Preparation method and application of lavender essential oil / paraffin composite core material microcapsule

Abstract

The application discloses a preparation method of lavender essential oil / paraffin composite core material microcapsules and application thereof, and belongs to the technical field of microcapsule preparation. The application provides composite core material microcapsules with enhanced temperature response release characteristics. By introducing a magnetic field regulation step in the emulsification and phase change curing process, the inner core forms an oriented phase change response structure unit, and cooperates with an OSA starch shell layer, so that the amplification of the temperature triggered release behavior is realized.

Description

Technical Field

[0001] This invention relates to a method for preparing lavender essential oil / paraffin composite core microcapsules and their application, belonging to the field of microcapsule preparation technology. Background Technology

[0002] Lavender essential oil possesses aromatic, antibacterial, and soothing bioactivities, and is widely used in daily chemicals, textile finishing, and functional sustained-release materials. However, essential oils are highly volatile and unstable, easily losing their activity due to heat and environmental influences. Therefore, they are usually protected through microencapsulation technology.

[0003] Existing technologies typically use composite coagulation to prepare essential oil microcapsules, but most microcapsules have limited sustained-release effects, and the essential oils still evaporate relatively quickly. Even microcapsules with added sustained-release agents result in a significant weakening of fragrance in fabrics after two months of storage. Furthermore, while composite coagulation methods offer milder conditions, they are extremely sensitive to process parameters such as pH, temperature, and stirring speed, leading to complex process control and sometimes poor reproducibility.

[0004] Paraffin undergoes a solid-liquid transition within a specific temperature range, significantly altering its volume, fluidity, and diffusion capacity, thus exhibiting potential temperature-responsive characteristics. However, in existing technologies, the co-encapsulation of paraffin and essential oils is mostly a simple physical mixing process. The phase transition behavior of paraffin only changes the core properties and is not effectively transformed into a structural trigger factor driving changes in shell permeability, thus limiting the temperature-sensitive release effect.

[0005] In the field of functional composite materials, applied physical fields (such as electric and magnetic fields) have been used to regulate particle orientation, construct anisotropic structures, or induce changes in internal phase distribution. For example, a magnetic field can cause a system containing magnetically responsive components to form an oriented structure during curing or phase transition, thereby altering the material's mechanical or transport properties. However, the aforementioned external field control techniques are mainly applied to magnetic composite materials, conductive materials, or structural functional materials. In essential oil microcapsule systems using natural polymers as wall materials, there are no reports of using magnetic fields to regulate the phase transition core microstructure during microcapsule formation.

[0006] Therefore, it is necessary to develop a new structural construction method that introduces external field control during the microcapsule formation process, so that the phase change material forms orientation-related microstructures in the core, thereby transforming the phase change behavior of paraffin into a structural response source that can drive the directional migration of essential oils, and achieving a significantly enhanced temperature-triggered release effect. Summary of the Invention

[0007] To address the aforementioned issues, this invention provides a composite core microcapsule with enhanced temperature-responsive release characteristics. By introducing a magnetic field modulation step during emulsification and phase change curing, the core forms oriented phase change-responsive structural units, which work synergistically with the OSA starch shell to amplify the temperature-triggered release behavior.

[0008] The first objective of this invention is to provide a method for preparing lavender essential oil / paraffin composite core microcapsules, comprising the steps of:

[0009] (1) After the paraffin wax is melted, it is mixed and stirred with lavender essential oil, and magnetic oxide particles with inert coating on the surface are added and stirred to obtain oil phase core liquid; OSA starch is dissolved in water to obtain wall material solution;

[0010] (2) Add the oil phase core liquid to the wall material solution and emulsify to obtain an emulsion; place the emulsion in a static magnetic field with a magnetic field strength of 0.1~0.6 T and a temperature of 45~55℃ for 5~20 min; after treatment, under the condition of maintaining the magnetic field, the emulsion crystallizes and rearranges.

[0011] (3) Remove the magnetic field and add CaCl2 to react; after the reaction, spray dry to obtain lavender essential oil / paraffin composite core material microcapsules;

[0012] In step (1), the mass ratio of paraffin to lavender essential oil is 1:0.8~2.5; the surface-inertly coated magnetic oxide particles are SiO2 coated Fe3O4 or surface-stearic acid modified Fe3O4, and the amount of surface-inertly coated magnetic oxide particles added is 0.1~1.0 wt% of the total mass of paraffin and lavender essential oil; the concentration of OSA starch in the wall material solution is 8~14 wt%;

[0013] In step (2), the mass ratio of the oil phase core liquid to the wall material solution is 1:2~6.

