A composite wall material phase change microcapsule and its preparation method

Abstract

The present invention discloses a composite wall material phase change microcapsule, its preparation method and application. Among them, the preparation method of the composite wall material phase change microcapsule includes the following steps: (1) uniformly mixing a molten phase change material, an organic ligand, a neutral surfactant and a mixed solvent, and shearing to obtain a phase change microemulsion; (2) preparing a mixed solution of a metal salt and a silicate, stirring and heating the phase change microemulsion obtained in step (1), and simultaneously dropping the mixed solution to obtain a solid-liquid mixture; (3) washing and drying the obtained solid-liquid mixture to obtain a composite wall material phase change microcapsule. The method provided by the present invention can synthesize the composite wall material phase change microcapsule in one step, and has the advantages of large heat storage capacity, high coating rate, simple synthesis method, and is conducive to large-scale popularization and use. The composite wall material phase change microcapsule obtained by the method provided by the present invention has the characteristics of outstanding mechanical strength and heat resistance stability, and also has strong adsorption performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of phase change energy storage materials, and particularly relates to a composite wall material phase change microcapsule and a preparation method thereof. Background Art

[0002] Phase change microcapsules refer to capsule-like energy storage materials with heat storage and temperature regulation functions, which are synthesized by methods such as interfacial polymerization, chemical deposition, simple coacervation, and complex coacervation, using substances such as polymer materials and inorganic materials as shell materials and phase change materials as core materials. When the environmental temperature rises to the phase change temperature of the microcapsules, the core material inside the phase change microcapsules will automatically absorb and store heat and undergo a phase change; when the environmental temperature drops, the stored heat can be released again. Due to the encapsulation effect of the wall material structure, the core material will not leak during the phase change cycle, greatly extending the service life of the phase change microcapsules and ensuring the exertion of their energy storage function. At present, phase change microcapsule products have been gradually applied to many technical fields such as industrial textiles, waste heat storage, building energy conservation, and aerospace.

[0003] For phase change microcapsules, when the applicable temperature range is selected, that is, when the phase change core material is fixed, the level of its heat storage and temperature regulation effect mainly depends on the encapsulation effect of the shell material. Moreover, the type and quality of the shell material also determine whether the phase change microcapsules can have more functions. In recent years, with the in-depth research on new porous coordination polymers, researchers have begun to develop a new generation of phase change microcapsule materials containing porous coordination polymer composite shell materials.

[0004] CN104745149A discloses a preparation method of a carbon material metal organic framework-based composite phase change material. First, a hydrothermal method is used to in-situ grow MOF particles on the surface of a carbon material modified with polyvinylpyrrolidone (PVP) to prepare a carbon material metal organic framework-based porous carrier material. Then, a solution impregnation method is used to disperse the carbon material@MOF porous carrier material in a prepared solution containing a phase change core material, and the phase change core material is adsorbed by using the ultra-large specific surface area and nano-pore structure of the metal organic framework material, and dried at a temperature higher than the phase change temperature to obtain a carbon material metal organic framework-based composite phase change material. This method uses a carbon material as a carrier, which can appropriately improve the heat transfer performance of the composite phase change material. However, when using the solution impregnation method to store the phase change core material, its storage capacity is limited and it is easy to lose after multiple cycles. Moreover, during the process of in-situ growing MOF particles, the MOF particles and the carbon material surface are only combined by van der Waals forces (i.e., intermolecular forces), and are easy to fall off after multiple uses, resulting in the loss of its function.

[0005] Fan Shuang (Research on the Application of Organic-Inorganic Nanocomposite Microspheres in Catalysis and Phase Change Energy Storage, Doctoral Dissertation, University of Science and Technology Beijing, 2017) disclosed a preparation method of a composite phase change energy storage material of octadecanoic acid (SA) / mesoporous silica (SO2) hollow microspheres. First, a mixed solution containing cetyltrimethylammonium bromide template agent, absolute ethanol, and ammonia water was prepared. Under magnetic stirring conditions, sulfonated polystyrene was added. At room temperature, 0.3 g of tetraethyl orthosilicate was added dropwise, and the mixture was stirred and reacted for 6 h. After completion, it was centrifuged and separated with an ethanol aqueous solution, and washed 3 times with deionized water and ethanol, and dried in air to obtain a white powder. Then, the obtained powder was calcined at 550 °C for 6 h in an air atmosphere to remove the template agent in the pores, and mesoporous silica hollow microspheres were obtained. A certain amount of octadecanoic acid was weighed and dissolved in absolute ethanol. Under magnetic stirring, a certain amount of mesoporous silica hollow microspheres was added, and the mixture was continuously stirred for 4 h. The mixed solution was placed in an oven at 80 °C and kept overnight, and the solvent was evaporated to obtain a composite phase change energy storage material of octadecanoic acid / mesoporous silica hollow microspheres. This method requires the prior preparation of mesoporous silica hollow microspheres and then the preparation of the phase change energy storage material, and the process is relatively cumbersome; moreover, octadecanoic acid and the hollow microspheres are only combined by intermolecular forces and are not firm, and there is an obvious potential leakage hazard after multiple uses. Summary of the Invention

[0006] In order to overcome the deficiencies of the prior art, the present invention provides a composite wall material phase change microcapsule and a preparation method thereof. The method provided by the present invention can synthesize the composite wall material phase change microcapsule in one step, and has a large heat storage capacity, a high coating rate, a simple synthesis method, and is conducive to large-scale popularization and use. The composite wall material phase change microcapsule obtained by using the method provided by the present invention has the characteristics of outstanding mechanical strength and heat resistance stability, and has strong adsorption performance.

