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

Abstract

The invention discloses a preparation method and application of a lavender essential oil / paraffin composite core material microcapsule, and belongs to the technical field of microcapsule preparation. According to the composite core material microcapsule with the temperature response release enhancing characteristic, a magnetic field regulation and control step is introduced in the emulsification and phase change curing process, so that a phase change response structure unit in oriented arrangement is formed in an inner core, the phase change response structure unit and an OSA starch shell layer are in synergistic effect, and amplification of the temperature trigger release behavior is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to a preparation method of a lavender essential oil / paraffin composite core material microcapsule and its application, and belongs to the technical field of microcapsule preparation. BACKGROUND

[0002] Lavender essential oil has biological activities such as fragrance regulation, bacteriostasis and soothing, and is widely used in daily chemical, textile finishing and functional slow-release material fields. However, essential oil has strong volatility and poor stability, and is easily affected by heat and environment to quickly lose activity, so it is usually protected by embedding through microcapsule technology.

[0003] The prior art usually uses a complex coacervation method to prepare essential oil microcapsules, but the slow-release effect of most microcapsules is limited, and the essential oil still volatilizes quickly. Even if the microcapsules with slow-release aids are added, the fragrance of the finished fabric is significantly weakened after two months of storage. At the same time, although the complex coacervation method and the like have mild conditions, they are extremely sensitive to process parameters such as pH, temperature and stirring speed, and the process control is complex, and sometimes the reproducibility is not good.

[0004] Paraffin wax undergoes solid-liquid transition in a specific temperature range, and its volume, fluidity and diffusion capacity change significantly, having potential temperature response characteristics. However, in the prior art, the co-embedding of paraffin wax and essential oil is usually simple physical mixing, and the phase change behavior of paraffin wax only changes the physical properties of the core, and is not effectively converted into a structural trigger factor for driving the change in shell permeability, so the temperature-sensitive release effect is limited.

[0005] In the field of functional composite materials, an external physical field (such as an electric field or a magnetic field) has been used to regulate the orientation of particles, construct anisotropic structures or induce changes in the internal phase distribution. For example, a magnetic field can form an oriented arrangement structure in a system containing a magnetic response component during solidification or phase transition, thereby changing the mechanical or transport properties of the material. However, the above-mentioned external field regulation technology is mainly applied in the field of magnetic composite materials, conductive materials or structural functional materials, and there is no report on using a magnetic field in the microcapsule formation process to regulate the microstructure of the phase change core in the essential oil microcapsule system with a natural polymer as the wall material.

[0006] Therefore, it is necessary to develop a new structure construction method to introduce an external field regulation means in the microcapsule formation process, so that the phase change material forms an orientation-related microstructure in the core, thereby converting the paraffin wax phase change behavior into a structural response source that can drive the directional migration of essential oil, and achieving significantly enhanced temperature-triggered release effect. SUMMARY

[0007] To solve the above problems, the application provides a composite core material microcapsule with enhanced temperature response release characteristics, which forms an oriented phase change response structure unit in the core by introducing a magnetic field regulation step in the emulsification and phase change curing process, and cooperates with the OSA starch shell layer to realize amplification of the temperature triggered release behavior.

[0008] The first object of the application is to provide a method for preparing lavender essential oil / paraffin composite core material microcapsules, comprising the following steps: (1) mixing and stirring paraffin after melting with lavender essential oil, adding surface inert coated magnetic oxide particles to obtain an oil phase core liquid; dissolving OSA starch in water to obtain a wall material solution; (2) adding the oil phase core liquid to the wall material solution to obtain an emulsion; placing 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, crystallizing and rearranging the emulsion under the condition that the magnetic field exists; (3) removing the magnetic field, adding CaCl2 to react; after reaction, spray drying 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 inert coated magnetic oxide particles are SiO2 coated Fe3O4 or surface stearic acid modified Fe3O4, and the addition amount of the surface inert coated magnetic oxide particles 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.

