Fragrance microcapsules based on SiO2-MOF wall material and their preparation method

Abstract

This invention discloses a fragrance microcapsule based on SiO2-MOF wall material and its preparation method, comprising the following steps: mixing the target fragrance oil, tetraethyl orthosilicate, and modified silane to form an oil phase; mixing an emulsifier, a protective colloid, and deionized water to form an aqueous phase; adding the oil phase to the aqueous phase for emulsification to form an O / W type emulsion; adjusting the pH to react and form a SiO2 shell; adding the reaction system to a zinc-based MOF seed suspension and stirring to react and form SiO2-MOF wall material fragrance microcapsules. This invention achieves a hybrid composite of silica and zinc-based MOF, unifying mechanical strength, programmable release, intelligent responsiveness, and complete biodegradability in an alcohol-free fragrance system. It overcomes the problems of "high performance-environmental protection" contradictions, pump blockage risks, and insufficient release control capabilities in existing technologies, achieving significant technological progress.

Description

Technical Field

[0001] This invention relates to the field of perfume preparation technology, specifically to a fragrance microcapsule based on SiO2-MOF wall material and its preparation method. Background Technology

[0002] In perfumes, alcohol stabilizes the properties of fragrance oils and dilutes their concentration, allowing perfumers to better control the scent, making it the ideal solvent. However, some people are allergic to alcohol, and its use presents drawbacks in terms of sensory stimulation and environmental friendliness in formulations. Therefore, researchers are working to develop new alcohol-free perfume technologies; this innovation, which also offers skincare benefits, may foreshadow the future of the perfume market. Common approaches to avoiding alcohol in perfumes involve maintaining pure essential oils or using other solubilizers, typically dissolving the fragrance in a water-based solvent. Water-based perfumes often suffer from weak scents, short-lasting fragrances, and monotonous aromas, limiting the amount of essential oils and the overall aesthetic appeal.

[0003] Meanwhile, fragrances are typically composed of volatile organic compounds, which are prone to volatilization and loss during storage and use, leading to problems such as short fragrance duration and insufficient aroma intensity. To solve this technical challenge, microencapsulation technology can be used to encapsulate fragrances in tiny containers, thereby controlling the release rate of the fragrance and extending the fragrance duration.

[0004] Existing flavor microencapsulation technologies can be mainly categorized as follows:

[0005] Organic polymer wall material microcapsules include gelatin, polyurethane, and melamine resin. Polyurethane microcapsules, prepared via interfacial polymerization, react petroleum-based polyols (such as polytetramethylene ether glycol and polyethylene glycol) with isocyanates to form wall materials, exhibiting good mechanical strength and encapsulation efficiency. However, these wall materials have inherent drawbacks: firstly, petroleum-based polyurethanes are difficult to degrade in the natural environment, with a biodegradation rate of less than 5% after 28 days, classifying them as typical environmentally durable microplastics and posing environmental problems; secondly, natural polymer wall materials such as gelatin lack sufficient mechanical strength, causing microcapsules to easily deform and adhere, leading to nozzle clogging in pumping applications.

[0006] Pure silica microcapsules: Research has disclosed a silica capsule encapsulating functional ingredients, using an alkoxysilane precursor to form the silica shell via a sol-gel method, which can be used to encapsulate fragrances and other ingredients. Other research has disclosed a controlled-release fragrance using porous nano-hollow silica as a carrier, storing fragrance molecules in the hollow structure and mesoporous channels of silica through physical adsorption, achieving a sustained-release effect. However, pure silica wall materials have the following problems: First, their excessively high mechanical strength (bursting strength can reach over 105 MPa) leads to high brittleness of the microcapsules, easily causing fragmentation and clogging of the pump head under pumping shear forces; second, the release regulation dimension is singular, relying solely on pore diffusion to control the release rate, with a 24-hour cumulative release rate of only about 40%, which cannot meet the needs of perfume products for immediate fragrance bursts and layered release; third, pure silica has a relatively low encapsulation rate for fragrances and lacks responsiveness to external stimuli (such as pH and temperature).

