Essential oil microcapsules, and methods and uses thereof

Abstract

This invention relates to the field of microcapsule preparation technology, specifically to an essential oil microcapsule, its preparation method, and its application. The preparation method includes the following steps: (1) dissolving a biodegradable polymer and a natural wax in an organic solvent to form a polymer solution and a wax solution, respectively; (2) mixing the polymer solution and the wax solution with an essential oil to obtain an oil phase solution; (3) dispersing the oil phase solution in an aqueous phase solution containing a protective colloid to obtain an oil-water dispersion system; (4) removing the organic solvent from the oil-water dispersion system by solvent evaporation, followed by solidification, separation, and drying to obtain the essential oil microcapsule. The shell of the essential oil microcapsule prepared by this invention is composed of a natural wax and a biodegradable polymer. The biodegradability of the shell achieves green environmental protection, while effectively improving the stability of the essential oil microcapsule in water-containing application systems such as daily chemical products. It can be widely used in daily chemical and related fields.

Description

Technical Field

[0001] This invention relates to the field of microcapsule preparation technology, specifically to an essential oil microcapsule, its preparation method, and its application. Background Technology

[0002] Essential oil microencapsulation technology encapsulates essential oils in wall materials, which can delay volatilization, improve stability, and achieve controlled release, and is widely used in daily chemical and related fields. Traditional wall materials mostly use non-degradable synthetic polymers (such as melamine-formaldehyde, urea-formaldehyde, polyurea, polyurethane, polyethylene, polypropylene, etc.), which can easily cause microplastic pollution.

[0003] Currently, research on the preparation of essential oil microcapsules with biodegradable wall materials mainly focuses on the following aspects: First, using methods such as complex coagulation and spray drying to prepare essential oil microcapsules with natural polymer materials such as gelatin, gum arabic, chitosan, β-cyclodextrin, protein, natural wax, starch and its derivatives as wall materials; second, using biodegradable synthetic polymers such as polylactic acid, polybutylene adipate / terephthalate, and ethyl cellulose to encapsulate essential oils to prepare essential oil microcapsules with biodegradable wall materials; and third, using inorganic wall materials such as silica and calcium carbonate to encapsulate essential oils to prepare essential oil microcapsules with inorganic wall materials. In addition, there is also work on preparing multi-shell and organic-inorganic composite wall materials for essential oil microcapsules based on the above methods. Natural wall materials and biodegradable synthetic polymer wall materials have solved the biodegradability problem of wall materials. However, natural wall materials are not water-resistant or have poor water resistance, and the water resistance of synthetic biodegradable wall materials also needs to be improved. Therefore, these wall materials are prone to gradual degradation in aqueous systems, especially in daily chemical products, leading to problems such as core material leakage due to erosion during storage. Although inorganic wall material fragrance oil microcapsules can solve the problem of microplastic pollution at the source, inorganic wall material microcapsules have poor practical application effects in daily chemical fields due to problems such as lack of shell toughness, relatively high density, and poor adsorption effect with application objects such as fabrics, ultimately preventing their comprehensive and efficient application.

[0004] Therefore, the preparation of essential oil microcapsules with biodegradable materials as wall materials, and the fact that these microcapsules have a certain degree of water solubility and can resist the degradation of the wall material in water-containing application systems such as daily chemical product matrices, is of great significance to the development of essential oil microcapsules in daily chemical and related fields. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a fragrance oil microcapsule, its preparation method, and its application. The shell of the fragrance oil microcapsule prepared by this invention is composed of natural wax and biodegradable polymer. The biodegradability of the shell achieves green and environmentally friendly properties, while effectively improving the stability of the fragrance oil microcapsule in water-containing application systems such as daily chemical products. It can be widely used in daily chemical and related fields.

[0006] This invention is achieved through the following technical solutions:

[0007] The first aspect of this invention relates to a method for preparing essential oil microcapsules, the method comprising the following steps:

[0008] (1) Dissolve the biodegradable polymer in organic solvent A and the natural wax in organic solvent B to form a polymer solution and a wax solution;

[0009] (2) The polymer solution, wax solution and essential oil are mixed to obtain a mixed oil phase solution;

[0010] (3) The mixed oil phase solution is dispersed in an aqueous phase solution containing a protective colloid to obtain an oil-water dispersion system;

[0011] (4) Organic solvent A and organic solvent B in the oil-water dispersion system are removed by solvent evaporation, and the system is solidified, washed, separated and dried to obtain the essential oil microcapsules; wherein the mass ratio of the natural wax to the biodegradable polymer in step (1) is 1:1-10.