[0009] In one embodiment, in step (1), the melting point of paraffin is 38-55℃, and it is completely melted by heating to 8-12℃ higher than the melting point; after melting, paraffin is mixed with lavender essential oil, and stirred at 55-70℃ and 200-600 rpm for 10-20 min.

[0010] 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 addition amount of the surface inert coated magnetic oxide particles 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%; the surface stearic acid modified Fe3O4 is octadecanoic acid (C 18 H 36 O2) modified Fe3O4.

[0011] In one embodiment, the particle size of the surface-inertly coated magnetic oxide particles in step (1) is 50 nm to 2 μm; after the surface-inertly coated magnetic oxide particles are added, the oil phase core solution is slowly added into the wall material solution under the condition that the temperature of the oil phase core solution is kept 5℃ higher than the melting point of the paraffin.

[0012] In one embodiment, the OSA starch is dissolved in water under the condition of 65-80℃ and 300-500 rpm stirring for 30-50 min, and the pH is adjusted to 6.8-8.2 to obtain the wall material solution in step (1).

[0013] In one embodiment, the oil phase core solution is slowly added into the wall material solution under the condition that the temperature of the oil phase core solution is kept 5℃ higher than the melting point of the paraffin in step (2).

[0014] In one embodiment, the oil phase core solution is slowly added into the wall material solution under the condition that the temperature of the oil phase core solution is 55-70℃ in step (2).

[0015] In one embodiment, the emulsification is 9000-14000 rpm for 3-6 min; the crystallization is to control the cooling rate at 2-5℃ / min, and the emulsion is cooled to 12-18℃ and kept for 10-20 min; and the rearrangement is to heat to 3-6℃ below the melting point of the paraffin and keep for 20-40 min in step (2).

[0016] In one embodiment, the rearrangement is to heat to 35-40℃ at the rate of 2-5℃ / min and keep for 20-40 min.

[0017] In one embodiment, the amount of CaCl2 added in step (3) is 0.5-2.0 wt% of the mass of the OSA starch; and the spray drying parameters are the inlet air temperature of 150-175℃ and the outlet air temperature of 75-90℃.

[0018] The second object of the present application is to provide the lavender essential oil / paraffin composite core material microcapsule prepared by any of the above methods.

[0019] The third object of the present application is to provide the application of the above-mentioned lavender essential oil / paraffin composite core material microcapsule in the fields of food preservation, textile processing, daily chemical products, medicine and health care, packaging materials, agricultural insect prevention and cosmetics.

[0020] In one embodiment, the application includes intelligent fabrics, heat-responsive fragrance materials and functional slow-release fields.

[0021] The fourth object of the present application is to provide a product containing the above-mentioned lavender essential oil / paraffin composite core material microcapsule, which includes a steam eye patch and a cigarette bursting bead.

[0022] A fifth object of the present application is to provide a method for improving the temperature-responsive release characteristics of lavender essential oil microcapsules, using paraffin, surface-inertly coated magnetic oxide particles to prepare lavender essential oil / paraffin composite core material microcapsules, comprising the steps of: (1) After the paraffin is melted, it is mixed and stirred with the lavender essential oil, surface-inertly coated magnetic oxide particles are added, and the oil phase core liquid is obtained by stirring; OSA starch is dissolved in water to obtain a wall material solution; (2) The oil phase core liquid is added to the wall material solution, and an emulsion is obtained by emulsification; the emulsion is treated in a static magnetic field with a magnetic field strength of 0.1-0.6 T and a temperature of 45-55°C for 5-20 min; after the treatment, the emulsion is crystallized and rearranged in the presence of the magnetic field; (3) The magnetic field is removed, CaCl2 is added for reaction, and then spray drying is performed to obtain lavender essential oil / paraffin composite core material microcapsules; In step (1), the mass ratio of paraffin to 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 addition amount of the surface-inertly coated magnetic oxide particles is 0.1-1.0 wt% of the total mass of paraffin and lavender essential oil; In step (2), the mass ratio of the oil phase core liquid to the wall material solution is 1:2-6.

