Recyclable phase change microcapsules and methods for making the same

Abstract

The application provides a recyclable phase change microcapsule and a preparation method thereof, and comprises the following steps: (1) preparing a surfactant solution; (2) adding a phase change material into the surfactant solution and uniformly dispersing to obtain an emulsified solution; (3) adding a solution containing magnetic metal ions into the emulsified solution and uniformly stirring to obtain a mixed solution; (4) adding a solution containing carbonate or hydroxyl into the mixed solution, so that the carbonate or hydroxyl reacts with the magnetic metal ions to form a coating wall material of the capsule; (5) performing cooling treatment on the solution in the stirring state in (4) until the microcapsule is coagulated into a small spherical shape, and then the recyclable phase change microcapsule is obtained after separation, washing and drying. The application can realize the repeated use of the microcapsule, and the capsule wall of the microcapsule is all inorganic material with magnetism, which has high flame retardance, mechanical strength and thermal conductivity, so that the microcapsule can be better used in the field of building energy-saving materials.

Description

Technical Field

[0001] This application belongs to the field of building energy-saving materials technology, and more specifically, relates to a recyclable phase change microcapsule and its preparation method. Background Technology

[0002] Phase change microcapsules are micron-sized particles containing phase change energy storage materials, encapsulated using film-forming technology. These particles are stable under normal conditions and possess a core-shell structure. Phase change materials (PCMs) are materials with heat storage capabilities that undergo phase changes (e.g., from solid to liquid) in response to temperature variations around the microcapsule. During these phase changes, they absorb or release significant amounts of heat energy, exhibiting high heat storage density, large capacity, and strong chemical stability. The microcapsules utilize the thermal effect of the PCM undergoing a phase change near its phase change temperature to absorb, store, or release heat. Microencapsulation isolates the PCM from the external environment, effectively protecting it from damage and offering advantages such as ease of use, storage, and transportation. Applications include building energy conservation, industrial heat recovery, indoor temperature control, and increasing automotive engine power.

[0003] Common phase change materials include straight-chain alkanes, polyethylene glycol, hydrated crystalline salts, eutectic hydrated salts, paraffins, and fatty acids. Wall materials are generally classified into organic, inorganic, and composite types. Organic wall materials are typically high-molecular polymers, commonly including polyamides, polyureas, urea-formaldehyde resins, melamine-formaldehyde resins, and polyurethanes. Inorganic wall materials include silicon dioxide, alumina, barium carbonate, and calcium carbonate. Generally, organic wall materials have lower thermal conductivity, while inorganic wall materials have higher thermal conductivity. However, organic wall materials are more stable, so composites of both are sometimes used for encapsulating phase change materials. Methods for preparing phase change microcapsules include in-situ polymerization, interfacial polymerization, suspension polymerization, and vulcanization spraying.

[0004] Although existing phase change microcapsules have achieved significant breakthroughs and successes in energy storage, temperature control, and use, they are directly disposed of as waste after use, rather than being repeatedly recycled, resulting in high usage costs. Chinese patent CN101574637B discloses magnetic phase change microcapsules and their preparation method. This method uses in-situ polymerization, interfacial polymerization, and complex condensation to prepare magnetic microcapsules. The wall material is a polymer formed by cross-linking monomers urea and formaldehyde. Nano-magnetic powder is added to the prepolymer formed by urea and formaldehyde, and the core material is then completely polymerized to form a magnetic microcapsule wall. However, this type of microcapsule is suitable for guiding and controlling fluid flow under an external magnetic field. Because it only involves adding a small amount of nano-magnetic powder to an organic polymer wall material, its magnetic properties are low, making it unsuitable for recyclable separation. Furthermore, the organic polymer wall material has low mechanical strength, poor thermal stability, chemical stability, and thermal conductivity, and may even contain some free formaldehyde, posing a threat to human health and the environment, making it unsuitable for use in building materials. Summary of the Invention

[0005] The purpose of this application is to provide a recyclable phase change microcapsule and its preparation method, so as to solve the technical problems of existing microcapsules that cannot be recycled and reused and have high usage costs.

