Silica microcapsule, preparation method thereof, phase change energy storage material and energy storage element

Abstract

The application provides a silica microcapsule, a preparation method of the silica microcapsule, a phase change energy storage material and an energy storage element. A water phase containing a block polymer is mixed with an oil-soluble solution containing a core material in a suitable pH environment to form a stable emulsion with good dispersibility, further, water glass is gelatinized and added into the emulsion in batches, and the mixing is terminated by pH determination, and the mixture is aged to obtain the silica microcapsule. The block polymer is used to improve the dispersibility of the emulsion, promote the uniform dispersion of the silica precursor in the emulsion, and obtain the silica microcapsule, so that the core material is efficiently loaded and encapsulated. The silica microcapsule prepared by the application can be used as an excellent carrier and is widely applied in daily chemical, pharmaceutical, building and energy fields.

Description

Technical Field

[0001] This invention relates to the field of silicon material technology, and in particular to silicon dioxide microcapsules and their preparation methods, phase change energy storage materials, and energy storage elements. Background Technology

[0002] Microencapsulation technology is a technique that uses film-forming materials to encapsulate solid, liquid, or gaseous core substances into tiny containers, typically ranging in size from micrometers to millimeters. The microcapsule structure consists of an inner core material and an outer wall material; this unique structure enables the effective encapsulation, protection, and controlled release of substances. Microencapsulation technology has been widely applied in numerous fields, including pharmaceuticals, food, cosmetics, textiles, and agriculture. Among the many wall material options, silica, as an inorganic material, has attracted widespread attention from the scientific and industrial communities in recent years. Compared to traditional organic block polymer wall materials, silica microcapsules exhibit unique physicochemical properties, including excellent mechanical strength, high thermal stability, and good biocompatibility. These properties make silica microcapsules a promising functional material, particularly in high-end applications such as drug delivery, self-healing materials, and phase change energy storage systems.

[0003] Traditional methods for preparing silica microcapsules mainly employ in-situ emulsion polymerization, interfacial polycondensation, and self-assembly. On the one hand, traditional methods typically use organosilicon sources (TEOS), which makes the preparation cost of silica microcapsules relatively high and their toxicity significant, limiting their application areas. On the other hand, silica microcapsules are primarily prepared in liquid systems, and the dispersion and stability of the system significantly affect the morphology and functionality of the prepared microcapsules. Traditional preparation methods still struggle to provide stable reaction systems, thus impacting the performance of the silica microcapsules. Summary of the Invention

[0004] Given the problems with existing technologies, it is necessary to provide a stable and dispersed reaction system that can control the morphology of silica microcapsules to achieve high encapsulation, high loading and excellent functionality, while also being economical and environmentally friendly, and having a wide range of applications.

[0005] In a first aspect, the present invention provides a silica microcapsule, which is prepared by water glass and an oil-soluble solution containing a core material, wherein the core material comprises a phase change material; the structure of the silica microcapsule includes a capsule wall and a core material enclosed by the capsule wall, wherein the mass ratio of the capsule wall to the core material is 1:(0.5-6), and the particle size of the silica microcapsule is 5μm-100μm.

[0006] In some embodiments, the encapsulation efficiency of the silica microcapsules is 69.5%-71%; and / or, the loading of the silica microcapsules is 46.6%-88.4%.

[0007] Secondly, the present invention also provides a method for preparing silica microcapsules, comprising the following steps: The block polymer and water are mixed to form a mixture, and the pH of the mixture is adjusted to 5-9 to form a premix. The premixed liquid is mixed with an oil-soluble solution containing the core material to form a first mixture; Water glass and sulfuric acid solution are mixed to form a capsule wall solution with a pH of 2.2-2.8. While stirring, the capsule wall solution is added in batches to the first mixture until the pH reaches 2.8-3.2, then the addition of the capsule wall solution is stopped to form the second mixture; The second mixture was aged to prepare silica microcapsules.

[0008] In some embodiments, the core material includes a phase change material; Optionally, the phase change material includes one or more of organic phase change materials, inorganic phase change materials, and organic-inorganic composite phase change materials; Further optionally, the organic phase change material includes one or more of aliphatic hydrocarbons, aliphatic alcohols, fatty acids, and esters; Further optionally, inorganic phase change materials include one or more of inorganic salts and their hydrates, metal-organic framework materials, and covalent organic framework materials.

[0009] In some embodiments, the preparation method further satisfies at least one of the following conditions (1) to (10): (1) The block polymer includes polyurethane; (2) The mass ratio of the block polymer to the water is 1:(5-100); Optionally, the mass ratio of the block polymer to the water is 1:(5-20). (3) The mass ratio of the block polymer to the oil-soluble solution containing the core material is 1:(0.1-20). Optionally, the mass ratio of the block polymer to the oil-soluble solution containing the core material is 1:(5-12). (4) Mix the block polymer with water and adjust the pH to 6-7.5; (5) The block polymer and water are mixed, and the pH value is adjusted to 5-9 using sulfuric acid solution, wherein the concentration of sulfuric acid solution is 0.1mol / L-5mol / L; (6) The concentration of the water glass is 0.2 mol / L-2 mol / L; (7) The modulus of the water glass is 1-4; (8) The concentration of the sulfuric acid solution is 0.1 mol / L-5 mol / L; (9) The aging temperature is 20℃-70℃; (10) The aging time is 10h-15h.