[0023] In one embodiment, the particle size of the surface-inertly coated magnetic oxide particles in step (1) is 50 nm-2 μm; after the surface-inertly coated magnetic oxide particles are added, high-speed stirring is performed at 50-70°C and 400-600 rpm for 5-10 min.

[0024] In one embodiment, the OSA starch is dissolved in water at 65-80°C and 300-500 rpm for 30-50 min, and the pH is adjusted to 6.8-8.2 to obtain the wall material solution.

[0025] 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 5°C higher than the melting point of paraffin.

[0026] In one embodiment, in step (1), the melting point of paraffin is 38-55°C, and it is completely melted by heating to 8-12°C above its melting point; after the paraffin is melted, it is mixed with the lavender essential oil, and stirred at 55-70°C and 200-600 rpm for 10-20 min; The emulsification in step (2) is 9000-14000 rpm for 3-6 min; the crystallization is to control the cooling rate at 2-5 ℃ / min, and the emulsion is cooled to 12-18 ℃ for 10-20 min; the rearrangement is to heat to 3-6 ℃ below the melting point of paraffin and keep for 20-40 min.

[0027] In an embodiment, the rearrangement is to heat to 35-40 ℃ at a rate of 2-5 ℃ / min for 20-40 min.

[0028] In an embodiment, the CaCl2 is added in step (3) in an amount of 0.5-2.0 wt% of the mass of the OSA starch; and the spray drying parameters are an inlet air temperature of 150-175 ℃ and an outlet air temperature of 75-90 ℃.

[0029] Advantages of the present application The present application introduces a magnetic field treatment in the oil droplet formation stage after emulsification, and disperses magnetic response particles in the composite oil phase, so that the internal part of the oil droplet forms a microstructure unit with an orientation feature in the solidification process of the phase change material. This structure is different from the isotropic solid-state core formed by traditional random crystallization, but forms a phase change response area with spatial distribution difference.

[0030] When the temperature rises close to the paraffin phase change temperature zone, the different orientation areas occur non-synchronous softening and reconstruction, thereby generating local structural rearrangement and direction-related volume change in the microcapsule, and forming non-uniform internal stress on the shell. This structural response mode is beneficial to opening more transient diffusion channels in a specific temperature range, so that the release rate of essential oil appears a significant jump, thereby significantly enhancing the temperature-triggered release effect; the microcapsules prepared by the present application have a response amplitude of 2.72 or more and an embedding rate of 80% or more.

[0031] Secondly, the present application sets a structure regulation step of "warming to 3-6 ℃ below the melting point and keeping" after the preliminary crystallization of paraffin, so that the completely frozen paraffin crystal network is changed into a multi-phase structure containing metastable interface and low crystallinity area. This structure still maintains the solid support effect at room temperature, but preferentially occurs local melting and interface rearrangement when close to the phase change temperature zone, forming an "easy trigger zone" in structure. Therefore, when the temperature rises, the core structure does not uniformly melt, but selectively and progressively reconstructs the structure, further amplifying the influence of the phase change behavior on the permeability of the shell.

[0032] In addition, the synergistic existence of the magnetic field induced orientation structure and the above-mentioned metastable phase transition structure makes the thermal phase transition of the paraffin change from a pure physical change to a response process with a structure driven characteristic, and realizes a coupling mechanism triggered by the core structure change and the shell permeability change. Compared with the system without the magnetic field and the temperature zone regulation treatment, the microcapsules of the application can still maintain good barrier properties under low temperature conditions, and the release rate is significantly improved when reaching the phase transition temperature zone, showing more obvious temperature response release behavior.