[0012] Preferably, the biodegradable polymer in step (1) is selected from at least one of polylactic acid (PLA), polycaprolactone (PCL), polyhydroxyalkanoate (PHA), polybutylene adipate / terephthalate (PBAT), 3-hydroxybutyrate / valerate copolymer (PHBV), carbon dioxide copolymer (PPC), polybutylene succinate (PBS), starch-based polymers and cellulose derivatives.

[0013] Preferably, the natural wax in step (1) is selected from at least one of white beeswax, carnauba wax, candelilla wax, rice bran wax and soybean wax.

[0014] Preferably, the organic solvent A and organic solvent B in step (1) are independently selected from at least one of dichloromethane, chloroform, petroleum ether, n-hexane, toluene, ethyl acetate and acetone.

[0015] Preferably, the mass ratio of the degradable polymer to organic solvent A in step (1) is 1:1.8-3.5.

[0016] Preferably, the mass ratio of the natural wax to the organic solvent B in step (1) is 1:2.2-4.2.

[0017] Preferably, the essential oil mentioned in step (2) is a natural or synthetic essential oil, selected from at least one of rose essential oil, lily essential oil, lavender essential oil, cherry blossom essential oil, agarwood essential oil, artemisia essential oil, osmanthus essential oil, lemon essential oil, peppermint essential oil, chamomile essential oil, cinnamon essential oil, thyme essential oil and clove essential oil.

[0018] Preferably, the protective colloid in step (3) is selected from at least one of polyvinyl alcohol (PVA), sodium polyacrylamide acrylate, styrene maleic anhydride, gum arabic, gelatin, sodium alginate and sodium carboxymethyl cellulose (CMC-Na).

[0019] Preferably, the protective colloid in step (3) is 0.5 wt.%-5.0 wt.% of the water content of the dispersed phase.

[0020] Preferably, the mass ratio of the mixed oil phase solution to the aqueous phase solution in step (3) is 1:2.5-3.5.

[0021] Preferably, in the mixed oil phase solution, the mass fraction of the biodegradable polymer is 10%-30%, the mass fraction of the natural wax is 5%-20%, and the mass fraction of the essential oil is 10%-70%.

[0022] Preferably, the temperature of the solvent evaporation method in step (4) is 30-80℃ and the evaporation time is 1-6 hours.

[0023] Preferably, the particle size of the prepared microcapsules is 1-100 μm.

[0024] A second aspect of the present invention relates to an essential oil microcapsule, which is prepared according to the above-described preparation method.

[0025] A third aspect of the present invention relates to the application of the essential oil microcapsules prepared according to the above preparation method in the preparation of daily chemical products.

[0026] The beneficial effects of the present invention are: (1) The method of the present invention uses biodegradable polymers and natural waxes as composite shells to coat essential oils to form essential oil microcapsules, thereby achieving biodegradable properties of the essential oil microcapsule shell to solve the microplastic pollution problem caused by the non-biodegradable polymer shell of the essential oil microcapsule, and achieving green environmental protection; (2) The method of the present invention overcomes the erosion and degradation of the biodegradable polymer shell by the aqueous application system by introducing hydrophobic natural waxes, thereby improving the stability of the biodegradable wall material essential oil microcapsules in the aqueous application system; (3) The method of the present invention uses physical methods to prepare essential oil microcapsules, the corresponding preparation process is simple, there are many biodegradable polymers, natural waxes, essential oils and organic solvents that can be selected, and the preparation can be completed under low temperature conditions. Therefore, it is of great significance for essential oil core materials that are prone to chemical reactions and has broad application potential in daily chemical products and other related fields. Detailed Implementation

[0027] The present invention will be further described below with reference to specific embodiments, and the advantages and features of the present invention will become clearer as a result. However, these embodiments are merely exemplary and do not constitute any limitation on the scope of the present invention. Those skilled in the art should understand that modifications or substitutions can be made to the details and form of the technical solutions of the present invention without departing from the spirit and scope of the present invention, but all such modifications and substitutions fall within the protection scope of the present invention.

[0028] Example 1

[0029] A method for preparing rose essential oil microcapsules with a composite shell of PLA and natural beeswax, comprising the following steps:

[0030] (1) Preparation of oil phase solution: Weigh 5g of polylactic acid (PLA) with an average molecular weight of 120,000 and dissolve it in 10g of dichloromethane, and dissolve 3g of natural beeswax in 10g of petroleum ether to form their respective homogeneous solutions;

[0031] (2) Preparation of mixed oil phase: The above PLA solution and natural beeswax solution are mixed evenly, and then 10g of rose essential oil is added. The mixture is stirred and mixed evenly to obtain a mixed oil phase of PLA / natural beeswax / rose essential oil.

