Long-lasting antimicrobial essential oil microcapsules, methods of making and use in detergents

Abstract

The application belongs to the technical field of daily chemicals, and particularly relates to long-acting antibacterial essential oil microcapsules, a preparation method thereof and application of the long-acting antibacterial essential oil microcapsules in detergents. The preparation method of the long-acting antibacterial essential oil microcapsules comprises the following steps: (1) dissolving polylactic acid in dichloromethane to obtain a polylactic acid dichloromethane solution, dispersing essential oil in water, adding a surfactant, and uniformly mixing to obtain an essential oil mixture; (2) mixing the essential oil mixture and the polylactic acid dichloromethane solution, and stirring until uniformly emulsified to obtain an emulsion; the essential oil is prepared by crushing and mixing Artemisia argyi and piper methysticum leaves, and then fermenting and extracting by a microwave extraction method; and (3) mixing the emulsion with a polyvinyl alcohol aqueous solution and an isopropyl alcohol aqueous solution, heating and stirring, allowing the organic solvent to volatilize completely, and separating out a solid product to obtain the long-acting antibacterial essential oil microcapsules. The antibacterial essential oil microcapsules prepared by the application have high initial antibacterial property, good slow-release effect and long-acting antibacterial property.

Description

Technical Field

[0001] This invention belongs to the field of daily chemical technology, specifically relating to a long-acting antibacterial essential oil microcapsule, its preparation method, and its application in detergents. Background Technology

[0002] With the improvement of people's living standards and the enhancement of health awareness, household detergents are no longer satisfied with basic stain removal functions. Consumers have placed higher demands on their antibacterial, bacteriostatic, and long-lasting hygiene protection capabilities. Adding antibacterial ingredients to laundry detergents, fabric softeners, and other detergents to give textiles antibacterial properties after washing has become an important development direction in the industry. Natural plant essential oils are gradually becoming ideal alternatives to chemical antibacterial agents. However, essential oils generally suffer from high volatility, poor water solubility, sensitivity to light and heat, and easy oxidation and degradation, which seriously restricts their practical application in detergents and daily personal care products. To solve these problems, using microencapsulation technology to encapsulate essential oils in polymer shells to form antibacterial microcapsules is currently the mainstream research direction.

[0003] Chinese Patent CN 115554940 B describes an antibacterial microcapsule, its preparation method, and its application. The method involves: (1) adding an antibacterial agent to water, then adding a surfactant to obtain an antibacterial agent mixture; (2) adding the antibacterial agent mixture to a polylactic acid solution and mixing thoroughly to obtain an emulsion; (3) mixing the emulsion with a polyvinyl alcohol aqueous solution and an isopropanol aqueous solution, stirring, removing the organic solvent, and separating the solid to obtain the antibacterial microcapsule. However, the antibacterial microcapsules prepared by this method have an antibacterial activity of less than 95%, and their long-lasting antibacterial effect needs improvement. Summary of the Invention

[0004] The purpose of this invention is to provide a long-acting antibacterial essential oil microcapsule, its preparation method, and its application in detergents. The antibacterial essential oil microcapsule prepared by this invention has high initial antibacterial activity, good sustained-release effect, and long-lasting antibacterial properties.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for preparing long-acting antibacterial essential oil microcapsules includes the following steps:

[0007] (1) Dissolve polylactic acid in dichloromethane to obtain polylactic acid dichloromethane solution, add essential oil to water, add surfactant, mix evenly to obtain essential oil mixture; The essential oil is obtained by crushing artemisia leaves and pheasant leaves separately, mixing them for fermentation, and then extracting by microwave method;

[0008] (2) Mix the essential oil mixture and polylactic acid dichloromethane solution and stir until uniform emulsification to obtain an emulsion;

[0009] (3) Mix the emulsion with polyvinyl alcohol aqueous solution and isopropanol aqueous solution, heat the mixture to evaporate the organic solvent, separate the solid product, and obtain long-acting antibacterial essential oil microcapsules.