[0033] Therefore, the application endows the microcapsules with enhanced release characteristics in a specific temperature range, and expands the application potential of the microcapsules in the fields of intelligent fabrics, heat responsive fragrance materials and functional release. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 Fig. 2 shows the influence of different magnetic field intensities on the release rate of the microcapsules. DETAILED DESCRIPTION

[0035] The preferred embodiments of the application are described below, and it should be understood that the embodiments are for better explaining the application and are not used to limit the application.

[0036] Raw materials used in the embodiments: The phase change paraffin was purchased from Dongguan Zhangmutou Shengbang Plastic Raw Material Business Department; The lavender essential oil was purchased from Xinjiang Tian Mountain Flower Sea Tourism Group Co., Ltd.; The SiO2 coated Fe3O4 was purchased from Sinopharm Chemical Reagent Co., Ltd.; The OSA starch was purchased from Cargill (China); The uncoated Fe3O4 was purchased from Sinopharm Chemical Reagent Co., Ltd.; The γ-Fe3O4 was purchased from Sinopharm Chemical Reagent Co., Ltd.; The Fe3O4 with a surface modified by stearic acid (octadecanoic acid, C 18 H 36 O2) was purchased from Sinopharm Chemical Reagent Co., Ltd.; Test method: Release rate detection method: 0.1 g of microcapsule powder was dispersed in 4 mL of anhydrous ethanol, and was placed under magnetic stirring at a target temperature for 1 h. After the end, it was naturally cooled to room temperature, centrifuged at 9000 rpm for 5 min, filtered through a 0.22 micron organic filter membrane, and the filtrate was subjected to ultraviolet spectrophotometric detection. According to the standard curve prepared in advance, the essential oil content in the solution was determined, which represented the essential oil release amount.

[0037] Another 0.1 g of microcapsule powder was set to 60 degrees for 5 h, and the rest of the operation was the same as above. The amount of essential oil in the solution represented the total amount of essential oil. The release rate was calculated according to the following formula: Release rate (%) = (A × 100% Differential scanning calorimetry (DSC) test method: The differential scanning calorimeter was used to determine the phase transition behavior of the microcapsule core. About 5-8 mg of microcapsule powder sample was placed in a sealed aluminum crucible, and an empty aluminum crucible was used as a reference. The test was carried out under a nitrogen protective atmosphere (flow rate 40-60 mL / min). The test temperature range was set to 20-60 ℃, and the heating rate was 5 ℃ / min. The onset melting temperature (T onset), peak melting temperature (T peak) and melting enthalpy (ΔH) of the sample were recorded. Each sample was tested in triplicate, and the average value was taken as the final result. By comparing the changes in the melting onset temperature and melting enthalpy under different treatment conditions, the influence of the magnetic field regulation on the crystalline structure and phase transition behavior of paraffin was analyzed.

[0038] X-ray diffraction (XRD) test method: The X-ray diffractometer was used to analyze the crystal structure of the paraffin in the microcapsule core. The microcapsule powder was evenly spread on the sample stage and tested at room temperature. The test used Cu Kα radiation source (λ = 0.15406 nm), working voltage 40 kV, current 30 mA, scanning range 2θ = 5°-40°, scanning rate 2° / min, step size 0.02°. The characteristic diffraction peak position and intensity were recorded, and the relative crystallinity was calculated by peak area integration method. By comparing the changes in the diffraction peak intensity and half-width of different samples, the influence of magnetic field treatment on the degree of order and crystalline structure of paraffin crystals was analyzed. According to the XRD diffraction data, the relative crystallinity of the sample was calculated by integration method. The crystalline diffraction peak area was recorded as A c , and the total diffraction area was recorded as A t , then the crystallinity was calculated as follows: Crystallinity (%) = (A c / A t ) × 100% Wherein, A c is the crystalline peak area integral value, and A t is the total area integral value of crystalline and amorphous peaks. Each sample was tested in triplicate, and the average value was taken as the final result.

[0039] The response amplitude is 40℃ release rate / 25℃ release rate.

