soluble monomer, an oil-soluble monomer, and a thermal conductive filler; Calculated by mass percentage, the core layer accounts for 80wt% - 90wt% of the hydrated salt phase change microcapsule. In the core layer, the proportion of the inorganic hydrated salt phase change material is 97wt% - 99wt%.

[0007] Preferably, the supercooling degree of the hydrated salt phase change microcapsule is 0.7 - 2.4 °C, the enthalpy value is 189.9 - 260.3 J / g, and the thermal conductivity is 1.09 - 2.24 W / (m·K).

[0008] The preparation method of the above-mentioned hydrated salt phase change microcapsule comprises the following steps: S1: Add inorganic hydrated salt phase change material, nucleating agent and water-soluble monomer into water, mix them evenly to obtain an aqueous solution; dissolve the emulsifier in an organic solvent, mix them evenly to obtain an oil phase solution; the emulsifier is a triblock copolymer; add the aqueous solution into the oil phase solution, stir and emulsify to obtain a W / O emulsion; S2: Add a catalyst or initiator to the W / O emulsion in sequence, then slowly add an oil-soluble monomer, and under stirring, make the water-soluble monomer and the oil-soluble monomer react to form a polymer shell under the action of the catalyst or initiator, encapsulating the inorganic hydrated salt phase change material and the nucleating agent; S3: Add the amino-functionalized thermal conductive material to the reaction system completed in step S2, continue to stir and react to obtain the hydrated salt phase change microcapsule.

[0009] Preferably, the emulsifier is at least one of P135, L-121, L-101, PLA-PEG-PLA and PS-PVP-PS.

[0010] Preferably, the nucleating agent is at least one of trisodium phosphate dodecahydrate, disodium hydrogen phosphate dodecahydrate, sodium borate decahydrate, sodium carbonate decahydrate, sodium phosphate decahydrate, nano-silicon dioxide and aluminum nitride.

[0011] Preferably, the mass ratio of the nucleating agent to the inorganic hydrated salt phase change material is (1~3):100.

[0012] Preferably, the water-soluble monomer is at least one of polyethylene glycol, diethylenetriamine, tetraethylenepentamine, sodium styrene sulfonate and acrylamide; the oil-soluble monomer is at least one of isophorone diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, epoxy acrylate, styrene and methyl methacrylate.

[0013] Preferably, the mass ratio of the inorganic hydrated salt phase change material to the water-soluble monomer and the oil-soluble monomer is 9.5:(0.6~1.5):(1.1~5); the mass ratio of the amino-functionalized thermal conductive material to the inorganic hydrated salt phase change material is (0.5~5):100.

[0014] Preferably, the amino-functionalized thermal conductive material is at least one of amino-functionalized carbon nanotubes, amino-functionalized graphene oxide, amino-functionalized silicon carbide and amino-functionalized boron nitride.

[0015] Compared with the prior art, the present invention has the following beneficial technical effects: The present invention discloses a preparation method of hydrated salt phase change microcapsules. First, through the reaction of water-soluble monomers and oil-soluble monomers under the action of a catalyst or initiator, a polymer shell layer is formed, and the encapsulated inorganic hydrated salt phase change material and nucleating agent are used as the core layer, effectively improving the structural stability and avoiding the problem of easy leakage of the phase change material. Second, a nucleating agent is added to the core layer, and the nucleating agent is used as the aqueous phase of the W / O emulsion, effectively suppressing the supercooling phenomenon of the hydrated salt. Third, when preparing the oil-phase solution, the emulsifier selected in the present invention is a triblock copolymer, which effectively stabilizes the emulsion interface, breaks through the limitation of the traditional method that a large amount of deionized water needs to be added to prepare a saturated solution, solves the problem of difficult emulsification in the preparation process of inorganic hydrated salt phase change microcapsules in the prior art, improves the coating rate and enthalpy value of the phase change material. Specifically, the mass fraction of the core material in the present invention is increased to 80% - 90%, and the enthalpy value of the phase change microcapsules is increased by more than 40%. Fourth, an aminated modified thermal conductive material is introduced into the shell layer. Through its covalent bonding and hydrogen bonding with the functional groups such as isocyanate groups on the surface shell layer material of the phase change microcapsules, an organic-inorganic composite double-shell structure is constructed on the surface of the microcapsules, effectively improving the thermal conductivity of the microcapsule material. That is, through a precise secondary coating process, while maintaining the energy storage characteristics of the phase change material, a high thermal conductivity characteristic of the outer shell layer is given, solving the technical bottleneck of the low thermal conduction efficiency of traditional phase change microcapsules. In summary, the present invention discloses hydrated salt phase change microcapsules with excellent characteristics of high thermal conductivity and low supercooling. The high thermal conductivity and low supercooling phase change microcapsules are composed of a nucleating agent-modified hydrated salt phase change core material and a polymer / thermal conductive material hybrid shell layer. The high thermal conductivity phase change microcapsules are first prepared into a nucleating agent-modified low supercooling inorganic hydrated salt phase change core material by the melt blending method, and then a polymer shell layer is induced to form at the oil-water interface through the W / O inverse emulsion template method. Finally, the modified thermal conductive material is introduced into the polymer shell layer by electrostatic interaction and hydrogen bonding to construct a high thermal conductivity shell layer. The phase change microcapsules prepared by the present invention have a coating rate higher than 80%, a supercooling degree lower than 3 °C, an apparent thermal conductivity greater than 1 W / (m·K), a controllable particle size distribution (5 - 70 μm), excellent encapsulation performance and cycle stability. Description of the Drawings