[0014] In one embodiment, the paraffin wax in step (1) has a melting point of 38~55℃ and is heated to 8~12℃ above its melting point to completely melt; after the paraffin wax melts, it is mixed with lavender essential oil and stirred at 55~70℃ and 200~600 rpm for 10~20 min.

[0015] In one embodiment, in step (1), the melting point of paraffin is 40~46℃, and it is heated to 55~60℃; the mass ratio of paraffin to lavender essential oil is 1:1.4~2.0; the amount of magnetic oxide particles with surface inert coating is 0.5~0.8 wt% of the total mass of paraffin and lavender essential oil; the concentration of OSA starch in the wall material solution is 8~12 wt%; and the surface stearic acid modified Fe3O4 is octadecanoic acid (C 18 H 36 Fe3O4 modified with O2.

[0016] In one embodiment, the particle size of the surface-inert magnetic oxide particles in step (1) is 50 nm to 2 μm; after adding the surface-inert magnetic oxide particles, the mixture is stirred at high speed at 50 to 70°C and 400 to 600 rpm for 5 to 10 minutes.

[0017] In one embodiment, in step (1), OSA starch is dissolved in water at 65~80°C and stirred at 300~500 rpm for 30~50 min, and the pH is adjusted to 6.8~8.2 to obtain a wall material solution.

[0018] In one embodiment, in step (2), the oil phase core liquid is slowly added to the wall material solution while the temperature of the oil phase core liquid is kept at more than 5°C above the melting point of paraffin.

[0019] In one embodiment, in step (2), the oil phase core liquid is slowly added to the wall material solution at a temperature of 55~70°C.

[0020] In one embodiment, in step (2), emulsification is performed at 9000~14000 rpm for 3~6 min; crystallization is performed by controlling the cooling rate at 2~5℃ / min to cool the emulsion to 12~18℃ and holding it for 10~20 min; rearrangement is performed by heating to 3~6℃ below the melting point of paraffin and holding it for 20~40 min.

[0021] In one embodiment, the rearrangement is performed by heating to 35-40°C at a rate of 2-5°C / min and holding for 20-40 min.

[0022] In one embodiment, the amount of CaCl2 added in step (3) is 0.5~2.0 wt% of the mass of OSA starch; the spray drying parameters are an inlet air temperature of 150~175℃ and an outlet air temperature of 75~90℃.

[0023] A second objective of this invention is to provide lavender essential oil / paraffin composite core microcapsules prepared by any of the methods described above.

[0024] A third objective of this invention is to provide the application of the above-mentioned lavender essential oil / paraffin composite core microcapsules in the fields of food preservation, textile processing, daily chemical products, pharmaceuticals and health care, packaging materials, agricultural pest control, and cosmetics.

[0025] In one embodiment, the application includes smart fabrics, heat-responsive fragrance materials, and functional sustained-release technologies.

[0026] A fourth objective of this invention is to provide a product containing the aforementioned lavender essential oil / paraffin composite core microcapsules, the product comprising a steam eye mask and a cigarette flavoring capsule.

[0027] The fifth objective of this invention is to provide a method for improving the temperature-responsive release characteristics of lavender essential oil microcapsules, which uses paraffin and surface-inert coated magnetic oxide particles to prepare lavender essential oil / paraffin composite core microcapsules, comprising the following steps:

[0028] (1) After the paraffin wax is melted, it is mixed and stirred with lavender essential oil, and magnetic oxide particles with inert coating on the surface are added and stirred to obtain oil phase core liquid; OSA starch is dissolved in water to obtain wall material solution;

[0029] (2) Add the oil phase core liquid to the wall material solution and emulsify to obtain an emulsion; place the emulsion in a static magnetic field with a magnetic field strength of 0.1~0.6 T and a temperature of 45~55℃ for 5~20 min; after treatment, under the condition of maintaining the magnetic field, the emulsion crystallizes and rearranges.

[0030] (3) Remove the magnetic field and add CaCl2 to react; after the reaction, spray dry to obtain lavender essential oil / paraffin composite core material microcapsules;

[0031] In step (1), the mass ratio of paraffin to essential oil is 1:0.8~2.5; the magnetic oxide particles with inert surface coating are SiO2 coated Fe3O4 or surface stearic acid modified Fe3O4, and the amount of magnetic oxide particles with inert surface coating added is 0.1~1.0 wt% of the total mass of paraffin and lavender essential oil.

[0032] In step (2), the mass ratio of the oil phase core liquid to the wall material solution is 1:2~6.

[0033] In one embodiment, the particle size of the surface-inert magnetic oxide particles in step (1) is 50 nm to 2 μm; after adding the surface-inert magnetic oxide particles, the mixture is stirred at high speed at 50 to 70°C and 400 to 600 rpm for 5 to 10 minutes.