[0006] To achieve the above objectives, a first aspect of this application provides a method for preparing recyclable phase change microcapsules, comprising the following steps:

[0007] (1) Prepare a surfactant solution;

[0008] (2) The phase change material is added to the surfactant solution and uniformly dispersed to obtain an emulsion solution;

[0009] (3) Add the solution containing magnetic metal ions to the emulsion solution and stir until it is fully complexed with the surfactant to obtain a mixed solution;

[0010] (4) Add a solution containing carbonate or hydroxide to the mixed solution so that the carbonate or hydroxide reacts with the magnetic metal ions to form the capsule's coating material.

[0011] (5) Cool the solution in (4) under stirring until the microcapsules solidify into small spheres, and then obtain recyclable phase change microcapsules after separation, washing and drying.

[0012] Furthermore, the phase change material includes at least one of paraffin, tetradecane, pentadecane, and octadecane.

[0013] Furthermore, the magnetic metal ions include at least one of trivalent iron, divalent cobalt, and divalent nickel.

[0014] Furthermore, the surfactant is at least one selected from sodium dodecylbenzenesulfonate, Span 80, sodium dodecylbenzene, polyvinyl alcohol, and sodium tetrapoly(propylene)sulfonate.

[0015] Furthermore, in steps (3) and (4), the solution containing magnetic metal ions and the solution containing carbonate or hydroxide ions are added by dripping, with the dripping rate controlled at 30 to 45 times per minute and the temperature of the dripping solution controlled at 65°C to 70°C.

[0016] Furthermore, in step (3), before adding the solution containing magnetic metal ions to the emulsion solution, the pH value of the emulsion solution is adjusted to 3.0.

[0017] Furthermore, in the emulsion solution, the mass ratio of the phase change material to the surfactant is 5:8.

[0018] Further, the solution containing carbonate or hydroxide ions is a sodium carbonate solution, the magnetic metal ion is a trivalent metal ion, and the molar ratio of the magnetic metal ion to the carbonate ion is 2:3; or the magnetic metal ion is a divalent metal ion, and the molar ratio of the magnetic metal ion to the carbonate ion is 1:1.

[0019] Further, the solution containing carbonate or hydroxide ions is a sodium hydroxide solution, the magnetic metal ion is a trivalent metal ion, and the molar ratio of the magnetic metal ion to the hydroxide ion is 1:3; or the magnetic metal ion is a divalent metal ion, and the molar ratio of the magnetic metal ion to the hydroxide ion is 1:2.

[0020] Further, the surfactant solution is prepared by dissolving the surfactant in deionized water at 60°C and stirring at a speed of 500 r / min to 800 r / min for 30 min until the surfactant is uniformly dispersed in the deionized water, thereby obtaining the surfactant solution.

[0021] Further, the emulsion solution is prepared by the following method: the phase change material is added to the surfactant solution at 60-65°C and melted, and stirred at 500 r / min for 30 min to uniformly disperse the phase change material into small spheres, thereby obtaining the emulsion solution.

[0022] A second aspect of this application provides a recyclable phase change microcapsule prepared using any of the methods described above.

[0023] Furthermore, the microcapsules have a particle size of 5–15 μm.

[0024] Compared with the prior art, this application has the following technical effects:

[0025] This application discloses a method for preparing recyclable phase change microcapsules. The method employs a self-assembly and precipitation method to prepare microcapsules with a carbonate / hydroxyl-magnetic metal ion precipitate as the capsule wall and a phase change material as the capsule core. Through the magnetism of the capsule wall, the microcapsules can still be adsorbed by a strong magnet for recycling after use, realizing the reuse of microcapsules. This reduces the cost of using microcapsules, alleviates the environmental pressure on the waste surrounding environment, and improves the environmental friendliness of microcapsules.