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required to be used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0017] Figure 1 This is the process flow diagram for preparing the high thermal conductivity and low supercooling inorganic hydrated salt phase change microcapsules of the present invention; Figure 2 This is the scanning electron microscope image of the high thermal conductivity and low supercooling inorganic hydrated salt phase change microcapsules prepared in Example 1 of the present invention; Figure 3 This is the cross-sectional scanning electron microscope image of the high thermal conductivity and low supercooling inorganic hydrated salt phase change microcapsules prepared in Example 1 of the present invention; Figure 4 This is the leakage experiment of the high thermal conductivity and low supercooling inorganic hydrated salt phase change microcapsules prepared in Example 1 of the present invention on an 85 °C hot stage; Figure 5 These are the DSC curves of the high thermal conductivity and low supercooling inorganic hydrated salt phase change microcapsules prepared in Example 1 after the 1st and 200th heating and cooling cycles. Detailed implementation manners

[0018] To enable those skilled in the art to understand the features and effects of the present invention, the following provides a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used herein shall have the ordinary meanings understood by those skilled in the art regarding the present invention. In case of conflict, the definitions in this specification shall prevail.

[0019] The theories or mechanisms described and disclosed herein, whether correct or incorrect, shall not limit the scope of the present invention in any way, that is, the content of the present invention can be implemented without being limited by any specific theory or mechanism.

[0020] In this article, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are only for the sake of brevity and convenience. Accordingly, the description of numerical ranges or percentage ranges should be regarded as having covered and specifically disclosed all possible sub-ranges and individual numerical values within the range (including integers and fractions).

[0021] In this article, unless otherwise specified, "comprising", "including", "containing", "having" or similar expressions cover the meanings of "consisting of..." and "consisting essentially of...". For example, "A comprises a" covers the meanings of "A comprises a and others" and "A only comprises a".

[0022] In this article, for the sake of brevity, not all possible combinations of all technical features in each embodiment or example have been described. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each embodiment or example can be combined arbitrarily, and all possible combinations should be considered as within the scope described in this specification.

[0023] Such as Figure 1As shown in the figure, the present invention provides a method for preparing hydrated salt phase change microcapsules, comprising the following steps: S1: Add an inorganic hydrated salt phase change material, a nucleating agent, and a water-soluble monomer into water, mix uniformly to obtain an aqueous solution; dissolve an emulsifier in an organic solvent, mix uniformly to obtain an oil-phase solution; add the aqueous solution into the oil-phase solution, stir and emulsify to obtain a W / O emulsion; The inorganic hydrated salt phase change material is at least one of sodium acetate trihydrate, sodium thiosulfate pentahydrate, barium hydroxide octahydrate, sodium sulfate decahydrate, sodium carbonate decahydrate, disodium hydrogen phosphate dodecahydrate, potassium alum dodecahydrate, ammonium alum dodecahydrate, and strontium chloride hexahydrate.

[0024] The nucleating agent is at least one of trisodium phosphate dodecahydrate, disodium hydrogen phosphate dodecahydrate, sodium borate decahydrate, sodium carbonate decahydrate, sodium phosphate decahydrate, nano-silica, and aluminum nitride.

[0025] The water-soluble monomer is at least one of polyethylene glycol, diethylenetriamine, tetraethylenepentamine, sodium p-styrenesulfonate, and acrylamide.

[0026] The emulsifier is at least one of P135, L-121, L-101, PLA-PEG-PLA, and PS-PVP-PS.

[0027] The above-mentioned P135 is a typical triblock copolymer, specifically a polyethylene oxide-dimeric hydroxystearate-polyethylene oxide triblock copolymer.

[0028] The above-mentioned L-121 and L-101 are both PEO-PPO-PEO, that is, a polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer.

[0029] The above-mentioned PLA-PEG-PLA is an emulsifier with hydrophobic polylactic acid (PLA) at both ends and hydrophilic polyethylene glycol (PEG) in the middle.

[0030] The above-mentioned PS-PVP-PS is an emulsifier with hydrophobic polystyrene (PS) at both ends and hydrophilic polyvinylpyrrolidone (PVP) in the middle.