[0034] In one embodiment, in step (1), OSA starch is dissolved in water at 65~80°C and stirred at 300~500 rpm for 30~50 min, and the pH is adjusted to 6.8~8.2 to obtain a wall material solution.

[0035] In one embodiment, in step (2), the oil phase core liquid is slowly added to the wall material solution while the temperature of the oil phase core liquid is kept at more than 5°C above the melting point of paraffin.

[0036] In one embodiment, the paraffin wax in step (1) has a melting point of 38~55℃ and is heated to 8~12℃ above its melting point to completely melt; after the paraffin wax melts, it is mixed with lavender essential oil and stirred at 55~70℃ and 200~600 rpm for 10~20 min.

[0037] In step (2), emulsification is performed at 9000~14000 rpm for 3~6 min; crystallization is performed by controlling the cooling rate at 2~5℃ / min to cool the emulsion to 12~18℃ and holding it for 10~20 min; rearrangement is performed by heating to 3~6℃ below the melting point of paraffin and holding it for 20~40 min.

[0038] In one embodiment, the rearrangement is performed by heating to 35-40°C at a rate of 2-5°C / min and holding for 20-40 min.

[0039] In one embodiment, the amount of CaCl2 added in step (3) is 0.5~2.0 wt% of the mass of OSA starch; the spray drying parameters are an inlet air temperature of 150~175℃ and an outlet air temperature of 75~90℃.

[0040] Beneficial effects of the present invention

[0041] This invention introduces a magnetic field during the oil droplet formation stage after emulsification and disperses magnetically responsive microparticles in the composite oil phase, causing the oil droplets to form microstructural units with orientation characteristics during the solidification process of the phase change material. This structure differs from the isotropic solid core formed by traditional random crystallization; instead, it forms phase change response regions with spatially differentiated distributions.

[0042] As the temperature rises nears the paraffin phase transition temperature range, asynchronous softening and reconstruction occur in different oriented regions, resulting in local structural rearrangement and orientation-related volume changes within the microcapsules, creating non-uniform internal stress on the shell. This structural response mode facilitates the opening of more transient diffusion channels within a specific temperature range, leading to a significant jump in the essential oil release rate and thus significantly enhancing the temperature-triggered release effect. The microcapsules prepared by this invention exhibit a response amplitude exceeding 2.72 and an encapsulation efficiency exceeding 80%.

[0043] Secondly, this invention incorporates a structural control step after the initial crystallization of paraffin wax: "warming to 3-6°C below the melting point and holding at that temperature." This transforms the completely frozen paraffin crystal network into a multiphase structure containing metastable interfaces and low-crystallinity regions. This structure maintains its solid-state support at room temperature, but preferentially undergoes localized melting and interface rearrangement near the phase transition temperature range, forming a structurally "easily triggered zone." Therefore, as the temperature rises, the core structure does not melt uniformly but undergoes selective, gradual structural reconstruction, further amplifying the impact of phase transition behavior on the shell permeability.

[0044] Furthermore, the synergistic existence of the magnetic field-induced orientation structure and the aforementioned metastable phase transition structure transforms the thermal phase transition of paraffin from a simple change in physical properties into a response process with structure-driven characteristics, realizing a coupling mechanism where changes in the core structure trigger changes in the shell permeability. Compared to systems without magnetic field and temperature regulation treatment, the microcapsules of this invention maintain good barrier properties at low temperatures, while the release rate significantly increases upon reaching the phase transition temperature range, exhibiting a more pronounced temperature-responsive release behavior.

[0045] Therefore, this invention endows microcapsules with enhanced release properties within a specific temperature range, expanding their application potential in the fields of smart fabrics, heat-responsive fragrance materials, and functional sustained-release. Attached Figure Description

[0046] Figure 1 The effect of different magnetic field strengths on the release rate of microcapsules. Detailed Implementation

[0047] The preferred embodiments of the present invention are described below. It should be understood that the embodiments are for better explanation of the present invention and are not intended to limit the present invention.

[0048] Raw materials used in the examples:

[0049] Phase change paraffin was purchased from Shengbang Plastic Raw Materials Business Department, Zhangmutou City, Dongguan.

[0050] The lavender essential oil was purchased from Xinjiang Tianshan Flower Sea Agricultural Tourism Group Co., Ltd.

[0051] SiO2-coated Fe3O4 was purchased from Sinopharm Chemical Reagent Co., Ltd.

[0052] OSA starch was purchased from Cargill (China);

[0053] Uncoated Fe3O4 was purchased from Sinopharm Chemical Reagent Co., Ltd.

[0054] γ-Fe3O4 was purchased from Sinopharm Chemical Reagent Co., Ltd.