[0010] Preferably, the method for preparing the essential oil includes the following steps:

[0011] (1) Dry the mugwort leaves and the leaves of the mountain pepper separately and pulverize them; mix the dried mugwort leaves and the leaves of the mountain pepper to obtain a mixed powder;

[0012] (2) Add water, glucose and peptone to the mixed powder, adjust the pH value, sterilize and cool to obtain fermentation material; add compound bacteria to fermentation material, fermentation, sterilize after fermentation to obtain fermentation product, concentrate fermentation product to obtain material to be microwave extracted;

[0013] (3) Transfer the material to be microwave extracted to a solvent-free microwave extraction bottle, perform microwave extraction, cool to room temperature after extraction, let stand, remove the oil layer, dry and dehydrate to obtain essential oil.

[0014] Artemisia argyi is a common raw material for antibacterial essential oils, but the initial antibacterial effects of essential oils made from Artemisia argyi or other common raw materials on the market are not ideal. This invention, by compounding Artemisia argyi and Litsea cubeba leaves in a specific mass ratio, utilizes a complex of *Lactobacillus plantarum* and *Lactobacillus rhamnosus* for anaerobic fermentation, and then combines this with solvent-free microwave extraction technology to prepare the essential oil, significantly enhancing its antibacterial activity. An unexpected discovery was made that the essential oil prepared through this specific fermentation and microwave extraction process exhibits excellent compatibility with polylactic acid (PLA) wall materials. The two materials have good interfacial compatibility, which can significantly improve the encapsulation efficiency and structural stability of microcapsules, contributing to long-lasting antibacterial effects.

[0015] Preferably, the polylactic acid comprises polylactic acid A, polylactic acid B, and polylactic acid C in a mass ratio of 1:(1.2-1.4):(0.3-0.5): the molecular weight Mn of polylactic acid A is 4500-5500 Da; the molecular weight Mn of polylactic acid B is 6500-7400 Da; and the molecular weight Mn of polylactic acid C is 9000-10000 Da.

[0016] Existing technologies often use polylactic acid (PLA) as a single wall material, which presents the problem of difficulty in controlling release behavior. This invention uses a blend of three PLAs with different molecular weight ranges as the wall material. The low molecular weight component ensures good dispersion and rapid shell formation, the medium molecular weight component provides skeletal support, and the high molecular weight component increases the density of the wall material and delays release. The three components work synergistically to achieve a balance between efficient initial encapsulation and long-term sustained release. After 50 standard washes, it still maintains an excellent antibacterial rate, which is significantly better than single or equal-proportion PLA wall materials.

[0017] This invention uses three polylactic acids with different molecular weight ranges in a specific mass ratio as microcapsule wall materials, which significantly improves the encapsulation efficiency and release behavior of microcapsules for essential oil core materials.

[0018] Preferably, dried mugwort leaves and Sichuan pepper leaves are mixed in a mass ratio of 1:(0.4-0.6).

[0019] Preferably, the compound bacteria are added to the fermentation material, and the amount of compound bacteria is (3-5) × 10. 9 CFU / mL fermentation material.

[0020] Preferred fermentation conditions: anaerobic fermentation at 35-37℃ for 24-28 hours.

[0021] Preferably, the compound bacteria include *Lactobacillus plantarum* and *Lactobacillus rhamnosus* with a live bacteria ratio of 1:(0.5-0.7).

[0022] Preferably, the microwave extraction conditions are: power set to 200-300W, microwave extraction for 1-2 hours.

[0023] The long-acting antibacterial essential oil microcapsules prepared by the method described above.

[0024] The application of the long-acting antibacterial essential oil microcapsules prepared by the aforementioned method in the preparation of detergents.

[0025] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows:

[0026] 1. This invention combines Artemisia argyi leaves and Litsea cubeba leaves in a specific mass ratio, uses a complex of Lactobacillus plantarum and Lactobacillus rhamnosus for anaerobic fermentation, and then combines solvent-free microwave extraction technology to prepare essential oils, which significantly enhances the antibacterial activity of the essential oils.

[0027] 2. This invention discovers that essential oils prepared through specific fermentation and microwave extraction processes have excellent compatibility with polylactic acid wall materials. There is good interfacial compatibility between the two, which can significantly improve the encapsulation efficiency and structural stability of microcapsules, and help to achieve long-lasting antibacterial effects.

