Double-coated colloidal sulfur as well as preparation method and application thereof

Abstract

The invention discloses a preparation method of double-coated colloidal sulfur, which comprises the following steps: (1) uniformly dispersing sulfur powder in an Arabic gum solution, and uniformly stirring to obtain a dispersion liquid; carrying out ball milling and filtering on the dispersion liquid to obtain primary wrapped colloidal sulfur; and (2) adding lipoic acid and polyhydric alcohol into the primary coated colloidal sulfur, stirring to react, and freeze-drying and crushing a reaction product to obtain secondary coated colloidal sulfur. The invention also provides the double-coated colloidal sulfur prepared by the preparation method and application of the double-coated colloidal sulfur. According to the preparation method of the double-coated colloidal sulfur, double coating is formed by using physical coating and chemical crosslinking, so that instability of single physical coating is avoided, the stability of the colloidal sulfur can be remarkably improved, and the colloidal sulfur can play a long-acting and stable role.

Description

Technical Field

[0001] The present invention belongs to the field of cosmetics, and in particular relates to colloidal sulfur and a preparation method and application thereof. Background Art

[0002] Sulfur is a light yellow crystal or powder with a special smell. It is insoluble in water and slightly soluble in alcohol. In nature, sulfur usually exists in the form of elemental sulfur, sulfide, and sulfate, and is commonly found in meteorites, volcanoes, hot springs, etc. Sulfur is widely used in agriculture, medicine, rubber, building materials and other fields. Sulfur also has antibacterial and anti-inflammatory properties, inhibits mold growth, and inhibits sebum leakage. It is widely used in daily chemical care and medicines. The "Guidelines for the Treatment of Acne in China" mentions that sulfur can be used as a topical treatment for acne. However, sulfur is insoluble in water and most solutions. Research on how to improve the application of sulfur is of great significance.

[0003] Colloidal sulfur was developed specifically to address sulfur application issues, providing solutions for various skin conditions, particularly acne, rosacea, seborrheic dermatitis, dandruff, and tinea versicolor. Acne and rosacea are primarily caused by excessive sebum secretion, which leads to abnormal keratin metabolism and the proliferation of Propionibacterium acnes. Colloidal sulfur not only regulates keratinocyte differentiation but also effectively inhibits the proliferation of Propionibacterium acnes. For seborrheic dermatitis and dandruff, colloidal sulfur's mechanism of action is primarily to remove excess sebum from the scalp and inhibit the proliferation of Malassezia, thereby achieving its therapeutic effects.

[0004] Colloidal sulfur primarily consists of sulfur and gum arabic or other coating materials. As research deepened, the outer coating material evolved from initial rubber and resin to high-viscosity or dispersible polymers such as gum arabic, xanthan gum, and hyaluronic acid, enhancing the mildness and environmental friendliness of the colloidal sulfur coating. Subsequently, to improve the stability of the colloidal sulfur coating, multiple coating technologies emerged. These technologies primarily incorporate additional coating layers onto the colloidal sulfur, thereby increasing its stability.

[0005] The single-layer coated colloidal sulfur or multi-layer coated colloidal sulfur in the prior art mainly has the following problems: 1. Poor stability: At present, colloidal sulfur mainly consists of single-layer coated colloidal sulfur and multi-layer coated colloidal sulfur. The coating form is mostly a long molecular chain polysaccharide colloid forming a layer or multiple layers of physical coating on the sulfur surface, thereby improving the situation that sulfur is insoluble and non-dispersible in water and expanding the application field of sulfur. However, the above-mentioned coating process is essentially a physical coating, and the improvement in stability is relatively limited. 2. Low safety: At present, multi-layer coated colloidal sulfur often uses emulsifiers, cross-linking agents, catalysts, etc. as a multi-layer coating technology. This type of preparation method requires the introduction of additional chemical reagents. Such substances will bring more irritation and safety hazards to patients with acne or skin lesions, and have problems such as strong irritation and poor safety. Therefore, how to improve the stability of colloidal sulfur while developing a colloidal sulfur with a simple preparation process, mild and non-irritating properties is an urgent problem to be solved. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the above background technology and provide a double-encapsulated colloidal sulfur with high stability, good safety and simple process, as well as a preparation method and application.