[0055] The surface is made of stearic acid (octadecanoic acid, C 18 H 36 The O2-modified Fe3O4 was purchased from Sinopharm Chemical Reagent Co., Ltd.

[0056] Test method:

[0057] Release rate detection method:

[0058] Take 0.1 g of microcapsule powder, disperse it in 4 mL of anhydrous ethanol, place it at the target temperature and magnetically stir for 1 h to release it. After that, let it cool naturally to room temperature, centrifuge at 9000 rpm for 5 min, filter it through a 0.22 μm organic filter membrane, and perform ultraviolet spectrophotometry on the filtrate. Determine the essential oil content in the solution according to the pre-prepared standard curve, which represents the amount of essential oil released.

[0059] Take another 0.1 g of microcapsule powder, and follow the same procedure as above, except that the temperature is set to 60 degrees Celsius and the release time is 5 hours. The amount of essential oil in the solution is measured to represent the total amount of essential oil. The release rate is calculated using the following formula:

[0060] Release rate (%) = ×100%

[0061] Differential Scanning Calorimetry (DSC) Method: The phase transition behavior of the microcapsule core was determined using a differential scanning calorimeter. Approximately 5–8 mg of microcapsule powder sample was placed in a sealed aluminum crucible, with an empty aluminum crucible used as a reference. The test was conducted under a nitrogen protective atmosphere (flow rate 40–60 mL / min). The test temperature range was set to 20–60 °C, with a heating rate of 5 °C / min. The initial melting temperature (T_onset), peak melting temperature (T_peak), and enthalpy of fusion (ΔH) of the sample were recorded. Each sample was measured in triplicate, and the average value was taken as the final result. By comparing the changes in melting initiation temperature and enthalpy of fusion under different treatment conditions, the influence of magnetic field modulation on the crystallization structure and phase transition behavior of paraffin was analyzed.

[0062] X-ray diffraction (XRD) testing methods:

[0063] X-ray diffraction (XRD) was used to analyze the crystal structure of paraffin cores in microcapsules. Microcapsule powder was uniformly spread on a sample stage and tested at room temperature. A Cu Kα radiation source (λ = 0.15406 nm) was used, with an operating voltage of 40 kV, a current of 30 mA, a scanning range of 2θ = 5°–40°, a scanning rate of 2° / min, and a step size of 0.02°. The positions and intensities of characteristic diffraction peaks were recorded, and the relative crystallinity was calculated using the peak area integration method. The influence of magnetic field treatment on the degree of order and crystal structure of paraffin crystals was analyzed by comparing the changes in diffraction peak intensity and full width at half maximum (FWHM) of different samples. The relative crystallinity of the samples was calculated using the integration method based on the XRD diffraction data. The area of ​​the crystalline diffraction peak was denoted as A. c The total diffraction area is denoted as A. t The crystallinity is then calculated using the following formula:

[0064] Crystallinity (%) = (A c / A t ) × 100%

[0065] Among them, A c A is the integral value of the crystalline peak area. t This represents the integral value of the total area of ​​crystalline and amorphous peaks. Each sample was measured three times, and the average value was taken as the final result.

[0066] The response range is the release rate at 40℃ / the release rate at 25℃.

[0067] Example 1

[0068] The steps for preparing lavender essential oil / paraffin composite core microcapsules are as follows:

[0069] (1) 40 g of phase change paraffin with a melting point of 42℃ was heated to 58℃, 60 g of lavender essential oil was added, and the mixture was stirred at 400 rpm for 15 min. 0.5 g of SiO2 was added to coat Fe3O4, and the mixture was stirred at 60℃ and 500 rpm for 8 min to obtain the oil phase core liquid. 100 g of OSA starch was dissolved in 900 g of deionized water, and the mixture was stirred at 75℃ (400 rpm) for 40 min. The pH was adjusted to 7.4 to obtain the wall material solution.

[0070] (2) At 58℃, the oil phase core liquid was added to the wall material solution at a mass ratio of 1:2 and emulsified at 12000 rpm for 5 min to obtain an emulsion; the emulsion was treated in a static magnetic field of 0.3T at 50℃ for 10 min.

[0071] (3) In a static magnetic field, the temperature is lowered to 15℃ at a cooling rate of 3℃ / min and held for 15 min; then it is raised to 37℃ at (3℃ / min) and held for 30 min.

[0072] (4) Remove the magnetic field, add 1 g of anhydrous CaCl2 solid, react for 20 min, and spray dry (inlet air 170℃, outlet air 80℃) to obtain lavender essential oil / paraffin composite core material microcapsules.