[0010] In some embodiments, during the process of adding the capsule wall solution to the first mixture for mixing, the mixing is carried out by homogenization at a speed of 5000 rpm to 15000 rpm.

[0011] In some embodiments, before adding the oil-soluble solution containing the core material for mixing, the premixed solution is further heated to 55°C-65°C; and / or, After mixing the premixed liquid with an oil-soluble solution containing the core material, the process further includes a defoaming step. Optionally, the defoaming process is carried out by stirring at a speed of 400 rpm to 500 rpm for a duration of 5 min to 20 min.

[0012] In some embodiments, the method for preparing the block polymer includes the following steps: Isocyanate, organotin catalyst and hydrophilic chain extender are reacted to form a prepolymer; Block polymers are prepared by reacting prepolymers with polyethylene glycol; Optionally, the isocyanate includes one or more of dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, toluene diisocyanate, phenyl diisocyanate and methylcyclohexyl diisocyanate; Optionally, the organotin catalyst comprises one or more of dibutyltin dilaurate, stannous octanoate, di(dodecyl sulfide)dibutyltin, and dibutyltin diacetate; Optionally, the hydrophilic chain extender includes one or more of dimethylolpropionic acid, dimethylolbutyric acid, sodium 1,2-propanediol-3-sulfonate, sodium 1,4-butanediol-2-sulfonate, diethylenetriamine, and N-methyldiethanolamine; Optionally, the number-average molecular weight of the polyethylene glycol is 600 g / mol to 3500 g / mol; Optionally, the mass ratio of the isocyanate to the organotin catalyst is 1:(0.0005-0.005). Optionally, the molar ratio of the isocyanate, the organotin catalyst and the hydrophilic chain extender is 1:(0.0005-0.005):(0.1-1.0).

[0013] In some embodiments, aging also includes washing and drying processes; Alternatively, the washing may be performed using one or more solvents selected from water, ethanol, and petroleum ether; Optionally, the drying temperature is 60℃-120℃ and the drying time is 12 h-36 h.

[0014] Thirdly, the present invention also provides a phase change energy storage material, which is prepared by silica microcapsules, wherein the silica microcapsules include the silica microcapsules provided in the first aspect, or silica microcapsules prepared by the method for preparing silica microcapsules provided in the second aspect.

[0015] Fourthly, the present invention also provides an energy storage element, the energy storage element comprising the phase change energy storage material provided in the third aspect.

[0016] Compared with the prior art, the beneficial effects of the technical solution of the present invention include: This invention involves mixing an aqueous phase containing a block polymer with an oil-soluble solution containing a core material to form a stable and well-dispersible oil-in-water emulsion. Water glass, after acidification, is then added to the emulsion in batches. The mixture is then aged to obtain silica microcapsules. This invention utilizes the block polymer to enhance the dispersibility of the emulsion, promoting the uniform dispersion of the silica precursor within the emulsion, resulting in silica microcapsules. This achieves efficient loading and encapsulation of the core material, thereby enhancing the functionality of the silica microcapsules. Attached Figure Description

[0017] Figure 1 The infrared spectrum of the block copolymer synthesized in Example 1 of the present invention is shown.

[0018] Figure 2 An optical microscope image of the microcapsules prepared in Example 1 of the present invention is shown.

[0019] Figure 3 The image shows a SEM image of the microcapsules prepared in Example 1 of the present invention.

[0020] Figure 4 The differential scanning calorimeter (DSC) diagrams of Embodiments 1 and 5-7 of the present invention are shown.

[0021] Figure 5 An optical microscope image of the microcapsules prepared in Example 2 of the present invention is shown.

[0022] Figure 6An optical microscope image of the microcapsules prepared in Example 3 of the present invention is shown.

[0023] Figure 7 An optical microscope image of the microcapsules prepared in Example 4 of the present invention is shown.

[0024] Figure 8 The image shows a SEM image of the microcapsules prepared in Comparative Example 1 of the present invention.

[0025] Figure 9 The image shows a SEM image of the microcapsules prepared in Comparative Example 2 of this invention. Detailed Implementation

[0026] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0028] As used herein, "optional," "optional," and "optional" refer to either "with" or "without" parallel options. If multiple "optional" entries appear in a technical solution, each "optional" entry is independent unless otherwise specified and there are no contradictions or mutual constraints. The term "and / or" as used herein includes any and all combinations of one or more related listed items. Unless otherwise specified, "multiple," "multiple," etc., as used herein refer to a quantity greater than 2 or equal to 2; for example, "one or more" indicates one, two, or more than two. In open-ended technical features or solutions described herein using words such as "containing," "including," and "comprising," unless otherwise specified, additional members beyond the listed members are not excluded. This can be considered as providing both a closed-ended feature or solution consisting of the listed members and an open-ended feature or solution that includes additional members beyond the listed members.

[0029] In this invention, the terms "first aspect," "second aspect," "third aspect," "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," "fourth," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on the quantity.

[0030] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0031] The preparation of silica microcapsules using traditional processes is challenging, resulting in numerous defects such as excessively large particle size, poor particle size distribution uniformity, and low encapsulation efficiency. These limitations significantly restrict the application of silica microcapsules. Furthermore, they also present problems such as high cost and poor environmental friendliness.