[0032] (3) Aqueous phase preparation and dispersion apparatus: 100g of 2.0wt% polyvinyl alcohol (PVA) aqueous solution was added to a 250mL three-necked flask (equipped with a mechanical stirrer and a water bath heating device);

[0033] (4) Formation of oil-water dispersion system: At room temperature (about 25°C) and a stirring rate of 500 rpm, the mixed oil phase obtained in step (2) is slowly added to the PVA aqueous phase in a three-necked flask and stirred for 15 minutes to form an oil-water dispersion system.

[0034] (5) Heating and evaporation curing: Set the water bath program: slowly heat to 55°C at a heating rate of 0.5°C / min and maintain at this temperature for 3 hours; then continue to heat to 60°C and maintain this temperature until the oil phase solvent (dichloromethane and petroleum ether) has fully evaporated;

[0035] (6) Post-processing: After the system is cooled to room temperature, the microcapsule product is collected by filtration. The obtained microcapsules are washed repeatedly with deionized water and anhydrous ethanol to remove residual polyvinyl alcohol (PVA) and unencapsulated essential oil, and finally rose essential oil microcapsules with a composite shell of PLA and natural beeswax are obtained.

[0036] Example 2

[0037] A method for preparing lily essential oil microcapsules with a composite shell of 3-hydroxybutyric acid / valerate copolymer and white beeswax, comprising the following steps:

[0038] (1) Preparation of oil phase solution: Weigh 20g of 3-hydroxybutyric acid / valerate copolymer (PHBV) with an average molecular weight of 50,000 and dissolve it in 30g of chloroform, and dissolve 10g of white beeswax in 30g of chloroform to form their respective homogeneous solutions;

[0039] (2) Preparation of mixed oil phase: The above PHBV solution and white beeswax solution were mixed evenly, and then 30g of lily essential oil was added. The mixture was stirred and mixed evenly to obtain a mixed oil phase of PHBV / white beeswax / lily essential oil.

[0040] (3) Aqueous phase preparation and dispersion apparatus: 400g of styrene maleic anhydride (SMA) aqueous solution with a mass fraction of 3.0wt% was added to a 1000 mL three-necked flask (equipped with a mechanical stirrer and a water bath heating device);

[0041] (4) Formation of oil-water dispersion system: At room temperature (about 25°C) and a stirring rate of 800 rpm, the mixed oil phase obtained in step (2) is slowly added to the SMA aqueous phase in a three-necked flask and stirred for 30 minutes to form an oil-water dispersion system.

[0042] (5) Heating and evaporation curing: Set the water bath program: slowly heat up to 58°C at a heating rate of 1°C / min and maintain at this temperature for 4 hours; then continue to heat up to 62°C and maintain this temperature for 1 hour until the oil phase solvent (chloroform) is fully evaporated;

[0043] (6) Post-processing: After the system is cooled to room temperature, the microcapsule product is collected by filtration. The obtained microcapsules are washed repeatedly with deionized water and anhydrous ethanol to remove residual styrene maleic anhydride and unencapsulated essential oil, and finally lily essential oil microcapsules with PHBV and white beeswax composite shell are obtained.

[0044] Example 3

[0045] A method for preparing agarwood essential oil microcapsules with a composite shell of poly(adipic acid / butylene terephthalate) and palm wax, comprising the following steps:

[0046] (1) Preparation of oil phase solution: Weigh 12g of polybutylene adipate / terephthalate (PBAT) with an average molecular weight of 80,000 and dissolve it in 24g of dichloromethane, and dissolve 6g of natural beeswax in 15g of n-hexane to form their respective homogeneous solutions;

[0047] (2) Preparation of mixed oil phase: The above PBAT solution and palm wax solution are mixed evenly, and then 8g of agarwood essential oil is added. The mixture is stirred and mixed evenly to obtain a mixed oil phase of PBAT / palm wax / agarwood essential oil.

[0048] (3) Aqueous phase preparation and dispersion apparatus: 180g of 3.0wt% sodium polyacrylamide aqueous solution was added to a 500mL three-necked flask (equipped with a mechanical stirrer and a water bath heating device);

[0049] (4) Formation of oil-water dispersion system: At room temperature (about 25°C) and a stirring rate of 200 rpm, the mixed oil phase obtained in step (2) is slowly added to the sodium polyacrylamide aqueous phase in a three-necked flask and stirred for 30 minutes to form an oil-water dispersion system.