[0031] The organic solvent is at least one of cyclohexane, toluene, acetone, dichloromethane, and carbon tetrachloride.

[0032] The mass ratio of the nucleating agent to the inorganic hydrated salt phase change material is (1~3):100. The addition amount of the nucleating agent determines the supercooling degree of the phase change material. Too much or too little addition will result in the failure of supercooling inhibition, and an appropriate amount will inhibit supercooling. The preferred mass ratio of the nucleating agent to the inorganic hydrated salt phase change material is 2:100.

[0033] The mass ratio of the emulsifier to the organic solvent is (0.5~3):100.

[0034] S2: Add a catalyst or initiator to the W / O emulsion in sequence, and then slowly add an oil-soluble monomer. Under stirring, the water-soluble monomer and the oil-soluble monomer react to form a polymer shell layer under the action of the catalyst or initiator, encapsulating the inorganic hydrated salt phase change material and the nucleating agent. More specifically: The catalyst is at least one of dibutyltin dilaurate, stannous octoate, trialkylphosphine, and tertiary amine.

[0035] The initiator is at least one of azobisisobutyronitrile, ammonium persulfate, and 1173 photoinitiator. Among them, 1173 photoinitiator is a highly efficient photosensitive initiator, and its chemical name is 2-hydroxy-2-methyl-1-phenyl-1-propanone.

[0036] The mass ratio of the inorganic hydrated salt phase change material to the water-soluble monomer and the oil-soluble monomer is 9.5:(0.6~1.5):(1.1~5). The mass ratio of the inorganic hydrated salt phase change material to the reaction monomers (water-soluble monomer and oil-soluble monomer) determines the proportion of the phase change material in the whole microcapsule and the cycle stability of the phase change microcapsule. The more the proportion of the inorganic hydrated salt, the greater the enthalpy value of the phase change microcapsule; the less the proportion of the reaction monomers, the thinner the final synthesized shell layer of the phase change microcapsule, and the worse the high and low temperature cycle resistance. Preferably, the mass ratio of the inorganic hydrated salt phase change material to the water-soluble monomer and the oil-soluble monomer is 9.5:1.0:3.5.

[0037] S3: Add an amino-functionalized thermal conductive material to the reaction system that has completed step S2, and continue stirring and reacting to obtain the hydrated salt phase change microcapsule.

[0038] The amino-functionalized thermal conductive material is at least one of amino-functionalized carbon nanotubes, amino-functionalized graphene oxide, amino-functionalized silicon carbide, and amino-functionalized boron nitride. The thermal conductive material is an amino-functionalized thermal conductive material. The amino group contained in the thermal conductive material can undergo an addition reaction with the residual isocyanate group of the shell material and be incorporated into the shell layer, or can form a hydrogen bond with the polar group of the shell material and be incorporated into the shell material, enhancing the structural stability of the material.

[0039] The mass ratio of the aminated thermally conductive material to the inorganic hydrated salt phase change material is (0.5-5):100. The amount of thermally conductive material added determines the thermal conductivity of the phase change microcapsule. If it is too little, the thermal conductivity of the phase change microcapsule is low; if it is too much, the shell density is affected, causing the shell material to be unable to withstand high and low temperature cycles and the shell material to rupture. Preferably, the mass ratio of the aminated thermally conductive material to the inorganic hydrated salt phase change material is 3:100.

[0040] Preferably, the above-mentioned S2~S3 are specifically as follows: first, a catalyst or an initiator is added dropwise to the W / O emulsion, and then an oil-soluble reaction monomer diluted with an organic solvent is slowly added dropwise, wherein the organic solvent is at least one of cyclohexane, toluene, acetone, dichloromethane and carbon tetrachloride. After the reaction, an amino-modified thermal conductive material is added to the system, and finally the product obtained by the reaction is washed with a hot cyclohexane solution, filtered and dried, and the obtained powder is the hydrated salt phase change microcapsule.

[0041] Further, in order to explain the process of the water-soluble monomer and the oil-soluble monomer in the present invention reacting to form a polymer shell under the action of a catalyst or an initiator, several specific raw materials are listed here for explanation: If the water-soluble monomers are polyethylene glycol and polyamine, the oil-soluble monomers are diisocyanates, and the catalyst is dibutyltin dilaurate, the reaction that occurs is an addition reaction between the alcohol hydroxyl group and the polyamine and the isocyanate group, the polyethylene glycol plays a chain extension role, and the polyamine plays a cross-linking role.

[0042] If the water-soluble monomer is acrylamide, the oil-soluble monomer is methyl methacrylate, and the initiator is ammonium persulfate, the reaction that occurs is free radical addition polymerization of the acrylic acid monomer.

[0043] If the water-soluble monomer is sodium p-styrene sulfonate, the oil-soluble monomer is epoxy acrylate, and the photoinitiator is 1173 photoinitiator, free radical addition polymerization occurs.

