Aromatic microcapsule with microcosmic shape regulated by magnetic field and preparation method thereof

Abstract

The present application relates to a kind of magnetic field regulated microcosmic shape aromatic microcapsule and its preparation method, which is specifically as follows: core material emulsion and first wall material / magnetizing agent solution are stirred and mixed, homogeneous emulsification is carried out under high-speed shearing machine, to obtain oil-in-water emulsion;Magnetic field induction is carried out in external magnetic field;Crosslinking agent solution is added and stirred, and first wall layer crosslinking solidification is carried out;After drying, second wall material salt solution is added and stirred, and second wall layer electrostatic adsorption is carried out;After drying, first wall material solution is added and stirred, and third wall layer electrostatic adsorption is carried out.Compared with prior art, the present application uses lavender essential oil as core material, quaternary ammonium salt chitosan and silicon dioxide as wall material, and forms aromatic microcapsule with adjustable microcosmic shape by magnetic field induction;The present application prepares microcapsule by layer-by-layer assembly method, and the preparation method has mild conditions and relatively simple and easy-to-control process, and the prepared microcapsule has high thermal stability, and its microcosmic shape can be regulated by magnetic field.

Description

Technical Field

[0001] This invention belongs to the field of microcapsule technology and relates to an aromatic microcapsule with magnetic field-controlled microscopic shape and its preparation method. Background Technology

[0002] The fragrance and flavor industry is a high-tech sector within the national economy, highly interconnected with other industries. It serves as a crucial raw material supplier for the fragrance, flavor, daily chemical, and food and beverage industries, and is closely linked to improving living standards and boosting domestic demand and consumption. The overall development level of the fragrance and flavor industry is an important indicator of a nation's economic and technological development.

[0003] Fragrances are easily oxidized under strong light or excessive heat, a problem that microencapsulation technology solves. Microencapsulation is a promising method for fragrance storage, encapsulating fragrances through physical or chemical methods. Fragrances and essential oils possess pleasant aromas and various benefits, offering broad application prospects. However, direct addition to consumer products has drawbacks such as short residence time and easy odor deterioration. Furthermore, releasing a large amount of odor in a short period can be an unpleasant experience, severely limiting the practical application of aromatic substances. Microencapsulation offers advantages such as improved essential oil stability, enhanced physical properties, slower release rates, and protection from environmental influences.

[0004] In some applications, it is desirable for microcapsules to release their core material through external mechanical stimulation. Therefore, designing methods with tunable mechanical properties is crucial. The shape and wall thickness of the microcapsule significantly influence its mechanical properties. Currently, commonly used mechanically stimulated microcapsules often use melamine-formaldehyde resin and urea-formaldehyde resin as wall materials. These manufacturing processes are not environmentally friendly and carry the risk of unreacted formaldehyde residue.

[0005] Patent CN104448088A discloses a method for preparing thermosensitive anisotropic magnetic microcapsules. The prepared magnetic microcapsule walls are composed of vinylcaprolactam, a crosslinking agent, and an auxiliary monomer copolymer. The core is not located at the center of the microspheres but rather close to one side of the outer wall of the microspheres, exhibiting an asymmetrical structure. Magnetic nanoparticles are relatively uniformly dispersed in the capsule walls, and the microspheres exhibit temperature sensitivity. This patent uses an oleic acid-modified magnetizing agent and non-polar raw materials together as the core phase. The polarity difference allows the modified magnetizing agent and the non-polar raw materials to be located at opposite ends of the capsule, forming an asymmetrical internal structure. However, if materials containing hydrophilic groups are used as the core material, this effect may not be achieved, which limits the scope of application. Furthermore, this method does not change the overall shape of the capsule and does not lower the threshold for triggering the release of the core material.