[0007] Metal-Organic Framework (MOF) wall microcapsules: Metal-organic frameworks are crystalline porous materials formed by the self-assembly of metal ions and organic ligands through coordination bonds. They possess ultra-high specific surface area, precisely tunable pore structure, and environmental responsiveness, and have attracted widespread attention in recent years for applications such as gas storage and drug delivery. Studies have shown that MOFs can be used to encapsulate natural active substances; for example, ZIF-8 can achieve an encapsulation efficiency of up to 92% for curcumin, enabling sustained release in aqueous solution for 14-21 days. However, pure MOF wall materials suffer from insufficient structural stability.

[0008] In summary, the existing technology lacks a microcapsule wall material solution that can simultaneously achieve excellent pumpability, programmable release behavior, good skin compatibility, and complete biodegradability in alcohol-free fragrance systems. Summary of the Invention

[0009] This invention addresses the shortcomings of existing technologies by providing a fragrance microcapsule based on SiO2-MOF wall material and its preparation method. By hybridizing silica (SiO2) and zinc-based metal-organic frameworks (MOFs), a unified mechanical strength, programmable release, intelligent responsiveness, and complete biodegradability are achieved in an alcohol-free fragrance system. This overcomes the problems of "high performance-environmental protection" contradiction, pump blockage risk, and insufficient release regulation capability in existing technologies, and represents a significant technological advancement.

[0010] To address the aforementioned technical problems, the first aspect of this invention provides a method for preparing flavor microcapsules based on SiO2-MOF wall material, comprising the following steps:

[0011] S1. Mix the target essential oil, tetraethyl orthosilicate (TEOS), and modified silane to form an oil phase;

[0012] S2. Mix the emulsifier, protective colloid, and deionized water to form an aqueous phase;

[0013] S3. Under high-speed shear conditions, the oil phase is added to the aqueous phase to emulsify and form an O / W type emulsion; the pH is adjusted to acidic and hydrolysis reaction is carried out, and then the pH is adjusted to alkaline. Tetraethyl orthosilicate and modified silane condense at the oil-water interface to form a SiO2 shell.

[0014] S4. Add the reaction system from step S3 to the zinc-based MOF seed suspension and stir to react. The zinc-based MOF crystals grow in situ on the surface and pores of the SiO2 shell to form SiO2-MOF wall material fragrance microcapsules.

[0015] This invention provides high-strength support (rupture strength up to 82.5 MPa) through a silica framework, ensuring that the microcapsules maintain their integrity and do not deform or break under pumping shear forces. Simultaneously, the introduction of zinc-based MOF components moderately adjusts the wall material's toughness, giving it just the right amount of brittleness while maintaining sufficient strength. This avoids the risk of brittle fragment blockage caused by overly hard pure silica wall materials, and also overcomes the problem of early deformation and adhesion caused by overly soft pure MOF wall materials. By optimizing the component ratio parameters, the microcapsule particle size is precisely controlled within 10-20 micrometers (far smaller than the minimum channel diameter of a standard perfume pump head), enabling 100 consecutive pumping cycles without clogging. This removes the technical obstacles for microcapsule perfumes to move from the laboratory to commercial applications.

[0016] This invention achieves complete biodegradability, completely eliminating the risk of microplastic pollution. In stark contrast to traditional wall materials such as petroleum-based polyurethane (with a 28-day degradation rate of <5%), the silica-zinc-based MOF hybrid wall material of this invention is completely biodegradable in the natural environment: the silica framework hydrolyzes into non-toxic silicic acid, and the zinc-based MOF dissociates into zinc ions (an essential trace element for the human body) and 2-methylimidazole (which can be further mineralized by microorganisms into carbon dioxide and water), achieving a 28-day biodegradation rate of 72.6%. All degradation products are environmentally compatible substances, lacking the physical form and chemical toxicity of microplastics, and do not accumulate in organisms. This allows perfume products to meet consumers' demands for long-lasting fragrance while completely eliminating the need for microplastic manufacturing.

[0017] This invention optimizes skin compatibility and safety by specifically selecting zinc-based MOF. Zinc is a trace element required for skin care and has excellent biocompatibility. At the same time, the silica shell further avoids direct contact between the MOF and the skin, ensuring the safety of the product for human use.