[0044] In addition, the present invention also discloses a hydrated salt phase-change microcapsule prepared based on the above method, wherein the hydrated salt phase-change microcapsule comprises a core layer and a shell layer; The core layer includes a nucleating agent and an inorganic hydrated salt phase change material, and the shell layer is a polymer layer formed by the reaction of a water-soluble monomer, an oil-soluble monomer and a thermally conductive filler; In terms of mass percentage, the core layer accounts for 80wt% to 90wt% of the hydrated salt phase change microcapsule, and the inorganic hydrated salt phase change material accounts for 97wt% to 99wt% of the core layer. The core layer accounts for 10wt% to 20wt% of the hydrated salt phase change microcapsule, and the thermal conductive filler accounts for 0.5wt% to 5wt% of the shell layer.

[0045] In addition, the supercooling degree of the hydrated salt phase change microcapsules prepared by the method of the present invention is 0.7 - 2.4 °C, the enthalpy value is 189.9 - 260.3 J / g, and the thermal conductivity is 1.09 - 2.24 W / (m·K).

[0046] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0047] Conventional instrument equipment in the art is used in the following embodiments. For the experimental methods without specific conditions noted in the following embodiments, they are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer. Various raw materials are used in the following embodiments. Unless otherwise stated, commercially available products are used, and their specifications are the conventional specifications in the art. In the specification of the present invention and the following embodiments, unless otherwise specified, "%" represents weight percentage, "parts" represents weight parts, and the ratio represents weight ratio.

[0048] In Examples 1 - 3, the main variable is the type of inorganic hydrated salt phase change material. Different hydrated salt phase change microcapsules are prepared by different inorganic hydrated salt phase change materials. Specifically: Example 1 A preparation method of hydrated salt phase change microcapsules includes the following steps: Weigh 9.5 g of inorganic hydrated salt phase change material sodium acetate trihydrate, 0.5 g of water, 0.19 g of disodium hydrogen phosphate dodecahydrate, and 0.6 g of water-soluble monomer diethylenetriamine into a 40 mL glass sample bottle. Then place the sample bottle in an environment at 65 °C for blending until evenly mixed to obtain a solution as the aqueous phase of the system; According to a mass ratio of 1:100, blend emulsifier ARLACEL-P135 with 20 g of cyclohexane solution in an environment at 65 °C until evenly mixed to obtain a solution as the oil phase of the system; Slowly drip the aqueous phase solution of the system into the oil phase solution of the system, adjust the rotation speed to 1000 rpm, and emulsify for 1 h to obtain a W / O emulsion; Drip 0.06 g of reaction catalyst dibutyltin dilaurate into the W / O emulsion system; Adjust the rotation speed to 400 rpm, slowly drip 2.0 g of oil-soluble monomer isophorone diisocyanate diluted with 5 g of cyclohexane. After the reaction monomer is added completely, react for 1.5 h; Add 0.285 g of aminated graphene oxide to the reaction system and continue to react for 2.5 h; The product obtained from the reaction was washed with hot cyclohexane, filtered by suction, and dried. The resulting powder was the high thermal conductivity and low supercooling hydrated salt phase change microcapsules.

[0049] Example 2 The difference between this example and Example 1 was that the inorganic hydrated salt phase change material was sodium carbonate decahydrate.

[0050] Example 3 The difference between this example and Example 1 was that the inorganic hydrated salt phase change material was sodium thiosulfate pentahydrate.

[0051] In Examples 4 to 6, the main variable was the addition amount of the nucleating agent disodium hydrogen phosphate dodecahydrate. Different hydrated salt phase change microcapsules were prepared by adjusting the addition amount of disodium hydrogen phosphate dodecahydrate. Specifically: Example 4 A preparation method of hydrated salt phase change microcapsules, comprising the following steps: Weigh 9.5 g of the inorganic hydrated salt phase change material sodium acetate trihydrate, 0.5 g of water, 0.095 g of disodium hydrogen phosphate dodecahydrate, and 0.6 g of the water-soluble monomer diethylenetriamine into a 40 mL glass sample bottle. Subsequently, place the sample bottle in an environment at 65 °C for blending until evenly mixed to obtain a solution as the aqueous phase of the system; According to a mass ratio of 1:100, blend the emulsifier ARLACEL-P135 with 20 g of cyclohexane solution in an environment at 65 °C until evenly mixed to obtain a solution as the oil phase of the system; Slowly drop the aqueous phase solution of the system into the oil phase solution of the system, adjust the rotation speed to 1000 rpm, and emulsify for 1 h to obtain a W / O emulsion; Drop 0.06 g of the reaction catalyst dibutyltin dilaurate into the W / O emulsion system; Adjust the rotation speed to 400 rpm, slowly drop 2.0 g of the oil-soluble monomer isophorone diisocyanate diluted with 5 g of cyclohexane, and react for 1.5 h after the addition of the reaction monomer is complete; Add 0.285 g of amino-functionalized graphene oxide to the reaction system and continue to react for 2.5 h; Wash the product obtained from the reaction with hot cyclohexane, filter by suction, and dry. The resulting powder was the high thermal conductivity and low supercooling hydrated salt phase change microcapsules.