[0050] (5) Heating and evaporation curing: Set the water bath program: slowly heat up to 38°C at a heating rate of 1.0°C / min and hold at this temperature for 2 hours; then continue to heat up to 65°C and hold at this temperature for 2 hours, and finally heat up to 70°C and hold at this temperature for 1 hour until the oil phase solvent (dichloromethane and n-hexane) has fully evaporated;

[0051] (6) Post-processing: After the system is cooled to room temperature, the microcapsule product is collected by filtration. The obtained microcapsules are washed repeatedly with deionized water and anhydrous ethanol to remove residual polyacrylamide sodium acrylate and unencapsulated essential oil, and finally agarwood essential oil microcapsules with PBAT and palm wax composite shell are obtained.

[0052] Example 4

[0053] A method for preparing agarwood essential oil microcapsules with a composite shell of ethyl cellulose and candelilla wax, comprising the following steps:

[0054] (1) Preparation of oil phase solutions: Weigh 5g of ethyl cellulose with an average molecular weight of 50,000 and dissolve it in 12g of dichloromethane, and dissolve 2g of candelilla wax in 8g of dichloromethane to form their respective homogeneous solutions;

[0055] (2) Preparation of mixed oil phase: The above ethyl cellulose solution and candelilla wax solution were mixed evenly, and then 5g of lavender essential oil was added. The mixture was stirred and mixed evenly to obtain a mixed oil phase of ethyl cellulose / candelilla wax / lavender essential oil.

[0056] (3) Aqueous phase preparation and dispersion apparatus: 80g of 0.5wt% gum arabic aqueous solution was added to a 150 mL three-necked flask (equipped with a mechanical stirrer and a water bath heating device);

[0057] (4) Formation of oil-water dispersion system: At room temperature (about 25°C) and a stirring rate of 200 rpm, the mixed oil phase obtained in step (2) is slowly added to the gum arabic aqueous solution in a three-necked flask and stirred for 30 minutes to form an oil-water dispersion system.

[0058] (5) Heating and evaporation curing: Set the water bath program: slowly heat to 35°C at a heating rate of 0.75°C / min and hold at this temperature for 3 hours; then continue to heat to 40°C and hold at this temperature for 2 hours until the oil phase solvent (dichloromethane) has fully evaporated;

[0059] (6) Post-processing: After the system is cooled to room temperature, the microcapsule product is collected by filtration. The obtained microcapsules are washed repeatedly with deionized water and anhydrous ethanol to remove residual gum arabic and unencapsulated essential oil, and finally agarwood essential oil microcapsules with a composite shell of ethyl cellulose and candelilla wax are obtained.

[0060] Example 5

[0061] A method for preparing cherry blossom essential oil microcapsules with a polycaprolactone / soybean wax composite shell, comprising the following steps:

[0062] (1) Preparation of oil phase solution: Weigh 30g of polycaprolactone with an average molecular weight of 100,000 and dissolve it in 100g of dichloromethane, and dissolve 12g of soybean wax in 30g of acetone to form their respective homogeneous solutions;

[0063] (2) Preparation of mixed oil phase: The above polycaprolactone solution and soybean wax solution were mixed evenly, and then 40g of cherry blossom essential oil was added. The mixture was stirred and mixed evenly to obtain a mixed oil phase of polycaprolactone / soybean wax / cherry blossom essential oil.

[0064] (3) Aqueous phase preparation and dispersion apparatus: 600g of 5.0wt% gelatin aqueous solution was added to a 1250 mL three-necked flask (equipped with a mechanical stirrer and a water bath heating device);

[0065] (4) Formation of oil-water dispersion system: At room temperature (about 25°C) and a stirring rate of 1500 rpm, the mixed oil phase obtained in step (2) is slowly added to the gelatin aqueous solution in a three-necked flask and stirred for 15 minutes to form an oil-water dispersion system.

[0066] (5) Heating and evaporation curing: Set the water bath program: slowly heat to 35°C at a heating rate of 1.0°C / min and hold at this temperature for 2 hours; then continue to heat to 55°C and hold at this temperature for 2 hours until the oil phase solvent (dichloromethane and acetone) has fully evaporated;

[0067] (6) Post-processing: After the system is cooled to room temperature, the microcapsule product is collected by filtration. The obtained microcapsules are washed repeatedly with deionized water and anhydrous ethanol to remove residual gelatin and unencapsulated essential oil, and finally cherry blossom essential oil microcapsules with polycaprolactone / soybean wax composite shell are obtained.