[0007] In order to solve the above technical problems, the technical solution proposed by the present invention is: A method for preparing double-coated colloidal sulfur comprises the following steps: (1) uniformly dispersing sulfur powder in a gum arabic solution and stirring the mixture to obtain a dispersion; ball milling and filtering the dispersion to obtain a single-layer coated colloidal sulfur; (2) Adding lipoic acid and polyol to the single-coated colloidal sulfur, stirring to react, and freeze-drying and crushing the reaction product to obtain double-coated colloidal sulfur.

[0008] In the above preparation method, preferably, the gum arabic solution is an aqueous solution containing 1-20% gum arabic by mass; the gum arabic comprises high-viscosity gum arabic and low-viscosity gum arabic, the viscosity of the high-viscosity gum arabic aqueous solution being 500-2000 mPa.s, and the viscosity of the low-viscosity gum arabic aqueous solution being no more than 100 mPa.s. More preferably, the mass ratio of the high-viscosity gum arabic to the low-viscosity gum arabic is 1:(3-5).

[0009] The present invention adopts a combination of high-viscosity gum arabic and low-viscosity gum arabic, mainly to improve the coating rate, mechanical properties, and chemical properties of sulfur. High-viscosity gum arabic has high viscosity and relatively low solubility in water (no more than 10%), while low-viscosity gum arabic has low viscosity and high solubility in water (up to 50% or more). Therefore, using low-viscosity gum arabic to coat sulfur can result in more gum arabic coating on the outside of the sulfur. In addition, the low-viscosity gum arabic has short chain segments, making it easier to coat the outside of the sulfur. Its usage is higher, and the exposed active groups are more likely to undergo subsequent secondary crosslinking, achieving double coating. However, the high-viscosity gum arabic has long chain segments, which can provide better mechanical properties after coating and improve its stability. By rationally controlling the usage of high-viscosity gum arabic and low-viscosity gum arabic, the coating rate, mechanical properties, and chemical properties can be guaranteed.

[0010] In the above preparation method, preferably, the ball milling and filtering steps include the following steps: ball milling the dispersion using a ball mill at a speed of 100-1000 rpm for 1-12 hours, and filtering the material through a 50-100 mesh screen after ball milling. The ball milling primarily adheres the gum arabic to the sulfur surface, forming a coating layer, which is a physical encapsulation process.

[0011] In the above preparation method, preferably, the added amount of the lipoic acid is 0.1-2% of the mass of the single-layer coated colloidal sulfur.

[0012] In the above preparation method, preferably, the polyol includes one or more of propylene glycol, butylene glycol, pentanediol and hexylene glycol; and the added amount of the polyol is 0.1-2% of the mass of the single-layer coated colloidal sulfur.

[0013] In the above preparation method, preferably, the mass ratio of the lipoic acid to the polyol is 1:(5-10).

[0014] In the present invention, the addition of lipoic acid and polyol can chemically react with the first coating layer of gum arabic, and the combination of the two has a better effect. However, the dosage ratio of lipoic acid and polyol needs to be reasonably controlled, and the amount of lipoic acid added should not be too large to avoid residual lipoic acid from generating odor.

[0015] In the above preparation method, preferably, the reaction temperature is controlled to be 10-60° C. and the reaction time is 1-3 hours during the stirring reaction. Under the above reaction temperature and reaction time, the secondary chemical cross-linking process can be successfully completed.

[0016] As a general technical concept, the present invention also provides a double-coated colloidal sulfur prepared by the above preparation method.

[0017] As a general technical concept, the present invention also provides an application of the double-encapsulated colloidal sulfur, wherein the double-encapsulated colloidal sulfur is added to cosmetics or skin care products.

