Solid lipid microcapsule with phase change characteristic as well as preparation method and application of solid lipid microcapsule

Abstract

The invention discloses a solid lipid microcapsule with a phase change characteristic and a preparation method and application thereof.The solid lipid microcapsule prepared through the method takes solid lipid with the phase change characteristic as a shell and an aqueous solution as a core and has the advantages of being uniform in structure, good in monodispersity, high in active matter loading capacity, excellent in thermal response release performance and the like; the shell thickness and size of the solid lipid microcapsule can be accurately controlled by controlling the flow velocity of the intermediate oil phase. The active matter is loaded in the inner water phase of the solid lipid microcapsule, so that the active matter can be isolated from the outside, and the active matter can be efficiently encapsulated. By heating the solid lipid microcapsule, the solid lipid capsule shell can be melted, so that the microcapsule is disintegrated, and the thermal control release of the active matter is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of microcapsules, and in particular relates to a solid lipid microcapsule with phase change characteristics, a preparation method and an application thereof. Background Art

[0002] Emulsions are mixtures of two immiscible liquids, one dispersed in the other. They are widely used in the personal care and food sectors to effectively deliver a variety of active ingredients. However, active ingredients carried by emulsions often deteriorate due to processes such as oxidation and degradation, which significantly affects the encapsulation efficiency of the active. A convenient way to avoid this deterioration is to utilize microcapsules, in which the active ingredient is encapsulated in an aqueous core surrounded by a protective shell. This can effectively store sensitive active substances such as vitamins, nutrients, and therapeutic agents and prevent them from oxidation and deterioration.

[0003] However, a key problem with microcapsules made from traditional hydrogel materials such as polysaccharides and proteins is that the solutes in their cores will diffuse out of the capsules during storage, especially when the solutes are small hydrophilic molecules with a molecular weight of less than 1000 Da. The size of such small solute molecules will be much smaller than the mesh size of the polymer network that constitutes the capsule shell, and the diffusion of solutes through the shell is inevitable. Therefore, it is almost impossible to perfectly encapsulate solutions containing salts, acids, bases, dyes or other small molecule active substances in the capsule for a long time. In addition, although microcapsules made from traditional materials offer the potential to encapsulate active substances to a certain extent, traditional shell materials lack the ability to release active substances on demand and leave footprints from shell residues when ruptured and released, limiting the wide applicability of these methods in applications.

[0004] A promising alternative is the use of thermoresponsive phase-change materials as shell materials. Capsules with shells composed of wax materials (alkanes and fatty acids) have been shown to be hermetically sealed, allowing for the encapsulation of active substances for extended periods of time. Furthermore, wax-based capsules can melt above their designed melting temperature to release their cargo on demand. Therefore, these capsules can effectively encapsulate and release any desired material, including reactive or unstable materials that are difficult to stably encapsulate under traditional conditions.

[0005] The traditional method for producing these core-shell microcapsules uses multiphase emulsion droplets prepared by bulk emulsification technology as templates, which generally results in microcapsules with high polydispersity and low loading efficiency. In addition, the structure and morphology of these microcapsules cannot be precisely controlled under traditional preparation methods, further limiting our ability to quantitatively encapsulate and control the release of active substances. Microfluidics is a method that uses microchannels and microfluidic control technology to perform microscale fluid operations and reactions. Microfluidics can achieve precise control of fluid mixing, dispersion, flow and other parameters during the preparation of multiphase emulsions, making it possible to prepare monodisperse multiphase emulsion droplets, thereby preparing microcapsules with precisely adjustable size, structure and composition.

[0006] Therefore, there is an urgent need to use microfluidic technology to develop a new type of microcapsule with good monodispersity and precisely adjustable size, structure and composition, which can be used as a new shell-core carrier to achieve long-term encapsulation and on-demand release of small molecule active substances, and further apply it to the personal care and food fields. Summary of the Invention

[0007] The purpose of this section is to summarize some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of this application to avoid obscuring the purpose of this section, the abstract and the title of the invention, and such simplifications or omissions should not be used to limit the scope of the present invention.

[0008] In view of the above problems and / or the problems existing in the prior art, the present invention is proposed.

[0009] Therefore, the object of the present invention is to overcome the deficiencies in the prior art and provide a method for preparing solid lipid microcapsules with phase change properties.