[0068] Comparative Example 1:

[0069] A method for preparing rose essential oil microcapsules with a PLA shell, comprising the following steps:

[0070] (1) Preparation of oil phase solution: Weigh 8g of polylactic acid (PLA) with an average molecular weight of 120,000 and dissolve it in 20g of dichloromethane to obtain PLA solution;

[0071] (2) Preparation of mixed oil phase: Add 10g of rose essential oil to the above PLA solution and continue to stir and mix evenly to obtain a mixed oil phase of PLA / rose essential oil;

[0072] (3) Aqueous phase preparation and dispersion apparatus: 100g of 2.0wt% polyvinyl alcohol (PVA) aqueous solution was added to a 250mL three-necked flask (equipped with a mechanical stirrer and a water bath heating device);

[0073] (4) Formation of oil-water dispersion system: At room temperature (about 25°C) and a stirring rate of 500 rpm, the mixed oil phase obtained in step (2) is slowly added to the PVA aqueous phase in a three-necked flask and stirred for 15 minutes to form an oil-water dispersion system.

[0074] (5) Heating and evaporation curing: Set the water bath program: slowly heat to 55°C at a heating rate of 0.5°C / min and maintain at this temperature for 3 hours; then continue to heat to 60°C and maintain this temperature until the oil phase solvent dichloromethane is fully evaporated;

[0075] (6) Post-processing: After the system is cooled to room temperature, the microcapsule product is collected by filtration. The obtained microcapsules are washed repeatedly with deionized water and anhydrous ethanol to remove residual polyvinyl alcohol (PVA) and unencapsulated essential oil, and finally rose essential oil microcapsules with PLA shell are obtained.

[0076] The difference from Example 1 is that the microcapsule shell does not contain natural wax, and its mass is added to the biodegradable polymer polylactic acid. Everything else is the same as in Example 1.

[0077] Comparative Example 2:

[0078] A method for preparing rose essential oil microcapsules with a natural beeswax shell, comprising the following steps:

[0079] (1) Preparation of oil phase solution: Weigh 8g of natural beeswax and dissolve it in 20g of petroleum ether to form a natural beeswax solution;

[0080] (2) Preparation of mixed oil phase: Add 10g of rose essential oil to the natural beeswax solution and continue to stir and mix evenly to obtain a mixed oil phase of natural beeswax / rose essential oil;

[0081] (3) Aqueous phase preparation and dispersion apparatus: 100g of 2.0wt% polyvinyl alcohol (PVA) aqueous solution was added to a 250mL three-necked flask (equipped with a mechanical stirrer and a water bath heating device);

[0082] (4) Formation of oil-water dispersion system: At room temperature (about 25°C) and a stirring rate of 500 rpm, the mixed oil phase obtained in step (2) is slowly added to the PVA aqueous phase in a three-necked flask and stirred for 15 minutes to form an oil-water dispersion system.

[0083] (5) Heating and evaporation curing: Set the water bath program: slowly heat to 55°C at a heating rate of 0.5°C / min and maintain at this temperature for 3 hours; then continue to heat to 60°C and maintain this temperature until the oil phase solvent (dichloromethane and petroleum ether) has fully evaporated;

[0084] (6) Post-processing: After the system is cooled to room temperature, the microcapsule product is collected by filtration. The obtained microcapsules are washed repeatedly with deionized water and anhydrous ethanol to remove residual polyvinyl alcohol (PVA) and unencapsulated essential oil, and finally rose essential oil microcapsules with natural beeswax shell are obtained.

[0085] The difference from Example 1 is that the microcapsule shell material does not contain the biodegradable polymer polylactic acid, and its mass is added to the natural wax. Everything else is the same as in Example 1.

[0086] Comparative Example 3:

[0087] A method for preparing rose essential oil microcapsules with a polystyrene and natural beeswax composite shell, comprising the following steps:

[0088] (1) Preparation of oil phase solution: Weigh 5g of polystyrene with an average molecular weight of 120,000 and dissolve it in 10g of dichloromethane, and dissolve 3g of natural beeswax in 10g of petroleum ether to form their respective homogeneous solutions;

[0089] (2) Preparation of mixed oil phase: The above polystyrene solution and natural beeswax solution are mixed evenly, and then 10g of rose essential oil is added. The mixture is stirred and mixed evenly to obtain a mixed oil phase of polystyrene / natural beeswax / rose essential oil.