[0040] Example 1 The lavender essential oil / paraffin composite core material microcapsule was prepared as follows: (1) 40 g phase change paraffin with a melting point of 42℃ was heated to 58℃, 60 g lavender essential oil was added, stirred at 400 rpm for 15 min, 0.5 g SiO2coated Fe3O4was added, stirred at 60℃ and 500 rpm for 8 min to obtain the oil phase core solution; 100 g OSA starch was dissolved in 900 g deionized water, stirred at 75℃ (400 rpm) for 40 min, and the pH was adjusted to 7.4 to obtain the wall material solution; (2) The oil phase core solution was added to the wall material solution at a mass ratio of 1:2 at 58℃, and emulsified at 12000 rpm for 5 min to obtain an emulsion; the emulsion was treated in a 0.3T static magnetic field at 50℃ for 10 min; (3) The temperature was reduced to 15℃ at a cooling rate of 3℃ / min in the static magnetic field, and maintained for 15 min; then increased to 37℃ at a rate of 3℃ / min and maintained for 30 min; (4) The magnetic field was removed, 1 g of anhydrous CaCl2solid was added, and reacted for 20 min, and then spray dried (inlet temperature 170℃, outlet temperature 80℃) to obtain lavender essential oil / paraffin composite core material microcapsules.

[0041] Comparative Example 1 Lavender essential oil / paraffin composite core material microcapsules were prepared without adding magnetic oxide particles and without being placed in a magnetic field, and the steps were as follows: (1) 40 g phase change paraffin with a melting point of 42℃ was heated to 58℃, 60 g lavender essential oil was added, stirred at 400 rpm for 15 min; (2) 100 g OSA starch was dissolved in 900 g deionized water, stirred at 75℃ for 40 min, and the pH was adjusted to 7.4 to obtain the wall material solution; the oil phase core solution was added to the wall material solution at a mass ratio of 1:2 at 58℃, and emulsified at 12000 rpm for 5 min to obtain an emulsion; (3) The emulsion was treated at 50℃ for 10 min, and then the temperature was reduced to 15℃ at a cooling rate of 3℃ / min, and maintained for 15 min; then increased to 37℃ and maintained for 30 min; (4) 1 g of anhydrous CaCl2solid was added, and reacted for 20 min, and then spray dried (inlet temperature 170℃, outlet temperature 80℃) to obtain powder microcapsules.

[0042] Example 2 On the basis of 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, and the remaining steps were kept unchanged. The release rate of lavender essential oil / paraffin composite core material microcapsules at 25℃ and 40℃ was detected under different magnetic field strengths.

[0043] The results are as follows: Figure 1As shown, the results show that with the increase of magnetic field strength, the cumulative release rate of microcapsules at 25°C gradually decreases, while the release rate at 40°C significantly increases, thereby continuously increasing the release transition multiple.

[0044] When no magnetic field is applied, the release transition multiple of the system is about 2.05, indicating that the paraffin crystals inside are in a random orientation structure, and the temperature responsiveness is weak; as the magnetic field strength increases to 0.3 T, the release transition multiple increases to about 2.72, indicating that the magnetic field induction has significantly promoted the directional arrangement of paraffin crystals; when the magnetic field strength is further increased to 0.5 T, the release transition multiple reaches about 3.03, indicating that a relatively stable oriented crystal structure has been formed inside the paraffin, effectively inhibiting 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 multiple only increases slightly to about 3.09, indicating that the oriented structure of the system has tended to be saturated, and further increasing the magnetic field strength has limited effect on the improvement of the orientation degree and release performance.

[0045] The above results show that appropriately increasing the magnetic field strength is beneficial to enhancing the orientation structure of paraffin crystals, thereby improving the temperature-responsive release performance of microcapsules, but when the magnetic field strength exceeds a certain threshold, the orientation effect tends to be stable, and considering the factors of comprehensive structural performance and energy consumption, the optimal magnetic field strength is 0.5 T.