[0026] The recyclable phase change microcapsules prepared in this application have capsule walls made entirely of magnetic inorganic materials, which have high flame retardancy, mechanical strength and thermal conductivity, as well as good thermal and chemical stability. They can also be well integrated with other building materials, making them more suitable for use in the field of building energy-saving materials. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 An optical microscope image of the microcapsule provided in Embodiment 1 of this application;

[0029] Figure 2 An optical microscope image of the microcapsule provided in Example 3 of this application. Detailed Implementation

[0030] To make the technical problems, technical solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0031] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0032] It should be understood that in the various embodiments of this application, the order of the above processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0033] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0034] The weights of the relevant components mentioned in the embodiments of this application can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Specifically, the mass described in the embodiments of this application can be a mass unit known in the chemical industry, such as μg, mg, g, or kg.

[0035] This application provides a method for preparing recyclable phase change microcapsules. The method uses paraffin as the phase change material and ferric carbonate or ferric hydroxide as the capsule wall. After paraffin forms tiny oil droplets in a sodium dodecylbenzenesulfonate solution, ferric ions complex with the sodium dodecylbenzenesulfonate on the surface of the paraffin droplets. Then, carbonate or hydroxide ions are added to cause a precipitation reaction on the oil droplet surface, generating ferric carbonate or ferric hydroxide precipitate as the capsule wall, thereby coating the oil droplets to form recyclable phase change microcapsules. Specifically, the method includes the following steps:

[0036] S1. Preparation of surfactant solution: Using a water bath heating pot, dissolve the surfactant in deionized water at 60°C, and stir at a speed of 500r / min to 800r / min for 30min until the surfactant is uniformly dispersed in the deionized water to obtain the surfactant solution.

[0037] S2. Add the phase change material to the surfactant solution and disperse it evenly to obtain an emulsion solution: Add 5g of phase change material to a surfactant solution at 60-65℃ to melt it, and stir at 500r / min for 30min to disperse the phase change material evenly into small spheres, thus obtaining an emulsion solution of phase change material and surfactant solution.

[0038] S3. A solution containing magnetic metal ions is added to an emulsion solution and stirred until homogeneous to obtain a mixed solution. The magnetic metal ions include at least one of ferric, cobalt, and nickel. For example, a ferric ion solution can be obtained by dissolving a reagent containing 0.05 mol of ferric ions in 50 ml of deionized water. The ferric ion solution is then added to an emulsion solution of phase change material and surfactant solution. The mixture is stirred at 65°C and a speed of 400 r / min to 500 r / min for 1 h to 1.5 h to obtain a mixed solution in which ferric ions and surfactant are fully complexed.

[0039] S4. Add a solution containing carbonate or hydroxide ions to the mixed solution, causing the carbonate or hydroxide ions to precipitate with the magnetic metal ions and form the capsule coating material. After separation, washing, and drying, recyclable phase change microcapsules are obtained. For example, dissolve 0.075 mol of sodium carbonate in 50 ml of deionized water to obtain a sodium carbonate solution. Add the sodium carbonate solution to the complexed mixed solution in S3, and stir thoroughly at 65°C and a speed of 400 r / min to 500 r / min for 1 h to 1.5 h, causing the carbonate ions to precipitate with the iron ions on the surface of the complex to form the coating material ferric carbonate. After cooling, solidification, separation, washing, and drying, recyclable phase change microcapsules are obtained.

[0040] The surfactant in step S1 above is at least one of the following surfactants: sodium dodecylbenzenesulfonate, Span 80, sodium dodecylbenzene, polyvinyl alcohol, and tetrapropylene benzenesulfonate. The surfactant has both lipophilic and hydrophilic groups, can aggregate at the oil / water interface, can reduce interfacial tension and reduce the energy required to form an emulsion, thereby enabling the phase change material to be emulsified into smaller droplets in the solution.

[0041] The core material phase change material used in step S2 includes at least one of the alkanes such as paraffin, tetradecane, pentadecane, and octadecane, as well as various mixed alkanes and other phase change materials that can be emulsified in water by surfactants. The mass ratio of phase change material to surfactant in step S2 is 5:8.