[0032] The present invention aims to develop a more economical and efficient preparation route that balances performance and cost.

[0033] In a first aspect, the present invention provides a silica microcapsule, which is prepared by water glass and an oil-soluble solution containing a core material, wherein the core material comprises a phase change material.

[0034] In some embodiments, the phase change material includes one or more of organic phase change materials, inorganic phase change materials, and organic-inorganic composite phase change materials. As a non-limiting example, organic phase change materials include one or more of aliphatic hydrocarbons, fatty alcohols, fatty acids, and esters. As a non-limiting example, inorganic phase change materials include one or more of inorganic salts and their hydrates, metal-organic frameworks, and covalent organic frameworks. It is understood that an "oil-soluble solution containing a core material" can be an oil-soluble core material, including but not limited to one or more of aliphatic hydrocarbons, fatty alcohols, fatty acids, and esters.

[0035] The structure of the silica microcapsule includes a capsule wall and a core material encapsulated by the capsule wall. The mass ratio of the capsule wall to the core material is 1:(0.5-6), including but not limited to 1:0.5, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6 or any combination thereof and values ​​within that range.

[0036] The silica microcapsules have a particle size of 5μm-100μm, including but not limited to 5μm, 10μm, 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, 100μm or any combination thereof and values ​​within that range.

[0037] This invention successfully prepared a silica microcapsule with uniform particle size distribution, suitable for stable industrial production. Furthermore, the silica microcapsules prepared by this invention exhibit high encapsulation capacity of the core material, with an encapsulation rate of 69.5%-71% and a loading of 46.6%-88.4%, making them highly valuable as a carrier.

[0038] Secondly, the present invention also provides a method for preparing silica microcapsules, comprising the following steps: S10. The block polymer and water are mixed to form a mixture, and the pH value of the mixture is adjusted to 5-9 to form a premix.

[0039] S20. The premixed liquid is mixed with an oil-soluble solution containing the core material to form a first mixture.

[0040] S30. Water glass and sulfuric acid solution are mixed to form a capsule wall solution, wherein the pH of the capsule wall solution is 2.2-2.8.

[0041] S40. While stirring, the capsule wall solution is added in batches to the first mixture until the pH is 2.8-3.2. Then, the addition of the capsule wall solution is stopped to form the second mixture.

[0042] S50. The second mixture is aged to prepare silica microcapsules.

[0043] This invention involves mixing an aqueous phase containing a block polymer with an oil phase containing a core material to form an emulsion, followed by the slow, batch-wise addition of water glass gel to prepare silica microcapsules. This technical solution utilizes the block polymer to enhance the stability of the emulsion, obtaining a uniform and stable dispersion emulsion, thereby preventing the aggregation of silica precursors and silica ions, thus achieving the preparation of small-sized and uniform silica microcapsules. Compared to the emulsifiers and dispersants used in traditional solutions, the block polymer used in this invention exhibits better dispersion and stabilization effects, possibly due to the interaction between the molecular structure characteristics of the block polymer and water glass.

[0044] Block polymers, as key components for improving emulsion stability and dispersibility, require their addition within a certain range. In some embodiments, the mass ratio of the block polymer to the water is 1:(5-100), including but not limited to 1:5, 1:10, 1:20, 1:30, 1:40, 1:50, 1:60, 1:70, 1:80, 1:90, 1:100, or any combination thereof and values ​​within that range. Further, a mass ratio of 1:(5-20) of the block polymer to the water yields a more stable dispersion system, better achieving the technical effects of the present invention. Even further, a mass ratio of 1:(9-15) of the block polymer to the water yields a more stable dispersion system, better achieving the technical effects of the present invention. It is understood that the mass ratio can be calculated using concentration, and a concentration range of 6wt%-12wt% of the block polymer in the mixture formed by the block polymer and the water is preferred.

[0045] As a key component of the aqueous phase, the mixing ratio of the block polymer with the oil phase needs to be controlled within a certain range to form a highly stable and dispersed emulsion. In some embodiments, the mass ratio of the block polymer to the oil-soluble solution containing the core material is 1:(0.1-20), including but not limited to 1:0.1, 1:1, 1:2, 1:5, 1:8, 1:10, 1:12, 1:15, 1:18, 1:20, or any combination thereof and values ​​within that range. Furthermore, a mass ratio of 1:(5-12) of the block polymer to the oil-soluble solution containing the core material yields a more stable and dispersed oil-in-water system, better achieving the technical effects of this invention.

[0046] In some embodiments, the block polymer and water are mixed, and the pH value is adjusted to 5-9, including but not limited to 5, 6, 7, 8, 9, or any combination thereof and values ​​within that range. Further, the block polymer and water are mixed, and the pH value is adjusted to 6-7.5, within which better stability of the dispersion system can be achieved. This invention requires pH control of the aqueous phase containing the block polymer to ensure emulsion stability. If the pH value exceeds this range, it may lead to rapid emulsion stratification, precipitation, or demulsification, failing to achieve the technical effects of this invention.

[0047] In some embodiments, the block polymer and water are mixed, and the pH value is adjusted to 5-9 using a sulfuric acid solution. The concentration of the sulfuric acid solution is 0.1 mol / L-5 mol / L, including but not limited to 0.1 mol / L, 0.5 mol / L, 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, or any combination thereof and values ​​within that range.