[0007] The first aspect of the present invention provides a preparation method of a composite wall material phase change microcapsule, comprising the following steps:

[0008] (1) Mixing the molten phase change material, organic ligand, neutral surfactant, and mixed solvent evenly, and shearing to obtain a phase change microemulsion;

[0009] (2) Preparing a mixed solution of metal salt and silicate, stirring and heating the phase change microemulsion obtained in step (1), and simultaneously dropping the mixed solution to obtain a solid-liquid mixture;

[0010] (3) Washing and drying the obtained solid-liquid mixture to obtain a composite wall material phase change microcapsule.

[0011] Further, in step (1), the phase change material is selected from one or more of n-alkanes, paraffins, and stearic acid esters with a phase change temperature of 20 °C to 30 °C, and paraffin is preferred.

[0012] Further, in step (1), the organic ligand is selected from one or more of pyromellitic acid, naphthalenedicarboxylic acid, and phenylacetic acid, and preferably phenylacetic acid.

[0013] Further, in step (1), the neutral surfactant is selected from one or more of nonylphenol polyoxyethylene ether-10, phenethylphenol polyoxyethylene ether-15, and isooctylphenol polyoxyethylene ether-15, and preferably isooctylphenol polyoxyethylene ether-15.

[0014] Further, in step (1), the mixed solvent is selected from an organic solvent and water, and preferably one or more of an ethanol aqueous solution, a methanol aqueous solution, and an acetone aqueous solution, and more preferably an ethanol aqueous solution, wherein the mass ratio of the organic solvent to water is 1:(15 - 45), and preferably 1:(20 - 30).

[0015] Further, in step (1), the mass ratio of the phase change material, the organic ligand, the neutral surfactant, and the mixed solvent is 1:(0.01 - 0.5):(0.05 - 0.5):(5 - 40), and preferably 1:(0.15 - 0.3):(0.08 - 0.25):(8 - 20).

[0016] Further, in step (1), after the phase change material, the organic ligand, the neutral surfactant, and the mixed solvent are mixed, high-speed shearing treatment is performed; for the shearing treatment, it is sheared at a temperature of 35°C to 70°C for 10 min to 40 min, and the shearing speed is 5000 rpm to 18000 rpm; the shearing temperature is preferably 45°C to 55°C; the shearing time is preferably 20 min to 30 min. The shearing speed is preferably 10000 rpm to 15000 rpm.

[0017] Further, in step (2), the stirring reaction speed is 200 rpm to 600 rpm, and preferably 300 rpm to 400 rpm. The heating temperature is 40°C to 75°C, and preferably 45°C to 55°C. The stirring reaction time is 0.5 h to 5 h, and preferably 1.5 h to 2.5 h.

[0018] Further, in step (2), the silicate is sodium silicate; the sodium silicate is selected from one or more of anhydrous sodium silicate, sodium silicate nonahydrate, and sodium silicate pentahydrate, and preferably anhydrous sodium silicate.

[0019] Further, in step (2), the metal salt is selected from one or more of cerium(III) nitrate hexahydrate, lanthanum(III) nitrate hexahydrate, yttrium(III) nitrate hexahydrate, and gadolinium(III) nitrate hexahydrate, and preferably gadolinium(III) nitrate hexahydrate, or gadolinium(III) nitrate hexahydrate and lanthanum(III) nitrate hexahydrate, wherein the mass ratio of gadolinium(III) nitrate hexahydrate to lanthanum(III) nitrate hexahydrate is 1:(0.1 - 0.3).

[0020] Further, in step (2), in the mixed solution, the mass concentration of the metal salt is 2% - 10%, preferably 3.5% - 6.5%; the mass concentration of the silicate is 15% - 75%, preferably 25% - 50%.

[0021] Further, in step (2), the dropping rate of the mixed solution is 2 g / min - 12 g / min, preferably 4 g / min - 5 g / min.

[0022] Further, in step (2), the mass ratio of the metal salt, the silicate to the organic ligand in step (1) is 1: (5.5 - 12): (0.2 - 1), preferably 1: (6 - 9): (0.35 - 0.65).

[0023] Further, in step (3), the drying temperature is 40°C - 110°C, preferably 60°C - 70°C. The drying time is 6 h - 30 h, preferably 8 h - 12 h.

[0024] The second aspect of the present invention provides a composite wall material phase change microcapsule obtained by the above preparation method.

[0025] Further, the microscopic morphology of the composite wall material phase change microcapsule is oval.

[0026] Further, the particle size of the composite wall material phase change microcapsule is 5 μm - 15 μm, the latent heat of fusion value is greater than 90 J / g, preferably 92 - 110 J / g; the coating rate is greater than 60%, and the thermal conductivity is 0.65 W·m -1 ·k -1 ~0.79 W·m -1 ·K -1 ,the compressive strength is 0.85 MPa - 1.36 MPa, the specific surface area is greater than 300 m 2 / g, preferably 305 - 380 m 2 / g; the pore volume is greater than 0.25 cm 3 / g, preferably 0.26 - 0.36 cm 3 / g.