[0018] The present invention provides a double-coated colloidal sulfur and its preparation method, which features stable coating, simple processing, stable efficacy, safety, reliability, and environmental friendliness. Starting from the optimization of the colloidal sulfur preparation process, the present invention applies high-energy ball milling technology to the colloidal sulfur preparation process. This not only simplifies and facilitates the colloidal sulfur preparation process, but also avoids the use of chemical additives, further improving the mildness and safety of the colloidal sulfur. Furthermore, the present invention utilizes lipoic acid and polyols as crosslinking agents to produce a double-coated colloidal sulfur. This double-coated colloidal sulfur forms a double-coated structure outside the sulfur, resulting in more stable chemical properties and a stronger sustained-release effect. Furthermore, the use of lipoic acid and polyols as crosslinking agents offers advantages such as being non-toxic and harmless, avoiding the use of chemical crosslinkers and reducing the introduction of impurities and irritants. This is expected to provide new directions for the development and application of colloidal sulfur. Specifically, the present invention has at least the following advantages: (1) Stable structure: In conventional double-coated or multi-coated colloidal sulfur, two different colloids are often used to coat sulfur twice or multiple times, thereby forming double-coated or multi-coated colloidal sulfur. However, its essence is still to coat different colloids / polysaccharide molecules on the outside of sulfur, which belongs to double or multiple physical coating. The present invention coats the outside of sulfur with a layer of gum arabic, and then uses lipoic acid and polyols to react chemically with gum arabic, and introduces it into the single-coated colloidal sulfur, forming a single-coated colloidal sulfur that reacts chemically with lipoic acid and polyols to achieve double coating. The prepared double-coated colloidal sulfur has a layer of physical coating of colloid and a layer of chemical cross-linking. Compared with repeated multiple physical coatings, it has a more stable structure and performance.

[0019] (2) Simple process: Conventional colloidal sulfur preparation requires high temperature or high pressure. The double-coated colloidal sulfur of the present invention is prepared by dissolving gum arabic, dispersing in a sulfur suspension, grinding with a ball mill, stirring and mixing, and freeze-drying. All preparation processes are carried out under normal pressure, which simplifies experimental and production conditions. This not only helps expand the production scale of colloidal sulfur, but also helps ensure the quality of the colloidal sulfur.

[0020] (3) High safety: Generally, the preparation process of colloidal sulfur requires the addition of a certain amount of emulsifier or cross-linking agent. In particular, in multi-coated colloidal sulfur, the cross-linking agent of the chemical reagent will introduce new impurities and irritants while achieving multi-coating. The reactive monomers used in the present invention are lipoic acid and polyols. These raw materials are all conventional raw materials in cosmetics, have no obvious irritation to the skin, and are more environmentally friendly. Therefore, the double-coated colloidal sulfur prepared by the present invention has higher safety.

[0021] Compared with the prior art, the advantages of the present invention are: 1. The present invention's method for preparing double-coated colloidal sulfur utilizes both physical coating and chemical crosslinking to achieve a double coating. First, gum arabic is used to form a physical coating on the outside of the sulfur. Then, lipoic acid and a polyol react with the gum arabic to form a double coating. This dual coating, combining physical coating and chemical crosslinking, avoids the instability of single physical coating, significantly improving the stability of the colloidal sulfur and ensuring its long-lasting stability.

[0022] 2. The preparation method of the double-encapsulated colloidal sulfur of the present invention has a simple preparation process and uses gum arabic, lipoic acid and polyols to achieve the coating. The above raw materials are conventional cosmetic raw materials, have high affinity for the skin, do not cause irritation, and have higher safety. DETAILED DESCRIPTION

[0023] In order to facilitate understanding of the present invention, the present invention will be described more comprehensively and meticulously below in conjunction with preferred embodiments, but the protection scope of the present invention is not limited to the following specific embodiments.

[0024] Unless otherwise defined, all technical terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0025] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0026] Example 1: A method for preparing double-coated colloidal sulfur comprises the following steps: (1) Weigh 2 g of high-viscosity gum arabic (its aqueous solution viscosity is about 700-900 mPa.s, and there is a certain fluctuation during measurement), prepare it into a 2% concentration aqueous solution, and after it is dispersed into a transparent and uniform aqueous solution, add 100 g of sulfur and disperse it evenly to obtain a sulfur suspension.

[0027] (2) Adjust the ratio of the balls in the ball mill to a diameter (mm) ratio of 15:10:5:3 and a mass (g) ratio of 50:150:200:100. Place the sulfur suspension into the ball mill and adjust the speed to 600 rpm. After grinding for 6 h, separate the balls from the material using an 80-mesh filter to obtain a single layer of coated colloidal sulfur.

[0028] (3) Accurately weigh 100g of single-coated colloidal sulfur, then accurately weigh 0.1g of lipoic acid and 1g of propylene glycol. Evenly disperse the lipoic acid in the propylene glycol. Add the dispersion to the single-coated colloidal sulfur and stir at 45°C for 1h. After stirring evenly, freeze-dry the colloidal sulfur to obtain double-coated colloidal sulfur. During the stirring process, the colloidal sulfur will gradually react and thicken, so the reaction needs to be monitored in real time.