[0006] Patent CN114177847A discloses a plant essential oil microcapsule and its preparation method. The preparation method includes at least the following steps: preparing a core material solution using plant essential oil; preparing a wall material solution using cyclodextrin; adding the core material solution to the wall material solution and homogenizing and emulsifying to obtain a cyclodextrin-coated monolayer microcapsule; and then further encapsulating the monolayer microcapsule with chitosan / sodium alginate to obtain a bilayer microcapsule. However, the multilayer encapsulation in this patent uses cyclodextrin and natural polysaccharide materials of chitosan and sodium alginate, which do not significantly improve mechanical stability.

[0007] Patent CN113351125A discloses a citrus essential oil microcapsule, its preparation method, and its application. The method includes: mixing chitosan quaternary ammonium salt with sodium alginate, acetic acid, and water to obtain a composite wall material solution; then mixing this solution with citrus essential oil and a composite emulsifier to obtain an emulsion; subjecting this emulsion to a coagulation reaction; and finally mixing it with calcium chloride for cross-linking and curing to obtain citrus essential oil microcapsules. However, this patent uses acetic acid to adjust the pH to increase the solubility of the chitosan quaternary ammonium salt, which may affect the flavor of the encapsulated essential oil; furthermore, the cross-linking agent in this patent is only for the calcium ions formed by the reaction of sodium alginate with calcium alginate. Summary of the Invention

[0008] The purpose of this invention is to overcome at least one defect of the prior art and provide an aromatic microcapsule with magnetic field-controlled microstructure and its preparation method. This invention prepares microcapsules by layer-by-layer assembly and forms aromatic microcapsules with controllable microstructure by magnetic field induction. The preparation method is mild, the process is relatively simple and easy to control, the prepared microcapsules have high thermal stability, and their microstructure can be controlled by magnetic field.

[0009] The objective of this invention can be achieved through the following technical solutions:

[0010] One of the technical solutions of the present invention is to provide a method for preparing aromatic microcapsules with magnetic field-controlled microstructures, the method comprising the following steps:

[0011] (1) Stir and mix the core material emulsion and the first wall material / magnetizing agent solution, and then homogenize and emulsify them under a high-speed shearing machine to obtain an oil-in-water emulsion;

[0012] (2) Magnetic field induction is performed in an external magnetic field;

[0013] (3) Add crosslinking agent solution and stir to carry out crosslinking and curing of the first wall layer, which has a protective effect on the core material;

[0014] (4) After drying, add the second wall material salt solution and stir to carry out electrostatic adsorption of the second wall layer, which increases the thermal stability of the microcapsules. Moreover, the mechanical strength of silica as the wall material is higher than that of natural polysaccharides, which increases the mechanical stability of the microcapsules.

[0015] (5) After drying, the first wall material solution is added and stirred to carry out electrostatic adsorption of the third wall layer, which protects the inner layer of the microcapsule and reduces the loss of the inner capsule.

[0016] Further, in step (1), the core material includes essential oils, such as lavender essential oil, thyme essential oil, jasmine essential oil, rose essential oil, laurel essential oil, or violet essential oil, and the mass fraction of the core material is 0.5-6%.

[0017] Emulsifiers include Tween (polysorbate) 80, Tween 60, Tween 20, Span (sorbitan fatty acid ester) 80, or sodium dodecyl sulfate, with an emulsifier mass fraction of 0.75-3%.

[0018] Further, in step (1), the first wall material includes quaternary ammonium salt chitosan or chitosan, and the mass fraction of the first wall material is 1.5-4.5%;

[0019] The magnetizing agent includes iron(II,III) oxide or γ-iron(II,III) oxide, with a mass fraction of 0.1-1%.

[0020] Furthermore, in step (1), the mass ratio of the core material emulsion to the first wall material / magnetizing agent solution is 1:(1-3);

[0021] The stirring rate is 500-1000 r / min, the temperature is 20-50℃, and the time is 60-240 min;

[0022] The shearing rate is 10000-22000 r / min, the temperature is 15-30℃, and the time is 1-10 min.

[0023] Furthermore, in step (2), the magnetic field strength is 10-300 mT, the induction temperature is 0-60℃, and the time is 2-48 h.