[0090] (3) Aqueous phase preparation and dispersion apparatus: 100g of 2.0wt% polyvinyl alcohol (PVA) aqueous solution was added to a 250mL three-necked flask (equipped with a mechanical stirrer and a water bath heating device);

[0091] (4) Formation of oil-water dispersion system: At room temperature (about 25°C) and a stirring rate of 500 rpm, the mixed oil phase obtained in step (2) is slowly added to the PVA aqueous phase in a three-necked flask and stirred for 15 minutes to form an oil-water dispersion system.

[0092] (5) Heating and evaporation curing: Set the water bath program: slowly heat to 55°C at a heating rate of 0.5°C / min and maintain at this temperature for 3 hours; then continue to heat to 60°C and maintain this temperature until the oil phase solvent (dichloromethane and petroleum ether) has fully evaporated;

[0093] (6) Post-processing: After the system is cooled to room temperature, the microcapsule product is collected by filtration. The obtained microcapsules are washed repeatedly with deionized water and anhydrous ethanol to remove residual polyvinyl alcohol (PVA) and unencapsulated essential oil, and finally rose essential oil microcapsules with polystyrene and natural beeswax composite shell are obtained.

[0094] The difference from Example 1 is that the polymer in the microcapsule shell is polystyrene. Everything else is the same as in Example 1.

[0095] Comparative Example 4:

[0096] A method for preparing rose essential oil microcapsules with a composite shell of PLA and natural beeswax, comprising the following steps:

[0097] (1) Preparation of oil phase solutions: Weigh 7.3g of polylactic acid (PLA) with an average molecular weight of 120,000 and dissolve it in 17.5g of dichloromethane, and dissolve 0.7g of natural beeswax in 2.5g of petroleum ether to form their respective homogeneous solutions;

[0098] (2) Preparation of mixed oil phase: The above PLA solution and natural beeswax solution are mixed evenly, and then 10g of rose essential oil is added. The mixture is stirred and mixed evenly to obtain a mixed oil phase of PLA / natural beeswax / rose essential oil.

[0099] (3) Aqueous phase preparation and dispersion apparatus: 100g of 2.0wt% polyvinyl alcohol (PVA) aqueous solution was added to a 250mL three-necked flask (equipped with a mechanical stirrer and a water bath heating device);

[0100] (4) Formation of oil-water dispersion system: At room temperature (about 25°C) and a stirring rate of 500 rpm, the mixed oil phase obtained in step (2) is slowly added to the PVA aqueous phase in a three-necked flask and stirred for 15 minutes to form an oil-water dispersion system.

[0101] (5) Heating and evaporation curing: Set the water bath program: slowly heat to 55°C at a heating rate of 0.5°C / min and maintain at this temperature for 3 hours; then continue to heat to 60°C and maintain this temperature until the oil phase solvent (dichloromethane and petroleum ether) has fully evaporated;

[0102] (6) Post-processing: After the system is cooled to room temperature, the microcapsule product is collected by filtration. The obtained microcapsules are washed repeatedly with deionized water and anhydrous ethanol to remove residual polyvinyl alcohol (PVA) and unencapsulated essential oil, and finally rose essential oil microcapsules with a composite shell of PLA and natural beeswax are obtained.

[0103] The difference from Example 1 is that the mass ratio of natural wax to biodegradable polymer in the wall material is changed. In this comparative example, the natural wax is 0.7g and the biodegradable polymer is 7.3g. The rest is the same as in Example 1.

[0104] Comparative Example 5:

[0105] A method for preparing rose essential oil microcapsules with a composite shell of PLA and natural beeswax, comprising the following steps:

[0106] (1) Preparation of oil phase solution: Weigh 3g of polylactic acid (PLA) with an average molecular weight of 120,000 and dissolve it in 6g of dichloromethane, and dissolve 5g of natural beeswax in 14g of petroleum ether to form their respective homogeneous solutions;

[0107] (2) Preparation of mixed oil phase: The above PLA solution and natural beeswax solution are mixed evenly, and then 10g of rose essential oil is added. The mixture is stirred and mixed evenly to obtain a mixed oil phase of PLA / natural beeswax / rose essential oil.

[0108] (3) Aqueous phase preparation and dispersion apparatus: 100g of 2.0wt% polyvinyl alcohol (PVA) aqueous solution was added to a 250mL three-necked flask (equipped with a mechanical stirrer and a water bath heating device);

[0109] (4) Formation of oil-water dispersion system: At room temperature (about 25°C) and a stirring rate of 500 rpm, the mixed oil phase obtained in step (2) is slowly added to the PVA aqueous phase in a three-necked flask and stirred for 15 minutes to form an oil-water dispersion system.