[0046] Example 3 On the basis of Example 1, the addition amount of SiO2-coated Fe3O4 in step (1) is changed to 0.1 wt% (i.e., 0.1 g), 0.3 wt% (i.e., 0.3 g), 0.8 wt% (i.e., 0.8 g), and 1 wt% (i.e., 1 g), respectively, and the remaining steps remain unchanged. The release rate of lavender essential oil / paraffin composite core material microcapsules at 25°C and 40°C is detected under different addition amounts of SiO2-coated Fe3O4.

[0047] As shown in Table 1, the results show that when the addition amount of magnetic particles is 0.1 wt%, the release transition multiple is about 2.13, indicating that the number of magnetic response units in the system is limited, and the orientation induction effect on paraffin crystals is weak; When the addition amount increases to 0.3 wt% and 0.5 wt%, the release transition multiple increases to about 2.41 and 2.72, respectively, indicating that the increase in the number of magnetic particles significantly enhances the magnetic field induction effect, gradually forming a directional arrangement structure of paraffin crystals, thereby effectively inhibiting low-temperature diffusion and enhancing the release in the melting zone; When the addition amount is further increased to 0.8 wt%, the release jump ratio reaches about 2.91, indicating that the orientation structure of the system is further improved; while continuously increasing to 1.0 wt%, the release jump ratio only increases slightly to about 2.97, and the increase is significantly slowed down, indicating that the paraffin structure in the system that can participate in orientation induction has tended to be saturated, and the excess magnetic particles have limited effect on structure optimization.

[0048] Table 1 Effect of different addition amounts of SiO2-coated Fe3O4 on the release rate of microcapsules

[0049] Example 4 On the basis of Example 1, the magnetic particles in step (1) were changed to uncoated Fe3O4, γ-Fe3O4, and Fe3O4 modified with stearic acid, respectively, and the remaining steps remained unchanged. The release rates of lavender oil / paraffin composite core microcapsules prepared with different magnetic particles were detected at 25°C and 40°C.

[0050] The results, as shown in Table 2, show that different magnetic particles have significant differences in paraffin crystal orientation induction ability due to differences in surface structure and interface compatibility.

[0051] Among them, the release jump ratio of the uncoated Fe3O4 system is about 2.43, indicating that it has a certain magnetic response ability, but due to the higher surface energy and limited dispersibility in the oil phase, the orientation induction effect on the paraffin crystal is relatively weak; The release jump ratio of the γ-Fe2O3 system is about 2.30, which is slightly lower than that of Fe3O4, indicating that its magnetic response ability and interface induction effect are relatively weak; the release jump ratio of the SiO2-coated Fe3O4 system is increased to about 2.72, indicating that the SiO2 coating layer effectively improves the dispersion stability of the magnetic particles in the oil phase, enabling them to be more uniformly distributed and effectively transfer the magnetic field induction effect, thereby enhancing the formation of paraffin crystal orientation structure; When further modified with stearic acid, the release jump ratio reaches about 2.94, indicating that the organic modification layer significantly improves the interface compatibility of the magnetic particles with the paraffin matrix, enabling the magnetic particles to more effectively participate in the crystal orientation induction process and form a more perfect orientation structure.

[0052] Table 2 Effect of different magnetic particles on the release rate of microcapsules

[0053] Comparative Example 2 On the basis of Example 1, the timing of the magnetic field treatment was changed to oil phase treatment before emulsification, and the steps were as follows: (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. (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. (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; (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.

[0054] Comparative Example 3 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: (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. (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. (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.