[0024] Furthermore, in step (3), the crosslinking agent includes sodium tripolyphosphate or glutaraldehyde, and the mass fraction of the crosslinking agent is 1-5%.

[0025] The mass ratio of core material emulsion to crosslinking agent solution is 1:(0.6-1.2);

[0026] The stirring rate is 500-1000 r / min, the temperature is 20-50℃, and the time is 60-240 min.

[0027] Furthermore, in step (4), the second wall material includes silicon dioxide, and the mass fraction of the second wall material is 2-5%.

[0028] Salts include sodium chloride, potassium chloride, or sodium carbonate, with a salt mass fraction of 0.6-2%.

[0029] Furthermore, in step (4), the mass ratio of the core material emulsion to the second wall material salt solution is 1:(1.5-4);

[0030] The stirring rate is 300-900 r / min, the temperature is 15-40℃, and the time is 30-120 min.

[0031] Further, in step (5), the first wall material includes quaternary ammonium salt chitosan or chitosan, and the mass fraction of the first wall material is 1.5-3%;

[0032] The mass ratio of the core material emulsion to the first wall material solution is 1:(3-6);

[0033] The stirring rate is 300-1200 r / min, the temperature is 15-40℃, and the time is 30-180 min.

[0034] One of the technical solutions of the present invention is to provide an aromatic microcapsule with magnetic field-controlled microstructure prepared by the method, the microcapsule comprising the following components by mass percentage: core material 0.06-0.71%, emulsifier 0.09-0.36%, first wall material 1.25-2.5%, magnetizing agent 0.035-0.35%, crosslinking agent 0.07-0.35%, second wall material 0.43-1.07%, and salt 0.1-0.43%, with the balance being water.

[0035] Compared with the prior art, the present invention has the following advantages:

[0036] (1) This invention uses essential oil as core material, quaternary ammonium salt chitosan or chitosan and silica as wall material, and uses a layer-by-layer assembly method to form microcapsules, and then uses magnetic field to induce the formation of aromatic microcapsules with controllable micro-shape.

[0037] (2) The preparation method of the present invention is mild and the process is relatively simple and easy to control. The prepared microcapsules have high thermal stability and mechanical stability, and their micro-shape can be controlled by magnetic field. Attached Figure Description

[0038] Figure 1 This is a scanning electron microscope image of the aromatic microcapsules with magnetic field-controlled microstructures in Comparative Example 6 of the present invention, without the application of a magnetic field during the magnetic field induction process.

[0039] Figure 2 This is a scanning electron microscope image of the aromatic microcapsules with magnetic field-controlled microstructure in Example 1 of the present invention after being subjected to a magnetic field for 6 hours during the magnetic field induction process;

[0040] Figure 3 This is a scanning electron microscope image of the aromatic microcapsules with magnetic field-controlled microstructure in Embodiment 2 of the present invention after 24 hours of magnetic field induction.

[0041] Figure 4 Thermogravimetric analysis (TGA) diagrams of the microcapsules or contents in Example 1 of the present invention and Comparative Examples 1, 2, 4 and 5 are shown.

[0042] Figure 5 Infrared images of the microcapsules or contents in Example 1 and Comparative Examples 1 to 5 of the present invention. Detailed Implementation

[0043] The present invention will now be described in detail with reference to specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0044] Unless otherwise specified, the equipment used in the following embodiments is conventional equipment in the art; unless otherwise specified, the reagents used are commercially available products or prepared by conventional methods in the art. In the following embodiments, unless otherwise described in detail, conventional experimental methods in the art can be used.

[0045] Example 1:

[0046] A magnetically regulated aromatic microcapsule comprises the following components by weight percentage: 0.71% lavender essential oil, 0.18% Tween 80, 1.60% quaternary ammonium chitosan, 0.07% iron oxide, 0.14% sodium tripolyphosphate, 0.64% silicon dioxide, 0.13% sodium chloride, and 96.53% deionized water.