[0028] 3. This invention uses three polylactic acid compounds with different molecular weight ranges as wall materials. The low molecular weight component ensures good dispersion and rapid shell formation, the medium molecular weight component provides skeletal support, and the high molecular weight component increases the density of the wall material and delays release. The three work together to achieve a balance between efficient initial encapsulation and long-term sustained release, and still maintains excellent antibacterial rate after 50 standard washes. Detailed Implementation

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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.

[0030] All raw materials used in the following embodiments of the present invention are commercially available products:

[0031] Lactobacillus plantarum: strain number: CICC 24810; Lactobacillus rhamnosus: strain number: CICC 22173, both from the China Industrial Microbial Culture Collection Center.

[0032] Example 1

[0033] This embodiment provides a long-acting antibacterial essential oil microcapsule, the preparation method of which includes the following steps:

[0034] (1) Polylactic acid includes polylactic acid A, polylactic acid B and polylactic acid C in a mass ratio of 1:1.3:0.4: The molecular weight Mn of polylactic acid A is 4500-5500 Da; the molecular weight Mn of polylactic acid B is 6500-7400 Da; the molecular weight Mn of polylactic acid C is 9000-10000 Da; polylactic acid is dissolved in dichloromethane to obtain a polylactic acid dichloromethane solution, and the mass fraction of polylactic acid in the polylactic acid dichloromethane solution is 9.5%; essential oil is dispersed in water, surfactant is added, and mixed evenly to obtain an essential oil mixture; the mass ratio of essential oil, water and surfactant is 0.43:10:0.24; the surfactant is composed of disodium cocoyl ethanolamide sulfosuccinate monoester and n-octyl glucoside in a mass ratio of 1:2.

[0035] (2) Mix the essential oil mixture and the polylactic acid dichloromethane solution, and stir until homogeneous emulsification to obtain an emulsion. The mass ratio of the essential oil mixture to the polylactic acid dichloromethane solution is 1.5:1;

[0036] (3) The emulsion was mixed with a 4.5 wt% aqueous solution of polyvinyl alcohol (PVA-1788, the same below) and a 5.5 wt% aqueous solution of isopropanol. The mass ratio of the emulsion, the polyvinyl alcohol aqueous solution and the isopropanol aqueous solution was 1:7:0.6. The mixture was heated slowly to 55°C to allow the dichloromethane to evaporate completely, and the solid product was separated to obtain long-acting antibacterial essential oil microcapsules.

[0037] The method for preparing the essential oil includes the following steps:

[0038] (1) Dry the mugwort leaves and the leaves of the mountain pepper to a moisture content of about 3wt%, and pulverize them to a particle size of less than 100 mesh; mix the mugwort leaves and the leaves of the mountain pepper in a mass ratio of 1:0.5 to obtain a mixed powder;

[0039] (2) Add 6 times the mass of water to the mixed powder, add 2% glucose and 1.0% peptone by mass of the mixed powder, stir evenly, adjust the pH to 6.5, sterilize, cool, and obtain the fermentation material; add the compound bacteria to the fermentation material, the amount of compound bacteria is 4×10 9 The CFU / mL fermentation material was anaerobically fermented at 37℃ for 25 hours (in a closed container). After fermentation, the material was sterilized to obtain the fermentation product. The product was then concentrated to a water content of 70 wt% to obtain the material to be microwaved. The compound bacteria included Lactobacillus plantarum and Lactobacillus rhamnosus with a live bacteria ratio of 1:0.6.

[0040] (3) Transfer the material to be microwave extracted to a solvent-free microwave extraction bottle, set the power to 200W, microwave extract for 1.2h, raise the system temperature from room temperature to 60℃ within 10min, cool to room temperature after completion, let stand for 60min, remove the oil layer, dry the oil layer with Na2SO4 to obtain essential oil.