[0010] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0011] The inner water phase, the molten middle oil phase, and the outer water phase are pumped into a microfluidic chip to obtain double emulsion droplets;

[0012] The double emulsion droplets were cooled in an ice bath to obtain solid lipid microcapsules;

[0013] Wherein, the inner aqueous phase and the outer aqueous phase are both polyvinyl alcohol solutions;

[0014] The intermediate oil phase comprises one or more of rice bran wax, candelilla wax, palm wax, beeswax, coconut oil fraction, palm kernel oil fraction, palm oil stearin, and camellia oil;

[0015] The double emulsion droplets are quickly passed into an ice water bath for 10 to 60 seconds to condense, and solid lipid capsules can be obtained without any special operation.

[0016] As a preferred embodiment of the method for preparing the solid lipid microcapsules with phase change properties of the present invention, the inner aqueous phase is a polyvinyl alcohol solution with a concentration of 0.1 to 1.0 wt%.

[0017] As a preferred embodiment of the method for preparing solid lipid microcapsules with phase change properties according to the present invention, the pumping flow rate of the inner aqueous phase is 1000 to 2800 μL / h.

[0018] As a preferred embodiment of the method for preparing solid lipid microcapsules with phase change properties of the present invention, the temperature of the intermediate oil phase is controlled at 50-65°C.

[0019] As a preferred embodiment of the method for preparing solid lipid microcapsules with phase change properties according to the present invention, the pumping flow rate of the intermediate oil phase is 1500 to 3000 μL / h.

[0020] As a preferred embodiment of the method for preparing solid lipid microcapsules with phase change properties according to the present invention, the pumping flow rate of the external aqueous phase is 8000 to 12000 μL / h.

[0021] As a preferred embodiment of the method for preparing solid lipid microcapsules with phase change properties of the present invention, the intermediate oil phase is a mixture of palm oil stearin and camellia oil or palm kernel oil and beeswax.

[0022] As a preferred embodiment of the method for preparing the solid lipid microcapsules with phase change properties of the present invention, the double emulsion droplets are in a W / O / W state.

[0023] Another object of the present invention is to overcome the deficiencies of the prior art and provide solid lipid microcapsules with phase change properties obtained by the preparation method.

[0024] Another object of the present invention is to overcome the deficiencies of the prior art and provide the use of the solid lipid microcapsules with phase change properties as active substance carriers in the fields of personal care and food, wherein: a water-soluble active substance is loaded in the inner aqueous phase of the solid lipid microcapsules to achieve long-term encapsulation and on-demand release of the water-soluble active substance, wherein the mass concentration of the water-soluble active substance is 0.2 to 2 wt%; the water-soluble active substance includes one or more of vitamin C, arbutin, catechin, caffeic acid, kojic acid, hydroquinone, ferulic acid, peptides, flavonoids and polyphenols.

[0025] Beneficial effects of the present invention:

[0026] (1) The solid lipid microcapsules prepared by the present invention, which have a solid lipid with phase change properties as a shell and an aqueous solution as a core, have the advantages of controllable structure, high active substance loading, good encapsulation performance, and excellent thermal responsive release performance. They can be well applied in personal care, food or other fields where they are used as active substance carriers.

[0027] (2) The present invention can precisely control the shell thickness and size of the solid lipid microcapsule by controlling the flow rate of the intermediate oil phase, thereby controlling the release of the microcapsule and increasing the loading capacity of the active substance; by loading the small molecule water-soluble active substance in the inner water phase of the solid lipid microcapsule, it can be isolated from the outside world, and the dense solid lipid shell can achieve long-term encapsulation of the active substance; by heating the solid lipid microcapsule, the solid lipid shell can be melted, causing the microcapsule to disintegrate, thereby achieving thermally controlled release of the active substance. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort. Among them:

[0029] Figure 1 These are related images of the solid lipid microcapsules in Example 1.

[0030] Figure 2 This is a laser confocal image of the solid lipid microcapsule loaded with FITC in Example 2.

[0031] Figure 3 This is a diagram showing the morphological changes of the solid lipid microcapsules during the heating process in Example 2.

[0032] Figure 4 This is a sample photo of solid lipid microcapsules loaded with rhodamine B dispersed in hydrogel in Example 3.

[0033] Figure 5 This is a leakage curve of the contents of the solid lipid microcapsules loaded with rhodamine B in the aqueous solution in Example 4.