[0073] Comparative Example 1

[0074] Lavender essential oil / paraffin composite core microcapsules were prepared without adding magnetic oxide particles or placing them under a magnetic field. The steps are as follows:

[0075] (1) Heat 40 g of phase change paraffin with a melting point of 42℃ to 58℃, add 60 g of lavender essential oil, and stir at 400 rpm for 15 min;

[0076] (2) Dissolve 100 g of OSA starch in 900 g of deionized water, stir at 75°C for 40 min, adjust pH to 7.4 to obtain wall material solution; at 58°C, add oil phase core liquid to wall material solution at a mass ratio of 1:2 and emulsify at 12000 rpm for 5 min to obtain emulsion.

[0077] (3) After treating the emulsion at 50°C for 10 min, the temperature was lowered to 15°C at a cooling rate of 3°C / min and held for 15 min; then the temperature was raised to 37°C and held for 30 min.

[0078] (4) Add 1 g of anhydrous CaCl2 solid, react for 20 min, and spray dry (inlet air 170℃, outlet air 80℃) to obtain powder microcapsules.

[0079] Example 2

[0080] Based on Example 1, the static magnetic field strength in step (2) was changed to 0 T, 0.1 T, 0.5 T and 0.6 T respectively, while the other steps remained the same. The release rate of lavender essential oil / paraffin composite core material microcapsules at 25℃ and 40℃ was detected under different magnetic field strengths.

[0081] The results are as follows Figure 1 As shown, the results indicate that as the magnetic field strength increases, the cumulative release rate of the microcapsules at 25°C gradually decreases, while the release rate at 40°C increases significantly, thereby continuously increasing the release transition factor.

[0082] Without a magnetic field, the release transition factor of the system is approximately 2.05, indicating that the internal crystals of paraffin exhibit a random orientation structure and weak temperature response. As the magnetic field strength increases to 0.3 T, the release transition factor increases to approximately 2.72, indicating that the magnetic field-induced effect has significantly promoted the oriented alignment of paraffin crystals. When the magnetic field strength is further increased to 0.5 T, the release transition factor reaches approximately 3.03, indicating that a relatively stable oriented crystal structure has formed inside the paraffin, effectively suppressing low-temperature diffusion and significantly enhancing release near the melting temperature. When the magnetic field strength is further increased to 0.6 T, the release transition factor only increases slightly to approximately 3.09, indicating that the oriented structure of the system is approaching saturation, and further increasing the magnetic field strength has limited effect on improving the degree of orientation and release performance.

[0083] The above results indicate that appropriately increasing the magnetic field strength is beneficial to enhancing the orientation structure of paraffin crystals, thereby improving the temperature response release performance of microcapsules. However, when the magnetic field strength exceeds a certain threshold, the orientation effect tends to stabilize. Considering both structural performance and energy consumption factors, the optimal magnetic field strength is 0.5 T.

[0084] Example 3

[0085] Based on Example 1, the amount of SiO2-coated Fe3O4 added in step (1) was changed to 0.1wt% (i.e., 0.1 g), 0.3wt% (i.e., 0.3 g), 0.8wt% (i.e., 0.8 g), and 1wt% (i.e., 1 g), while the other steps remained the same. The release rate of lavender essential oil / paraffin composite core microcapsules at 25°C and 40°C was detected under different amounts of SiO2-coated Fe3O4 added.

[0086] The results are shown in Table 1. The results show that when the amount of magnetic particles added is 0.1 wt%, the release transition factor is about 2.13, indicating that the number of magnetic response units in the system is limited and the induction effect on the orientation of paraffin crystals is weak.

[0087] When the amount added was increased to 0.3 wt% and 0.5 wt%, the release transition factor increased to about 2.41 and 2.72, respectively, indicating that the increase in the number of magnetic particles significantly enhanced the magnetic field induction effect, causing the paraffin crystals to gradually form an oriented arrangement structure, thereby effectively inhibiting low-temperature diffusion and enhancing the release in the molten zone;

[0088] When the addition amount was further increased to 0.8 wt%, the release transition factor reached about 2.91, indicating that the orientation structure of the system was further improved; however, when it was further increased to 1.0 wt%, the release transition factor only increased slightly to about 2.97, and the increase slowed down significantly, indicating that the paraffin structure in the system that can participate in orientation induction has become saturated, and the effect of excessive magnetic particles on structural optimization is limited.

[0089] Table 1. Effect of different SiO2-coated Fe3O4 addition amounts on microcapsule release rate

[0090]

[0091] Example 4

[0092] Based on Example 1, the magnetic particles in step (1) were changed to uncoated Fe3O4, γ-Fe3O4, and Fe3O4 with surface stearic acid modification, while the other steps remained the same. The release rate of the lavender essential oil / paraffin composite core microcapsules prepared with different magnetic particles was detected at 25°C and 40°C.

