A multifunctional inorganic double-shell phase change microcapsule and its preparation method

Abstract

The present application relates to a kind of multifunctional inorganic double-shell material phase change microcapsules, including phase change core material and the shell material of two layers inside and outside, the shell material inside is zinc oxide, the shell material outside is inorganic metal chloride or inorganic metal sulfide.The present application also provides the preparation method of the preparation of the multifunctional inorganic double-shell material phase change microcapsules, by the method prepared by the microcapsule with double-layer inorganic shell material, not only maintains the original phase change heat storage performance of microcapsule, also increases the compression resistance (pressure resistance) ability, and improves thermal conductivity, can make microcapsule in more fields or complex environment application;In addition, the formation of outer shell material can give the shell material inside the coated microcapsule does not have the performance, such as light absorption performance, improve the utilization rate of solar energy of phase change material.

Description

Technical Field

[0001] This invention belongs to the field of phase change energy storage microcapsule preparation, specifically relating to a multifunctional inorganic double-shell phase change microcapsule and its preparation method. Background Technology

[0002] With societal development, the demand for energy is increasing. However, due to the non-renewable nature of fossil fuels such as oil, coal, and natural gas, these resources can no longer meet the demand. Therefore, there is an urgent need to seek new clean and renewable energy sources or improve the utilization rate of existing energy sources. Among various energy storage technologies, phase change materials (PCMs) have attracted widespread attention because they can undergo phase transitions according to their surrounding environment, absorbing or releasing large amounts of heat energy to achieve energy storage and release, effectively improving energy utilization efficiency. However, PCMs are prone to leakage during phase transitions, limiting their use. To address this issue, research has found that encapsulation can significantly improve leakage. Phase change microcapsules encapsulate PCMs in the form of tiny particles or droplets within a wall material made of polymers or inorganic materials, forming a micro-encapsulation technology with a distinct "core-shell" structure.

[0003] With the development of microencapsulation technology, it has been applied in an increasing number of fields such as construction, military, and textiles. However, problems such as low mechanical strength and limited functionality of microcapsule shells have also become increasingly prominent. To address these issues, research has found that further coating the microcapsule shell with another layer of shell material, forming organic-inorganic bilayer shells and inorganic-inorganic bilayer shells, can not only improve the mechanical strength of the microcapsules, but also endow the original microcapsules with new properties, expanding their application prospects. However, compared to organic shell materials, which inevitably contain more formaldehyde, researchers have focused their attention on inorganic-inorganic bilayer shell microcapsules. For example, Chinese patent CN 105238361 A discloses a method for preparing phase change material microcapsules coated with silver / silica as the wall material, where the outer Ag shell material endows the microcapsules with excellent antibacterial properties. Summary of the Invention

[0004] To address the problems of low mechanical strength of the shell material, easy leakage of the core material, and limited functionality of microcapsules in current microencapsulated phase change materials, this invention provides a phase change microcapsule with a double-shell structure, using zinc oxide as the inner shell material and inorganic metal sulfides, inorganic metal chlorides, etc., as the outer shell material. While ensuring the original phase change energy storage performance of the microcapsule and improving its mechanical strength, the multifunctionality of the outer inorganic shell material also endows the microcapsule with new properties, thereby obtaining an inorganic double-shell phase change microcapsule with multiple functions.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] This invention first provides a multifunctional inorganic double-shell phase change microcapsule, comprising a phase change core material and inner and outer shells. The inner shell is zinc oxide, and the outer shell is an inorganic metal chloride or inorganic metal sulfide prepared from zinc oxide by electrochemical adsorption.

[0007] In some respects, the phase change core material is one or more alkanes.