[0110] (5) Heating and evaporation curing: Set the water bath program: slowly heat to 55°C at a heating rate of 0.5°C / min and maintain at this temperature for 3 hours; then continue to heat to 60°C and maintain this temperature until the oil phase solvent (dichloromethane and petroleum ether) has fully evaporated;

[0111] (6) Post-processing: After the system is cooled to room temperature, the microcapsule product is collected by filtration. The obtained microcapsules are washed repeatedly with deionized water and anhydrous ethanol to remove residual polyvinyl alcohol (PVA) and unencapsulated essential oil, and finally rose essential oil microcapsules with a composite shell of PLA and natural beeswax are obtained.

[0112] The difference from Example 1 is that the mass ratio of natural wax to biodegradable polymer in the wall material is changed. In this comparative example, the natural wax is 5g and the biodegradable polymer is 3g. The rest is the same as in Example 1.

[0113] Experiment Example 1: Stability Experiment of Microcapsules

[0114] First, the encapsulation efficiency of the prepared microcapsules was measured using a UV spectrophotometer. A certain amount of dried essential oil microcapsules were weighed and immersed in a certain amount of ethanol-water solution. The microcapsules in the ethanol were then broken up using a cell disruptor, and the solution was filtered to obtain an ethanol solution containing essential oil. Simultaneously, a series of standard solutions of different concentrations were prepared using the essential oil components from the microcapsules. The absorbance values ​​corresponding to different concentrations of essential oil were measured using a UV spectrophotometer, and a standard curve was obtained by plotting the concentration and absorbance data. Next, the content of essential oil dissolved in ethanol was obtained using the standard curve, and finally, the encapsulation efficiency of the essential oil microcapsules was calculated based on the content.

[0115] Then, the essential oil microcapsules were added to the laundry detergent matrix to prepare a suspension containing 0.5% essential oil microcapsules, which was stored for 30 days. The stability of the microcapsules in the laundry detergent matrix was observed periodically. After sampling, the surface of the microcapsule samples was washed with water to remove the adhering laundry detergent matrix, and then the microcapsules were dried. Finally, the retention rate of the essential oil in the laundry detergent matrix containing the essential oil microcapsules was measured using the aforementioned ultraviolet spectrophotometer.

[0116] The experimental results are shown in Table 1.

[0117] Table 1: Stability test results of microcapsules in various examples and comparative examples

[0118]

[0119] Conclusion: The above experiments show that using a composite of biodegradable polymers and natural waxes to prepare the shell of essential oil microcapsules can achieve an encapsulation efficiency of >90%, and the fragrance retention efficiency remains as high as 80% after soaking in laundry detergent matrix for 30 days. For microcapsules using only biodegradable polymers or waxes as the shell, the encapsulation efficiency is either low, or the fragrance retention efficiency is poor after soaking in daily chemical matrix for 30 days. Furthermore, when the wax content exceeds the given range or the microcapsule shell material does not contain biodegradable polymers, the microcapsules exhibit severe adhesion, making them unsuitable for microcapsule product production. While microcapsules using a composite shell of non-biodegradable polymers and waxes can achieve an encapsulation efficiency of >90% and a fragrance retention efficiency of >80% after soaking in daily chemical matrix for 30 days, the non-biodegradable polymers cause plastic pollution, making them unsuitable for microcapsule product production as well.

[0120] Experimental Example 2: Shell Material Degradation Performance Test

[0121] The degradation data of microcapsules under different conditions were determined using micromanipulation techniques. By analyzing and calculating the data of microcapsules under different conditions, the degradation performance of microcapsules was finally determined.

[0122] Microcapsules were weighed to a specific mass and then immersed in a laundry detergent matrix solution. Samples were collected periodically to study the degradation behavior of the microcapsules. The degradation behavior of the microcapsules was measured using a micromanipulation platform (MF-WSF1, Kunming, China). The diameter of each particle was determined using images from an optical microscope. Suitable particles were selected and compressed by applying force through a probe to obtain force-displacement curves. For each sample, at least 35 particles were uniformly selected within a particle size range of 20–60 μm. The hardness of the microcapsules was then calculated using the force-displacement curves.

[0123] The hardness (H) of the microcapsules can be obtained from the slope of the linear plastic region of the force-displacement curve, which indicates the hardness deviation from the Hertzian characteristics. H is calculated using the following formula:

[0124]

[0125] Where F is the applied force, δ is the displacement, and R is the diameter.