[0027] Further, for the composite wall material phase change microcapsule, under the conditions of 25°C and 100 kPa, the formaldehyde gas adsorption capacity is 60 cm 3 / g - 80 cm 3 / g, and the carbon dioxide gas adsorption capacity is 30 cm 3 / g - 50 cm 3 / g.

[0028] The third aspect of the present invention provides a composite wall material phase change microcapsule obtained by the above preparation method for solar heat storage and temperature regulation, building insulation or indoor air purification.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] (1) In the method adopted by the present invention, the organic ligand component, due to containing both a lipophilic aromatic ring structure and a hydrophilic carboxyl functional group structure, acts as a surfactant and is easily dispersed around the melted phase change material in an aqueous solution; the neutral surfactant and the organic ligand component act synergistically, which helps to reduce the polarity of the phase change microemulsion system and enhance the system stability, enabling the phase change microcapsules to have a relatively regular morphology and a relatively uniform particle size distribution, thereby improving the encapsulation rate of the phase change microcapsules. In addition, the carboxyl functional group in the organic ligand component can dissociate a certain number of hydrogen ions, making the emulsion system acidic and used for the hydrolysis reaction of the silicate component, that is, realizing the complexation reaction of the organic ligand and metal ions and the formation of microcapsules in one step, and simplifying the preparation process of the composite wall material phase change microcapsules.

[0031] (2) For the composite wall material phase change microcapsules prepared by the present invention, the silica component in the wall material can improve the mechanical strength and heat resistance stability of the phase change microcapsules, and the porous coordination polymer component endows the phase change microcapsules with more functions, such as purifying harmful gases, etc. Description of the Drawings

[0032] Figure 1 FT-IR spectrum of the composite wall material phase change microcapsules prepared in Example 1;

[0033] Figure 2 SEM photograph of the composite wall material phase change microcapsules prepared in Example 1;

[0034] Figure 3 SEM photograph of the composite wall material phase change microcapsules prepared in Comparative Example 1;

[0035] Figure 4 SEM photograph of the composite wall material phase change microcapsules prepared in Comparative Example 2;

[0036] Figure 5 Formaldehyde adsorption amounts of the composite wall material phase change microcapsules prepared in Examples 1 and 3 and Comparative Examples 1-2;

[0037] Figure 6 Carbon dioxide adsorption amounts of the composite wall material phase change microcapsules prepared in Examples 1 and 3 and Comparative Examples 1-2. Detailed Embodiments

[0038] The preparation method and effect of the composite wall material phase change microcapsules of the present invention will be further described below through examples. The examples are implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific operation processes are given, but the protection scope of the present invention is not limited to the following examples.

[0039] In the following examples, the experimental methods, unless otherwise specified, are all conventional methods in the art. The experimental materials used in the following examples, unless otherwise specified, are all purchased from conventional biochemical reagent stores.

[0040] The morphology and particle size of the composite wall material phase change microcapsules were observed by a Hitachi S-4700 field emission scanning electron microscope (SEM) in Japan.

[0041] The latent heat of phase change value during the melting process of the composite wall material phase change microcapsules was measured by a differential scanning calorimeter (DSC). The instrument model was DSC-60 Plus of Shimadzu Corporation in Japan. Under a nitrogen atmosphere, the temperature test range was -20°C to 50°C, the heating rate was 10°C / min, and the sample weight was about 3.5 mg.

[0042] The thermal conductivity of the composite wall material phase change microcapsule sample was measured by a DRL-III-P thermal conductivity tester of Xiangyi Instrument Co., Ltd.

[0043] The compressive strength of the composite wall material phase change microcapsule sample was measured by a YL-C10K pressure testing machine of Guangdong Yuelian Instrument Co., Ltd.

[0044] N2 adsorption-desorption analysis was carried out by a 3H-2000PM high-performance specific surface and micropore analyzer of Beijing Beishide Instrument Technology Co., Ltd. The sample was vacuum degassed at 180°C for 12 h, weighed and then transferred to the analysis station. The N2 adsorption-desorption isotherm was measured at 77K, and the specific surface area and pore volume were calculated by the BET method.

[0045] The calculation formula for the encapsulation rate of the phase change microcapsules is:

[0046] Encapsulation rate / % = (latent heat of fusion value of microcapsules / latent heat of fusion value of phase change material) × 100%.

[0047] Example 1

[0048] Take 10 g of paraffin with a melting phase transition temperature of 25 °C, 2.5 g of phthalic acid, 1 g of isooctylphenol polyoxyethylene ether - 15, and mix them with 100 g of an ethanol aqueous solution. Among them, the mass ratio of ethanol to deionized water is 1:25. Under the conditions of 50 °C and 12,000 rpm, carry out high - speed shearing reaction for 25 min to obtain a phase - change microemulsion. Place the phase - change microemulsion in a four - necked flask, transfer it to an electrically heated mantle containing a mechanical stirrer, and under the conditions of 50 °C and 350 rpm, stir and react for 2 h. At the same time, dropwise add 100 g of an aqueous solution containing gadolinium nitrate hexahydrate, lanthanum nitrate hexahydrate, and sodium silicate at a rate of 4.5 g / min. The mass concentration of gadolinium nitrate hexahydrate and lanthanum nitrate hexahydrate is 5%, among which, the mass ratio of gadolinium nitrate hexahydrate to lanthanum nitrate hexahydrate is 1:0.2, and the mass concentration of sodium silicate is 35%. Filter the obtained solid - liquid mixture, repeatedly rinse it with deionized water, and place the filtrate in a blast drying oven for drying treatment at 65 °C for 10 h to obtain composite wall - material phase - change microcapsules. Among them, Figure 1 is the infrared spectrum (FT - IR) of the composite wall - material phase - change microcapsules prepared in this example; Figure 2 is the scanning electron microscope photograph (SEM) of the composite wall - material phase - change microcapsules prepared in this example, and the microscopic morphology is oval. In addition, the adsorption capacity of the composite wall - material phase - change microcapsules prepared in this example for formaldehyde is shown in Figure 5 and the adsorption capacity for carbon dioxide is shown in Figure 6 .