[0018] Furthermore, in S1, the modified silane is selected from one or more of methyltrimethoxysilane (MTMS), methyltriethoxysilane (MTES), and phenyltrimethoxysilane (PTMS).

[0019] Furthermore, in S1, the target essential oil, tetraethyl orthosilicate, and modified silane are present in parts by mass of 5-15 parts, 3-8 parts, and 0.2-1.5 parts, respectively.

[0020] Furthermore, in S2, the emulsifier is selected from one or more of Tween-80, polyvinyl alcohol (PVA), OP-10 (polyoxyethylene octylphenol ether-10), sodium dodecyl sulfate (SDS), and hexadecyltrimethylammonium bromide (CTAB).

[0021] And / or, the protective colloid is selected from one or more of polyvinyl alcohol, polyvinylpyrrolidone (PVP), and gelatin.

[0022] Furthermore, in S2, the mass fractions of the emulsifier, protective colloid, and deionized water are 0.5-3.0 parts, 0.2-1.5 parts, and 70-90 parts, respectively.

[0023] Furthermore, in S3, the rotation speed of the high-speed shearing is 5000-15000 rpm; the pH value of the acid is 2.0-4.5; the temperature of the hydrolysis reaction is 30-50℃; and the pH value of the alkaline reaction is 7.5-10.

[0024] Furthermore, in S4, the temperature of the stirring reaction is 40-60°C.

[0025] Further, in S4, the zinc-based MOF is selected from one or more of ZIF-8, ZIF-7, and MOF-5, preferably ZIF-8. The ZIF-8 seed suspension is prepared by reacting 0.1-1.0 parts by weight of a zinc source and 0.3-1.5 parts by weight of an organic ligand dissolved in methanol solvent, and then dissolved in formaldehyde; the zinc source is selected from one or more of zinc nitrate hexahydrate, zinc acetate dihydrate, and zinc chloride; the organic ligand is selected from one or more of 2-methylimidazole, benzimidazole, and terephthalic acid.

[0026] Furthermore, the zinc-based MOF content in the wall material of the SiO2-MOF wall material fragrance microcapsules is 5-30% by mass.

[0027] The second aspect of the present invention provides fragrance microcapsules of SiO2-MOF wall material prepared by the preparation method described in the first aspect.

[0028] A third aspect of the present invention provides an alcohol-free fragrance composition comprising fragrance microcapsules of the SiO2-MOF wall material described in the second aspect.

[0029] A fourth aspect of the present invention provides a method for preparing the alcohol-free perfume composition described in the third aspect, comprising the following steps:

[0030] (1) Mix the humectant with deionized water to form a homogeneous solution, add a rheology modifier and adjust the pH to 7-8 to obtain an aqueous carrier;

[0031] (2) Disperse the fragrance microcapsules of the SiO2-MOF wall material described in the second aspect in the aqueous carrier to obtain the alcohol-free perfume composition.

[0032] This invention constructs a dual release mechanism of "friction triggering + pH response," achieving intelligent controlled release of fragrance. Unlike existing pure silica wall materials that rely solely on physical diffusion for release, this invention introduces zinc-based MOFs to impart pH-responsive properties to the wall material. Specifically, the pH of the aqueous carrier is adjusted to 7.0-8.0 (neutral to weakly alkaline), creating a difference from the acidic pH (4.5-6.5) of human skin. Utilizing the stability of zinc-based MOFs under neutral conditions and the breaking of coordination bonds under acidic conditions, intelligent release with "stable storage and accelerated use" is achieved. Upon skin application, friction triggers the wall material to break, resulting in an immediate fragrance burst; subsequently, the weakly acidic environment of the skin triggers partial disintegration of the ZIF-8 structure or opening of pores, accelerating the continuous release of fragrance. The synergistic effect of the dual mechanisms results in a 24-hour cumulative release rate of 78.5%, significantly superior to the 41.2% of pure silica wall materials.

[0033] This invention achieves a unified approach to mechanical strength, programmable release, intelligent responsiveness, and complete biodegradability for the first time in an alcohol-free fragrance system through a hybrid design of silica and zinc-based MOF. It overcomes the problems of "high performance-environmental protection" contradiction, pump blockage risk, and insufficient release control capability in existing technologies, and has achieved significant technological progress.