[0008] This invention also provides a method for preparing multifunctional inorganic double-shell phase change microcapsules, comprising the following steps:

[0009] 1) Add the phase change core material and emulsifier to the solvent and emulsify at high speed to form an O / W solution;

[0010] 2) After emulsification is complete, slowly add the zinc source solution dropwise to the O / W solution while continuing to stir;

[0011] 3) Add saturated alkaline solution dropwise and continue stirring;

[0012] 4) The solution after the reaction was aged, and then filtered, washed and dried to obtain zinc oxide microcapsules;

[0013] 5) Disperse zinc oxide microcapsules in a surfactant solution, slowly add a metal salt solution, and continue stirring;

[0014] 6) Add reducing agent, continue stirring, and finally obtain multifunctional inorganic double-shell phase change microcapsules by filtration, washing and drying.

[0015] Furthermore, in step 1), the emulsifier is one of the anionic emulsifiers sodium dodecyl sulfate and sodium dodecylbenzene sulfonate, the solvent is one of N / N-dimethylformamide solution and anhydrous ethanol, and the emulsification rate is 8000-12000 r / min.

[0016] Furthermore, the emulsification conditions in step 1) are a water bath at 20–60°C.

[0017] Furthermore, in step 2), the zinc source is one of zinc acetate, zinc nitrate, and zinc sulfate, and the concentration of the zinc source solution is 0.5–1 g / mL.

[0018] Furthermore, the mass ratio of the phase change core material, emulsifier, solvent, and zinc source is 1:(0.05~0.2):(3~10):(0.2~1).

[0019] Furthermore, in step 3), the alkaline solution is either a sodium hydroxide solution or a potassium hydroxide solution.

[0020] Furthermore, in step 4), the aging conditions are to let it stand in an oven at 60-90°C for 5-12 hours.

[0021] Furthermore, in step 5), the surfactant is one of sodium polystyrene sulfonate, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, or polyethylene glycol block polypropylene glycol block polyethylene glycol, and the mass ratio of zinc oxide microcapsules to surfactant is 1:(0.1-0.4).

[0022] Furthermore, in step 5), the metal salt is a copper source, a cadmium source, or a silver source, the mass ratio of zinc oxide microcapsules to metal salt is 1:(0.25-2), and the concentration of metal salt is 0.05-0.1 g / mL.

[0023] Preferably, the copper source is CuSO4 or Cu(NO3)2, the cadmium source is CdCl2 or CdNO3, and the silver source is AgNO3.

[0024] Furthermore, in step 6), the reducing agent is a sulfide or chloride, and the mass ratio of the metal salt source to the reducing agent is 1:(0.3-1).

[0025] Preferably, the sulfide is Na2S or K2S, and the chloride is NaCl.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] This invention utilizes a chemical precipitation method to prepare zinc oxide microcapsules. Under the action of solvents and emulsifiers, zinc source ions are deposited on the surface of a phase change material. A zinc hydroxide shell is formed under alkaline conditions, and then the material is further aged at alkaline high temperature to undergo phase changes and lattice-concentrated atomic recombination, ultimately preparing zinc oxide microcapsules.

[0028] The microcapsules with a double-layered inorganic shell prepared by this invention not only maintain the original phase change heat storage performance of the microcapsules, but also have the following advantages compared to a single-layered shell: 1. Increased pressure resistance, enabling the microcapsules to be used in more fields or complex environments; 2. The formation of the outer shell increases its conductive / heat-receiving area, enabling better heat conduction / reception and improving its thermal conductivity, allowing the phase change material to respond more quickly to changes in ambient temperature; 3. The formation of the outer shell can endow the inner shell with properties that the encapsulated microcapsules do not possess or improve their relatively weaker properties. For example, zinc oxide is white and has poor light absorption properties, but its outer shell can improve its light absorption properties, thereby improving the utilization rate of solar energy by the phase change material.

[0029] The microcapsules prepared by this invention have better density and stronger mechanical properties. Moreover, the multifunctionality of the outer shell material endows the microcapsules with new properties, such as photothermal conversion performance and light absorption performance. In addition, the presence of formaldehyde is avoided, which improves the application prospects and commercial value of the microcapsules. Attached Figure Description

[0030] Figure 1 Here is a scanning electron microscope (SEM) image of the silver chloride / zinc oxide double-shell microcapsules in Example 1;

[0031] Figure 2 The image shows a differential scanning calorimetry (DSC) cycle diagram of the silver chloride / zinc oxide double-shell microcapsules in Example 1.