[0029] Example 2: A method for preparing double-coated colloidal sulfur comprises the following steps: (1) Weigh 20g of low-viscosity gum arabic (its aqueous solution viscosity is less than 100mPa.s, and there is a certain fluctuation during measurement), prepare it into a 20% concentration aqueous solution, and after it is dispersed into a transparent and uniform aqueous solution, add 100g of sulfur and disperse it evenly to obtain a sulfur suspension.

[0030] (2) Adjust the ratio of the balls in the ball mill to a diameter (mm) ratio of 15:10:5:3 and a mass (g) ratio of 50:150:200:100. Place the sulfur suspension into the ball mill jar and adjust the speed to 1000 rpm. After grinding for 4 hours, separate the balls from the material using a 50-mesh filter to obtain a single layer of coated colloidal sulfur.

[0031] (3) Accurately weigh 100g of single-coated colloidal sulfur, then accurately weigh 0.2g of lipoic acid and 1g of hexanediol. Evenly disperse the lipoic acid in the hexanediol. Add the dispersion to the single-coated colloidal sulfur and stir at 45°C for 1h. After stirring evenly, freeze-dry the colloidal sulfur to obtain double-coated colloidal sulfur. During the stirring process, the colloidal sulfur will gradually react and thicken, so the reaction needs to be monitored in real time.

[0032] Example 3: A method for preparing double-coated colloidal sulfur comprises the following steps: (1) Weigh 5g of high-viscosity gum arabic (the viscosity of its aqueous solution is about 1800-2000mPa.s, and there is a certain fluctuation during measurement), and then accurately weigh 15g of low-viscosity gum arabic (the viscosity of its aqueous solution is less than 100mPa.s, and there is a certain fluctuation during measurement), and prepare a 20% concentration aqueous solution. After dispersing into a transparent and uniform aqueous solution, add 100g of sulfur and disperse it evenly to obtain a sulfur suspension.

[0033] (2) Adjust the ratio of the balls in the ball mill to a diameter (mm) ratio of 15:10:5:3 and a mass (g) ratio of 50:150:200:100. Place the sulfur suspension into the ball mill jar and adjust the speed to 800 rpm. After grinding for 2 h, separate the balls from the material using a 100-mesh filter to obtain a single layer of coated colloidal sulfur.

[0034] (3) Accurately weigh 100g of single-coated colloidal sulfur, then accurately weigh 0.2g of lipoic acid and 1.2g of butanediol. Evenly disperse the lipoic acid in the butanediol. Add the dispersion to the single-coated colloidal sulfur and stir at 45°C for 2h. After stirring evenly, freeze-dry the colloidal sulfur to obtain double-coated colloidal sulfur. During the stirring process, the colloidal sulfur will gradually react and thicken, so the reaction needs to be monitored in real time.

[0035] Example 4: A method for preparing double-coated colloidal sulfur comprises the following steps: (1) Weigh 2 g of high-viscosity gum arabic (its aqueous solution viscosity is about 700-900 mPa.s, and there is a certain fluctuation during measurement), and then weigh 8 g of low-viscosity gum arabic (its aqueous solution viscosity is less than 100 mPa.s, and there is a certain fluctuation during measurement), and prepare a 10% concentration aqueous solution. After dispersing into a transparent and uniform aqueous solution, add 100 g of sulfur and disperse it evenly to obtain a sulfur suspension.

[0036] (2) Adjust the ratio of the balls in the ball mill to a diameter (mm) ratio of 15:10:5:3 and a mass (g) ratio of 50:150:200:100. Place the sulfur suspension into the ball mill and adjust the speed to 100 rpm. After grinding for 12 hours, separate the balls from the material using an 80-mesh filter to obtain a single layer of coated colloidal sulfur.

[0037] (3) Accurately weigh 100g of single-coated colloidal sulfur, then accurately weigh 0.2g of lipoic acid and 1.6g of butanediol. Evenly disperse the lipoic acid in the butanediol. Add the dispersion to the single-coated colloidal sulfur and stir at 45°C for 2h. After stirring evenly, freeze-dry the colloidal sulfur to obtain double-coated colloidal sulfur. During the stirring process, the colloidal sulfur will gradually react and thicken, so the reaction needs to be monitored in real time.