[0034] Furthermore, the humectant is selected from one or more of glycerin, butylene glycol, propylene glycol, 1,3-butanediol, sorbitol, sodium hyaluronate, and polyethylene glycol; the rheology modifier is selected from one or more of xanthan gum, sodium carboxymethyl cellulose, carbomer, hydroxyethyl cellulose, guar gum, or gellan gum.

[0035] Furthermore, the mass ratio of the humectant, deionized water, rheology modifier, and fragrance microcapsules is (2-8):(85-95):(0.2-1.5):(0.5-3.0).

[0036] The beneficial effects of this invention are:

[0037] This invention provides high-strength support through a SiO2 framework, ensuring that the microcapsules maintain their integrity and do not deform or rupture under pumping shear forces. Simultaneously, the introduction of zinc-based MOF components moderately adjusts the wall material's toughness, giving it just the right amount of brittleness while maintaining sufficient strength. By optimizing the component ratio and interfacial polymerization process, the particle size is controlled to be much smaller than the pump head's minimum aperture (≥100µm) and uniform in size, physically eliminating the possibility of clogging. Furthermore, xanthan gum forms a weak three-dimensional network structure in the aqueous phase, providing sufficient yield stress to suspend the microcapsules and prevent sedimentation when stationary, and shear thinning during pumping to ensure fluidity. These three elements work synergistically to achieve stable pumping of the perfume.

[0038] This invention constructs a dual synergistic release mechanism: the mechanical strength of the microcapsule wall material ensures its stability under pumping shear force, while frictional breakage occurs under normal skin application force, achieving immediate release; the zinc-based MOF component in the wall material is pH-responsive, undergoing protonation in the weakly acidic environment of the skin (pH approximately 5.5), leading to partial disintegration of the MOF structure or opening of pores, further accelerating the sustained release of fragrance. This dual mechanism of "friction-activated, pH-accelerated" ensures both an immediate burst of fragrance upon application and subsequent sustained release, and the release rate can be programmed by adjusting the MOF content and SiO2 shell thickness.

[0039] The degradation mechanism of the SiO2-zinc-based MOF hybrid wall material of this invention is based on a synergistic "hierarchical hydrolysis-coordination dissociation" process involving two components. In the natural environment, water first penetrates into the hybrid structure, contacts the amorphous SiO2 framework, and initiates the hydrolysis reaction of its surface silanol groups, generating soluble silica monomers. This process causes the SiO2 network to gradually dissolve and release the embedded MOF nanocrystals. The exposed MOF crystals then interact with water molecules and weakly acidic media in the environment, and their coordination bonds break under hydrolysis. This hierarchical degradation mechanism of "first framework hydrolysis, then ligand dissociation" avoids the slow degradation of single SiO2 wall materials and overcomes the problems of unstable structure and uncontrollable degradation of pure MOF wall materials. Ultimately, it achieves more than 70% complete biodegradation within 28 days, and the degradation products are all environmentally friendly substances. This solves the potential environmental accumulation problems caused by traditional petroleum-based polymer wall materials or some cosmetic ingredients, and is in line with the trend of green cosmetics. Attached Figure Description

[0040] To more clearly illustrate the technical solution of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1Here is a SEM image of the microcapsules obtained in Example 1 of this invention;

[0042] Figure 2 Here is a SEM image of the microcapsules obtained in Comparative Example 1 of this invention;

[0043] Figure 3 Here is a SEM image of the microcapsules obtained in Comparative Example 2 of the present invention;

[0044] Figure 4 This is a SEM image of the microcapsules obtained in Comparative Example 3 of the present invention. Detailed Implementation

[0045] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] Example 1

[0047] This embodiment relates to a method for preparing fragrance microcapsules based on SiO2-ZIF-8 wall material, including the following steps:

[0048] 1. Microcapsule preparation:

[0049] (1) Preparation of ZIF-8 seed suspension: 0.3 parts by weight of zinc nitrate hexahydrate and 0.7 parts by weight of 2-methylimidazole (Hmim) were dissolved in 8 parts by weight of methanol respectively. After mixing, the mixture was allowed to stand at room temperature for 24 hours. After centrifugation, the supernatant was discarded. The precipitate was washed with methanol 2-3 times and dried under vacuum at 40°C for 12 hours to obtain ZIF-8 nano-seed powder. 0.5 parts by weight of ZIF-8 nano-seed powder was weighed and dispersed in 8 parts by weight of formaldehyde. The mixture was ultrasonically treated for 15 minutes to obtain a uniform ZIF-8 seed suspension.