[0093] The results are shown in Table 2. The results indicate that different magnetic particles have significantly different abilities to induce the orientation of paraffin crystals due to differences in surface structure and interfacial compatibility.

[0094] Among them, the release transition factor of the uncoated Fe3O4 system is about 2.43, indicating that although it has a certain magnetic response capability, its orientation induction effect on paraffin crystals is relatively weak due to its high surface energy and limited dispersibility in the oil phase.

[0095] The release transition factor of the γ-Fe2O3 system is about 2.30, which is slightly lower than that of Fe3O4, indicating that its magnetic response capability and interfacial induction effect are relatively weak. The release transition factor of the SiO2-coated Fe3O4 system is increased to about 2.72, indicating that the SiO2 coating layer effectively improves the dispersion stability of magnetic particles in the oil phase, enabling them to be more uniformly distributed and effectively transmit the magnetic field induction effect, thereby enhancing the formation of the paraffin crystal orientation structure.

[0096] When Fe3O4 was further modified with stearic acid, the release transition factor reached about 2.94, indicating that the organic modification layer significantly improved the interfacial compatibility between the magnetic particles and the paraffin matrix, enabling the magnetic particles to participate more effectively in the crystal orientation induction process and form a more perfect orientation structure.

[0097] Table 2. Effect of different magnetic particles on microcapsule release rate

[0098]

[0099] Comparative Example 2

[0100] Based on Example 1, the timing of the magnetic field treatment was changed to pre-emulsification oil phase treatment, and the steps are as follows:

[0101] (1) 40 g of phase change paraffin with a melting point of 42℃ was heated to 58℃, 60 g of lavender essential oil was added, and the mixture was stirred at 400 rpm for 15 min. 0.5 g of SiO2 was added to coat Fe3O4, and the mixture was stirred at 60℃ and 500 rpm for 8 min to obtain the oil phase core liquid. 100 g of OSA starch was dissolved in 900 g of deionized water, and the mixture was stirred at 75℃ and 400 rpm for 40 min. The pH was adjusted to 7.4 to obtain the wall material solution.

[0102] (2) The oil phase core liquid was subjected to a static magnetic field of 0.3T at 50℃ for 10 min, and then the temperature was lowered to 15℃ at a cooling rate of 3℃ / min and held for 15 min; then it was raised to 37℃ at (3℃ / min) and held for 30 min, and the magnetic field was removed.

[0103] (3) At 58℃, the oil phase core liquid was added to the wall material solution at a mass ratio of 1:2 and emulsified at 12000 rpm for 5 min to obtain the emulsion;

[0104] (4) Add 1 g of anhydrous CaCl2, react for 20 min, and spray dry (inlet air 170℃, outlet air 80℃) to obtain lavender essential oil / paraffin composite core material microcapsules.

[0105] Comparative Example 3

[0106] Based on Example 1, the timing of the magnetic field treatment was changed to simultaneous treatment during the emulsification process, and the steps are as follows:

[0107] (1) 40 g of phase change paraffin with a melting point of 42℃ was heated to 58℃, 60 g of lavender essential oil was added, and the mixture was stirred at 400 rpm for 15 min. 0.5 g of SiO2 was added to coat Fe3O4, and the mixture was stirred at 60℃ and 500 rpm for 8 min to obtain the oil phase core liquid. 100 g of OSA starch was dissolved in 900 g of deionized water, and the mixture was stirred at 75℃ and 400 rpm for 40 min. The pH was adjusted to 7.4 to obtain the wall material solution.

[0108] (2) At 58℃, the oil phase core liquid was added to the wall material solution at a mass ratio of 1:2 and emulsified at 12000 rpm for 5 min. At the same time, a static magnetic field of 0.3T was applied for 10 min. Then, the temperature was lowered to 15℃ at a cooling rate of 3℃ / min and held for 15 min. Then, the temperature was raised to 37℃ (3℃ / min) and held for 30 min. The magnetic field was then removed.

[0109] (3) Add 1 g of anhydrous CaCl2, react for 20 min, and spray dry (inlet air 170℃, outlet air 80℃) to obtain lavender essential oil / paraffin composite core material microcapsules.

[0110] Comparative Example 4

[0111] Based on Example 1, the timing of the magnetic field treatment was changed to crystallization followed by magnetic field treatment, and the steps are as follows:

[0112] (1) 40 g of phase change paraffin with a melting point of 42℃ was heated to 58℃, 60 g of lavender essential oil was added, and the mixture was stirred at 400 rpm for 15 min. 0.5 g of SiO2 was added to coat Fe3O4, and the mixture was stirred at 60℃ and 500 rpm for 8 min to obtain the oil phase core liquid. 100 g of OSA starch was dissolved in 900 g of deionized water, and the mixture was stirred at 75℃ and 400 rpm for 40 min. The pH was adjusted to 7.4 to obtain the wall material solution.