[0042] The ferric reagent used in step S3 above is ferric chloride or other ferric reagents, and can also be a soluble reagent containing divalent cobalt or divalent nickel. After adding the ferric ion solution in step S3, the ferric ions undergo a complexation reaction with the divalent oxygen on the surfactant, and the resulting complex of ferric ions and surfactant encapsulates the phase change material droplets. Other metal ions such as divalent cobalt or divalent nickel can also be added, which will similarly undergo a complexation reaction with the divalent oxygen on the surfactant. For example, divalent nickel ions can form highly sensitive ternary colored complexes with chromium azurite S (CAS) and trimethylolpropionate bromide to coat the phase change material. It should be noted that before adding ferric ions in step S3, the pH of the emulsion solution in step S2 is adjusted to 3.0 to prevent the formation of ferric hydroxide, which would affect the complexation with the surfactant.

[0043] The reagent used in step S4 above can be sodium carbonate, or it can be replaced with 0.15 mol of sodium hydroxide or other soluble reagents containing hydroxide and carbonate ions. After adding sodium carbonate solution in step S4, the added carbonate ions react with the iron ions on the surface of the complex in step S3 to form ferric carbonate precipitate, which then forms an iron carbonate coating on the surface of the phase change material microdroplets. Although the generated iron carbonate is magnetic, its stability in solution is poor and it will decompose into iron hydroxide. Therefore, adding a reagent that can hydrolyze to release hydroxide ions can also directly prepare the iron hydroxide capsule wall, which also has the characteristic of being adsorbed by a strong magnet.

[0044] In steps S3 and S4 above, the solution containing magnetic metal ions and the solution containing carbonate or hydroxide ions are added by dropping, with the dropping rate controlled at 30 to 45 times per minute and the temperature of the solution being dropped controlled at 65°C to 70°C.

[0045] The following examples illustrate a recyclable phase change microcapsule and its preparation method according to embodiments of this application.

[0046] Example 1

[0047] Example 1 of this application provides a recyclable phase change microcapsule and a method for preparing the same, comprising the following steps:

[0048] (1) Preparation of core material emulsion: Weigh 8g of sodium dodecylbenzenesulfonate (SDBS) as emulsifier, dissolve it in 200mL of deionized water at 60℃ and stirring at 600r / min to obtain sodium dodecylbenzenesulfonate solution. Weigh 5g of paraffin wax and add it to the sodium dodecylbenzenesulfonate solution. Stir at 65℃ for 30min at a stirring speed of 500r / min to obtain a completely dispersed paraffin wax emulsion.

[0049] (2) Encapsulation of the capsule wall: Take 8g of ferric chloride and dissolve it completely in 50ml of deionized water to obtain a ferric chloride solution. Keep the ferric chloride solution at a temperature of 65℃ in a water bath. Then, add the ferric chloride solution to the core material emulsion obtained in step (1) at a rate of 30 drops / min to 45 drops / min. Stir at a speed of 500r / min and a temperature of 65℃ for 1h to obtain a complex of iron ions and sodium dodecylbenzene sulfonate. Take 7.5g of anhydrous sodium carbonate and dissolve it completely in 50ml of deionized water to obtain a sodium carbonate solution. Keep the sodium carbonate solution at a temperature of 65℃ in a water bath. Then, add the sodium carbonate solution to the complex solution at a rate of 30 drops / min to 45 drops / min. Stir at a speed of 500r / min and a temperature of 65℃ for 1h to allow ferric carbonate to fully precipitate on the surface of the paraffin to form the capsule wall. Turn off the water bath heating pot and let it cool naturally while stirring at a speed of 500r / min to solidify to room temperature. After filtration, the microcapsules were rinsed with water and dried at 50°C for 24 hours to obtain phase change microcapsules.

[0050] The prepared phase change microcapsules were analyzed by optical microscopy, such as... Figure 1 As shown, the microcapsules exhibit good sphericity, with a relatively complete coating of ferric carbonate on the paraffin surface and a consistent overall particle size. Instrumental testing revealed that the microcapsules underwent normal phase transitions, absorbing, storing, and releasing heat, and their heat storage capacity remained almost unchanged during cyclic testing. They can also be recovered under the attraction of a strong magnet, demonstrating recyclability.