[0034] Figure 6 Dimensions of solid lipid microcapsules prepared at different oil phase flow rates in Example 5 of the present invention.

[0035] Figure 7 The figure is a graph showing the encapsulation efficiency of FITC in solid lipid microcapsules prepared with different oil phase compositions in Example 6 of the present invention.

[0036] Figure 8This is a diagram of the air tightness of the solid lipid oil shell prepared with different oil phase compositions in Example 7 of the present invention.

[0037] Figure 9 This is a trend diagram of the capsule wall thickness and protective performance of the solid lipid microcapsules loaded with ascorbic acid under UV and oxygen conditions in Example 8 of the present invention. DETAILED DESCRIPTION

[0038] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0039] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0040] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive of other embodiments.

[0041] Unless otherwise specified, the raw materials used in the present invention are commonly available in the market.

[0042] The abbreviations used in the present invention correspond to the following:

[0043] PKS: palm kernel stearin;

[0044] BW: beeswax.

[0045] Example 1

[0046] This embodiment provides a method for preparing solid lipid microcapsules with phase change properties, specifically:

[0047] A 0.5 wt% polyvinyl alcohol solution was used as the inner aqueous phase, 98 wt% PKS and 2 wt% BW were used as the oil phase, and a 5 wt% polyvinyl alcohol solution was used as the outer aqueous phase.

[0048] The aqueous phase and oil phase were pumped into the microfluidic chip via a syringe pump, with the flow rate of the inner aqueous phase at 1800 μL / h, the flow rate of the molten oil phase at 2000 μL / h, and the flow rate of the outer aqueous phase at 12000 μL / h to obtain W / O / W double emulsion droplets with a core-shell structure.

[0049] The double emulsion droplets were passed into an ice-water bath for condensation for 30 seconds to form solid lipid microcapsules.

[0050] Figure 1 Related images of microscope images of solid lipid microcapsules, including (a) real image, (b) simulation image, and (c) microscope image of the prepared solid lipid microcapsules. Figure 1 c It can be seen that the solid lipid microcapsules prepared in this example have a high degree of uniformity and a complete and clear shell-core structure, and their monodispersity is good.

[0051] Example 2

[0052] This embodiment provides a solid lipid microcapsule with phase change properties for the loading and release of active substances, specifically:

[0053] The small molecule water-soluble active substance fluorescein isothiocyanate (FITC) is loaded into the inner aqueous phase of the solid lipid microcapsule. Specifically, the difference from Example 1 is that a polyvinyl alcohol solution with a concentration of 0.5 wt % is used as the inner aqueous phase, to which 0.2 wt % FITC is added. The rest of the preparation method is the same as that of Example 1, to obtain solid lipid microcapsules loaded with FITC;

[0054] The prepared solid lipid microcapsules were placed on a heating table and maintained at a heating rate of 2°C / min, and the state of the solid lipid microcapsules was continuously observed.

[0055] Figure 2 This is a laser confocal image of a FITC-loaded solid lipid microcapsule. As can be seen, the solid lipid microcapsule has a complete core-shell structure. Under 488nm laser excitation, the core emits strong green fluorescence, indicating that FITC is successfully encapsulated within the aqueous core of the solid lipid microcapsule. The absence of green fluorescence from the exterior of the microcapsule indicates no FITC leakage from the external phase, demonstrating the solid lipid microcapsule's excellent encapsulation capacity for FITC. Furthermore, based on size-mass analysis, the FITC aqueous core accounts for 69.7% by weight of the solid lipid microcapsule, demonstrating the ability of the solid lipid microcapsule to encapsulate high loadings of small molecule actives.

[0056] Figure 3 Figure 3 shows the morphological changes of solid lipid microcapsules during heating. As can be seen, the solid lipid wall gradually melts during heating. When the temperature reaches 36°C, the microcapsules completely melt and disintegrate, gradually releasing their water cores into the environment, thereby releasing the loaded FITC. This demonstrates that solid lipid microcapsules have good thermal-responsive release capabilities for FITC.

[0057] Example 3

[0058] This embodiment provides an application of solid lipid microcapsules with phase change properties in the fields of personal care and food, specifically:

[0059] The water-soluble active substance Rhodamine B is loaded in the inner aqueous phase of the solid lipid microcapsule. Specifically, the difference from Example 1 is that a polyvinyl alcohol solution with a concentration of 0.5 wt% is used as the inner aqueous phase, and 0.2 wt% of Rhodamine B is added thereto. The other steps are the same as in Example 1 to obtain solid lipid microcapsules loaded with Rhodamine B.