[0048] This invention utilizes low-cost water glass to prepare silica microcapsules. During the preparation process, it is necessary to control the water glass and its gelation process.

[0049] In some embodiments, the concentration of the water glass is 0.2 mol / L to 2 mol / L, including but not limited to 0.2 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.8 mol / L, 1 mol / L, 1.2 mol / L, 1.34 mol / L, 1.5 mol / L, 1.8 mol / L, 2 mol / L, or any range formed by both of the foregoing and values ​​within that range. Furthermore, a concentration of 1 mol / L to 1.5 mol / L better achieves the technical effects of the present invention.

[0050] In some embodiments, the modulus of the water glass is 1-4, including but not limited to 1, 1.5, 2, 2.5, 3, 3.5, 4, or any combination thereof and values ​​within that range. Furthermore, a modulus of 3-4 for the water glass better achieves the technical effects of the present invention.

[0051] In some embodiments, the concentration of sulfuric acid in the preparation of the capsule wall solution is 0.1 mol / L to 5 mol / L, including but not limited to 0.1 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L, 5 mol / L, or any range formed by both of the foregoing and values ​​within that range. Furthermore, a sulfuric acid solution concentration of 2 mol / L to 3 mol / L better achieves the technical effects of the present invention.

[0052] In some embodiments, the aging temperature is 20°C-70°C, including but not limited to 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, or any combination thereof and values ​​within that range. Furthermore, aging within a temperature range of 50°C-70°C yields better results.

[0053] In some embodiments, the aging time is 10h-15h, including but not limited to 10h, 11h, 12h, 13h, 14h, 15h or any of the foregoing ranges and values ​​within that range.

[0054] In some embodiments, during the process of adding the capsule wall solution to the first mixture for mixing, the mixing is carried out by homogenization, and the homogenization speed is 5000rpm-15000rpm, including but not limited to 5000rpm, 6000rpm, 7000rpm, 8000rpm, 9000rpm, 10000rpm, 11000rpm, 12000rpm, 13000rpm, 14000rpm, 15000rpm or any combination thereof and values ​​within the range.

[0055] In some embodiments, before adding the oil-soluble solution containing the core material for mixing, the premixed liquid is further heated to 55°C-65°C, including but not limited to 55°C, 56°C, 57°C, 58°C, 59°C, 60°C, 61°C, 62°C, 63°C, 64°C, 65°C, or any combination thereof and values ​​within those ranges. Preheating the premixed liquid can further promote emulsion formation and improve the stability and dispersibility of the emulsion.

[0056] In some embodiments, after mixing the premixed liquid with the oil-soluble solution containing the core material, a defoaming step is further included. As a non-limiting example, the defoaming step is performed by stirring; further, the stirring speed is 400 rpm-500 rpm, and the stirring time is 5 min-20 min.

[0057] In this invention, block polymers are a key component of the aqueous phase and a key factor affecting the stability and dispersibility of emulsions. The molecular structure of the block polymers also has a very important impact on the performance of the emulsions, including the block ratio, degree of polymerization, molecular weight, and block molecular chain structure, etc.

[0058] In some embodiments, the method for preparing the block polymer includes the following steps: T10. Isocyanate, organotin catalyst and hydrophilic chain extender are reacted to form a prepolymer.

[0059] T20. React the prepolymer with polyethylene glycol to prepare a block polymer.

[0060] In some embodiments, the isocyanate includes one or more of dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, toluene diisocyanate, phenyl diisocyanate, and methylcyclohexyl diisocyanate.

[0061] In some embodiments, the organotin catalyst comprises one or more of dibutyltin dilaurate, stannous octoate, di(dodecyl sulfide)dibutyltin, and dibutyltin diacetate.

[0062] In some embodiments, the hydrophilic chain extender includes one or more of dimethylolpropionic acid, dimethylolbutyric acid, sodium 1,2-propanediol-3-sulfonate, sodium 1,4-butanediol-2-sulfonate, diethylenetriamine, and N-methyldiethanolamine.

[0063] In some embodiments, the number-average molecular weight of the polyethylene glycol is 600 g / mol to 3500 g / mol, including but not limited to 600 g / mol, 800 g / mol, 1000 g / mol, 1500 g / mol, 1800 g / mol, 2000 g / mol, 2500 g / mol, 3000 g / mol, 3500 g / mol, or any combination thereof and values ​​within that range. The use of polyethylene glycol with a number-average molecular weight of 800 g / mol to 1200 g / mol in this invention better achieves the technical effects of the invention.

[0064] In some embodiments, the mass ratio of the isocyanate to the organotin catalyst is 1:(0.0005-0.005), including but not limited to 1:0.0005, 1:0008, 1:0.001, 1:0.0015, 1:0.002, 1:0025, 1:0.003, 1:0035, 1:0.004, 1:0.0045, 1:0.005, or any range formed by both of the foregoing and values ​​within that range. Furthermore, a mass ratio of the isocyanate to the organotin catalyst of 1:(0.001-0.005) better achieves the technical effects of the present invention.