[0052] Example 5 The difference between this example and Example 2 was that the addition amount of disodium hydrogen phosphate dodecahydrate was 0.19 g.

[0053] Example 6 The difference between this example and Example 2 was that the addition amount of disodium hydrogen phosphate dodecahydrate was 0.285 g.

[0054] In Examples 7 to 9, the main variables are water-soluble monomers and oil-soluble monomers. Different shell materials are obtained by adjusting the types of water-soluble monomers and oil-soluble monomers. Specifically: Example 7 A method for preparing hydrated salt phase change microcapsules includes the following steps: Weigh 9.5 g of sodium acetate trihydrate, 0.5 g of water, 0.19 g of disodium hydrogen phosphate dodecahydrate, 0.11 g of diethylenetriamine, and 1.24 g of PEG-400 as water-soluble monomers, add them to a 40 mL glass sample bottle, and then place the sample bottle in an environment at 65 °C for blending until evenly mixed to obtain a solution as the aqueous phase of the system; According to a mass ratio of 1:100, blend emulsifier ARLACEL-P135 with 20 g of cyclohexane solution in an environment at 65 °C until evenly mixed to obtain a solution as the oil phase of the system; Slowly drip the aqueous phase solution of the system into the oil phase solution of the system, adjust the rotation speed to 1000 rpm, and emulsify for 1 h to obtain a W / O emulsion; Drip 0.06 g of reaction catalyst dibutyltin dilaurate into the W / O emulsion system; Adjust the rotation speed to 400 rpm, slowly drip 1.1 g of isophorone diisocyanate diluted with 5 g of cyclohexane, and react for 1.5 h after the addition of the reaction monomers is complete; Add 0.285 g of aminated graphene oxide to the reaction system and continue to react for 2.5 h; Wash, filter by suction, and dry the product obtained from the reaction with hot cyclohexane. The obtained powder is high thermal conductivity and low supercooling hydrated salt phase change microcapsules.

[0055] Example 8 A method for preparing hydrated salt phase change microcapsules includes the following steps: Weigh 9.5 g of sodium acetate trihydrate, 0.5 g of water, 0.19 g of disodium hydrogen phosphate dodecahydrate, and 0.61 g of sodium p-styrenesulfonate, add them to a 40 mL glass sample bottle, and then place the sample bottle in an environment at 65 °C for blending until evenly mixed to obtain a solution as the aqueous phase of the system; According to a mass ratio of 1:100, blend emulsifier ARLACEL-P135 with 20 g of cyclohexane solution in an environment at 65 °C until evenly mixed to obtain a solution as the oil phase of the system; Slowly drip the aqueous phase solution of the system into the oil phase solution of the system, adjust the rotation speed to 1000 rpm, and emulsify for 1 h to obtain a W / O emulsion; Add 0.06 g of photoinitiator 1173 to the W / O emulsion system; Adjust the rotation speed to 400 rpm, and slowly add 1.84 g of epoxy acrylate diluted with 5 g of cyclohexane dropwise. After the reaction monomer is completely added, react for 1.5 h under ultraviolet light irradiation; Add 0.285 g of amino-functionalized graphene oxide to the reaction system and continue to react for 2.5 h; Wash the product obtained from the reaction with hot cyclohexane, filter by suction, and dry. The obtained powder is the high-thermal-conductivity and low-supercooling hydrated salt phase change microcapsule.

[0056] Example 9 A preparation method of hydrated salt phase change microcapsules, comprising the following steps: Weigh 9.5 g of sodium acetate trihydrate, 0.5 g of water, 0.19 g of disodium hydrogen phosphate dodecahydrate, and 1.02 g of acrylamide, add them to a 40 mL glass sample bottle, and then place the sample bottle in an environment at 65 °C for blending until evenly mixed to obtain a solution as the aqueous phase of the system; According to a mass ratio of 1:100, blend the emulsifier ARLACEL-P135 with 20 g of cyclohexane solution in an environment at 65 °C until evenly mixed to obtain a solution as the oil phase of the system; Slowly drop the aqueous phase solution of the system into the oil phase solution of the system, adjust the rotation speed to 1000 rpm, and emulsify for 1 h to obtain a W / O emulsion; Add 0.06 g of ammonium persulfate to the W / O emulsion system; Adjust the rotation speed to 400 rpm, and slowly add 1.43 g of methyl methacrylate diluted with 5 g of cyclohexane dropwise. After the reaction monomer is completely added, react for 1.5 h; Add 0.285 g of amino-functionalized graphene oxide to the reaction system and continue to react for 2.5 h; Wash the product obtained from the reaction with hot cyclohexane, filter by suction, and dry. The obtained powder is the high-thermal-conductivity and low-supercooling hydrated salt phase change microcapsule.