[0049] Preparation method of gadolinium - based porous coordination polymer: Take 2.5 g of phthalic acid and dissolve it in 100 g of an ethanol aqueous solution. Among them, the mass ratio of ethanol to deionized water is 1:25. Place the above - mentioned solution in a four - necked flask, transfer it to an electrically heated mantle containing a mechanical stirrer, and under the conditions of 50 °C and 350 rpm, stir and react for 2 h. At the same time, dropwise add 100 g of an aqueous solution of gadolinium nitrate hexahydrate and lanthanum nitrate hexahydrate at a rate of 4.5 g / min. The mass concentration of gadolinium nitrate hexahydrate and lanthanum nitrate hexahydrate is 5%, among which, the mass ratio of gadolinium nitrate hexahydrate to lanthanum nitrate hexahydrate is 1:0.2. Filter the obtained solid - liquid mixture, repeatedly rinse it with deionized water, and place the filtrate in a blast drying oven for drying treatment at 65 °C for 10 h to obtain gadolinium - based porous coordination polymer. The infrared spectrum (FT - IR) of the obtained gadolinium - based porous coordination polymer is shown in Figure 1 .

[0050] Example 2

[0051] Same as Example 1, except that lanthanum nitrate hexahydrate is omitted, and other reaction conditions and material compositions remain unchanged to obtain composite wall - material phase - change microcapsules. The appearance morphology of the composite wall - material phase - change microcapsules prepared in this example is the same as that of Figure 2 and is oval.

[0052] Example 3

[0053] Take 10 g of paraffin with a melting-phase transition temperature of 25 °C, 1.5 g of benzene diacetic acid, 0.8 g of isooctylphenol polyoxyethylene ether-15, and 80 g of an ethanol aqueous solution and mix them. Among them, the mass ratio of ethanol to deionized water is 1:20. Under the conditions of 45 °C and 10,000 rpm, carry out high-speed shearing reaction for 20 min to obtain a phase-change microemulsion. Put the phase-change microemulsion in a four-necked flask, transfer it to an electric heating mantle containing a mechanical stirrer, and stir and react at 45 °C and 300 rpm for 1.5 h. At the same time, dropwise add 100 g of an aqueous solution containing gadolinium nitrate hexahydrate and sodium silicate at a rate of 4 g / min. The mass concentration of gadolinium nitrate hexahydrate is 3.5%, and the mass concentration of sodium silicate is 25%. Filter the obtained solid-liquid mixture, rinse it repeatedly with deionized water, and place the filtrate in a blast drying oven for drying at 60 °C for 8 h to obtain composite wall material phase-change microcapsules. The appearance morphology of the prepared composite wall material phase-change microcapsules in this example is the same as Figure 2 elliptical. The adsorption amount of the prepared composite wall material phase-change microcapsules in this example for formaldehyde is shown in Figure 3 , and the adsorption amount for carbon dioxide is shown in Figure 4 .

[0054] Example 4

[0055] Take 10 g of paraffin with a melting-phase transition temperature of 25 °C, 3 g of benzene diacetic acid, 2.5 g of isooctylphenol polyoxyethylene ether-15, and 200 g of an ethanol aqueous solution and mix them. Among them, the mass ratio of ethanol to deionized water is 1:30. Under the conditions of 55 °C and 15,000 rpm, carry out high-speed shearing reaction for 30 min to obtain a phase-change microemulsion. Put the phase-change microemulsion in a four-necked flask, transfer it to an electric heating mantle containing a mechanical stirrer, and stir and react at 55 °C and 400 rpm for 2.5 h. At the same time, dropwise add 100 g of an aqueous solution containing gadolinium nitrate hexahydrate and sodium silicate at a rate of 5 g / min. The mass concentration of gadolinium nitrate hexahydrate is 6.5%, and the mass concentration of sodium silicate is 50%. Filter the obtained solid-liquid mixture, rinse it repeatedly with deionized water, and place the filtrate in a blast drying oven for drying at 70 °C for 12 h to obtain composite wall material phase-change microcapsules. The appearance morphology of the prepared composite wall material phase-change microcapsules in this example is the same as Figure 2 elliptical.

[0056] Example 5

[0057] Same as Example 1, except that n-heptadecane is used instead of paraffin, and other reaction conditions and material compositions remain unchanged to obtain composite wall material phase-change microcapsules. The appearance morphology of the prepared composite wall material phase-change microcapsules in this example is the same as Figure 2 elliptical.

[0058] Example 6

[0059] Same as Example 1, except that vinyl stearate is used instead of paraffin wax, and other reaction conditions and material compositions remain unchanged, to obtain composite wall material phase change microcapsules. The appearance and morphology of the composite wall material phase change microcapsules prepared in this example are the same as Figure 2 elliptical.