[0065] In some embodiments, the molar ratio of the isocyanate, the organotin catalyst, and the hydrophilic chain extender is 1:(0.0005-0.005):(0.1-1.0), including but not limited to 1:0.05:0.1, 1:0.05:0.5, 1:0.05:1, 1:0.1:0.1, 1:0.1:0.5, 1:0.1:1, 1:0.5:0.1, 1:0.5:0.5, 1:0.5:1, 1:1:0.1, 1:1:0.5, 1:1:1, 1:1.5:0.1, 1:1.5:0.5, 1:1.5:1, or any of the foregoing ranges and values ​​within those ranges. Furthermore, the molar ratio of the isocyanate, the organotin catalyst and the hydrophilic chain extender is 1:(0.001-0.005):(0.1-1.0), which can better achieve the technical effect of the present invention.

[0066] In some embodiments, aging also includes washing and drying processes.

[0067] In some embodiments, washing is performed using one or more solvents selected from water, ethanol, and petroleum ether.

[0068] In some embodiments, the drying temperature is 60°C-120°C and the drying time is 12 h-36 h.

[0069] Thirdly, the present invention also provides a phase change energy storage material, which is prepared by silica microcapsules, wherein the silica microcapsules include the silica microcapsules provided in the first aspect, or silica microcapsules prepared by the method for preparing silica microcapsules provided in the second aspect.

[0070] The silica microspheres prepared by this invention not only possess excellent encapsulation and loading capabilities, but also exhibit superior microstructure and morphology in the formed silica capsule walls, such as high density, high mechanical properties, and excellent surface properties, thereby achieving the following application advantages: Encapsulation of phase change materials (PCMs) can reduce leakage, and high encapsulation efficiency significantly improves their thermal properties. Excellent mechanical properties also ensure the long-term stability of the PCMs. Superior surface properties not only improve heat transfer efficiency but also ensure interfacial stability between microcapsules, further enhancing thermal conductivity. In some embodiments, the silica microcapsules have a melting point of 53.6℃-55.9℃.

[0071] In some embodiments, the phase transition enthalpy of the silica microcapsules is 89.1 kJ / kg-169.1 kJ / kg.

[0072] Fourthly, the present invention also provides an energy storage element, the energy storage element comprising the phase change energy storage material provided in the third aspect.

[0073] It is understood that the silica microcapsules prepared by this invention have broad application prospects in fields such as heat insulation, drug loading, and functional fillers.

[0074] It should be noted that the experimental methods in the following embodiments of the present invention, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All commonly used chemical reagents used in the embodiments are commercially available products, or can be prepared by those skilled in the art using known methods.

[0075] Preparation of block polymers: 44.5g of isophorone diisocyanate was heated to 70°C, then 0.1g of dibutyltin dilaurate was added, followed by the slow addition of 11.9g of N-methyldiethanolamine. After the addition was complete, the mixture was reacted at 70°C for 2 hours. The reaction product was then added to 200g of polyethylene glycol (number average molecular weight of 1000g / mol) heated to 80°C, and reacted at 80°C for 2 hours to obtain the block copolymer.

[0076] The infrared spectra of the block copolymers prepared in this invention are shown in the appendix. Figure 1 As shown, see appendix Figure 1 The infrared spectrum of the synthesized block copolymer showed infrared peaks for urethane and hydroxyl groups, while the infrared peak for isocyanate groups disappeared. This indicates that the block copolymer was successfully synthesized. Other block polymers can also be prepared using similar methods.

[0077] Example 1 2g of the above block copolymer was dispersed in 18g of water and the pH was adjusted to 6.2. Then the dispersion was placed in a 60°C water bath, 9g of paraffin was added and homogenized at 15K rpm for 5 min to form an oil-in-water emulsion. Then the mixture was stirred at 500 rpm for 10 min to remove excess air bubbles and form emulsion A.

[0078] Solution B was prepared by adding 1.34 mol / L water glass (modulus 3.5) dropwise to 3 mol / L sulfuric acid until the pH reached 2.5. Solution B was then slowly added dropwise to emulsion A while it was being stirred. The addition was stopped when the pH reached 3.0, and the mixture was aged at 60°C for 12 hours. The product was obtained by centrifugation and washing with water, ethanol, and petroleum ether. Finally, the product was dried in a 60°C oven for 24 hours to obtain silica / paraffin microcapsules.

[0079] Example 2 1.5g of the above block copolymer was dispersed in 18g of water and the pH was adjusted to 6.2. The dispersion was then placed in a 60°C water bath, 9g of paraffin was added, and the mixture was homogenized at 15K rpm for 5 min to form an oil-in-water emulsion. The mixture was then stirred at 500 rpm for 10 min to remove excess air bubbles and form emulsion A.

[0080] Solution B was prepared by adding 1.34 mol / L water glass (modulus 3.5) dropwise to 3 mol / L sulfuric acid until the pH reached 2.5. Solution B was then slowly added dropwise to emulsion A while it was being stirred. The addition was stopped when the pH reached 3.0, and the mixture was aged at 60°C for 12 hours. The product was obtained by centrifugation and washing with water, ethanol, and petroleum ether. Finally, the product was dried in a 60°C oven for 24 hours to obtain silica / paraffin microcapsules.

[0081] Example 3 1.25g of the above block copolymer was dispersed in 18g of water and the pH was adjusted to 6.2. The dispersion was then placed in a 60°C water bath, 9g of paraffin was added, and the mixture was homogenized at 15K rpm for 5 min to form an oil-in-water emulsion. The mixture was then stirred at 500 rpm for 10 min to remove excess air bubbles and form emulsion A.