[0057] The main variables in Examples 10 to 12 are the addition amounts of water-soluble monomers and oil-soluble monomers, that is, the core-shell ratio is adjusted to prepare different hydrated salt phase change microcapsules. Specifically: Example 10 A preparation method of hydrated salt phase change microcapsules, comprising the following steps: Weigh 9.5 g of sodium acetate trihydrate, 0.5 g of water, 0.19 g of disodium hydrogen phosphate dodecahydrate, and 1.5 g of water-soluble monomer diethylenetriamine, place them in a 40 mL glass sample bottle, and then place the sample bottle in an environment at 65 °C for blending until evenly mixed to obtain a solution as the aqueous phase of the system; Blend emulsifier ARLACEL-P135 and 20 g of cyclohexane solution in an environment at 65 °C according to a mass ratio of 1:100 until evenly mixed to obtain a solution as the oil phase of the system; Slowly drip the aqueous phase solution of the system into the oil phase solution of the system, adjust the rotation speed to 1000 rpm, and emulsify for 1 h to obtain a W / O emulsion; Drip 0.06 g of reaction catalyst dibutyltin dilaurate into the W / O emulsion system; Adjust the rotation speed to 400 rpm, slowly drip 5.0 g of oil-soluble monomer isophorone diisocyanate diluted with 5 g of cyclohexane, and react for 1.5 h after the addition of the reaction monomer is complete; Add 0.285 g of aminated graphene oxide to the reaction system and continue to react for 2.5 h; Wash, filter by suction, and dry the product obtained from the reaction with hot cyclohexane. The obtained powder is the high thermal conductivity and low supercooling hydrated salt phase change microcapsule.

[0058] Example 11 The difference between this example and Example 9 is that the addition amount of water-soluble monomer diethylenetriamine is 1.0 g, and the addition amount of oil-soluble monomer isophorone diisocyanate is 3.5 g.

[0059] Example 12 The difference between this example and Example 9 is that the addition amount of water-soluble monomer diethylenetriamine is 0.6 g, and the addition amount of oil-soluble monomer isophorone diisocyanate is 2.0 g.

[0060] The main variable in Examples 13 to 15 is the addition amount of the thermal conductive material. Different hydrated salt phase change microcapsules are prepared by adjusting the addition amount of the thermal conductive material. Specifically: Example 13 A preparation method of hydrated salt phase change microcapsules includes the following steps: Weigh 9.5 g of inorganic hydrated salt phase change material sodium acetate trihydrate, 0.5 g of water, 0.19 g of disodium hydrogen phosphate dodecahydrate, and 0.6 g of water-soluble monomer diethylenetriamine in a 40 mL glass sample bottle, and then place the sample bottle in an environment at 65 °C for blending until evenly mixed to obtain a solution as the aqueous phase of the system; Mix the emulsifier ARLACEL-P135 with 20 g of cyclohexane solution at a mass ratio of 1:100 in an environment of 65 °C until evenly mixed to obtain a solution as the oil phase of the system; Slowly add the aqueous solution of the system to the oil-phase solution of the system, adjust the rotation speed to 1000 rpm, and emulsify for 1 h to obtain a W / O emulsion; Add 0.06 g of the reaction catalyst dibutyltin dilaurate to the W / O emulsion system; Adjust the rotation speed to 400 rpm, slowly add 2.0 g of the oil-soluble monomer isophorone diisocyanate diluted with 5 g of cyclohexane, and react for 1.5 h after the addition of the reaction monomer is complete; Add 0.0475 g of amino-functionalized graphene oxide to the reaction system and continue to react for 2.5 h; Wash the product obtained from the reaction with hot cyclohexane, filter by suction, and dry. The resulting powder is the hydrated salt phase change microcapsule with high thermal conductivity and low supercooling.

[0061] Example 14 The difference between this example and Example 13 is that the addition amount of the thermal conductive material, i.e., amino-functionalized graphene oxide, is 0.285 g.

[0062] Example 15 The difference between this example and Example 13 is that the addition amount of the thermal conductive material, i.e., amino-functionalized graphene oxide, is 0.475 g.