[0055] Comparative Example 4 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: (1) 40 g phase change paraffin with a melting point of 42 ℃ was heated to 58 ℃, 60 g lavender essential oil was added, stirred at 400 rpm for 15 min, 0.5 g SiO2coated Fe3O4was added, stirred at 60 ℃ and 500 rpm for 8 min to obtain the oil phase core solution; 100 g OSA starch was dissolved in 900 g deionized water, stirred at 75 ℃ and 400 rpm for 40 min, and the pH was adjusted to 7.4 to obtain the wall material solution; (2) At 58 ℃, the oil phase core solution was added to the wall material solution according to a mass ratio of 1:2, and emulsified at 12000 rpm for 5 min to obtain an emulsion; (3) The temperature was reduced to 15 ℃ at a cooling rate of 3 ℃ / min and maintained for 15 min; then treated in a static magnetic field of 0.3T for 10 min, the magnetic field was removed, and then increased to 37 ℃ at a rate of 3 ℃ / min and maintained for 30 min; (4) 1 g anhydrous CaCl2was added and reacted for 20 min, and then spray dried (inlet temperature 170 ℃, outlet temperature 80 ℃) to obtain lavender essential oil / paraffin composite core material microcapsules.

[0056] Comparative Example 5 On the basis of Example 1, step (3) was omitted, and the remaining steps were kept unchanged to prepare the microcapsules.

[0057] The microcapsules prepared in Example 1 and Comparative Examples 1-5 were detected for release rates at 25 ℃ and 40 ℃.

[0058] The results are shown in Table 3, which show that different magnetic field treatment methods have a significant effect on the orientation structure of paraffin crystals and the release behavior. 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 weak temperature responsiveness.

[0059] Under the condition of applying a magnetic field but without magnetic field-induced cooling and heating, the release rates at 25 ℃ and 40 ℃ decrease and increase respectively, and the release response amplitude increases to about 2.55, indicating that the magnetic field can induce the orientation of magnetic particles to some extent, but the crystallization process of paraffin is not completed under the induction of the magnetic field, resulting in limited orientation structure; In addition, the timing of magnetic field treatment needs to be after emulsification or simultaneously, and the cooling and heating steps in the magnetic field, i.e. the cooling crystallization and heating rearrangement processes of paraffin under the action of the magnetic field, increase the response amplitude to 2.72, indicating that the crystallization process induced by the magnetic field can effectively promote the formation of stable oriented crystal structure of paraffin molecules along the direction of the magnetic field, thereby significantly inhibiting the diffusion at low temperature and enhancing the release performance in the melting zone.

[0060] Table 3

[0061] Example 5 1. Structure characterization The structure of the lavender essential oil / paraffin composite core material microcapsules prepared under the magnetic field intensity of 0 T and 0.5 T in Example 1 and Example 2 was characterized, and the results are shown in Table 4.

[0062] The results show that the magnetic field treatment significantly changes the spatial arrangement mode and crystallization behavior of paraffin crystals, thereby forming an anisotropic structure with obvious orientation characteristics. The polarized light microscope (POM) observation results show that the orientation factor of the control group without magnetic field treatment is only 0.07, and the relative birefringence intensity is 1.00, indicating that the paraffin crystals are randomly oriented. Under the condition of 0.3 T magnetic field treatment, the orientation factor increases to 0.21, and the relative birefringence intensity increases to 1.34, indicating that the paraffin crystals begin to form a preliminary directional arrangement along the magnetic field direction. When the magnetic field intensity increases to 0.5 T, the orientation factor further increases to 0.29, and the relative birefringence intensity reaches 1.58, indicating that the paraffin crystals have formed a relatively obvious orientation structure, and the anisotropy of the system is significantly enhanced.

[0063] The X-ray diffraction (XRD) test results further show that the magnetic field treatment does not change the crystal structure of paraffin, but has a certain influence on the crystallinity and grain structure. The relative crystallinity of paraffin without magnetic field is 71.2%, while under the conditions of 0.3 T and 0.5 T magnetic field treatment, it decreases to 66.8% and 63.1% respectively, and the half-peak width of the diffraction peak increases from 0.32 to 0.36 and 0.39, indicating that the magnetic field induction restricts the free growth of the crystal, reduces the grain size and forms a restricted crystalline structure with oriented arrangement. This structural feature is beneficial to the formation of anisotropic diffusion channels, thereby affecting the release behavior.