[0047] A method for preparing aromatic microcapsules with magnetic field-controlled microstructures, comprising the following steps:

[0048] (1) Prepare 33.3g of core material emulsion with 6% lavender essential oil and 1.5% Tween 80, and 66.7g of first wall material / magnetizing agent solution with 3% quaternary ammonium salt chitosan and 0.3% iron oxide. Mix the two solutions and stir at 700r / min and 25℃ for 240min. Shear the mixture for 3min in a high shear dispersion emulsifier FA25D-021-S FLUKO at 19000r / min and 25℃ to obtain an oil-in-water emulsion.

[0049] (2) The oil-in-water emulsion was placed in a magnetic field of 300 mT and induced at 25°C for 6 h;

[0050] (3) Add 20g of a crosslinking agent solution with a mass fraction of 2% sodium tripolyphosphate, and stir at 600r / min and 25℃ for 120min to carry out the first quaternary ammonium salt chitosan wall layer crosslinking and curing.

[0051] (4) After drying, add 60g of the second wall material salt solution with a mass fraction of 3% silica and a mass fraction of 0.6% sodium chloride, and stir at 900r / min and 25℃ for 60min to carry out electrostatic adsorption of the second silica wall layer.

[0052] (5) After drying, add 100g of the first wall material solution with a mass fraction of 2.5% quaternary ammonium salt chitosan, stir at 750r / min and 25℃ for 120min, and carry out electrostatic adsorption of the third quaternary ammonium salt chitosan wall layer to form the final aromatic microcapsules.

[0053] Comparative Example 1:

[0054] Lavender essential oil.

[0055] Comparative Example 2:

[0056] A non-magnetic single-layer wall material empty capsule and its preparation method, which only performs steps (1) and (3) of Example 1, but without adding lavender essential oil and iron tetroxide.

[0057] Comparative Example 3:

[0058] A non-magnetic single-layer wall material aromatic microcapsule and its preparation method are described, which only perform steps (1) and (3) of Example 1, but without adding iron tetroxide.

[0059] Comparative Example 4:

[0060] A magnetic field-controlled single-layer wall material aromatic microcapsule and its preparation method, only steps (1) to (3) of Example 1 are performed.

[0061] Comparative Example 5:

[0062] A magnetic field-controlled microstructure of a double-walled aromatic microcapsule and its preparation method, only steps (1) to (4) of Example 1 are performed.

[0063] Comparative Example 6:

[0064] An aromatic microcapsule with uncontrolled microscopic shape by magnetic field and its preparation method are basically the same as those in Example 1, except that step (2) is not performed.

[0065] Example 2:

[0066] A magnetic field-controlled aromatic microcapsule and its preparation method are basically the same as those in Example 1, except that step (2) involves magnetic field induction for 24 hours.

[0067] like Figures 1 to 3As shown, the microcapsules in Comparative Example 6, without magnetic field treatment, were spherical, while those in Example 1 formed polyhedral structures after 6 hours of magnetic field induction, and the microcapsules in Example 2, after 24 hours of magnetic field induction, were mostly cuboids. This indicates that the magnetic field plays a role in inducing changes in the shape of the microcapsules.

[0068] Thermogravimetric analysis of aromatic microcapsules with magnetic field-controlled microshapes involves the following steps: in a nitrogen environment, the temperature is increased at a rate of 10℃ / min, and the test temperature range is 40-800℃. The weight loss curves of Example 1 and Comparative Examples 1, 2, 4 and 5 are analyzed.

[0069] like Figure 4 As shown, the lavender essential oil in Comparative Example 1 began to lose weight rapidly at 87.8℃ and was almost completely volatilized at 131.0℃;

[0070] Comparative Example 2: The non-magnetic monolayer empty capsule lost 9.26% of its weight before 249.5℃. From 249.5℃ onwards, it lost weight rapidly. During this stage, the polymer underwent a large amount of thermal decomposition, and the weight loss reached 56.91%, which slowed down the rate of weight loss.