[0113] (2) At 58℃, the oil phase core liquid was added to the wall material solution at a mass ratio of 1:2 and emulsified at 12000 rpm for 5 min to obtain the emulsion;

[0114] (3) The temperature was lowered to 15℃ at a cooling rate of 3℃ / min and held for 15 min; then it was treated in a 0.3T static magnetic field for 10 min, the magnetic field was removed, and then the temperature was raised to 37℃ (3℃ / min) and held for 30 min.

[0115] (4) Add 1 g of anhydrous CaCl2, react for 20 min, and spray dry (inlet air 170℃, outlet air 80℃) to obtain lavender essential oil / paraffin composite core material microcapsules.

[0116] Comparative Example 5

[0117] Based on Example 1, step (3) is omitted, while the remaining steps remain the same, and microcapsules are prepared.

[0118] The release rates of the microcapsules prepared in Example 1 and Comparative Examples 1-5 were tested at 25°C and 40°C.

[0119] The results are shown in Table 3. The results show that different magnetic field treatments have a significant impact on the orientation structure and release behavior of paraffin crystals. The response amplitude of the control group without magnetic field treatment is 2.05, indicating that the paraffin crystals are in a random orientation state and have a weak temperature response.

[0120] Under the condition of applying a magnetic field but without cooling or heating treatment in the magnetic field, the release rate at 25℃ and 40℃ decreased and increased, respectively, and the release response amplitude increased to about 2.55, indicating that the magnetic field can induce the orientation of magnetic particles to a certain extent. However, since the paraffin crystallization process was not completed under the induction of the magnetic field, the final orientation structure was limited.

[0121] In addition, the magnetic field treatment needs to be carried out after or simultaneously with emulsification, and cooling and heating steps should be performed in the magnetic field. That is, the cooling crystallization and heating rearrangement process of paraffin is completed under the action of the magnetic field. The response amplitude increased to 2.72, indicating that the crystallization process induced by the magnetic field can effectively promote the formation of a stable oriented crystal structure of paraffin molecules along the direction of the magnetic field, thereby significantly inhibiting low-temperature diffusion and enhancing the release performance of the molten zone.

[0122] Table 3

[0123]

[0124] Example 5

[0125] 1. Structural characterization

[0126] The lavender essential oil / paraffin composite core microcapsules prepared under magnetic field strengths of 0T and 0.5T in Examples 1 and 2 were subjected to structural characterization, and the results are shown in Table 4.

[0127] The results showed that magnetic field treatment significantly altered the spatial arrangement and crystallization behavior of paraffin crystals, resulting in an anisotropic structure with distinct orientation characteristics. Polarizing microscopy (POM) observations revealed that the orientation factor of the untreated control group was only 0.07, and the relative birefringence intensity was 1.00, indicating that the paraffin crystals exhibited a random orientation distribution. Under a magnetic field treatment of 0.3 T, the orientation factor increased to 0.21, and the relative birefringence intensity increased to 1.34, indicating that the paraffin crystals began to form a preliminary oriented arrangement along the magnetic field direction. When the magnetic field strength was increased to 0.5 T, the orientation factor further increased to 0.29, and the relative birefringence intensity reached 1.58, indicating that the paraffin crystals had formed a more obvious orientation structure, and the anisotropy of the system was significantly enhanced.

[0128] X-ray diffraction (XRD) results further indicated that magnetic field treatment did not alter the crystal structure of paraffin, but it did have some impact on crystallinity and grain structure. The relative crystallinity of paraffin without a magnetic field was 71.2%, while it decreased to 66.8% and 63.1% under magnetic field treatments of 0.3 T and 0.5 T, respectively. Simultaneously, the full width at half maximum (FWHM) of the diffraction peaks increased from 0.32 to 0.36 and 0.39, respectively. This suggests that the magnetic field-induced effect restricted the free growth of crystals, reducing grain size and forming a confined crystalline structure with oriented alignment. This structural characteristic facilitates the formation of anisotropic diffusion channels, thereby affecting the release behavior.