[0051] Example 2

[0052] Embodiment 2 of this application provides a recyclable phase change microcapsule and a method for preparing the same, comprising the following steps:

[0053] (1) Preparation of core material emulsion: Weigh 8g of sodium dodecylbenzenesulfonate (SDBS) as emulsifier, dissolve it in 200mL of deionized water at 60℃ and stirring at 600r / min to obtain sodium dodecylbenzenesulfonate solution. Weigh 5g of paraffin wax and add it to the sodium dodecylbenzenesulfonate solution. Stir at 65℃ for 30min at a stirring speed of 500r / min to obtain a completely dispersed paraffin wax emulsion.

[0054] (2) Encapsulation of the capsule wall: Dissolve 8g of ferric chloride completely in 50ml of deionized water to obtain a ferric chloride solution. Keep the ferric chloride solution at a temperature of 65℃ in a water bath. Then, add the ferric chloride solution to the core material emulsion obtained in step (1) at a rate of 30 drops / min to 45 drops / min. Stir at a speed of 500r / min and a temperature of 65℃ for 1h to obtain a complex of iron ions and sodium dodecylbenzene sulfonate. Dissolve 6g of sodium hydroxide completely in 50ml of deionized water to obtain a sodium hydroxide solution. Keep the sodium hydroxide solution at a temperature of 65℃ in a water bath. Then, add the sodium hydroxide solution to the complex solution at a rate of 30 drops / min to 45 drops / min. Stir at a speed of 500r / min and a temperature of 65℃ for 1h to allow ferric hydroxide to fully precipitate on the surface of the paraffin to form the capsule wall. Turn off the water bath and let it cool naturally while stirring at a speed of 500r / min to solidify to room temperature. After filtration, the microcapsules were rinsed with water and dried at 50°C for 24 hours to obtain phase change microcapsules.

[0055] Optical microscopy analysis of the prepared microcapsules revealed good sphericity, a relatively complete coating of ferric hydroxide on the paraffin surface, and a generally uniform particle size. Instrument testing showed that the microcapsules could undergo normal phase transitions, absorbing, storing, and releasing heat, and their heat storage capacity remained almost unchanged during cyclic testing. They were also recyclable, able to be recovered under the attraction of a strong magnet.

[0056] Example 3

[0057] Embodiment 3 of this application provides a recyclable phase change microcapsule and a method for preparing the same, comprising the following steps:

[0058] (1) Preparation of core material emulsion: Weigh 5g of sodium dodecylbenzenesulfonate (SDBS) as emulsifier, dissolve it in 200mL of deionized water at 60℃ and stirring at 600r / min to obtain a sodium dodecylbenzenesulfonate solution. Weigh 5g of paraffin wax and add it to the sodium dodecylbenzenesulfonate solution. Stir at 65℃ for 30min at a stirring speed of 500r / min to obtain a completely dispersed paraffin wax emulsion.

[0059] (2) Encapsulation of the capsule wall: Take 8g of ferric chloride and dissolve it completely in 50ml of deionized water to obtain a ferric chloride solution. Keep the ferric chloride solution at a temperature of 65℃ in a water bath. Then, add the ferric chloride solution to the core material emulsion obtained in step (1) at a rate of 30 drops / min to 45 drops / min. Stir at a speed of 500r / min and a temperature of 65℃ for 1h to obtain a complex of iron ions and sodium dodecylbenzene sulfonate. Take 7.5g of anhydrous sodium carbonate and dissolve it completely in 50ml of deionized water to obtain a sodium carbonate solution. Keep the sodium carbonate solution at a temperature of 65℃ in a water bath. Then, add the sodium carbonate solution to the complex solution at a rate of 30 drops / min to 45 drops / min. Stir at a speed of 500r / min and a temperature of 65℃ for 1h to allow ferric carbonate to fully precipitate on the surface of the paraffin to form the capsule wall. Turn off the water bath heating pot and let it cool naturally while stirring at a speed of 500r / min to solidify to room temperature. After filtration, the microcapsules were rinsed with water and dried at 50°C for 24 hours to obtain phase change microcapsules.