[0060] Carbomer U20 was prepared into a 5 wt % aqueous solution, and a small amount of 10 wt % arginine solution was added to adjust the viscosity until the solution became a gel texture. The prepared solid lipid microcapsules loaded with rhodamine B were added to the gel and stirred evenly.

[0061] Figure 4 This image shows a sample of solid lipid microcapsules loaded with rhodamine B dispersed in a hydrogel. It can be seen that the solid lipid microcapsules loaded with rhodamine B can be stably and evenly dispersed in the gel matrix. Combined with their thermoresponsive release capability demonstrated in Example 2, it is expected that they can release the encapsulated active ingredient at human body temperature. The sample shown in this image can be considered a manifestation of the application of solid lipid microcapsules in the personal care and food industries.

[0062] Example 4

[0063] This example provides a method for evaluating the encapsulation performance of solid lipid microcapsules with phase change properties for small molecule active substances, specifically:

[0064] The water-soluble active substance rhodamine B was loaded in the inner aqueous phase of the solid lipid microcapsule. Specifically, the difference from Example 1 was that a polyvinyl alcohol solution with a concentration of 0.5 wt% was used as the inner aqueous phase, and 2 wt% of rhodamine B was added thereto. The rest of the preparation method was the same as that in Example 1 to obtain solid lipid microcapsules loaded with rhodamine B.

[0065] The prepared solid lipid microcapsules were dispersed in deionized water to form suspensions and stored at 4°C and 25°C for 28 days. The rhodamine b content in the external aqueous phase of the microcapsule suspension was measured on days 1, 3, 5, 7, 14, 21, and 28 to characterize the extent of microcapsule content leakage.

[0066] Figure 5 The following graph shows the leakage of the contents of solid lipid microcapsules loaded with rhodamine B in aqueous solutions. This indicates that, due to the compactness of their capsule walls, solid lipid microcapsules can achieve long-term encapsulation of small molecule active substances, such as rhodamine B, in aqueous solutions, compared to traditional hydrogel capsule walls.

[0067] Example 5

[0068] This example investigates the effect of varying the flow rate of the intermediate oil phase on the structure of the prepared solid lipid microcapsules. This example differs from Example 1 in that the flow rates of the molten oil phase were adjusted to 1500, 2000, 2500, and 3000 μL / h, respectively. The remaining steps were the same as in Example 1 to obtain the corresponding solid lipid microcapsules.

[0069] Figure 6 Figures show the size of solid lipid microcapsules produced at different oil phase flow rates, including (a) microscopic images and (b) the relationship between shell and core size and flow rate. As can be seen, as the oil phase flow rate increases, the solid lipid microcapsule size also increases, and the shell thickness increases. Furthermore, the ratio of the inner phase flow rate to the middle phase flow rate and the ratio of the core particle size to the microcapsule particle size are positively correlated linearly. When the oil phase flow rate is 2000 μL / h, the solid lipid microcapsules produced have an appropriate wall thickness and the best structural uniformity.

[0070] Example 6

[0071] This example investigates the effect of varying the composition of the intermediate oil phase on the encapsulation performance of the prepared solid lipid microcapsules. This example differs from Example 1 in that the composition of the intermediate oil phase was adjusted to 100 wt% PKS, 60 wt% PKS and camellia oil, or 80 wt% of a mixture of PKS and camellia oil. All other steps were the same as in Example 1, yielding the corresponding FITC-loaded solid lipid microcapsules.