[0032] Figure 3 The image shows the photothermal conversion of the copper sulfide / zinc oxide double-shell microcapsules in Example 2.

[0033] Figure 4 The image shows the light absorption of the cadmium sulfide / zinc oxide double-shell microcapsules in Example 3. Detailed Implementation

[0034] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0035] Example 1

[0036] 1) Weigh 30g of n-octadecane, 3g of sodium dodecyl sulfate (SDS) and 150g of N / N-dimethylformamide solution, place them in a 1L beaker, and emulsify them at a high speed of 10000r / min for 1.5h under a water bath heating at 50℃ to obtain a uniform O / W emulsion.

[0037] 2) After emulsification, reduce the rotation speed to 800 r / min; then weigh 20 g of zinc acetate and dissolve it in 25 mL of deionized water to prepare a solution with a concentration of 0.8 g / mL, and slowly add it dropwise to the O / W emulsion, and continue stirring for 4 h;

[0038] 3) Then weigh 40 mL of saturated KOH solution and slowly add it dropwise into the beaker, and continue stirring for 2 hours;

[0039] 4) After the reaction is complete, place the beaker in an 80℃ oven and let it stand for 10 hours. Then, filter, wash, and dry to obtain zinc oxide microcapsules.

[0040] 5) At room temperature, first weigh 1.5g of sodium polystyrene sulfonate and 10g of NaCl and dissolve them in 150mL of deionized water. Then weigh 5g of zinc oxide microcapsules and add them to the solution. Stir for 3 hours to disperse the solution evenly. Then add 30mL of AgNO3 solution with a concentration of 0.08g / mL and continue stirring for 3 hours.

[0041] 6) Add 0.5g NaCl to the mixture and continue the reaction for 2 hours. Finally, filter, wash and dry to obtain silver chloride / zinc oxide bishell microcapsules.

[0042] like Figure 1 As shown, the prepared silver chloride / zinc oxide double-shell microcapsules are regular spherical with a diameter ranging from 4 to 9 μm.

[0043] like Figure 2 As shown, the phase transition temperature of the prepared silver chloride / zinc oxide double-shell microcapsules is 20-30℃, the latent heat of phase transition crystallization enthalpy is 160.69J / g, and the melting enthalpy is 164.64J / g.

[0044] Example 2

[0045] 1) Weigh 30g of n-octadecane, 3g of sodium dodecyl sulfate (SDS) and 150g of N / N-dimethylformamide solution, place them in a 1L beaker, and emulsify them at a high speed of 10000r / min for 1.5h under a water bath heating at 50℃ to obtain a uniform O / W emulsion.

[0046] 2) After emulsification, reduce the rotation speed to 800 r / min; then weigh 20 g of zinc nitrate and dissolve it in 25 mL of deionized water to prepare a solution with a concentration of 0.8 g / mL, and slowly add it dropwise to the O / W emulsion, and continue stirring for 4 h;

[0047] 3) Then weigh 40 mL of saturated NaOH solution and slowly add it dropwise into the beaker, and continue stirring for 2 hours;

[0048] 4) After the reaction is complete, the beaker is placed in an 80℃ oven and left to stand for 10 hours. Then, it is filtered, washed and dried to obtain zinc oxide microcapsules.

[0049] 5) At room temperature, first weigh 1.5g of sodium dodecylbenzenesulfonate and dissolve it in 150mL of deionized water, then weigh 5g of zinc oxide microcapsules and add them to the solution and stir for 3h to disperse them evenly. Then add 28mL of CuSO4 solution with a concentration of 0.08g / mL and continue stirring for 3h.

[0050] 6) Add 1.2g Na2S to it, continue the reaction for 2h, and finally obtain copper sulfide / zinc oxide bishell microcapsules by filtration, washing and drying.