[0071] The rapid weight loss of the single-layer essential oil microcapsules in Comparative Example 4 started at 237.3℃, which was 149.5℃ higher than that of pure lavender essential oil in Comparative Example 1, confirming the protective effect of the microcapsules on the core material.

[0072] Comparative Example 5, with its bilayer essential oil microcapsules enhanced with a silica layer, began to lose weight rapidly from 244.2℃, an increase of 6.9℃. Moreover, the weight loss rate was much lower than that of the monolayer microcapsules in Comparative Example 4 (which decreased from 6.54% / min to 3.42% / min), confirming that the silica layer increased the thermal stability of the microcapsules.

[0073] The weight loss rate of the three-layer essential oil microcapsules in Example 1 was higher than that of the two-layer microcapsules in Comparative Example 5. This is because the outermost quaternary ammonium salt chitosan was not cross-linked with a cross-linking agent, and this layer has lower stability. However, the amount of weight loss shows that it has a protective effect on the inner layer of the microcapsule, reducing the weight loss of the inner capsule.

[0074] like Figure 5 As shown, the lavender essential oil in Comparative Example 1 was measured at 3463.14 cm⁻¹. -1 The broad absorption peak at 1737.32 cm⁻¹ is attributed to the stretching vibrations of intermolecular hydrogen bonds. -1 The characteristic peak originates from the C=O bond of linalyl acetate, at 919.24 cm⁻¹. -1 The peak at 689.73 cm⁻¹ is a characteristic peak of the carboxyl group. -1 The peak represents the cis dihydrogen of the C=C bond;

[0075] Comparative Example 2: Non-magnetic single-layer empty capsule at 3443.30 cm⁻¹ -1 and 1642.61cm-1 The peak at 1126.85 cm⁻¹ represents the amino groups (NH stretching and bending vibrations) of chitosan. -1 and 3443cm -1 It is a characteristic peak of quaternary ammonium salts, at 974.43 cm⁻¹. -1 These are characteristic peaks of sodium tripolyphosphate (STP).

[0076] Comparative Example 3: Non-magnetic single-layer essential oil microcapsules containing lavender essential oil at a depth of 1737.32 cm. -1 The characteristic peaks also contain characteristic peaks of quaternary ammonium salt chitosan and sodium tripolyphosphate, confirming that the microcapsules contain lavender essential oil;

[0077] Comparative Example 4: Linaloyl acetate in single-layer essential oil microcapsules at 1737.32 cm⁻¹ -1 The characteristic peak of C=O, and 569.39 cm⁻¹ -1 The stretching vibration of the Fe-O bond at 569.39 cm⁻¹ was observed, with the presence of iron(III) oxide at 569.39 cm⁻¹, compared to the non-magnetic monolayer essential oil microcapsules in Comparative Example 3. -1 The characteristic absorption peaks proved that lavender essential oil and iron oxide were encapsulated in microcapsules;

[0078] Compared with the single-layer essential oil microcapsules of Comparative Example 4, the bilayer essential oil microcapsules of Comparative Example 5 showed improvement at a depth of 966.35 cm⁻¹. -1 The newly appearing absorption peak at 794.15 cm⁻¹ confirms the presence of the Si-O bond. -1 and 475.95cm -1 The broad peak at that location is also a characteristic peak of silica, proving that silica is encapsulated on the microcapsule;

[0079] Example 1: The absorption peak of the three-layer essential oil microcapsules included the characteristic absorption peaks of silica and linalyl acetate, at 1069 cm⁻¹. -1 The stretching vibration peak of the CO bond on the quaternary ammonium salt was significantly stronger than that of the two-layer capsule, confirming the existence of the third quaternary ammonium salt chitosan wall layer.