[0041] Example 2

[0042] This embodiment provides a long-acting antibacterial essential oil microcapsule, the preparation method of which includes the following steps:

[0043] (1) Polylactic acid includes polylactic acid A, polylactic acid B and polylactic acid C in a mass ratio of 1:1.2:0.4: The molecular weight Mn of polylactic acid A is 4500-5500 Da; the molecular weight Mn of polylactic acid B is 6500-7400 Da; the molecular weight Mn of polylactic acid C is 9000-10000 Da; polylactic acid is dissolved in dichloromethane to obtain a polylactic acid dichloromethane solution, and the mass fraction of polylactic acid in the polylactic acid dichloromethane solution is 9.8%; essential oil is dispersed in water, surfactant is added, and mixed evenly to obtain an essential oil mixture; the mass ratio of essential oil, water and surfactant is 0.43:10:0.24; the surfactant is composed of disodium cocoyl ethanolamide sulfosuccinate monoester and n-octyl glucoside in a mass ratio of 1:2.

[0044] (2) Mix the essential oil mixture and the polylactic acid dichloromethane solution, and stir until homogeneous emulsification to obtain an emulsion. The mass ratio of the essential oil mixture to the polylactic acid dichloromethane solution is 1.5:1;

[0045] (3) The emulsion was mixed with a 4.5 wt% aqueous solution of polyvinyl alcohol (PVA-1788) and a 5.5 wt% aqueous solution of isopropanol, with a mass ratio of 1:7:0.6. The mixture was heated slowly to 55°C to allow the dichloromethane to evaporate completely, and the solid product was separated to obtain long-acting antibacterial essential oil microcapsules.

[0046] The method for preparing the essential oil includes the following steps:

[0047] (1) Dry the mugwort leaves and the leaves of the mountain pepper to a moisture content of about 3wt%, and pulverize them to a particle size of less than 100 mesh; mix the mugwort leaves and the leaves of the mountain pepper in a mass ratio of 1:0.4 to obtain a mixed powder;

[0048] (2) Add 6 times the mass of water to the mixed powder, add 2% glucose and 1.0% peptone by mass of the mixed powder, stir evenly, adjust the pH to 6.5, sterilize, cool, and obtain the fermentation material; add the compound bacteria to the fermentation material, the amount of compound bacteria is 4×10 9 The CFU / mL fermentation material was anaerobically fermented at 37℃ for 24 hours (in a closed container). After fermentation, the material was sterilized to obtain the fermentation product. The product was then concentrated to a water content of 70wt% to obtain the material to be microwave extracted. The compound bacteria included Lactobacillus plantarum and Lactobacillus rhamnosus with a live bacteria ratio of 1:0.7.

[0049] (3) Transfer the material to be microwave extracted to a solvent-free microwave extraction bottle, set the power to 200W, microwave extract for 1.2h, raise the system temperature from room temperature to 60℃ within 10min, cool to room temperature after completion, let stand for 60min, remove the oil layer, dry the oil layer with Na2SO4 to obtain essential oil.

[0050] Comparative Example 1

[0051] The difference between this comparative example and Example 1 is that the polylactic acid includes polylactic acid A and polylactic acid B in a mass ratio of 1:1.2: the molecular weight Mn of polylactic acid A is 4500-5500 Da; the molecular weight Mn of polylactic acid B is 6500-7400 Da.

[0052] Comparative Example 2

[0053] The difference between this comparative example and Example 1 is that the polylactic acid includes polylactic acid A, polylactic acid B and polylactic acid C in a mass ratio of 1:1:1: The molecular weight Mn of polylactic acid A is 4500-5500 Da; the molecular weight Mn of polylactic acid B is 6500-7400 Da; and the molecular weight Mn of polylactic acid C is 9000-10000 Da.

[0054] Comparative Example 3

[0055] The difference between this comparative example and Example 1 is that the preparation method of the essential oil includes the following steps:

[0056] (1) Dry the mugwort leaves and the leaves of the mountain pepper to a moisture content of 3wt%, and pulverize them to less than 100 mesh; mix the mugwort leaves and the leaves of the mountain pepper in a mass ratio of 1:0.5 to obtain a mixed powder;

[0057] (2) Add 6 times the mass of water to the mixed powder, add 2% glucose and 1.0% peptone by mass of the mixed powder, stir evenly, adjust the pH to 6.5, sterilize, cool, and obtain the fermentation material; add the compound bacteria to the fermentation material, the amount of compound bacteria is 4×10 9 The CFU / mL fermentation material was anaerobic fermented at 37℃ for 25 hours. After fermentation, the material was sterilized to obtain the fermentation product, which was then concentrated and spray-dried to obtain the material to be critically extracted. The compound bacteria included Lactobacillus plantarum and Lactobacillus rhamnosus with a live bacteria ratio of 1:0.6.