[0126] Based on the measured hardness data of the microparticles, the degradation rate of the microparticles is determined by the following formula:

[0127]

[0128] The experimental results are shown in Table 2.

[0129] Table 2: Experimental results of shell degradation performance of microcapsules in various examples and comparative examples

[0130]

[0131] Conclusion: The above experiments show that, compared to microcapsules using only biodegradable polymers as the shell, microcapsules prepared by combining biodegradable polymers and natural waxes can effectively resist the degradation of the detergent matrix, improving the stability of the microcapsules in the detergent matrix. Compared to microcapsules using only natural waxes as the shell, the addition of biodegradable polymers can solve the adhesion problem of microcapsules, which is beneficial to the development of microcapsule products. Furthermore, when the ratio of biodegradable polymers to waxes as the shell is not appropriate, the microcapsules either degrade too quickly or adhere severely, which is not conducive to the preparation of microcapsule products. Regarding microcapsules using non-biodegradable polymers and waxes as the composite shell, although the shell can effectively resist the degradation of the detergent matrix, the non-biodegradable polymers cause plastic pollution and are therefore unsuitable for the production of microcapsule products.

[0132] The above detailed description is a specific description of one of the feasible embodiments of the present invention. This embodiment is not intended to limit the patent scope of the present invention. All equivalent implementations or modifications that do not depart from the present invention should be included within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a microcapsule of an essential oil, characterized in that, The preparation method comprises the following steps: (1) Dissolve the biodegradable polymer in organic solvent A and the natural wax in organic solvent B to form a polymer solution and a wax solution; (2) The polymer solution, wax solution and essential oil are mixed to obtain a mixed oil phase solution; (3) The mixed oil phase solution is dispersed in an aqueous phase solution containing a protective colloid to obtain an oil-water dispersion system; (4) Organic solvent A and organic solvent B in the oil-water dispersion system are removed by solvent evaporation, followed by solidification, washing, separation and drying to obtain the essential oil microcapsules; in The mass ratio of the natural wax to the biodegradable polymer in step (1) is 2-3:5; the biodegradable polymer in step (1) is selected from at least one of polylactic acid, polycaprolactone, polybutylene adipate / terephthalate, 3-hydroxybutyric acid / valerate copolymer, carbon dioxide copolymer, polybutylene succinate, starch-based polymer and cellulose derivative; the natural wax in step (1) is selected from at least one of beeswax, carnauba wax, candelilla wax, rice bran wax and soybean wax; the mass ratio of the biodegradable polymer to organic solvent A in step (1) is 1:1.8-3.5; the mass ratio of the natural wax to organic solvent B is 1:2.2-4.2; In the mixed oil phase solution, the mass fraction of biodegradable polymer is 10%-30%, the mass fraction of natural wax is 5%-20%, and the mass fraction of essential oil is 10%-70%. The essential oil is selected from at least one of the following: rose essential oil, lily essential oil, lavender essential oil, agarwood essential oil, artemisia essential oil, osmanthus essential oil, lemon essential oil, peppermint essential oil, chamomile essential oil, cinnamon essential oil, thyme essential oil, and clove essential oil.

2. The production method according to claim 1, characterized by, The organic solvent A and organic solvent B mentioned in step (1) are independently selected from at least one of dichloromethane, chloroform, petroleum ether, n-hexane, toluene, ethyl acetate and acetone.

3. The preparation method according to claim 1, characterized in that, The protective colloid in step (3) is selected from at least one of polyvinyl alcohol, sodium polyacrylamide acrylate, styrene maleic anhydride, gum arabic, gelatin, sodium alginate and sodium carboxymethyl cellulose, and the mass fraction of the protective colloid in the aqueous solution is 0.5 wt.%-5.0 wt.%; the mass ratio of the mixed oil phase solution to the aqueous phase solution in step (3) is 1:2.5-3.

5.

4. The preparation method according to claim 1, characterized in that, The temperature for solvent evaporation in step (4) is 30-80℃, and the evaporation time is 1-6 hours.

5. A microcapsule of an essential oil, characterized in that, The essential oil microcapsules are prepared by the preparation method according to any one of claims 1-4, and the particle size of the microcapsules is 1-100 μm.

6. The use of a fragrance oil microcapsule prepared by the preparation method according to any one of claims 1-4 or the fragrance oil microcapsule according to claim 5 in the preparation of daily chemical products.

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