[0072] Figure 7Figure 2 shows the FITC encapsulation efficiency curves for solid lipid microcapsules prepared with different oil phase compositions (a) microscopy image, (b) FITC encapsulation efficiency curve. As can be seen, with increasing PKS content in the molten oil phase, the surface morphology of the solid lipid microcapsules obtained after condensation becomes more uniform and dense. The surface of the microcapsules obtained after adding 2% BW is also more uniform and dense than when the molten oil phase composition is 100% PKS. Similarly, with increasing PKS content in the molten oil phase, the FITC encapsulation efficiency of the corresponding solid lipid microcapsules also increases. This is primarily because when the molten oil phase consists of PKS and camellia oil, PKS gradually solidifies into solid oil crystals at room temperature, while camellia oil remains in a liquid state. The mixture of the two maintains an oil gel morphology at room temperature, with the solid PKS serving as the gel network. This less dense oil gel serves as the capsule shell, allowing FITC within the capsule to diffuse outward through the gel, resulting in a decrease in the FITC encapsulation efficiency of the solid lipid microcapsules. In addition, compared to the molten oil phase composition of 100% PKS, the microcapsule encapsulation efficiency of FITC after adding 2% BW was further increased. This is because PKS and BW are both solid oils at room temperature and have different melting points. During the condensation process of their mixture from the molten state, the oils with different melting points may cause sequential crystallization, allowing the lower melting point groups to fill the initial cracks and pores formed by the crystallization of the higher melting point groups, thereby forming a more uniform and dense shell, further improving the encapsulation capacity of the solid lipid microcapsules for FITC.

[0073] Example 7

[0074] This example explores the effect of the intermediate oil phase composition on the airtightness of the prepared solid lipid microcapsules, specifically:

[0075] A 10% sucrose solution was added to the bottom of the centrifuge tube, followed by the addition of 3 mL of different intermediate oil phases dyed with Nile Red (98% PKS + 2% BW, 100% PKS, 80% PKS + 20% camellia oil, and 60% PKS + 40% camellia oil). After the oil phase solidified, 20 mL of deionized water was added as a sucrose receiving solution. The centrifuge tube was stored at 4 ° C for 21 days, and the sucrose concentration in the receiving solution was detected every 24 hours using a microplate reader. Other operations were the same as in Example 1 to prepare solid lipid microcapsules loaded with Nile Red.

[0076] Since sucrose molecules and gas molecules are both small molecules and easier to characterize than gases, sucrose is selected here as a model small molecule to characterize the permeability of the oil shell to small molecules, so as to further investigate the air tightness of the corresponding solid lipid microcapsules.

[0077] Figure 8The air tightness diagram of the solid lipid oil shell prepared with different oil phase compositions, wherein (a) is a schematic diagram of the air tightness experiment, and (b) is a sucrose concentration curve of the receiving liquid. It can be seen that as the PKS content in the molten oil phase increases, the corresponding solid lipid oil shell has a worse permeability to sucrose molecules, and compared with the molten oil phase composition of 100% PKS, the permeability of the microcapsules to sucrose molecules after adding 2% BW is further reduced. The reason for this phenomenon is similar to that in Comparative Example 2. This is because when the molten oil phase is PKS and camellia oil, the mixture of the two maintains an oil gel morphology with solid PKS acting as a gel network at room temperature. When this non-dense oil gel acts as an oil shell, sucrose can diffuse upward through the shell layer, resulting in a decrease in the permeability of the solid lipid oil shell to sucrose molecules. Similarly, the mixture of PKS and BW may cause sequential crystallization during the condensation process from the molten state, thereby forming a more uniform and dense shell, which further leads to a decrease in the permeability of the solid lipid oil shell to sucrose molecules.

[0078] Under the conditions of Example 1, 98wt% PKS and 2wt% BW are compounded as the oil phase to make the solid lipid capsule wall the densest and the solid lipid microcapsule's encapsulation ability for the water core the best; at the same time, the flow rate lines of each phase in Example 1 make the shell thickness and core size of the prepared solid lipid microcapsule both in the optimal state. Under these conditions, FITC is loaded into the water core of the solid lipid microcapsule, which can enable the solid lipid microcapsule to have stable encapsulation and good thermal response release ability for FITC.

[0079] Example 8

[0080] This example provides a method for evaluating the UV and oxidative protection performance of solid lipid microcapsules with phase change properties for active substances contained therein, specifically:

[0081] The water-soluble active substance ascorbic acid was loaded into the inner aqueous phase of the solid lipid microcapsule, wherein the concentration of ascorbic acid was 5 wt %. The rest of the preparation method was the same as that in Example 5, and solid lipid microcapsules with different capsule wall thicknesses loaded with ascorbic acid were obtained.