[0058] (3) The material to be extracted was placed in a supercritical CO2 extractor and extracted for 2.5 h with petroleum ether as the carrier under the conditions of pressure of 20 MPa, temperature of 50 °C and flow rate of 20 L / h. The flow rate of the carrier was controlled at 0.05 mL / min. The extract was transferred to a separation vessel and the separation pressure was controlled at 4 MPa and the separation temperature at 50 °C. The separation was carried out under reduced pressure. After the system was depressurized to atmospheric pressure, the oily product in the separation vessel was collected to obtain the essential oil.

[0059] Comparative Example 4

[0060] The difference between this comparative example and Example 1 is that the weight ratio of mugwort leaves and pheasant leaves is 1:1.

[0061] Comparative Example 5

[0062] The difference between this comparative example and Example 1 is that the leaves of the wild chrysanthemum are replaced with those of the wild chrysanthemum.

[0063] Comparative Example 6

[0064] The difference between this comparative example and Example 1 is that the compound bacteria includes *Lactobacillus plantarum* and *Lactobacillus rhamnosus* strains with a live bacteria ratio of 1:1.

[0065] Performance testing

[0066] 1. Initial antibacterial activity: The long-acting antibacterial essential oil microcapsules of Examples 1-2 and Comparative Examples 1-6 were added to water at a weight percentage of 1% and dispersed evenly; then pure cotton fabric was completely immersed in the solution for 2 minutes, and then removed and rolled with rollers to achieve a liquid-squeezing rate of 90%. The fabric was then baked at 90°C for 3 minutes and then at 150°C for 3 minutes. After baking, the antibacterial effect of the pure cotton fabric against Escherichia coli and Staphylococcus aureus was tested according to GB / T20944.3-2008.

[0067] 2. Long-lasting antibacterial test: After drying, the fabric was washed 20 times according to the standard procedure for household washing and drying (GB / T 8629-2017) and then dried. The antibacterial effect of pure cotton fabric against Escherichia coli and Staphylococcus aureus was tested according to GB / T 20944.3-2008.

[0068] The test results are shown in Table 1.

[0069] Table 1 Performance Test Results

[0070]

[0071] As shown in Table 1, the antibacterial essential oil microcapsules of Examples 1-2 have high initial antibacterial activity, good sustained-release effect, and long-lasting antibacterial properties.

[0072] In this invention, the terpenoids, phenols, and aldehydes in Artemisia argyi and Litsea cubeba leaves undergo microbial metabolic transformation during fermentation, producing more small-molecule secondary metabolites with antibacterial activity. A significant synergistic antibacterial effect exists between the two, with significantly higher antibacterial rates against Escherichia coli and Staphylococcus aureus than essential oils blended with other plants. Fermentation using a specific ratio of *Lactobacillus plantarum* and *Lactobacillus rhamnosus* effectively decomposes cellulose and pectin in plant cell walls, promoting the full release of active ingredients while avoiding excessive degradation of the target product. Solvent-free microwave extraction technology utilizes water as the microwave absorption medium for rapid extraction at low temperatures, maximizing the retention of heat-sensitive antibacterial components and avoiding the loss of effective components or solvent residues caused by traditional steam distillation or organic solvent extraction. Experiments show that microcapsules prepared from the essential oil extracted using this invention achieve an initial antibacterial rate of over 95%, and the antibacterial rate remains above 85% after 20 washes. Changing the extraction method or the plant ratio significantly reduces the antibacterial rate.