[0063] Comparative Example 1 The difference between this comparative example and Example 1 is that no nucleating agent, i.e., disodium hydrogen phosphate dodecahydrate, is added. The specific process is as follows: Weigh 9.5 g of sodium acetate trihydrate, 0.5 g of water, and 0.6 g of diethylenetriamine into a 40 mL glass sample bottle, and then place the sample bottle in an environment of 65 °C for blending until evenly mixed to obtain a solution as the aqueous phase of the system; Mix the emulsifier ARLACEL-P135 with 20 g of cyclohexane solution at a mass ratio of 1:100 in an environment of 65 °C until evenly mixed to obtain a solution as the oil phase of the system; Slowly add the aqueous solution of the system to the oil-phase solution of the system, adjust the rotation speed to 1000 rpm, and emulsify for 1 h to obtain a W / O emulsion; Add 0.06 g of the reaction catalyst dibutyltin dilaurate to the W / O emulsion system; Adjust the rotation speed to 400 rpm, slowly add 2.0 g of the oil-soluble monomer isophorone diisocyanate diluted with 5 g of cyclohexane, and react for 1.5 h after the addition of the reaction monomer is complete; Add 0.285 g of amino-functionalized graphene oxide to the reaction system and continue the reaction for 2.5 h; Wash the product obtained from the reaction with hot cyclohexane, filter it by suction, and dry it. The resulting powder is the high thermal conductivity and low supercooling hydrated salt phase change microcapsule.

[0064] Comparative Example 2 The difference between this comparative example and Example 1 is that no thermal conductive material, i.e., amino-functionalized graphene oxide, is added. The specific process is as follows: Weigh 9.5 g of sodium acetate trihydrate, 0.5 g of water, 0.19 g of disodium hydrogen phosphate dodecahydrate, and 0.6 g of diethylenetriamine into a 40 mL glass sample bottle. Then place the sample bottle in an environment at 65 °C for blending until evenly mixed to obtain a solution as the aqueous phase of the system; According to a mass ratio of 1:100, blend the emulsifier ARLACEL-P135 with 20 g of cyclohexane solution in an environment at 65 °C until evenly mixed to obtain a solution as the oil phase of the system; Slowly add the aqueous phase solution of the system to the oil phase solution of the system, adjust the rotation speed to 1000 rpm, and emulsify for 1 h to obtain a W / O emulsion; Add 0.06 g of the reaction catalyst dibutyltin dilaurate to the W / O emulsion system; Adjust the rotation speed to 400 rpm, and slowly add 2.0 g of the oil-soluble monomer isophorone diisocyanate diluted with 5 g of cyclohexane. After the reaction monomer is completely added, react for 3 h; Wash the product obtained from the reaction with hot cyclohexane, filter it by suction, and dry it. The resulting powder is the high thermal conductivity and low supercooling hydrated salt phase change microcapsule.

[0065] The properties of the high thermal conductivity and low supercooled hydrated salt phase change microcapsules prepared in Examples 1-13 of the present invention and the hydrated salt phase change microcapsules prepared in Comparative Examples 1 and 2 are shown in Table 1. As can be seen from Table 1, the method for preparing hydrated salt phase change microcapsules proposed in Examples 1-3 of the present invention is not only applicable to the coating of sodium acetate trihydrate, but also applicable to inorganic hydrated salts such as sodium carbonate decahydrate and sodium thiosulfate pentahydrate. The prepared phase change microcapsules have a coating rate of more than 88%, showing high enthalpy characteristics. From Examples 4-6 and Comparative Example 1, it can be seen that adding 2 wt% of nucleating agent can reduce the supercooling degree of sodium acetate trihydrate from the initial 12 °C to 1.1 °C. An appropriate amount of nucleating agent can provide heterogeneous nucleation sites for the hydrated salt phase change material, reduce the energy required for crystal nucleus formation, and shorten the nucleation time. From Examples 7-9, it can be seen that the selection of the shell material of the method for preparing hydrated salt phase change microcapsules proposed in the present invention is not limited to polyurethane resin, but can also be acrylic resin, and shows high enthalpy characteristics. From Examples 10-12, it can be seen that the enthalpy value of the phase change microcapsules is mainly related to the proportion of hydrated salt in the phase change microcapsules. As the proportion of hydrated salt in the phase change microcapsules increases, the enthalpy value of the phase change microcapsules increases from 222.6 J / g to 258.9 J / g. From Examples 13-15 and Comparative Example 2, it can be seen that introducing a thermal conductive material into the shell material can build a high thermal conductivity path between the inside and the shell of the phase change microcapsules, significantly improve the thermal conductivity of the phase change microcapsules, and increase the thermal conductivity of the phase change microcapsules from the initial 0.54 W / (m·K) to 2.24 W / (m·K). The increase in thermal conductivity makes the phase change microcapsules respond more quickly to heat, manifested as faster heat storage and heat release rates, thereby effectively suppressing the supercooling phenomenon and reducing the supercooling degree from 1.4 °C to 0.9 °C.

[0066] Table 1 Properties of the high thermal conductivity and low supercooled hydrated salt phase change microcapsules of the present invention and the hydrated salt phase change microcapsules of the comparative examples

[0067] Figure 2 This is the scanning electron microscope image of the high thermal conductivity and low supercooled inorganic hydrated salt phase change microcapsules prepared in Example 1 of the present invention. As can be seen from the figure, the phase change microcapsules are highly dispersed, showing a complete spherical structure, with a particle size distribution of 5-70 μm, suitable for many application scenarios.