[0064] The differential scanning calorimetry (DSC) test results show that the magnetic field treatment also has a certain influence on the thermal behavior of paraffin. The melting peak temperature of paraffin without magnetic field is 41.8℃, the initial melting temperature is 38.5℃, and the melting enthalpy is 62.4 J / g; under the condition of magnetic field treatment, the melting peak temperature slightly increases to 42.2℃ and 42.5℃, while the initial melting temperature decreases to 37.7℃ and 36.9℃, and the melting enthalpy decreases to 58.7 J / g and 55.8 J / g, indicating that the oriented structure formed by magnetic field induction makes part of the crystal region in a restricted state, reduces the overall crystalline integrity, and forms oriented crystal regions with different thermal stability, thereby widening the melting interval.

[0065] Table 4

[0066] 2. Other properties The representative non-magnetic field treatment comparative example, complete magnetic field treatment example and high magnetic particle addition amount example were selected for product particle property analysis, and the results are shown in Table 5. The results show that the microcapsules of each group have high embedding rate and good particle size uniformity, but there are still some differences under different conditions.

[0067] In the comparative example 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 embedding rate was 78.4%, indicating that the system could form a stable coating structure, but due to the lack of magnetic field induction, the interface structure between paraffin and wall material was relatively loose, and part of the core material was lost during preparation.

[0068] Under the condition of complete magnetic field induction treatment, the average particle size of the microcapsules was 19.8 μm, the PDI was 0.19, and the embedding rate was increased to 84.7%, indicating that the magnetic field induction was conducive to forming a more stable interface structure, which made the paraffin more uniformly fixed in the microcapsules during crystallization, thereby improving the embedding efficiency and improving the particle size uniformity.

[0069] When the magnetic particle addition amount 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 embedding rate slightly decreased to 81.9%, indicating that excessive magnetic particles could cause local aggregation of the system, which reduced the emulsion stability, thereby having certain adverse effects on the particle size uniformity and embedding structure.

[0070] Table 5

[0071] Although the present application has been disclosed with the above preferred embodiments, it is not intended to limit the present application, and any person skilled in the art can make various modifications and modifications without departing from the spirit and scope of the present application. Therefore, the protection scope of the present application should be defined 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. (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 (2), emulsification is performed at 9000~14000 rpm for 3~6 min; Crystallization involves controlling the cooling rate at 2-5℃ / min, cooling the emulsion to 12-18℃, and holding it for 10-20 min; rearrangement involves heating to 3-6℃ below the melting point of paraffin and holding it for 20-40 min.

4. 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℃.

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

6. The application of the lavender essential oil / paraffin composite core microcapsules as described in claim 5 in the fields of food preservation, textile processing, daily chemical products, pharmaceuticals and health care, packaging materials, agricultural pest control and cosmetics.

7. A product characterized in that, The product contains the lavender essential oil / paraffin composite core material microcapsules as described in claim 5, and the product includes steam eye masks and cigarette capsules.

8. A method for improving the temperature-responsive release characteristics of lavender essential oil microcapsules, characterized in that, Lavender essential oil / paraffin composite core microcapsules were prepared using paraffin wax and surface-inert coated magnetic oxide particles, 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. (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.

9. The method according to claim 8, characterized in that, In step (1), the melting point of paraffin is 38~55℃. Heat it to 8~12℃ above its melting point and it will melt completely. After the paraffin melts, mix it with lavender essential oil and stir at 55~70℃ and 200~600 rpm for 10~20 min. In step (2), emulsification is performed at 9000~14000 rpm for 3~6 min; Crystallization involves controlling the cooling rate at 2-5℃ / min, cooling the emulsion to 12-18℃, and holding it for 10-20 min; rearrangement involves heating to 3-6℃ below the melting point of paraffin and holding it for 20-40 min.

10. The method according to claim 8, 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℃.

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