[0073] Low molecular weight polylactic acid (PLA) A exhibits good flowability and emulsifying dispersion, enabling it to rapidly form an initial coating layer at the oil-water interface. Medium molecular weight PLA B serves as the main framework, providing moderate mechanical strength and a stable shell structure. High molecular weight PLA C, through its longer molecular chains, increases the density of the wall material, effectively delaying the diffusion and release of the essential oil core material. The synergistic effect of the three PLA molecules allows the microcapsules to maintain high antibacterial activity in the initial stage, with high encapsulation efficiency and controllable release, while also maintaining excellent antibacterial effects after multiple washes. In contrast, Comparative Example 1, using only two PLA molecules, and Comparative Example 2, a mixture of three PLA molecules in equal proportions, showed significantly inferior sustained-release performance compared to Example 1, indicating that the specific compounding ratio of the present invention helps achieve long-lasting antibacterial effects.

[0074] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing long-acting antibacterial essential oil microcapsules, characterized in that, Includes the following steps: (1) Dissolve polylactic acid in dichloromethane to obtain polylactic acid dichloromethane solution, add essential oil to water, add surfactant, mix evenly to obtain essential oil mixture; The essential oil is obtained by crushing artemisia leaves and pheasant leaves separately, mixing them for fermentation, and then extracting by microwave method; (2) Mix the essential oil mixture and the polylactic acid dichloromethane solution, stir, and obtain an emulsion; (3) Mix the emulsion with polyvinyl alcohol aqueous solution and isopropanol aqueous solution, heat the mixture to evaporate the organic solvent, separate the solid product, and obtain long-acting antibacterial essential oil microcapsules.

2. The method for preparing long-acting antibacterial essential oil microcapsules according to claim 1, characterized in that, Polylactic acid includes polylactic acid A, polylactic acid B, and polylactic acid C in a mass ratio of 1:(1.2-1.4):(0.3-0.5): the molecular weight Mn of polylactic acid A is 4500-5500 Da; the molecular weight Mn of polylactic acid B is 6500-7400 Da; and the molecular weight Mn of polylactic acid C is 9000-10000 Da.

3. The method for preparing long-acting antibacterial essential oil microcapsules according to claim 1, characterized in that, The method for preparing the essential oil includes the following steps: (1) Dry the mugwort leaves and the leaves of the mountain pepper separately and pulverize them; mix the dried mugwort leaves and the leaves of the mountain pepper to obtain a mixed powder; (2) Add water, glucose and peptone to the mixed powder, adjust the pH value, sterilize and cool to obtain fermentation material; add compound bacteria to fermentation material, fermentation, sterilize after fermentation to obtain fermentation product, concentrate fermentation product to obtain material to be microwave extracted; (3) Transfer the material to be microwave extracted to a solvent-free microwave extraction bottle, perform microwave extraction, cool to room temperature after extraction, let stand, remove the oil layer, dry and dehydrate to obtain essential oil.

4. The method for preparing long-acting antibacterial essential oil microcapsules according to claim 3, characterized in that, Mix dried mugwort leaves and Sichuan pepper leaves in a mass ratio of 1:(0.4-0.6).

5. The method for preparing long-acting antibacterial essential oil microcapsules according to claim 3, characterized in that, The compound bacteria were added to the fermentation material at a dosage of (3-5) × 10. 9 CFU / mL fermentation material.

6. The method for preparing long-acting antibacterial essential oil microcapsules according to claim 3, characterized in that, Fermentation conditions: Anaerobic fermentation at 35-37℃ for 24-28 hours.

7. The method for preparing long-acting antibacterial essential oil microcapsules according to claim 3, characterized in that, The compound bacteria include *Lactobacillus plantarum* and *Lactobacillus rhamnosus* with a live bacteria ratio of 1:(0.5-0.7).

8. The method for preparing long-acting antibacterial essential oil microcapsules according to claim 1, characterized in that, The conditions for microwave extraction are: power set to 200-300W, microwave extraction for 1-2 hours.

9. A long-acting antibacterial essential oil microcapsule prepared by the preparation method according to any one of claims 1-8.

10. The use of a long-acting antibacterial essential oil microcapsule prepared by the method according to any one of claims 1-8 in the preparation of detergents.

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