[0050] (2) Preparation of oil phase: Weigh 8.0 parts by weight of the target essential oil, 4.5 parts by weight of tetraethyl orthosilicate (TEOS) and 0.5 parts by weight of methyltrimethoxysilane (MTMS), stir and mix until homogeneous and transparent to form oil phase.

[0051] (3) Preparation of aqueous phase: Dissolve 1.5 parts by weight of Tween-80 and 0.5 parts by weight of polyvinyl alcohol (PVA) in 83.5 parts by weight of deionized water and stir until completely dissolved to form an aqueous phase.

[0052] (4) Emulsification and Sol-Gel Shell Formation: Under high-speed shearing conditions of 10,000 rpm, the oil phase prepared in step (2) was slowly added to the aqueous phase prepared in step (3), and emulsification was continued for 5 minutes to form a stable O / W type emulsion. The emulsion was transferred to a reaction vessel, and the pH was adjusted to 4.0 with dilute hydrochloric acid. The reaction was carried out at 40°C for 2 hours. Subsequently, the pH was adjusted to 8.0 with ammonia water to promote the condensation of TEOS and MTMS at the oil-water interface to form a silica primary shell. The reaction was continued with stirring for 1 hour.

[0053] (5) In-situ growth of ZIF-8: The above ZIF-8 seed suspension was slowly added dropwise to the reaction system of step (4), and the reaction was continued to be stirred at 50°C for 12 hours, so that ZIF-8 crystals grew in situ on the surface and pores of the silica shell to form silica-ZIF-8 hybrid wall material microcapsules.

[0054] (6) Post-processing: After the reaction is completed, the system is cooled to room temperature, the microcapsules are collected by centrifugation, washed three times with deionized water and ethanol alternately, and dried under vacuum at 40°C to obtain SiO2-ZIF-8 hybrid wall material fragrance microcapsule powder.

[0055] 2. Preparation and bottling of alcohol-free perfumes:

[0056] (1) Preparation of aqueous carrier: 91.2wt% deionized water, 5wt% glycerol, 3wt% butanediol, 0.8wt% xanthan gum (xanthan gum was dispersed in water and dissolved evenly in advance), stir until completely hydrated and uniform, and then adjust the pH to 7.5 with citric acid.

[0057] (2) Adding microcapsules: The SiO2-ZIF-8 hybrid wall material fragrance microcapsule powder prepared in step 1 is slowly added to the above-mentioned aqueous carrier at a mass ratio of 2.0% of the total system under low-speed stirring, and the mixture is continuously homogenized until it is evenly dispersed to obtain alcohol-free microcapsule perfume.

[0058] (3) Filling: The prepared microcapsule perfume is placed on a magnetic stirrer and slowly stirred to maintain uniformity, and then vacuum filtered through a 45μm nylon filter membrane. The filtered perfume is filled into sterilized glass perfume bottles, with a filling capacity of 50.0mL per bottle. The commercial perfume pump head is installed and tightened immediately after filling.

[0059] Comparative Example 1

[0060] The comparative example uses pure silica wall material. The specific steps are different from those in Example 1: steps (1) and (5) in step 1 are omitted, while other steps and parameters remain unchanged.

[0061] Comparative Example 2

[0062] This comparative example uses pure ZIF-8 wall material, and the specific steps are as follows:

[0063] (1) Preparation of ZIF-8 precursor solution: 0.3 parts by weight of zinc nitrate hexahydrate and 0.7 parts by weight of 2-methylimidazole were dissolved in 8 parts by weight of methanol.

[0064] (2) Emulsification of fragrance: 8.0 parts by weight of the target fragrance oil and 1.5 parts by weight of Tween-80 are added to 100 parts by weight of deionized water and emulsified at 10,000 rpm to form an O / W emulsion.