[0082] Solution B was prepared by adding 1.34 mol / L water glass (modulus 3.5) dropwise to 3 mol / L sulfuric acid until the pH reached 2.5. Solution B was then slowly added dropwise to emulsion A while it was being stirred. The addition was stopped when the pH reached 3.0, and the mixture was aged at 60°C for 12 hours. The product was obtained by centrifugation and washing with water, ethanol, and petroleum ether. Finally, the product was dried in a 60°C oven for 24 hours to obtain silica / paraffin microcapsules.

[0083] Example 4 1g of the above block copolymer was dispersed in 18g of water and the pH was adjusted to 6.2. The dispersion was then placed in a 60°C water bath, 9g of paraffin was added, and the mixture was homogenized at 15K rpm for 5 min to form an oil-in-water emulsion. The mixture was then stirred at 500 rpm for 10 min to remove excess air bubbles and form emulsion A.

[0084] Solution B was prepared by adding 1.34 mol / L water glass (modulus 3.5) dropwise to 3 mol / L sulfuric acid until the pH reached 2.5. Solution B was then slowly added dropwise to emulsion A while it was being stirred. The addition was stopped when the pH reached 3.0, and the mixture was aged at 60°C for 12 hours. The product was obtained by centrifugation and washing with water, ethanol, and petroleum ether. Finally, the product was dried in a 60°C oven for 24 hours to obtain silica / paraffin microcapsules.

[0085] Example 5 2g of the above block copolymer was dispersed in 18g of water and the pH was adjusted to 6.2. Then the dispersion was placed in a 60°C water bath, 7.5g of paraffin was added and homogenized at 15K rpm for 5 min to form an oil-in-water emulsion. Then the mixture was stirred at 500 rpm for 10 min to remove excess air bubbles and form emulsion A.

[0086] Solution B was prepared by adding 1.34 mol / L water glass (modulus 3.5) dropwise to 3 mol / L sulfuric acid until the pH reached 2.5. Solution B was then slowly added dropwise to emulsion A while it was being stirred. The addition was stopped when the pH reached 3.0, and the mixture was aged at 60°C for 12 h. The product was obtained by centrifugation at 6000 rpm and washing with water, ethanol, and petroleum ether. Finally, the product was dried in a 60°C oven for 24 h to obtain silica / paraffin microcapsules.

[0087] Example 6 2g of the above block copolymer was dispersed in 18g of water and the pH was adjusted to 6.2. Then the dispersion was placed in a 60°C water bath, 6g of paraffin was added and homogenized at 15K rpm for 5 min to form an oil-in-water emulsion. Then the mixture was stirred at 500 rpm for 10 min to remove excess air bubbles and form emulsion A.

[0088] Solution B was prepared by adding 1.34 mol / L water glass (modulus 3.5) dropwise to 3 mol / L sulfuric acid until the pH reached 2.5. Solution B was then slowly added dropwise to emulsion A while it was being stirred. The addition was stopped when the pH reached 3.0, and the mixture was aged at 60°C for 12 hours. The product was obtained by centrifugation and washing with water, ethanol, and petroleum ether. Finally, the product was dried in a 60°C oven for 24 hours to obtain silica / paraffin microcapsules.

[0089] Example 7 2g of the above block copolymer was dispersed in 18g of water and the pH was adjusted to 6.2. Then, the dispersion was placed in a 60°C water bath, 4.5g of paraffin was added, and the mixture was homogenized at 15K rpm for 5 min to form an oil-in-water emulsion. The mixture was then stirred at 500 rpm for 10 min to remove excess air bubbles and form emulsion A.

[0090] Solution B was prepared by adding 1.34 mol / L water glass (modulus 3.5) dropwise to 3 mol / L sulfuric acid until the pH reached 2.5. Solution B was then slowly added dropwise to emulsion A while it was being stirred. The addition was stopped when the pH reached 3.0, and the mixture was aged at 60°C for 12 hours. The product was obtained by centrifugation and washing with water, ethanol, and petroleum ether. Finally, the product was dried in a 60°C oven for 24 hours to obtain silica / paraffin microcapsules.

[0091] Comparative Example 1 44.5 g of isophorone diisocyanate was heated to 70 °C, then 0.1 g of dibutyltin dilaurate was added, followed by the slow addition of 11.9 g of N-methyldiethanolamine. After the addition was complete, the mixture was reacted at 70 °C for 2 h. The reaction product was then added to 100 g of polyethylene glycol (number average molecular weight of 1000 g / mol) heated to 80 °C, and reacted at 80 °C for 2 h to obtain a block copolymer.

[0092] 2g of the above block copolymer was dispersed in 18g of water and the pH was adjusted to 6.2. Then the dispersion was placed in a 60°C water bath, 9g of paraffin was added and homogenized at 15K rpm for 5 min to form an oil-in-water emulsion. Then the mixture was stirred at 500 rpm for 10 min to remove excess air bubbles and form emulsion A.

[0093] 1.34 mol / L of water glass with a modulus of 3.5 was added dropwise to 3 mol / L sulfuric acid until the pH reached 2.5, forming solution B. Solution B was then slowly added dropwise to emulsion A while it was being stirred. The addition was stopped when the pH reached 3.0, and the mixture was aged at 60°C for 12 hours. The product was obtained by centrifugation and washing with water, ethanol, and petroleum ether.