[0051] like Figure 3 As shown, the prepared copper sulfide / zinc oxide double-shell microcapsules, as tested by the photothermal conversion system, have a high photothermal conversion efficiency of 98.6%, which is 59.7% higher than that of pure zinc oxide microcapsules (38.9%).

[0052] Example 3

[0053] 1) Weigh 30g of n-octadecane, 3g of sodium dodecyl sulfate (SDS) and 150g of N / N-dimethylformamide solution, place them in a 1L beaker, and emulsify them at a high speed of 10000r / min for 1.5h under a water bath heating at 50℃ to obtain a uniform O / W emulsion.

[0054] 2) After emulsification, reduce the rotation speed to 800 r / min; then weigh 20 g of zinc nitrate and dissolve it in 25 mL of deionized water to prepare a solution with a concentration of 0.8 g / mL, and slowly add it dropwise to the O / W emulsion, and continue stirring for 4 h;

[0055] 3) Then weigh 40 mL of saturated NaOH solution and slowly add it dropwise into the beaker, and continue stirring for 2 hours;

[0056] 4) After the reaction is complete, the beaker is placed in an 80℃ oven and left to stand for 10 hours. Then, it is filtered, washed and dried to obtain zinc oxide microcapsules.

[0057] 5) At room temperature, first weigh 1.3g of polyethylene glycol-blocked polypropylene glycol-blocked polyethylene glycol (PEG-PPG-PEG) and dissolve it in 150mL of deionized water. Then weigh 5g of zinc oxide microcapsules and add them to the solution. Stir for 3 hours to disperse the solution evenly. Then add 32mL of CdCl2 solution with a concentration of 0.08g / mL and continue stirring for 3 hours.

[0058] 6) Add 1.1g Na2S to it, continue the reaction for 2h, and finally obtain cadmium sulfide / zinc oxide bishell microcapsules by filtration, washing and drying.

[0059] like Figure 4 As shown, the prepared cadmium sulfide / zinc oxide bishell microcapsules have good light absorption properties. In the light wavelength range of 400-500nm, the absorption rate of cadmium sulfide / zinc oxide bishell microcapsules for visible light is higher than 70%.

[0060] Example 4

[0061] 1) Weigh 30g of n-octadecane, 3g of sodium dodecylbenzenesulfonate (SDBS) and 150g of anhydrous ethanol, place them in a 1L beaker, and emulsify them at a high speed of 8000r / min for 1.5h under a water bath heating at 60℃ to obtain a uniform O / W emulsion.

[0062] 2) After emulsification, reduce the rotation speed to 1000 r / min; then weigh 20 g of zinc nitrate and dissolve it in 25 mL of deionized water to prepare a solution with a concentration of 0.8 g / mL, and slowly add it dropwise to the O / W emulsion, and continue stirring for 6 h;

[0063] 3) Then weigh 40 mL of saturated KOH solution and slowly add it dropwise into the beaker, and continue stirring for 4 hours;

[0064] 4) After the reaction is complete, the beaker is placed in a 70℃ oven and left to stand for 5 hours. Then, it is filtered, washed, and dried to obtain zinc oxide microcapsules.

[0065] 5) At room temperature, first weigh 1.5g of sodium dodecyl sulfate and dissolve it in 150mL of deionized water, then weigh 5g of zinc oxide microcapsules and add them to the solution and stir for 3 hours to disperse them evenly. Then add 30mL of AgNO3 solution with a concentration of 0.08g / mL and continue stirring for 2 hours.

[0066] 1.1g of Na2S was added, and the reaction was continued for 1 hour. Finally, the mixture was filtered, washed, and dried to obtain silver sulfide / zinc oxide bishell microcapsules.