[0038] Example 5: A method for preparing double-coated colloidal sulfur comprises the following steps: (1) Weigh 5 g of high-viscosity gum arabic (the viscosity of its aqueous solution is about 1800-2000 mPa.s, and there is a certain fluctuation during measurement), and then weigh 5 g of low-viscosity gum arabic (the viscosity of its aqueous solution is less than 100 mPa.s, and there is a certain fluctuation during measurement), and prepare a 10% concentration aqueous solution. After dispersing into a transparent and uniform aqueous solution, add 100 g of sulfur and disperse it evenly to obtain a sulfur suspension.

[0039] (2) Adjust the ratio of the balls in the ball mill to a diameter (mm) ratio of 15:10:5:3 and a mass (g) ratio of 50:150:200:100. Place the sulfur suspension into the ball mill and adjust the speed to 100 rpm. After grinding for 12 hours, separate the balls from the material using an 80-mesh filter to obtain a single layer of coated colloidal sulfur.

[0040] (3) Accurately weigh 100g of single-coated colloidal sulfur, then accurately weigh 0.2g of lipoic acid, 0.8g of butanediol, and 0.8g of hexanediol. Evenly disperse the lipoic acid in the polyol. Add the dispersion to the single-coated colloidal sulfur and stir at 45°C for 2h. After stirring evenly, freeze-dry the colloidal sulfur to obtain double-coated colloidal sulfur. During the stirring process, the colloidal sulfur will gradually react and thicken, so the reaction needs to be monitored in real time.

[0041] Example 6: A method for preparing double-coated colloidal sulfur comprises the following steps: (1) Weigh 2 g of high-viscosity gum arabic (its aqueous solution viscosity is about 700-900 mPa.s, and there is a certain fluctuation during measurement), and then weigh 8 g of low-viscosity gum arabic (its aqueous solution viscosity is less than 100 mPa.s, and there is a certain fluctuation during measurement), and prepare a 10% concentration aqueous solution. After dispersing into a transparent and uniform aqueous solution, add 100 g of sulfur and disperse it evenly to obtain a sulfur suspension.

[0042] (2) Adjust the ratio of the balls in the ball mill to a diameter (mm) ratio of 15:10:5:3 and a mass (g) ratio of 50:150:200:100. Place the sulfur suspension into the ball mill and adjust the speed to 100 rpm. After grinding for 12 hours, separate the balls from the material using an 80-mesh filter to obtain a single layer of coated colloidal sulfur.

[0043] (3) Accurately weigh 100g of single-coated colloidal sulfur, then accurately weigh 0.2g of lipoic acid and 0.6g of butanediol. Evenly disperse the lipoic acid in the butanediol. Add the dispersion to the single-coated colloidal sulfur and stir at 45°C for 2h. After stirring evenly, freeze-dry the colloidal sulfur to obtain double-coated colloidal sulfur. During the stirring process, the colloidal sulfur will gradually react and thicken, so the reaction needs to be monitored in real time.

[0044] The process parameters of the preparation methods in Examples 1-6 are shown in Table 1 below.

[0045] Table 1: Comparison of process parameters in Examples 1-6

[0046] Comparative Example 1: A method for preparing a single-layer coated colloidal sulfur comprises the following steps: (1) Weigh 2 g of high-viscosity gum arabic (its aqueous solution viscosity is about 700-900 mPa.s, and there is a certain fluctuation during measurement), and then weigh 8 g of low-viscosity gum arabic (its aqueous solution viscosity is less than 100 mPa.s, and there is a certain fluctuation during measurement), and prepare a 10% concentration aqueous solution. After dispersing into a transparent and uniform aqueous solution, add 100 g of sulfur and disperse it evenly to obtain a sulfur suspension.

[0047] (2) The ratio of the balls in the ball mill was adjusted to a diameter (mm) ratio of 15:10:5:3 and a mass (g) ratio of 50:150:200:100. The sulfur suspension was placed in a ball mill at a speed of 100 rpm. After milling for 6 h, the balls were separated from the material using a filter to obtain single-layered colloidal sulfur. The single-layered colloidal sulfur was freeze-dried to obtain the sample of Comparative Example 1.