[0068] Figure 3 This is the cross-sectional scanning electron microscope image of the high thermal conductivity and low supercooled inorganic hydrated salt phase change microcapsules prepared in Example 1 of the present invention. As can be seen from the figure, the phase change microcapsules show an obvious core-shell structure, where the thickness of the shell material is 0.92 μm, proving the successful preparation of the phase change microcapsules.

[0069] Figure 4Leakage experiment of the high thermal conductivity and low supercooling inorganic hydrated salt phase change microcapsules prepared in Example 1 of the present invention on a hot stage at 85 °C. As can be seen from the figure, the phase change microcapsules do not leak after being placed on the hot stage at 85 °C for 1 h, showing excellent anti-leakage characteristics.

[0070] Figure 5 DSC curves of the high thermal conductivity and low supercooling inorganic hydrated salt phase change microcapsules prepared in Example 1 after the 1st and 200th thermal cycles. As can be seen from the figure, the phase change microcapsules still have a relatively high melting enthalpy value after 200 cycles in a high-low temperature cycling oven at 20-80 °C, and the remaining enthalpy rate is as high as 97.26%, showing excellent thermal cycling stability.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A hydrated salt phase change microcapsule, characterized in that: The hydrated salt phase change microcapsule comprises a core layer and a shell layer; the core layer comprises a nucleating agent and an inorganic hydrated salt phase change material, and the shell layer is a polymer layer formed by the reaction of a water-soluble monomer, an oil-soluble monomer and a thermal conductive filler; Calculated by mass percentage, the core layer accounts for 80wt% to 90wt% of the hydrated salt phase change microcapsule, and in the core layer, the inorganic hydrated salt phase change material accounts for 97wt% to 99wt%.

2. A hydrated salt phase change microcapsule according to claim 1, characterized in that: The supercooling degree of the hydrated salt phase change microcapsule is 0.7-2.4°C, the enthalpy value is 189.9-260.3 J / g, and the thermal conductivity is 1.09-2.24 W / (m·K).

3. A method for preparing a hydrated salt phase change microcapsule according to any one of claims 1 to 2, characterized in that: The following steps are involved: S1: adding an inorganic hydrated salt phase change material, a nucleating agent and a water-soluble monomer into water, and mixing them uniformly to obtain an aqueous phase solution; dissolving an emulsifier in an organic solvent, and mixing them uniformly to obtain an oil phase solution; the emulsifier is a triblock copolymer; adding the aqueous phase solution into the oil phase solution, stirring and emulsifying, to obtain a W / O emulsion; S2: adding a catalyst or an initiator to the W / O emulsion in sequence, and then slowly adding an oil-soluble monomer, and stirring, so that the water-soluble monomer and the oil-soluble monomer react under the action of the catalyst or the initiator to form a polymer shell layer, which wraps the inorganic hydrated salt phase change material and the nucleating agent; S3: adding the aminated modified thermal conductive material to the reaction system after completing step S2, and continuing to stir the reaction to obtain the hydrated salt phase change microcapsules.

4. The method for preparing a hydrated salt phase change microcapsule according to claim 3, characterized in that: The emulsifier is at least one of P135, L-121, L-101, PLA-PEG-PLA and PS-PVP-PS.

5. The method for preparing a hydrated salt phase change microcapsule according to claim 3, characterized in that: The nucleating agent is at least one of trisodium phosphate dodecahydrate, disodium hydrogen phosphate dodecahydrate, sodium borate decahydrate, sodium carbonate decahydrate, sodium phosphate decahydrate, nano silicon dioxide and aluminum nitride.

6. The method for preparing a hydrated salt phase change microcapsule according to claim 3, characterized in that: The mass ratio of the nucleating agent to the inorganic hydrated salt phase change material is (1-3):

100.

7. The method for preparing a hydrated salt phase change microcapsule according to claim 3, characterized in that: The water-soluble monomer is at least one of polyethylene glycol, diethylenetriamine, tetraethylenepentamine, sodium p-styrene sulfonate and acrylamide; the oil-soluble monomer is at least one of isophorone diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, epoxy acrylate, styrene and methyl methacrylate.

8. The method for preparing a hydrated salt phase change microcapsule according to claim 3, characterized in that: The mass ratio of the inorganic hydrated salt phase change material to the water-soluble monomer and the oil-soluble monomer is 9.5:(0.6~1.5):(1.1~5); the mass ratio of the amino-modified thermal conductive material to the inorganic hydrated salt phase change material is (0.5~5):

100.

9. The method for preparing a hydrated salt phase change microcapsule according to claim 3, characterized in that: The aminated thermally conductive material is at least one of aminated carbon nanotubes, aminated graphene oxide, aminated silicon carbide and aminated boron nitride.

10. Use of a hydrated salt phase change microcapsule according to any one of claims 1 to 2 in the field of heat storage.

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