[0060] Example 7

[0061] Same as Example 1, except that pyromellitic acid is used instead of phthalic acid, and other reaction conditions and material compositions remain unchanged, to obtain composite wall material phase change microcapsules. The appearance and morphology of the composite wall material phase change microcapsules prepared in this example are the same as Figure 2 elliptical.

[0062] Example 8

[0063] Same as Example 1, except that naphthalenedicarboxylic acid is used instead of phthalic acid, and other reaction conditions and material compositions remain unchanged, to obtain composite wall material phase change microcapsules. The appearance and morphology of the composite wall material phase change microcapsules prepared in this example are the same as Figure 2 elliptical.

[0064] Example 9

[0065] Same as Example 1, except that nonylphenol polyoxyethylene ether-10 is used instead of isooctylphenol polyoxyethylene ether-15, and other reaction conditions and material compositions remain unchanged, to obtain composite wall material phase change microcapsules. The appearance and morphology of the composite wall material phase change microcapsules prepared in this example are the same as Figure 2 elliptical.

[0066] Example 10

[0067] Same as Example 1, except that phenethylphenol polyoxyethylene ether-15 is used instead of isooctylphenol polyoxyethylene ether-15, and other reaction conditions and material compositions remain unchanged, to obtain composite wall material phase change microcapsules. The appearance and morphology of the composite wall material phase change microcapsules prepared in this example are the same as Figure 2 elliptical.

[0068] Example 11

[0069] Same as Example 1, except that an aqueous methanol solution is used instead of an aqueous ethanol solution, and other reaction conditions and material compositions remain unchanged, to obtain composite wall material phase change microcapsules. The appearance and morphology of the composite wall material phase change microcapsules prepared in this example are the same as Figure 2 elliptical.

[0070] Example 12

[0071] Same as Example 1, except that an aqueous acetone solution is used instead of an aqueous ethanol solution, and other reaction conditions and material compositions remain unchanged, to obtain composite wall material phase change microcapsules. The appearance and morphology of the composite wall material phase change microcapsules prepared in this example are the same as Figure 2 elliptical.

[0072] Example 13

[0073] Same as Example 1, except that during the high-speed shearing reaction, the reaction temperature was increased to 55 °C, the reaction time was shortened to 20 min, and the reaction rotation speed was increased to 15,000 rpm, while other reaction conditions and material compositions remained unchanged, obtaining composite wall material phase change microcapsules. The appearance morphology of the prepared composite wall material phase change microcapsules in this example is the same as that of Figure 2 elliptical.

[0074] Example 14

[0075] Same as Example 1, except that during the mechanical stirring reaction, the reaction temperature was decreased to 45 °C, the reaction rotation speed was increased to 400 rpm, and the reaction time was extended to 2.5 h, while other reaction conditions and material compositions remained unchanged, obtaining composite wall material phase change microcapsules. The appearance morphology of the prepared composite wall material phase change microcapsules in this example is the same as that of Figure 2 elliptical.

[0076] Example 15

[0077] Same as Example 1, except that cerium nitrate hexahydrate was used instead of gadolinium nitrate hexahydrate, while other reaction conditions and material compositions remained unchanged, obtaining composite wall material phase change microcapsules. The appearance morphology of the prepared composite wall material phase change microcapsules in this example is the same as that of Figure 2 elliptical.

[0078] Example 16

[0079] Same as Example 1, except that lanthanum nitrate hexahydrate was used instead of gadolinium nitrate hexahydrate, while other reaction conditions and material compositions remained unchanged, obtaining composite wall material phase change microcapsules. The appearance morphology of the prepared composite wall material phase change microcapsules in this example is the same as that of Figure 2 elliptical.

[0080] Example 17

[0081] Same as Example 1, except that yttrium nitrate hexahydrate was used instead of gadolinium nitrate hexahydrate, while other reaction conditions and material compositions remained unchanged, obtaining composite wall material phase change microcapsules. The appearance morphology of the prepared composite wall material phase change microcapsules in this example is the same as that of Figure 2 elliptical.

[0082] Example 18

[0083] Same as Example 1, except that sodium silicate nonahydrate was used instead of anhydrous sodium silicate, while other reaction conditions and material compositions remained unchanged, obtaining composite wall material phase change microcapsules. The appearance morphology of the prepared composite wall material phase change microcapsules in this example is the same as that of Figure 2 elliptical.

[0084] Example 19

[0085] Same as Example 1, except that sodium metasilicate pentahydrate is used instead of anhydrous sodium metasilicate, and other reaction conditions and material compositions remain unchanged, to obtain composite wall material phase change microcapsules. The appearance morphology of the composite wall material phase change microcapsules prepared in this example is the same as that of Figure 2 elliptical.

[0086] Example 20

[0087] Same as Example 1, except that the dropping rate is increased to 5 g / min, and other reaction conditions and material compositions remain unchanged, to obtain composite wall material phase change microcapsules. The appearance morphology of the composite wall material phase change microcapsules prepared in this example is the same as that of Figure 2 elliptical.

[0088] Example 21

[0089] Same as Example 1, except that during the air-blowing drying process, the drying temperature is increased to 70 °C and the drying time is shortened to 8 h, and other reaction conditions and material compositions remain unchanged, to obtain composite wall material phase change microcapsules. The appearance morphology of the composite wall material phase change microcapsules prepared in this example is the same as that of Figure 2 elliptical.