[0048] Comparative Example 2: A method for preparing double-coated colloidal sulfur comprises the following steps: (1) Weigh 2g of high-viscosity gum arabic (its aqueous solution viscosity is about 700-900mPa.s, and there is a certain fluctuation during measurement), and then weigh 8g of low-viscosity gum arabic (its aqueous solution viscosity is less than 100mPa.s, and there is a certain fluctuation during measurement), and prepare a 10% concentration aqueous solution. After dispersing into a transparent and uniform aqueous solution, add 100g of sulfur to obtain a uniform suspension after dispersion.

[0049] (2) Adjust the ratio of the balls in the ball mill to a diameter (mm) ratio of 15:10:5:3 and a mass (g) ratio of 50:150:200:100. Place the sulfur suspension into the ball mill and adjust the speed to 100 rpm. After grinding for 6 hours, separate the balls from the material using a filter to obtain a single-layer coated colloidal sulfur.

[0050] (3) Take 100 g of the coated colloidal sulfur and accurately weigh 5 g of lipoic acid, stir at 45°C for 2 h, and freeze-dry the colloidal sulfur after stirring to obtain the sample of Comparative Example 2. During the stirring process, the colloidal sulfur will gradually react and thicken, so the reaction needs to be monitored in real time.

[0051] Comparative Example 3: A method for preparing double-coated colloidal sulfur comprises the following steps: (1) Weigh 2g of high-viscosity gum arabic (its aqueous solution viscosity is about 700-900mPa.s, and there is a certain fluctuation during measurement), and then weigh 8g of low-viscosity gum arabic (its aqueous solution viscosity is less than 100mPa.s, and there is a certain fluctuation during measurement), and prepare a 10% concentration aqueous solution. After dispersing into a transparent and uniform aqueous solution, add 100g of sulfur to obtain a uniform suspension after dispersion.

[0052] (2) Adjust the ratio of the balls in the ball mill to a diameter (mm) ratio of 15:10:5:3 and a mass (g) ratio of 50:150:200:100. Place the sulfur suspension into the ball mill and adjust the speed to 100 rpm. After grinding for 6 hours, separate the balls from the material using a filter to obtain a single-layer coated colloidal sulfur.

[0053] (3) Take 100 g of the single-layer coated colloidal sulfur and add 10 g of butanediol. Stir at 45°C for 2 h. After stirring evenly, freeze-dry the colloidal sulfur to obtain Comparative Example 3. During the stirring process, the colloidal sulfur will gradually react and thicken. The reaction needs to be monitored in real time.

[0054] Comparative Example 4: A method for preparing uncoated colloidal sulfur comprises the following steps: (1) Take 100g of deionized water, add 100g of sulfur, and disperse to obtain a uniform suspension.

[0055] (2) The suspension was homogenized using a high-speed homogenizer with a homogenization time of 10 min and a homogenization speed of 5000-6000 r / min. The material was freeze-dried to obtain the comparative example 4 sample.

[0056] The performance test plan and test results are as follows: 1. Free sulfur content test The samples from the examples and comparative examples were prepared into 10% aqueous solutions. After uniform dispersion, they were ultrasonically treated for 30 minutes and then centrifuged at 12,000 rpm for 10 minutes. The supernatant was collected, filtered, and the sulfur content was measured using a liquid chromatography instrument. The encapsulation efficiency of the double-encapsulated colloidal sulfur was calculated using the following formula: Encapsulation efficiency = (original sulfur content in the colloidal sulfur - free sulfur content in the extract) / original sulfur content in the colloidal sulfur * 100%. The results are shown in Table 2 below.

[0057] Table 2: Encapsulation efficiency of double-coated colloidal sulfur in the products of Examples and Comparative Examples

[0058] Analysis of the data shows that the encapsulation rate of uncoated sulfur is 0. After one coat, the encapsulation rate reaches over 85%, and after a second coat, the encapsulation rate rises to over 95%. These results demonstrate that double coating can improve the encapsulation rate of sulfur, enhance the stability of colloidal sulfur raw materials, and reduce irritation.

[0059] 2. Particle size test Example 1, Example 2, Comparative Example 1 and Comparative Example 4 were prepared into 10% aqueous solutions, and the particle size of each sample was tested using a particle size tester. The results are shown in Table 3 below.

[0060] Experimental method: Take a small amount of the solution to be tested and add it dropwise to the sample test tank. Once the concentration reaches the measurement standard, the measurement can be started. The background value needs to be removed before measurement.