[0065] (3) Direct coating of ZIF-8: The emulsion in step (2) is mixed with the ZIF-8 precursor solution and stirred at 50°C for 12 hours to allow ZIF-8 to directly nucleate and grow on the surface of the essential oil droplets to form a shell.

[0066] (4) Post-processing: Same as step 1 (6) in Example 1, to obtain pure ZIF-8-encapsulated flavor microcapsules.

[0067] (5) The preparation and filling of alcohol-free perfume are the same as step 2 in Example 1.

[0068] Comparative Example 3

[0069] This comparative example uses polyurethane wall material, and the specific steps are as follows:

[0070] (1) Preparation of the oil phase: Weigh 5.0 parts by weight of polyethylene glycol-2000 (PEG-2000) (petroleum-based polyether polyol, hydroxyl value of about 56 mg KOH / g, molecular weight 2000) and 0.5 parts by weight of 1,4-butanediol (as a chain extender), and dissolve them in 20.0 parts by weight of the target essential oil. Since PEG has strong hydrophilicity, in order to ensure its full dissolution in the oil phase, heat to 45°C and stir until completely dissolved to form a homogeneous and transparent oil phase.

[0071] (2) Preparation of aqueous phase: Dissolve 2.0 parts by weight of polyether siloxane emulsifier and 1.5 parts by weight of polyvinyl alcohol (PVA) in 200 parts by weight of deionized water and stir until completely dissolved to form an aqueous phase.

[0072] (3) Emulsification and interfacial polymerization: Under stirring at 3000 rpm, the oil phase prepared in step (1) was slowly added to the aqueous phase prepared in step (2), and emulsification was continued for 5 minutes to form a stable O / W type emulsion. The emulsion was transferred to a constant temperature reactor at 25°C, and 1.8 parts by weight of water-dispersible isocyanate (a hydrophilic modifier based on toluene diisocyanate TDI) was slowly added dropwise. The reaction was carried out under gentle stirring for 5 hours to allow PEG-2000 and isocyanate to polymerize at the oil-water interface to form a polyurethane wall material with PEG as the soft segment.

[0073] (4) Post-processing: After the reaction is complete, the emulsion is filtered through a 200-mesh sieve to remove any possible large particle aggregates. The microcapsule suspension is washed three times with deionized water to remove unreacted monomers and emulsifiers, yielding a wet cake of PEG-type petroleum-based polyurethane wall material fragrance microcapsules (solid content approximately 30%).

[0074] (5) The preparation and filling of alcohol-free perfume are the same as step 2 in Example 1.

[0075] Test case

[0076] 1. Mechanical property testing: Assessment of wall material strength and fracture resistance

[0077] The perfumes obtained in the examples and comparative examples were dropped onto a clean silicon wafer or glass slide and dried to form a monolayer film. Individual microcapsules were compressed using a nanoindenter, and force-displacement curves were recorded. The critical force (F) at which the microcapsule ruptured was read from the curve and divided by the microcapsule diameter (D) to obtain the rupture force per unit diameter (RFD, N / mm), which serves as a key indicator for evaluating mechanical strength.

[0078] 2. Pumping test: Simulating actual use and assessing blockages.

[0079] The microcapsule perfume samples prepared for the examples and comparative examples were pressed against the pump head with a constant force and frequency (1 time / second) for 50-100 consecutive cycles. Throughout the process, the smoothness of liquid dispensing, the uniformity of atomization, and the presence of any blockages or significant pressure increases were observed and recorded. After the test, the pump head was disassembled and inspected for any particulate matter deposits inside.

[0080] 3. Aroma release test: quantitative and sensory evaluation

[0081] Quantitative release analysis was performed using gas chromatography-mass spectrometry: a quantitative amount of microcapsule perfume was sprayed onto a skin-like material. At set time points (0, 1, 4, 8, and 24 hours after application), the coated area was subjected to standardized rubbing (using a rubbing head with a fixed weight). The released fragrance was immediately captured using a thermal desorption tube, and then qualitative and quantitative analysis was performed using GC-MS to obtain the release rate and cumulative release curves.