[0060] The prepared microcapsules were analyzed by optical microscopy, such as... Figure 2 As shown, when ferric chloride is added to complex with sodium dodecylbenzenesulfonate on the surface of paraffin, a significant amount of paraffin oil droplets remain free on the solution surface. After encapsulation, the microcapsules are filtered, resulting in a substance resembling chocolate chunks. Microcapsules are present but surrounded by a mixture of paraffin and ferric carbonate. This is because the amount of the emulsifier sodium dodecylbenzenesulfonate is too small, failing to form stable, dispersed paraffin droplets. The paraffin remains unencapsulated, causing the microcapsules and excess ferric carbonate precipitate to connect and form a mixture.

[0061] Example 4

[0062] Example 4 of this application provides a recyclable phase change microcapsule and a method for preparing the same, comprising the following steps:

[0063] (1) Preparation of core material emulsion: Weigh 8g of sodium dodecylbenzenesulfonate (SDBS) as emulsifier, dissolve it in 200mL of deionized water at 60℃ and stirring at 600r / min to obtain sodium dodecylbenzenesulfonate solution. Weigh 5g of paraffin wax and add it to the sodium dodecylbenzenesulfonate solution. Stir at 65℃ for 30min at a stirring speed of 500r / min to obtain a completely dispersed paraffin wax emulsion.

[0064] (2) Encapsulation of the capsule wall: Take 5g of ferric chloride and dissolve it completely in 50ml of deionized water to obtain a ferric chloride solution. Keep the ferric chloride solution at a temperature of 65℃ in a water bath. Then, add the ferric chloride solution to the core material emulsion obtained in step (1) at a rate of 30 drops / min to 45 drops / min. Stir at a speed of 500r / min and a temperature of 65℃ for 1h to obtain a complex of iron ions and sodium dodecylbenzene sulfonate. Take 5g of anhydrous sodium carbonate and dissolve it completely in 50ml of deionized water to obtain a sodium carbonate solution. Keep the sodium carbonate solution at a temperature of 65℃ in a water bath. Then, add the sodium carbonate solution to the complex solution at a rate of 30 drops / min to 45 drops / min. Stir at a speed of 500r / min and a temperature of 65℃ for 1h to allow ferric carbonate to fully precipitate on the surface of the paraffin to form the capsule wall. Turn off the water bath and let it cool naturally while stirring at a speed of 500r / min to solidify to room temperature. After filtration, the microcapsules were rinsed with water and dried at 50°C for 24 hours to obtain phase change microcapsules.

[0065] Optical microscopy analysis of the prepared phase change microcapsules revealed good sphericity, but the coating of ferric carbonate on the paraffin surface was incomplete, with uncoated paraffin microspheres present. Under strong magnetic attraction, few microcapsules were recovered. The reason for this was attributed to the insufficient addition of ferric chloride and sodium carbonate, resulting in incomplete coating of the paraffin surface with ferric carbonate.

[0066] Example 5

[0067] Example 5 of this application provides a recyclable phase change microcapsule and a method for preparing the same, comprising the following steps:

[0068] (1) Preparation of core material emulsion: Weigh 8g of sodium dodecylbenzenesulfonate (SDBS) as emulsifier, dissolve it in 200mL of deionized water at 60℃ and stirring at 600r / min to obtain sodium dodecylbenzenesulfonate solution. Weigh 5g of paraffin wax and add it to the sodium dodecylbenzenesulfonate solution. Stir at 65℃ for 30min at a stirring speed of 500r / min to obtain a completely dispersed paraffin wax emulsion.

[0069] (2) Encapsulation of the capsule wall: Take 8g of ferric chloride and dissolve it completely in 50ml of deionized water to obtain a ferric chloride solution. Keep the ferric chloride solution at a temperature of 65℃ in a water bath. Then, add the ferric chloride solution to the core material emulsion obtained in step (1) at a rate of 30 drops / min to 45 drops / min. Stir at a speed of 500r / min and a temperature of 65℃ for 1h to obtain a complex of iron ions and sodium dodecylbenzene sulfonate. Take 7.5g of anhydrous sodium carbonate and dissolve it completely in 50ml of deionized water to obtain a sodium carbonate solution. Keep the sodium carbonate solution at a temperature of 65℃ in a water bath. Then, add the sodium carbonate solution to the complex solution at a rate of 30 drops / min to 45 drops / min. Stir at a speed of 500r / min and a temperature of 65℃ for 1h to allow ferric carbonate to fully precipitate on the surface of the paraffin to form the capsule wall. Turn off the water bath heating pot and let it cool naturally while stirring at a speed of 1000r / min to solidify to room temperature. After filtration, the microcapsules were rinsed with water and dried at 50°C for 24 hours to obtain phase change microcapsules.