[0080] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for preparing aromatic microcapsules with magnetic field-controlled microstructure, characterized in that, The method includes the following steps: (1) The core material emulsion and the first wall material / magnetizing agent solution are stirred and mixed, and then homogenized and emulsified under a high-speed shearing machine to obtain an oil-in-water emulsion; (2) Magnetic field induction is performed in an external magnetic field; (3) Add crosslinking agent solution and stir to perform crosslinking and curing of the first wall layer; (4) After drying, add the second wall material salt solution and stir to carry out electrostatic adsorption of the second wall layer; (5) After drying, add the first wall material solution and stir to carry out electrostatic adsorption of the third wall layer; In steps (1) and (5), the first wall material includes quaternary ammonium salt chitosan; In step (1), the magnetizing agent includes iron(II,III) oxide or γ-iron(II,III) oxide, and the mass fraction of the magnetizing agent is 0.1-1%. In step (2), the magnetic field strength is 300 mT and the induction time is 2-48 h; The second wall material in step (4) includes silicon dioxide; Salts include sodium chloride, potassium chloride, or sodium carbonate.

2. The method of claim 1, wherein the magnetic field is applied to the microcapsules in the form of a magnetic field gradient. In step (1), the core material includes essential oils, such as lavender essential oil, thyme essential oil, jasmine essential oil, rose essential oil, laurel essential oil, or violet essential oil, with a core material mass fraction of 0.5-6%. Emulsifiers include Tween 80, Tween 60, Tween 20, Span 80, or sodium dodecyl sulfate, with a mass fraction of 0.75-3%.

3. The method of claim 1, wherein the magnetic field is applied to the microcapsules in the form of a magnetic field gradient. In step (1), the mass fraction of the first wall material is 1.5-4.5%.

4. The method of claim 1, wherein the magnetic field is applied to the microcapsules in the form of a magnetic field gradient. In step (1), the mass ratio of the core material emulsion to the first wall material / magnetizing agent solution is 1:(1-3); The stirring rate is 500-1000 r / min, the temperature is 20-50 ℃, and the time is 60-240 min; The shearing rate was 10000-22000 r / min, the temperature was 15-30 ℃, and the time was 1-10 min.

5. The method of claim 1, wherein the magnetic field is applied to the microcapsules in the form of a magnetic field gradient. The induction temperature in step (2) is 0-60 ℃.

6. The method of claim 1, wherein the magnetic field is applied to the microcapsules in the form of a magnetic field gradient. In step (3), the crosslinking agent includes sodium tripolyphosphate or glutaraldehyde, and the mass fraction of the crosslinking agent is 1-5%. The mass ratio of core material emulsion to crosslinking agent solution is 1:(0.6-1.2); The stirring rate is 500-1000 r / min, the temperature is 20-50 ℃, and the time is 60-240 min.

7. The method of claim 1, wherein the magnetic field is applied to the microcapsules in the form of a magnetic field gradient. In step (4), the mass fraction of the second wall material is 2-5%; The salt content is 0.6-2% by mass.

8. The method of claim 1, wherein the magnetic field is applied to the microcapsules in the form of a magnetic field gradient. In step (4), the mass ratio of the core material emulsion to the second wall material salt solution is 1:(1.5-4); The stirring rate is 300-900 r / min, the temperature is 15-40 ℃, and the time is 30-120 min.

9. The method of claim 1, wherein the magnetic field is applied to the microcapsules in the form of a magnetic field gradient. In step (5), the mass fraction of the first wall material is 1.5-3%; The mass ratio of the core material emulsion to the first wall material solution is 1:(3-6); The stirring rate is 300-1200 r / min, the temperature is 15-40 ℃, and the time is 30-180 min.

10. A magnetic-field-regulated microshaped aromatic microcapsule prepared by the method of any one of claims 1 to 9, characterized in that, The microcapsule comprises the following components by weight percentage: core material 0.06-0.71%, emulsifier 0.09-0.36%, first wall material 1.25-2.5%, magnetizer 0.035-0.35%, crosslinking agent 0.07-0.35%, second wall material 0.43-1.07%, and salt 0.1-0.43%, with the balance being water.

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