[0067] Comparative Examples

[0068] 1) Weigh 30g of n-octadecane, 3g of sodium dodecylbenzenesulfonate (SDBS) and 150g of anhydrous ethanol, place them in a 1L beaker, and emulsify them at a high speed of 8000r / min for 1.5h under a water bath heating at 60℃ to obtain a uniform O / W emulsion.

[0069] 2) After emulsification, reduce the rotation speed to 1000 r / min; then weigh 20 g of zinc nitrate and dissolve it in 25 mL of deionized water to prepare a solution with a concentration of 0.8 g / mL, and slowly add it dropwise to the O / W emulsion, and continue stirring for 6 h;

[0070] 3) Then weigh 40 mL of saturated KOH solution and slowly add it dropwise into the beaker, and continue stirring for 4 hours;

[0071] 4) After the reaction is complete, the beaker is placed in a 70℃ oven and left to stand for 5 hours. Then, it is filtered, washed and dried to obtain zinc oxide microcapsules.

[0072] The double-shell microcapsules prepared in Examples 1-4 and the comparative examples were subjected to pressure resistance and thermal conductivity tests, and the results are as follows:

[0073] The results above show that the preparation of inorganic double-shell microcapsules increases the pressure resistance of the microcapsules. At the same time, the formation of the outer shell increases the conductive / heat-receiving area and improves the thermal conductivity of the outer shell compared to pure zinc oxide microcapsules (comparative example). It can also endow the inner shell with properties that the microcapsules do not have or improve upon their relatively weak properties.

Claims

1. A method for preparing multifunctional inorganic double-shell material phase change microcapsules, characterized in that, The application relates to a phase change microcapsule with a phase change core material and an inner and outer shell material, wherein the inner shell material is zinc oxide, and the outer shell material is silver chloride, copper sulfide or cadmium sulfide, and comprises the following steps: 1) adding a phase change core material and an emulsifier into a solvent to form an O / W solution through high-speed emulsification; 2) after the emulsification, slowly adding a zinc source solution into the O / W solution and continuing to stir; 3) adding a basic saturated solution and continuing to stir; 4) aging the reacted solution, and then performing suction filtration, washing and drying to obtain zinc oxide microcapsules; 5) dispersing the zinc oxide microcapsules in a surfactant solution, slowly adding a metal salt solution, and continuously stirring; 6) adding a reducing agent and continuing to stir, and finally performing suction filtration, washing and drying to obtain multifunctional inorganic double-shell phase change microcapsules; In the step 5), the surfactant is one of sodium polystyrene sulfonate, sodium dodecyl sulfate, sodium dodecyl benzene sulfonate and polyethylene glycol block polypropylene glycol block polyethylene glycol, and the mass ratio of the zinc oxide microcapsules to the surfactant is 1:(0.1-0.4); In the step 5), the metal salt is a copper source, a cadmium source or a silver source, and the mass ratio of the zinc oxide microcapsules to the metal salt is 1:(0.25-2), and the concentration of the metal salt is 0.05-0.1 g / mL; In the step 6), the reducing agent is a sulfide or a chloride, and the mass ratio of the metal salt source to the reducing agent is 1:(0.3-1).

2. The method of claim 1, wherein: In the step 1), the emulsifier is one of anionic emulsifiers of sodium dodecyl sulfate and sodium dodecyl benzene sulfonate, the solvent is one of N / N-dimethylformamide solution and anhydrous ethanol, and the emulsification speed is 8000-12000 r / min.

3. The method of claim 1, wherein: In the step 2), the zinc source is one of zinc acetate, zinc nitrate and zinc sulfate, and the concentration of the zinc source solution is 0.5-1 g / mL.

4. The method of claim 1, wherein: The mass ratio of the phase change core material, the emulsifier, the solvent and the zinc source is 1:(0.05-0.2):(3-10):(0.2-1).

5. The method of claim 1, wherein: In the step 3), the basic solution is one of sodium hydroxide solution and potassium hydroxide solution.

6. The method of claim 1, wherein: In the step 4), the aging condition is that the solution is placed in an oven at 60-90 DEG C for 5-12 h.

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