[0082] Human sensory evaluation: Equal amounts of microcapsule perfume samples from the examples and comparative examples were sprayed onto a fixed area on the inner forearm of volunteers. Trained evaluators evaluated the fragrance intensity, characteristics, and persistence at preset time points (2, 4, 8, and 24 hours) under blind testing conditions.

[0083] 4. Biodegradability test: Verifying environmental friendliness

[0084] The microcapsules prepared in the examples and comparative examples were purified and used for testing according to the following steps: the microcapsules were dispersed in petroleum ether, sonicated for 15 minutes, centrifuged and the supernatant was discarded; this was repeated 3 times until the supernatant was colorless and odorless, washed 3 times each with ethanol and deionized water to remove water-soluble impurities, and dried under vacuum at 40°C to constant weight.

[0085] The test was conducted according to ISO 17556:2012, "Determination of final aerobic biodegradability of plastic materials in soil". 100 mg of purified sample was weighed and mixed with 300 g of standard farmland soil, then placed in a 500 mL sealed culture bottle and incubated at 25 ± 2 °C in the dark for 28 days. The released CO2 was absorbed with 0.1 M NaOH solution, and the CO2 release was determined periodically by titration. Three replicates were set up for each sample, and a blank soil control group was also included.

[0086] After degradation, soil leachate was analyzed by ICP-MS (to detect Zn). 2+ The release rate and plant growth inhibition assays (OECD 208) were used to assess the eco-safety of the degradation products.

[0087] Table 1 shows the results of mechanical property tests, pumping tests, aroma release tests, and biodegradability tests for the examples and comparative samples.

[0088] Table 1

[0089]

[0090] As shown in Table 1, the microcapsules obtained in Example 1 have good mechanical properties, pumpability, aroma release and biodegradability.

[0091] Comparative Example 1 used pure silica as the wall material without introducing ZIF-8. Experimental results showed that the burst strength of the microcapsules made of pure SiO2 wall material reached 105.3 MPa, significantly higher than the 82.5 MPa of Example 1. This excessively high mechanical strength caused the microcapsules to become clogged after approximately 70 pumping cycles, due to the wall material's excessive hardness and brittleness, making it prone to fragmentation under shear force. Simultaneously, its 24-hour cumulative release rate was only 41.2%, far lower than the 78.5% of Example 1, indicating that the pure SiO2 wall material had excessively strong barrier properties to fragrance, resulting in slow aroma release and a poor user experience. Therefore, the introduction of ZIF-8 is necessary to regulate the mechanical properties of the wall material and optimize its release behavior.

[0092] Comparative Example 2 used only ZIF-8 as the wall material, without constructing a silica framework. Experimental results showed that its tensile strength was only 42.8 MPa, indicating that the wall material was too soft, leading to severe clogging after approximately 40 pumping cycles. Simultaneously, the 24-hour release rate was as high as 89.7%, exhibiting a significant "burst release" phenomenon, making long-term sustained release impossible. Therefore, constructing a silica framework is essential for maintaining the integrity of the microcapsule structure, achieving high encapsulation efficiency, and controlling release.

[0093] Comparative Example 3 used a traditional polyurethane interfacial polymerization method to prepare microcapsules, representing existing technology for petroleum-based non-degradable wall materials. Experimental results showed that within a 28-day testing period, the biodegradation rate of Example 1 reached 72.6%, significantly higher than the less than 5% of the petroleum-based polyurethane wall material in Comparative Example 3. ICP-MS analysis of the soil extract after degradation showed that the zinc ion release concentration was below 5 ppm, meeting the requirements of cosmetic safety technical specifications; plant growth inhibition tests showed that the degradation products had no significant effect on the germination rate of wheat seeds. These data confirm that the hybrid wall material of this invention can be completely degraded into non-toxic products in the natural environment after use and disposal, completely eliminating the risk of microplastic pollution.