[0090] Comparative Example 1

[0091] Same as Example 1, except that in the preparation process of the phase change core material emulsion, isooctylphenol polyoxyethylene ether-15 is omitted, and other reaction conditions and material compositions remain unchanged, to obtain composite wall material phase change microcapsules. Figure 3 This is the scanning electron microscope photo (SEM) of the composite wall material phase change microcapsules prepared in this comparative example. The formaldehyde adsorption amount of the composite wall material phase change microcapsules prepared in this comparative example is shown in Figure 5 , and the carbon dioxide adsorption amount is shown in Figure 6 .

[0092] Comparative Example 2

[0093] Same as Example 1, except that in the preparation process of the phase change core material emulsion, the ethanol aqueous solution is replaced with deionized water, and other reaction conditions and material compositions remain unchanged, to obtain composite wall material phase change microcapsules. Figure 4 This is the scanning electron microscope photo (SEM) of the composite wall material phase change microcapsules prepared in this comparative example. The formaldehyde adsorption amount of the composite wall material phase change microcapsules prepared in this comparative example is shown in Figure 5 , and the carbon dioxide adsorption amount is shown in Figure 6 .

[0094] Comparative Example 3

[0095] Same as Example 1, except that when dropping the mixed solution into the phase change microemulsion, the dropping method is not adopted, but the prepared solution is directly poured into the phase change microemulsion for reaction, and other reaction conditions and material compositions remain unchanged, to obtain composite wall material phase change microcapsules.

[0096] Comparative Example 4

[0097] According to the method described in CN104745149A, 50 mg of carbon nanotubes were dispersed in 40 mL of an aqueous solution of PVP, and ultrasonically dispersed for 1 h, and then stirred overnight at room temperature. The precipitate was centrifuged and redispersed in 15 mL of water. To the mixed solution, 2 mmol of chromium nitrate, 2 mmol of terephthalic acid and 5 mmol of sodium hydroxide were added, and stirred at room temperature for 5 min, then transferred to a reaction kettle, kept at 150 °C for 12 h, filtered and washed, and dried in a vacuum drying oven at 60 °C for 24 h to obtain a carbon nanotube@Cr-MIL-101-NH2 support material. 0.107 g of the support material was evacuated at 150 °C for 4 h to remove the guest small molecules in the pores. The filtered support material was dispersed in 10 mL of absolute ethanol containing 0.25 g of PEG2000, and stirred at 60 °C for 2 h to obtain a homogeneous solution. The mixed solution was placed in an 80 °C drying oven and kept warm for 36 h, and the carbon nanotube@Cr-MIL-101-NH2 loaded PEG2000 composite phase change material was collected.

[0098] Comparative Example 5

[0099] According to the method described by Fan Shuang (Research on the Application of Organic-Inorganic Nanocomposite Microspheres in Catalysis and Phase Change Energy Storage, Doctoral Dissertation, University of Science and Technology Beijing, 2017), 0.3 g of cetyltrimethylammonium bromide was used as a template and dissolved in a mixed solution of 80 mL of deionized water, 60 mL of absolute ethanol and ammonia water under ultrasonic conditions. Under vigorous magnetic stirring, 0.1 g of sulfonated PS was added and dispersed in the above solution. At room temperature, 0.3 g of tetraethyl orthosilicate was added dropwise and stirred for 6 h. After the reaction, the obtained precipitate was centrifuged with water and ethanol, and washed 3 times with deionized water and ethanol, and dried in air to obtain a white powder. The obtained powder was calcined at 550 °C for 6 h in an air atmosphere with a heating rate of 2 °C / min to remove the template agent in the pores, and mesoporous silica hollow microspheres were obtained. A certain amount of stearic acid was weighed and dissolved in absolute ethanol, and under magnetic stirring, a certain amount of mesoporous silica hollow microspheres was added and stirred continuously for 4 h. The mixed solution was placed in an 80 °C oven and kept warm overnight, and the solvent was evaporated to obtain a stearic acid / mesoporous silica hollow microsphere composite phase change energy storage material.

[0100] Test Example 1

[0101] The physical and chemical properties of the composite wall material phase change microcapsules in Examples 1-21 and Comparative Examples 1-5 were measured, and the specific results are shown in Table 1.

[0102] Table 1 Performance of the phase change microcapsules prepared in Examples and Comparative Examples