[0094] Comparative Example 2 44.5 g of isophorone diisocyanate was heated to 70 °C, then 0.1 g of dibutyltin dilaurate was added, followed by the slow addition of 11.9 g of N-methyldiethanolamine. After the addition was complete, the mixture was reacted at 70 °C for 2 h. The reaction product was then added to 80 g of polyethylene glycol (number average molecular weight of 400 g / mol) heated to 80 °C, and reacted at 80 °C for 2 h to obtain a block copolymer.

[0095] 2g of the above block copolymer was dispersed in 18g of water and the pH was adjusted to 6.2. Then the dispersion was placed in a 60°C water bath, 9g of paraffin was added and homogenized at 15K rpm for 5 min to form an oil-in-water emulsion. Then the mixture was stirred at 500 rpm for 10 min to remove excess air bubbles and form emulsion A.

[0096] 1.34 mol / L of water glass with a modulus of 3.5 was added dropwise to 3 mol / L sulfuric acid until the pH reached 2.5, forming solution B. Solution B was then slowly added dropwise to emulsion A while it was being stirred. The addition was stopped when the pH reached 3.0, and the mixture was aged at 60°C for 12 hours. The product was obtained by centrifugation and washing with water, ethanol, and petroleum ether.

[0097] See appendix Figure 2 To be continued Figure 9 From the microscopic morphology, we can see that: Appendix Figure 2 and attached Figure 3 These are microscope images and SEM images of the microcapsules, from which we can clearly see the microcapsule structure.

[0098] Appendix Figure 5 -Appendix Figure 7 These are optical microscope images of microcapsules synthesized with different block copolymer contents. From them, we can see that as the block copolymer content decreases, the particle size of the microcapsules slowly increases, the monodispersity deteriorates, and the formation of microcapsules can be basically maintained even when the block copolymer content is as low as 1g.

[0099] Appendix Figure 8 These are scanning electron microscope images of silica synthesized by reducing the polyethylene glycol content in block copolymers. From these images, we can see that silica cannot form microcapsules at this stage. Figure 9 The image shows a scanning electron microscope (SEM) image of silica synthesized by replacing polyethylene glycol with a number-average molecular weight of 1000 g / mol with polyethylene glycol with a number-average molecular weight of 400 g / mol. From this image, we can see that the silica cannot completely encapsulate the oil phase, forming a curved structure instead of microcapsules.

[0100] Experimental Example 1 The silica / paraffin microcapsules prepared in Examples 1 and 5-7 were subjected to performance testing. The test indicators included melting point, phase transition enthalpy, loading, and encapsulation efficiency. The test results are shown in the appendix. Figure 4 See Table 1.

[0101] Table 1: Performance test results of silica / paraffin microcapsules

[0102] See appendix Figure 4 Differential scanning calorimetry (DSC) curves for Examples 1 and 5-7 are presented. We can observe that the latent heat of the composite phase change material increases with the increase of the oil phase.

[0103] As shown in Table 1, the phase change enthalpy of the composite phase change material is lower than that of the paraffin phase change material, which is related to the addition of the silica shell. Table 1 also shows that the silica microcapsules prepared in Example 1 have the best thermal performance, with a phase change enthalpy of 169.1 kJ / kg. Furthermore, the phase change enthalpy decreases with decreasing paraffin content. Simultaneously, the silica microcapsules at this stage also exhibit a high and stable encapsulation efficiency of approximately 70.1% for the solid-liquid phase change material.

[0104] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0105] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. 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, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A silica microcapsule, characterized by, The silica microcapsules are prepared by water glass and an oil-soluble solution containing a core material, wherein the core material includes a phase change material; the structure of the silica microcapsules includes a capsule wall and a core material enclosed by the capsule wall, wherein the mass ratio of the capsule wall to the core material is 1:0.5-6, and the particle size of the silica microcapsules is 5μm-100μm; The method for preparing the silica microcapsules includes the following steps: The block polymer and water are mixed to form a mixture, and the pH of the mixture is adjusted to 5-9 to form a premix. The premixed liquid is mixed with an oil-soluble solution containing the core material to form a first mixture; Water glass and sulfuric acid solution are mixed to form a capsule wall solution with a pH of 2.2-2.

8. While stirring, the capsule wall solution is added in batches to the first mixture until the pH reaches 2.8-3.2, then the addition of the capsule wall solution is stopped to form the second mixture; The second mixture was aged to prepare silica microcapsules; The block polymer includes polyurethane, and the preparation method of the block polymer includes the following steps: Isocyanate, organotin catalyst and hydrophilic chain extender are reacted to form a prepolymer; Block polymers are prepared by reacting prepolymers with polyethylene glycol; The number-average molecular weight of the polyethylene glycol is 600 g / mol to 3500 g / mol; The mass ratio of the isocyanate to the organotin catalyst is 1:0.0005-0.005; The molar ratio of the isocyanate, the organotin catalyst, and the hydrophilic chain extender is 1:0.0005-0.005:0.1-1.0; The amount of polyethylene glycol added is 200 g.