[0082] The prepared solid lipid microcapsules with different wall thicknesses were dispersed in deionized water to prepare a suspension. A portion was placed under a UV irradiator at a wavelength of 320 nm and a power of 30,000 μW / cm 2 After irradiation at 100W for 4 hours, the ascorbic acid content in the inner water core was measured to characterize the UV protection of the microcapsules for the active ingredients contained within. Another aliquot of the suspension was stored open at 4°C and 25°C for 7 days. The ascorbic acid content in the inner water core was measured on day 7 to characterize the oxidative protection of the microcapsules for the active ingredients contained within.

[0083] Figure 9(a) shows the relationship between ascorbic acid activity and capsule wall thickness of solid lipid microcapsules loaded with ascorbic acid under UV. It can be seen that as the capsule wall thickness increases, the UV protection effect of solid lipid microcapsules for ascorbic acid is better. This is because the opacity of the solid lipid capsule wall can resist UV penetration to a certain extent. Similarly, Figure 9 As shown in (b), as the thickness of the solid lipid microcapsule wall increases, its oxidative protection effect on ascorbic acid is better. This is because the thickness of the capsule wall directly affects the airtightness of the entire microcapsule. The thicker the capsule wall, the more difficult it is for air to penetrate into the microcapsule, thereby better isolating oxygen from the active substance.

[0084] In summary, the solid lipid microcapsules prepared by the present invention have a solid lipid with phase change properties as the shell and an aqueous solution as the core, and have the advantages of controllable structure, high active substance loading, good encapsulation performance, and excellent thermal response release performance. By controlling the flow rate of the intermediate oil phase, the present invention can accurately control the shell thickness and size of the solid lipid microcapsule, thereby controlling the release of the microcapsule and increasing the loading capacity of the active substance; by loading the small molecule water-soluble active substance in the inner aqueous phase of the solid lipid microcapsule, it can be isolated from the outside world, and the dense solid lipid capsule shell can achieve long-term encapsulation of the active substance; by heating the solid lipid microcapsule, the solid lipid capsule shell can be melted, causing the microcapsule to disintegrate, thereby achieving thermally controlled release of the active substance.

[0085] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for preparing solid lipid microcapsules with phase change properties, characterized in that: include, The inner water phase, the molten middle oil phase, and the outer water phase are pumped into a microfluidic chip to obtain double emulsion droplets; The double emulsion droplets were cooled in an ice bath to obtain solid lipid microcapsules; Wherein, the inner aqueous phase and the outer aqueous phase are both polyvinyl alcohol solutions; The intermediate oil phase comprises one or more of rice bran wax, candelilla wax, palm wax, beeswax, coconut oil fraction, palm kernel oil fraction, palm oil stearin, and camellia oil.

2. The method for preparing solid lipid microcapsules with phase change properties according to claim 1, wherein: The inner aqueous phase is a polyvinyl alcohol solution with a concentration of 0.1 to 1.0 wt%.

3. The method for preparing solid lipid microcapsules with phase change properties as claimed in claim 2, wherein: The pumping flow rate of the inner aqueous phase is 1000-2800 μL / h.

4. The method for preparing solid lipid microcapsules with phase change properties according to claim 1, wherein: The temperature of the intermediate oil phase is controlled at 50-65°C.

5. The method for preparing solid lipid microcapsules with phase change properties according to claim 4, wherein: The pumping flow rate of the intermediate oil phase is 1500 to 3000 μL / h.

6. The method for preparing solid lipid microcapsules with phase change properties according to claim 1, wherein: The pumping flow rate of the external aqueous phase is 8000-12000 μL / h.

7. The method for preparing solid lipid microcapsules with phase change properties according to claim 1, wherein: The intermediate oil phase is a mixture of palm oil stearin and camellia oil or palm kernel oil and beeswax.

8. The method for preparing solid lipid microcapsules with phase change properties according to claim 1, wherein: The double emulsion droplets are in a W / O / W state.

9. Solid lipid microcapsules with phase change properties obtained by the preparation method according to any one of claims 1 to 8.

10. Use of the solid lipid microcapsules with phase change properties obtained by the preparation method according to claim 9, characterized in that: Water-soluble active substances are loaded into the inner aqueous phase of the solid lipid microcapsules to achieve long-term encapsulation and on-demand release of the water-soluble active substances, wherein the mass concentration of the water-soluble active substances is 0.2 to 2 wt %; the water-soluble active substances include one or more of vitamin C, arbutin, catechin, caffeic acid, kojic acid, hydroquinone, ferulic acid, peptides, flavonoids and polyphenols.

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