[0061] Table 3: Particle size of double-coated colloidal sulfur in the examples and comparative examples

[0062] Analysis of the data reveals that the D50 of the unmilled sulfur was 57.63 μm. However, after ball milling, the particle size of the colloidal sulfur from Comparative Example 1 was reduced to 5.65 μm, demonstrating a significant reduction in the particle size after milling. However, after double coating, the particle size of the colloidal sulfur increased from approximately 5 μm to between 15 and 20 μm. These results indicate that double coating has an impact on the particle size of the colloidal sulfur, increasing it to some extent. This may be because chemical crosslinking links the individual colloidal sulfur particles together, forming relatively larger particles.

[0063] 3. Antibacterial effect test The colloidal sulfur prepared in Examples 1-6 and Comparative Examples 1-3 was prepared into a 0.1% solution using bacterial culture medium. This solution was then inoculated with Propionibacterium acnes and cultured in a shake flask. Samples were taken for dilution and streaking on days 1, 2, 3, 4, and 7. The inhibitory rates of colloidal sulfur against Propionibacterium acnes were calculated and are shown in Table 4 below.

[0064] Table 4: Inhibition rate of colloidal sulfur on Propionibacterium acnes in Examples and Comparative Examples

[0065] Analysis of the data reveals that on the first day, all samples exhibited a 100% inhibition rate against P. acnes. However, over time, by the seventh day, the inhibition rates of Examples 1-6 were all above 79%, while those of Comparative Examples 1-3 dropped to approximately 60%. These results demonstrate that after double coating, the colloidal sulfur exhibits greater stability, more uniform sustained release, and a longer duration, resulting in a more sustained antibacterial effect. However, the comparative examples exhibited a slightly lower coating efficiency and a faster sustained release rate, leading to excessive sustained release of colloidal sulfur and a shorter duration of antibacterial activity, resulting in a poorer sustained antibacterial effect, resulting in the aforementioned results.

Claims

1. A method for preparing double-coated colloidal sulfur, characterized in that: The following steps are involved: (1) uniformly dispersing sulfur powder in a gum arabic solution and stirring the mixture to obtain a dispersion; ball milling and filtering the dispersion to obtain a single-layer coated colloidal sulfur; (2) Adding lipoic acid and polyol to the single-coated colloidal sulfur, stirring to react, and freeze-drying and crushing the reaction product to obtain double-coated colloidal sulfur.

2. The preparation method according to claim 1, characterized in that The gum arabic solution is an aqueous solution with a mass fraction of gum arabic of 1-20%; and the gum arabic includes high-viscosity gum arabic and low-viscosity gum arabic, the viscosity of the high-viscosity gum arabic aqueous solution is 500-2000 mPa.s, and the viscosity of the low-viscosity gum arabic aqueous solution does not exceed 100 mPa.s.

3. The preparation method according to claim 2, characterized in that The mass ratio of the high-viscosity gum arabic to the low-viscosity gum arabic is 1:(3-5).

4. The preparation method according to claim 1, characterized in that Ball milling and filtration The method comprises the following steps: performing ball milling treatment on the dispersion liquid by using a ball mill, wherein the rotation speed of the ball mill is 100-1000 revolutions per minute, and the ball milling time is 1-12 hours; after the ball milling is completed, filtering the material body with a sieve with a mesh size of 50-100 meshes.

5. The preparation method according to claim 1, characterized in that The added amount of the lipoic acid is 0.1-2% of the mass of the one layer of coated colloidal sulfur.

6. The preparation method according to claim 1, characterized in that The polyol includes one or more of propylene glycol, butanediol, pentanediol and hexanediol; the added amount of the polyol is 0.1-2% of the mass of the single-layer coated colloidal sulfur.

7. The preparation method according to claim 1, characterized in that The mass ratio of the lipoic acid to the polyol is 1:(5-10).

8. The preparation method according to claim 1, characterized in that During the stirring reaction, the reaction temperature is controlled to be 10-60°C and the reaction time is 1-3h.

9. Double-coated colloidal sulfur prepared by the method according to any one of claims 1 to 8.

10. Use of the double-coated colloidal sulfur according to claim 9, characterized in that: The double-encapsulated colloidal sulfur is added to cosmetics or skin care products.

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