[0103] Sample Particle size / μm <![CDATA[Latent heat of fusion value / J·g -1 > <![CDATA[Latent heat of fusion value a / J·g -1 > Coating rate / % <![CDATA[Thermal conductivity / W·m -1 ·K -1 > Compressive strength / MPa <![CDATA[Specific surface area / (m 2 ·g -1 )]]> <![CDATA[Pore volume / (cm 3 ·g -1 )]]> Paraffin wax — 161.7 — — 0.12 — — — Gadolinium-based porous coordination polymer 0.5 — — — 1.57 0.36 970 0.62 Example 1 10 110 107.2 68 0.79 1.36 375 0.36 Example 2 9 108.7 105.9 67 0.75 1.30 357 0.34 Example 3 8 100.2 95.0 62 0.67 0.88 320 0.29 Example 4 13 105.1 101.4 65 0.73 1.28 355 0.32 Example 5 7.5 100.2 96.0 62 0.68 0.90 315 0.27 Example 6 12 100.2 93.5 62 0.66 0.87 310 0.26 Example 7 11 98.6 94.0 61 0.66 0.88 310 0.27 Example 8 13 98.6 95.0 61 0.67 0.86 315 0.28 Example 9 12 100.2 93.8 62 0.69 0.88 320 0.26 Example 10 12 98.6 93.5 61 0.68 0.88 315 0.27 Example 11 9.5 101.8 97.6 63 0.7 0.95 330 0.29 Example 12 11 98.6 93.5 61 0.66 0.86 305 0.27 Example 13 12 103.4 98.7 64 0.69 0.89 325 0.30 Example 14 11 100.2 97.5 62 0.72 1.18 330 0.32 Example 15 12 101.8 96.0 63 0.7 1.15 320 0.29 Example 16 13 103.4 99.6 64 0.69 1.20 320 0.28 Example 17 14 105.1 100.0 65 0.73 1.25 345 0.33 Example 18 11 105.1 101.4 65 0.72 1.18 335 0.30 Example 19 9.5 103.4 99.0 64 0.73 1.30 330 0.31 Example 20 10.7 100.2 97.5 62 0.68 0.90 320 0.28 Example 21 10.5 106.7 101.8 66 0.73 1.30 345 0.32 Comparative Example 1 3.5 72.7 65.6 45 0.43 0.69 230 0.18 Comparative Example 2 18 59.8 47.6 37 0.39 0.46 200 0.13 Comparative Example 3 20 51.7 40.5 32 0.30 0.42 180 0.12 Comparative Example 4 — 80.0 71.8 — 0.59 0.57 225 0.20 Comparative Example 5 1 78.0 70.9 — 0.49 0.67 175 0.15

[0104] Among them, a represents the latent heat of fusion value after 20 consecutive cycles of use.

[0105] From Table 1, Figure 1 and Figure 2 it can be seen that the composite wall material phase change microcapsules prepared by the present invention have good physical and chemical properties and an oval microscopic morphology. In the infrared spectrum of the sample of Example 1, the infrared characteristic peaks of silica, porous coordination polymer and paraffin wax appear simultaneously, indicating that the composite wall material has successfully coated the phase change core material paraffin wax. The latent heat of fusion value and the coating rate of the sample of Example 1 are 110 J·g -1 and 68% respectively. After 20 consecutive cycles of use, the latent heat of fusion value still remains at 107.2 J·g -1 , and the thermal conductivity, compressive strength, specific surface area and pore volume are 0.87 W·m -1 ·k -1 , 1.36 MPa, 375 m 2 / g and 0.36 cm 3 / g respectively. While the latent heat of fusion values of the samples of Comparative Examples 1-5 are generally lower than 80 J·g -1 , and their specific surface areas and pore volumes are lower than 250 m 2 / g and 0.2 cm 3 / g respectively. From Figure 3 and Figure 4 it can be seen that the microscopic morphology of the samples prepared in the comparative examples is irregular. In the sample of Comparative Example 1, obvious adhesion phenomenon appears, which indicates that the preparation method of the present invention can appropriately reduce the polarity of the phase change microemulsion system, improve the stability of the phase change microemulsion system, and make the composite wall material phase change microcapsule product have a regular morphology, a relatively uniform particle size, and a high coating rate.

[0106] Test Example 2

[0107] Determine the adsorption properties of the composite wall material phase change microcapsules in Examples 1 and 3 and Comparative Examples 1-2. The specific results are shown in Table 2. Use the HPVA-100 high-pressure gas adsorption instrument of Micromeritics Company, USA to test the adsorption properties of the samples for formaldehyde and carbon dioxide. Before the test, the samples are vacuum degassed at 180 °C in the device for 12 h, and the adsorption conditions are 25 °C and 100 kPa.

[0108] Table 2 Adsorption properties of composite wall material phase change microcapsules for different gases

[0109] Sample <![CDATA[Formaldehyde adsorption capacity / (cm 3 ·g -1 )]]> <![CDATA[Carbon dioxide adsorption capacity / (cm 3 ·g -1 )]]> Example 1 80 50 Example 3 68 40 Comparative Example 1 42 23 Comparative Example 2 30 17

[0110] From Table 2, Figure 5 and Figure 6It can be seen that the adsorption amounts of the example samples for formaldehyde and carbon dioxide are significantly higher than those of the comparative example samples, which is consistent with the test results of specific surface area and pore volume in Table 1, indicating that for the composite wall material phase change microcapsules prepared by the present invention, the silica component in the wall material can improve the mechanical strength and heat resistance stability of the phase change microcapsules, and the porous coordination polymer component endows the phase change microcapsules with more functions, such as purifying harmful gases, etc.

Claims

1. A preparation method of composite wall material phase change microcapsules, comprising the following steps: (1) Mix the molten phase change material, organic ligand, neutral surfactant and mixed solvent uniformly, and shear to obtain a phase change microemulsion; (2) Prepare a mixed solution of metal salt and silicate, stir and heat the phase change microemulsion obtained in step (1), and simultaneously dropwise add the mixed solution to obtain a solid-liquid mixture; (3) Wash and dry the obtained solid-liquid mixture to obtain composite wall material phase change microcapsules; In step (1), the organic ligand is selected from one or more of pyromellitic acid, naphthalenedicarboxylic acid, and phenylacetic acid; In step (2), the metal salt is selected from one or more of cerium nitrate hexahydrate, lanthanum nitrate hexahydrate, yttrium nitrate hexahydrate, and gadolinium nitrate hexahydrate.