[0094] Figure 1 The image shows the SEM image of the microcapsules obtained in Example 1. It can be seen that the microcapsules are spherical and regular, with uniform crystals embedded on the surface. The average particle size is 18.5±2.1μm and the encapsulation efficiency is 92.3±3.5%. Figure 2 The image shows the SEM image of the microcapsules obtained in Comparative Example 1. The microcapsules are spherical and regular with smooth surfaces, and the average particle size is 16.8±1.9μm with an encapsulation efficiency of 88.7±4.2%. Figure 3 The image shows the SEM image of the microcapsules obtained in Comparative Example 2. It can be seen that the pure ZIF-8 wall material microcapsules have irregular morphology, severe aggregation, and extremely wide particle size distribution (up to 35.6 μm, with a distribution range of ±8.4 μm). The encapsulation efficiency is only 54.6 ± 12.8%, which is much lower than that in Example 1. Figure 4 The image shows a SEM image of the microcapsules obtained in Comparative Example 3. It can be seen that the polyurethane wall material is comparable to that of Example 1 in terms of microcapsule morphology, particle size distribution, and encapsulation efficiency, indicating that Example 1 has reached the level of traditional mature materials in terms of application performance.

[0095] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

Claims

1. A method for preparing a flavor microcapsule based on a SiO2-MOF wall material, characterized by, Includes the following steps: S1. Mix the target essential oil, tetraethyl orthosilicate, and modified silane to form an oil phase; S2. Mix the emulsifier, protective colloid, and deionized water to form an aqueous phase; S3. Under high-speed shear conditions, the oil phase is added to the aqueous phase to emulsify and form an O / W type emulsion; the pH is adjusted to acidic and hydrolysis reaction is carried out, and then the pH is adjusted to alkaline. Tetraethyl orthosilicate and modified silane condense at the oil-water interface to form a SiO2 shell. S4. Add the reaction system from step S3 to the zinc-based MOF seed suspension and stir to react. The zinc-based MOF crystals grow in situ on the surface and pores of the SiO2 shell to form SiO2-MOF wall material fragrance microcapsules.

2. The method for preparing a fragrance microcapsule based on a SiO2-MOF wall material according to claim 1, characterized by, In S1, the modified silane is selected from one or more of methyltrimethoxysilane, methyltriethoxysilane, and phenyltrimethoxysilane.

3. The method for preparing flavor microcapsules based on SiO2-MOF wall material as described in claim 1, characterized in that, In S2, the emulsifier is selected from one or more of Tween 80, polyvinyl alcohol, OP-10, sodium dodecyl sulfate, and hexadecyltrimethylammonium bromide; And / or, the protective colloid is selected from one or more of polyvinyl alcohol, polyvinylpyrrolidone, and gelatin.

4. The method for preparing fragrance microcapsules based on SiO2-MOF wall material as described in claim 1, characterized in that, In S3, the rotation speed of the high-speed shearing is 5000-15000 rpm; the pH value of the acid is 2.0-4.5, and the pH value of the alkaline is 7.5-10.

5. The method for preparing fragrance microcapsules based on SiO2-MOF wall material as described in claim 1, characterized in that, In S4, the temperature of the stirring reaction is 40-60℃.

6. A fragrance microcapsule of SiO2-MOF wall material prepared by the preparation method according to any one of claims 1-5.

7. An alcohol-free perfume composition, characterized in that, Fragrance microcapsules including the SiO2-MOF wall material as described in claim 6.

8. A method for preparing the alcohol-free perfume composition according to claim 7, characterized in that, Includes the following steps: (1) Mix the humectant with deionized water to form a homogeneous solution, add a rheology modifier and adjust the pH to 7-8 to obtain an aqueous carrier; (2) Disperse the fragrance microcapsules of the SiO2-MOF wall material according to claim 6 in the aqueous carrier to obtain the alcohol-free perfume composition.

9. The method for preparing the alcohol-free perfume composition as described in claim 8, characterized in that, The humectant is selected from one or more of glycerin, butylene glycol, propylene glycol, 1,3-butanediol, sorbitol, sodium hyaluronate, and polyethylene glycol; the rheology modifier is selected from one or more of xanthan gum, sodium carboxymethyl cellulose, carbomer, hydroxyethyl cellulose, guar gum, or gellan gum.

10. The method for preparing the alcohol-free perfume composition according to claim 8, characterized in that, The mass ratio of the humectant, deionized water, rheology modifier, and fragrance microcapsules is (2-8):(85-95):(0.2-1.5):(0.5-3.0).

Images