2. The silica microcapsule according to claim 1, characterized in that, The phase change material includes one or more of organic phase change materials, inorganic phase change materials, and organic-inorganic composite phase change materials; The organic phase change material includes one or more of aliphatic hydrocarbons, fatty alcohols, fatty acids, and esters; The inorganic phase change material includes one or more of inorganic salts and their hydrates; The organic-inorganic composite phase change material includes one or more of metal-organic framework materials and covalent organic framework materials.

3. The silica microcapsule according to claim 1 or 2, characterized in that, The encapsulation efficiency of the silica microcapsules is 69.5%-71%; and / or the loading of the silica microcapsules is 46.6%-88.4%.

4. A method for producing a silica microcapsule, characterized by, Includes the following steps: The block polymer and water are mixed to form a mixture, and the pH of the mixture is adjusted to 5-9 to form a premix. The premixed liquid is mixed with an oil-soluble solution containing the core material to form a first mixture; Water glass and sulfuric acid solution are mixed to form a capsule wall solution with a pH of 2.2-2.

8. While stirring, the capsule wall solution is added in batches to the first mixture until the pH reaches 2.8-3.2, then the addition of the capsule wall solution is stopped to form the second mixture; The second mixture was aged to prepare silica microcapsules; The block polymer includes polyurethane, and the preparation method of the block polymer includes the following steps: Isocyanate, organotin catalyst and hydrophilic chain extender are reacted to form a prepolymer; Block polymers are prepared by reacting prepolymers with polyethylene glycol; The number-average molecular weight of the polyethylene glycol is 600 g / mol to 3500 g / mol; The mass ratio of the isocyanate to the organotin catalyst is 1:0.0005-0.005; The molar ratio of the isocyanate, the organotin catalyst, and the hydrophilic chain extender is 1:0.0005-0.005:0.1-1.0; The amount of polyethylene glycol added is 200 g.

5. The method for producing the silica microcapsule according to claim 4, characterized by, The core material includes a phase change material; The phase change material includes one or more of organic phase change materials, inorganic phase change materials, and organic-inorganic composite phase change materials; The organic phase change material includes one or more of aliphatic hydrocarbons, fatty alcohols, fatty acids, and esters; The inorganic phase change material includes one or more of inorganic salts and their hydrates; The organic-inorganic composite phase change material includes one or more of metal-organic framework materials and covalent organic framework materials.

6. The method for producing the silica microcapsule according to claim 4, characterized by, The preparation method also satisfies at least one of the following conditions (1) to (9): (1) The mass ratio of the block polymer to the water is 1:5-100; (2) The mass ratio of the block polymer to the oil-soluble solution containing the core material is 1:0.1-20; (3) Mix the block polymer with water and adjust the pH to 6-7.5; (4) The block polymer and water are mixed, and the pH value is adjusted to 5-9 using sulfuric acid solution, wherein the concentration of sulfuric acid solution is 0.1mol / L-5mol / L; (5) The concentration of the water glass is 0.2 mol / L-2 mol / L; (6) The modulus of the water glass is 1-4; (7) The concentration of the sulfuric acid solution is 0.1 mol / L-5 mol / L; (8) The aging temperature is 20℃-70℃; (9) The aging time is 10h-15h.

7. The method for preparing silica microcapsules according to claim 6, characterized in that, The mass ratio of the block polymer to the water is 1:5-20; and / or the mass ratio of the block polymer to the oil-soluble solution containing the core material is 1:0.1-1.

2.

8. The method for preparing silica microcapsules according to claim 4, characterized in that, During the process of adding the capsule wall solution to the first mixture, homogenization is performed at a speed of 5000 rpm-15000 rpm; and / or, Before adding the oil-soluble solution containing the core material for mixing, the method further includes heating the premixed solution to 55°C-65°C; and / or, After mixing the premixed liquid with an oil-soluble solution containing the core material, the process further includes a defoaming step. The defoaming process is carried out by stirring at a speed of 400 rpm to 500 rpm for a duration of 5 min to 20 min.

9. The method for preparing silica microcapsules according to claim 4, characterized in that, The method for preparing the block polymer also satisfies at least one of the following conditions (1) to (3): (1) The isocyanate includes one or more of dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, toluene diisocyanate, phenyl dimethylene diisocyanate and methylcyclohexyl diisocyanate; (2) The organotin catalyst includes one or more of dibutyltin dilaurate, stannous octanoate, di(dodecyl sulfide)dibutyltin and dibutyltin diacetate; (3) The hydrophilic chain extender includes one or more of dimethylolpropionic acid, dimethylolbutyric acid, sodium 1,2-propanediol-3-sulfonate, sodium 1,4-butanediol-2-sulfonate, diethylenetriamine and N-methyldiethanolamine.

10. The method for preparing silica microcapsules according to any one of claims 4 to 9, characterized in that, The aging process also includes washing and drying. The washing process uses one or more solvents selected from water, ethanol, and petroleum ether. The drying temperature is 60℃-120℃, and the drying time is 12 h-36 h.

11. A phase change energy storage material, characterized in that, The phase change energy storage material is prepared by silica microcapsules, wherein the silica microcapsules include the silica microcapsules according to any one of claims 1 to 3, or silica microcapsules prepared by the method of preparing silica microcapsules according to any one of claims 4 to 10.

12. An energy storage element, characterized in that, The energy storage element includes the phase change energy storage material as described in claim 11.

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