2. The method according to claim 1, wherein In step (1), the phase change material is selected from one or more of normal alkanes, paraffins, and stearic acid esters with a phase change temperature of 20°C to 30°C; the neutral surfactant is selected from one or more of nonylphenol polyoxyethylene ether-10, phenethylphenol polyoxyethylene ether-15, and isooctylphenol polyoxyethylene ether-15.

3. The method according to claim 1, wherein In step (1), the mixed solvent is selected from organic solvents and water, where the mass ratio of organic solvent to water is 1:(15 - 45).

4. The method according to claim 1, wherein In step (1), the mixed solvent is selected from one or more of ethanol aqueous solution, methanol aqueous solution, and acetone aqueous solution.

5. The method according to claim 1, characterized in that, In step (1), the mixed solvent is selected from ethanol aqueous solution.

6. The method according to claim 1, wherein In step (1), the mixed solvent is selected from organic solvents and water, where the mass ratio of organic solvent to water is 1:(20 - 30).

7. The method according to claim 1, characterized in that, In step (1), the mass ratio of the phase change material, organic ligand, neutral surfactant and mixed solvent is 1:(0.01 - 0.5):(0.05 - 0.5):(5 - 40).

8. The method according to claim 1, wherein In step (1), the mass ratio of the phase change material, organic ligand, neutral surfactant and mixed solvent is 1:(0.15 - 0.3):(0.08 - 0.25):(8 - 20).

9. The method according to claim 1, wherein In step (1), after mixing the phase change material, organic ligand, neutral surfactant and mixed solvent, perform high-speed shearing treatment; the shearing treatment is carried out at a temperature of 35°C to 70°C for 10 min to 40 min, and the shearing speed is 5000 rpm to 18000 rpm.

10. The method according to claim 1, characterized in that, In step (2), the stirring reaction speed is 200 rpm to 600 rpm; the heating temperature is 40°C to 75°C; the stirring reaction time is 0.5 h to 5 h.

11. The method according to claim 1, characterized in that, In step (2), the stirring reaction speed is 300 rpm to 400 rpm; the heating temperature is 45°C to 55°C; the stirring reaction time is 1.5 h to 2.5 h.

12. The method according to claim 1, characterized in that, In step (2), the silicate is sodium silicate; the sodium silicate is selected from one or more of anhydrous sodium silicate, sodium silicate nonahydrate, and sodium silicate pentahydrate.

13. The method according to claim 1, wherein In step (2), the silicate is sodium silicate; the sodium silicate is selected from anhydrous sodium silicate.

14. The method according to claim 1, characterized in that, In step (2), the metal salt is selected from gadolinium nitrate hexahydrate, or gadolinium nitrate hexahydrate and lanthanum nitrate hexahydrate, where the mass ratio of gadolinium nitrate hexahydrate to lanthanum nitrate hexahydrate is 1:(0.1 - 0.3).

15. The method according to claim 1, wherein In step (2), in the mixed solution, the mass concentration of the metal salt is 2% - 10%; the mass concentration of the silicate is 15% - 75%.

16. The method according to claim 1, characterized in that, In step (2), in the mixed solution, the mass concentration of the metal salt is 3.5% - 6.5%; the mass concentration of the silicate is 25% - 50%.

17. The method according to claim 1, wherein In step (2), the dropping rate of the mixed solution is 2 g / min - 12 g / min.

18. The method according to claim 1, wherein In step (2), the dropping rate of the mixed solution is 4 g / min - 5 g / min.

19. The method according to claim 1, wherein In step (2), the mass ratio of the metal salt, the silicate to the organic ligand in step (1) is 1:(5.5 - 12):(0.2 - 1).

20. The method according to claim 1, wherein In step (2), the mass ratio of the metal salt, the silicate to the organic ligand in step (1) is 1:(6 - 9):(0.35 - 0.65).

21. The method according to claim 1, characterized in that, In step (3), the drying temperature is 40°C - 110°C; the drying time is 6 h - 30 h.

22. The method according to claim 1, characterized in that, In step (3), the drying temperature is 60°C - 70°C; the drying time is 8 h - 12 h.

23. The composite wall material phase change microcapsule prepared by the method according to any one of claims 1 - 21.

24. The composite wall material phase change microcapsule according to claim 23, characterized in that, The particle size of the composite wall material phase change microcapsules described is 5 μm to 15 μm, the latent heat of fusion value is greater than 90 J / g; the coating rate is greater than 60%, and the thermal conductivity is 0.65 W·m -1 ·k -1 ~0.79 W·m -1 ·K -1 , the compressive strength is 0.85 MPa to 1.36 MPa, and the specific surface area is greater than 300 m 2 / g; the pore volume is greater than 0.25 cm 3 / g.

25. The composite wall material phase change microcapsule according to claim 23, characterized in that, The latent heat of fusion of the composite wall material phase change microcapsules described is 92 to 110 J / g; the specific surface area is 305 to 380 m 2 / g; the pore volume is 0.26 to 0.36 cm 3 / g.

26. The composite wall material phase change microcapsule according to claim 23, characterized in that, The described composite wall material phase change microcapsules have a formaldehyde gas adsorption capacity of 60 cm 3 / g to 80 cm 3 / g and a carbon dioxide gas adsorption capacity of 30 cm 3 / g to 50 cm 3 / g under the conditions of 25°C and 100 kPa.

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