[0129] Differential scanning calorimetry (DSC) results showed that magnetic field treatment also had a certain impact on the thermal behavior of paraffin. Without a magnetic field, the peak melting temperature of paraffin was 41.8℃, the initial melting temperature was 38.5℃, and the enthalpy of melting was 62.4 J / g. Under magnetic field treatment, the peak melting temperature slightly increased to 42.2℃ and 42.5℃, while the initial melting temperature decreased to 37.7℃ and 36.9℃, respectively, and the enthalpy of melting decreased to 58.7 J / g and 55.8 J / g. This indicates that the orientation structure induced by the magnetic field confined some crystal regions, reducing the overall crystal integrity, while simultaneously forming orientation crystal regions with different thermal stability, thereby widening the melting range.

[0130] Table 4

[0131]

[0132] 2. Other performance characteristics

[0133] Representative examples of non-magnetic field treatment, complete magnetic field treatment, and high magnetic particle addition were selected for product particle property analysis. The results are shown in Table 5. The results show that the microcapsules of each group have high encapsulation rate and good particle size uniformity, but there are still some differences under different conditions.

[0134] In the control group without magnetic field treatment, the average particle size of the microcapsules was 18.6 μm, the particle size distribution was relatively uniform (PDI was 0.21), and the encapsulation rate was 78.4%, indicating that the system could form a stable encapsulation structure. However, due to the lack of magnetic field induction, the interface structure between paraffin and wall material was relatively loose, and some core material was lost during the preparation process.

[0135] Under complete magnetic field-induced treatment conditions, the average particle size of the microcapsules was 19.8 μm, the PDI was 0.19, and the encapsulation efficiency increased to 84.7%. This indicates that magnetic field induction is beneficial to the formation of a more stable interface structure, which allows paraffin to be more uniformly fixed inside the microcapsules during the crystallization process, thereby improving the encapsulation efficiency and particle size uniformity.

[0136] When the amount of magnetic particles added was further increased to 1.0 wt%, the average particle size of the microcapsules increased to 22.4 μm, the PDI increased to 0.26, and the encapsulation rate decreased slightly to 81.9%. This indicates that excessive magnetic particles may lead to local agglomeration of the system, which reduces the emulsion stability and has a certain adverse effect on the particle size uniformity and encapsulation structure.

[0137] Table 5

[0138]

[0139] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A method for preparing lavender essential oil / paraffin composite core microcapsules, characterized in that, Including the following steps: (1) After the paraffin wax is melted, it is mixed and stirred with lavender essential oil, and magnetic oxide particles with inert coating on the surface are added and stirred to obtain oil phase core liquid; OSA starch is dissolved in water to obtain wall material solution; (2) Add the oil phase core liquid to the wall material solution and emulsify to obtain an emulsion; place the emulsion in a static magnetic field with a magnetic field strength of 0.1~0.6 T and a temperature of 45~55℃ for 5~20 min; after treatment, under the condition of maintaining the magnetic field, the emulsion crystallizes and rearranges. Among them, emulsification is emulsification at 9000~14000 rpm for 3~6 min; crystallization is to control the cooling rate at 2~5℃ / min, cool the emulsion to 12~18℃, and hold it for 10~20 min; rearrangement is to heat to 3~6℃ below the melting point of paraffin and hold it for 20~40 min. (3) Remove the magnetic field and add CaCl2 to react; after the reaction, spray dry to obtain lavender essential oil / paraffin composite core material microcapsules; In step (1), the mass ratio of paraffin to lavender essential oil is 1:0.8~2.5; the surface-inertly coated magnetic oxide particles are SiO2 coated Fe3O4 or surface-stearic acid modified Fe3O4, and the amount of surface-inertly coated magnetic oxide particles added is 0.1~1.0 wt% of the total mass of paraffin and lavender essential oil; the concentration of OSA starch in the wall material solution is 8~14 wt%; In step (2), the mass ratio of the oil phase core liquid to the wall material solution is 1:2~6.

2. The method according to claim 1, characterized in that, In step (1), the melting point of paraffin is 38~55℃. It is heated to 8~12℃ above its melting point and completely melted. After the paraffin melts, it is mixed with lavender essential oil and stirred at 55~70℃ and 200~600 rpm for 10~20 min.

3. The method according to claim 1, characterized in that, In step (3), the amount of CaCl2 added is 0.5~2.0 wt% of the mass of OSA starch; the spray drying parameters are an inlet air temperature of 150~175℃ and an outlet air temperature of 75~90℃.

4. Lavender essential oil / paraffin composite core microcapsules prepared by the method according to any one of claims 1 to 3.

5. The application of the lavender essential oil / paraffin composite core microcapsules as described in claim 4 in the fields of textile processing and daily chemical products.

6. A steam eye mask, characterized in that, The steam eye mask contains the lavender essential oil / paraffin composite core material microcapsules as described in claim 4.

7. A cigarette flavor capsule, characterized in that, The cigarette flavoring capsule contains the lavender essential oil / paraffin composite core material microcapsule as described in claim 4.

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