[0070] Optical microscopy analysis of the prepared phase change microcapsules revealed a large number of paraffin microspheres in the SEM (scanning electron microscope). Iron carbonate was not coated on the paraffin microspheres. The reason for this is that during the cooling time after microcapsule formation, the iron carbonate precipitate on the surface of the microcapsules was centrifuged away at a high rotation speed, leaving only the paraffin microspheres.

[0071] Example 6

[0072] Embodiment 6 of this application provides a recyclable phase change microcapsule and a method for preparing the same, comprising the following steps:

[0073] (1) Preparation of core material emulsion: Weigh 8g of sodium dodecylbenzenesulfonate (SDBS) as emulsifier, dissolve it in 200mL of deionized water at 60℃ and stirring at 600r / min to obtain sodium dodecylbenzenesulfonate solution. Weigh 5g of paraffin wax and add it to the sodium dodecylbenzenesulfonate solution. Stir at 65℃ for 30min at a stirring speed of 500r / min to obtain a completely dispersed paraffin wax emulsion.

[0074] (2) Encapsulation of the capsule wall: 12g of ferric chloride was completely dissolved in 50ml of deionized water to obtain a ferric chloride solution. The ferric chloride solution was kept at a temperature of 65℃ in a water bath. Then, the ferric chloride solution was added dropwise to the core material emulsion obtained in step (1) at a rate of 30 drops / min to 45 drops / min. The mixture was stirred at a speed of 500r / min and a temperature of 65℃ for 1h to obtain a complex of iron ions and sodium dodecylbenzene sulfonate. 12g of anhydrous sodium carbonate was completely dissolved in 50ml of deionized water to obtain a sodium carbonate solution. The sodium carbonate solution was kept at a temperature of 65℃ in a water bath. Then, the sodium carbonate solution was added dropwise to the complex solution at a rate of 30 drops / min to 45 drops / min. The mixture was stirred at a speed of 500r / min and a temperature of 65℃ for 1h to allow ferric carbonate to fully precipitate on the surface of the paraffin to form the capsule wall. The water bath was turned off and allowed to cool naturally. At the same time, the mixture was stirred at a speed of 1000r / min to solidify to room temperature. After filtration, the microcapsules were rinsed with water and dried at 50°C for 24 hours to obtain phase change microcapsules.

[0075] Optical microscopy analysis of the prepared phase change microcapsules revealed good sphericity, a relatively complete ferric carbonate coating on the paraffin surface, and a generally uniform particle size. However, the surface ferric carbonate precipitate layer was relatively thick, containing numerous ferric carbonate fragments. Instrumental testing showed that the microcapsules could undergo phase transitions normally, absorbing, storing, and releasing heat. Furthermore, their heat storage capacity remained almost unchanged during cyclic testing. They could also be recovered under the attraction of a strong magnet, demonstrating recyclability.

[0076] The micromorphological characterization results of the microcapsules prepared in Examples 1-6 of this application are shown in Table 1 below.

[0077] Table 1. Micromorphological characterization of the recyclable microcapsules prepared in Examples 1-6

[0078]

[0079] The recyclability of the microcapsules prepared in Examples 1-6 of this application was tested. Strong magnets were used to adsorb and recover them, and the recovered substances were weighed and counted. The results are shown in Table 2 below.

[0080] Table 2. Recyclability characterization of the recyclable microcapsules prepared in Examples 1-6

[0081]

[0082] This application provides a method for preparing recyclable phase change microcapsules, which involves preparing microcapsules with ferric carbonate or ferric hydroxide as the capsule wall and paraffin as the core. The magnetic properties of the ferric carbonate or ferric hydroxide in the capsule wall allow the microcapsules to be reclaimed by a strong magnet after use, enabling reuse. This reduces the cost of using microcapsules, alleviates the environmental impact of waste, and improves the environmental friendliness of microcapsules.

[0083] When the microcapsule wall used in the embodiments of this application is ferric carbonate, even if it decomposes under special conditions, it will decompose into more stable ferric hydroxide and continue to coat the paraffin surface as the capsule wall. Moreover, it also has the ability to be recycled by a strong magnet. At the same time, it can improve the bonding ability, flame retardancy and mechanical strength of the microcapsules with other building materials, and can be better used in the field of building energy-saving materials.

[0084] In the embodiments of this application, by using appropriate emulsifiers and ratios, the core material paraffin can be better dispersed in deionized water to form a stable oil-in-water emulsion. This results in the prepared phase change microcapsules having a higher phase change enthalpy value, as well as strong stability, without phase separation, and the ability to be repeatedly recycled.

[0085] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for preparing recyclable phase change microcapsules, characterized in that: Includes the following steps: (1) Prepare surfactant solution with deionized water; (2) The phase change material is added to the surfactant solution and uniformly dispersed to obtain an emulsion solution; (3) Add the solution containing magnetic metal ions to the emulsion solution and stir until it is fully complexed with the surfactant to obtain a mixed solution; (4) Add a solution containing carbonate or hydroxide to the mixed solution so that the carbonate or hydroxide reacts with the magnetic metal ions to form the coating material of the capsule. (5) Stir the solution in (4) at a speed of 500 r / min, solidify to room temperature, until the microcapsules solidify into small spheres, and then obtain recyclable phase change microcapsules after separation, washing and drying; The phase change material includes at least one of paraffin, tetradecane, pentadecane, and octadecane; The magnetic metal ions include at least one of trivalent iron, divalent cobalt, and divalent nickel; The surfactant is at least one of sodium dodecylbenzenesulfonate, Span 80, sodium dodecylbenzene, polyvinyl alcohol, and tetrapropylene benzenesulfonate. In steps (3) and (4), the solution containing magnetic metal ions and the solution containing carbonate or hydroxide ions are added by dripping, with the dripping speed controlled at 30 times / min to 45 times / min and the temperature of the dripping solution controlled at 65 ℃ to 70 ℃. In step (3), before adding the solution containing magnetic metal ions to the emulsion solution, the pH value of the emulsion solution is adjusted to 3.0; In the emulsion solution, the mass ratio of the phase change material to the surfactant is 5:8; The solution containing carbonate or hydroxide ions is a sodium carbonate solution, the magnetic metal ions are trivalent metal ions, and the molar ratio of the magnetic metal ions to the carbonate ions is 2:3; or the magnetic metal ions are divalent metal ions, and the molar ratio of the magnetic metal ions to the carbonate ions is 1:

1. The solution containing carbonate or hydroxide ions is a sodium hydroxide solution, the magnetic metal ion is a trivalent metal ion, and the molar ratio of the magnetic metal ion to the hydroxide ion is 1:3; or the magnetic metal ion is a divalent metal ion, and the molar ratio of the magnetic metal ion to the hydroxide ion is 1:

2.

2. The method for preparing a recyclable phase change microcapsule as described in claim 1, characterized in that: The surfactant solution is prepared by dissolving the surfactant in deionized water at 60 °C and stirring at a speed of 500 r / min to 800 r / min for 30 min until the surfactant is uniformly dispersed in the deionized water, thereby obtaining the surfactant solution. The emulsion solution is prepared by the following method: the phase change material is added to the surfactant solution at 60~65 °C and melted, and stirred at 500 r / min for 30 min to uniformly disperse the phase change material into small spheres, thereby obtaining the emulsion solution.

3. A recyclable phase change microcapsule, characterized in that: It is prepared using the preparation method described in claim 1 or 2.

4. A recyclable phase change microcapsule as described in claim 3, characterized in that: The microcapsules have a particle size of 5~15 μm.

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