Plant-based skin lightening soap and low temperature process for its preparation

Abstract

This invention discloses a plant-based brightening handmade soap and its low-temperature preparation process. The soap uses natural silk protein soap base as a base, compounded with shea butter, castor oil, nano pearl powder, silk protein stock solution, niacinamide, panthenol, and herbal compound powder. It is prepared through low-temperature aqueous phase extraction, low-temperature melting below 50℃ throughout the process, and the segmented addition of heat-sensitive active ingredients. This invention uses purified water and a portion of glycerin as the extraction medium, extracting the herbal powder under low-temperature conditions, supplemented by intermittent ultrasonic oscillation. After extraction, no residue is filtered, and all the material is added to the soap, avoiding organic solvent residue. This also ensures uniform dispersion of the herbal powder, solving the problem of powder agglomeration clogging pores. The resulting soap shows no irritation in patch tests, high hardness, strong resistance to softening and crumbling, and a shelf life of over 24 months at room temperature, achieving a balance between gentle cleansing, brightening and moisturizing, and stable durability.

Description

Technical Field

[0001] This invention relates to the field of daily chemical personal care products technology, and in particular to a plant-based brightening handmade soap and its low-temperature preparation process. Background Technology

[0002] There are many types of handmade soap products on the market, some of which claim to contain added herbal ingredients to enhance the washing and care experience. These products are usually made by directly mixing crushed herbal raw materials into the soap base, or by extracting the effective components of the herbs through high-temperature decoction and then compounding them with the soap base.

[0003] First, current processes directly add herbal powder to the soap base. Due to the poor compatibility between the powder and the soap base, this easily leads to powder agglomeration and clumping, resulting in a noticeably grainy soap. This not only causes discomfort and friction on the skin but also clogs pores, leading to problems like closed comedones or acne. Second, the high-temperature water extraction or high-temperature melting and mixing processes destroy the heat-sensitive active substances in the herbs and added skincare ingredients (such as proteins and vitamin derivatives), significantly reducing the product's actual efficacy. The finished product is also prone to softening, yellowing, and a short shelf life. Third, existing products often lack systematic consideration in their formulation, resulting in a single oil system with insufficient moisturizing and nourishing capabilities. The resulting soap softens easily when exposed to water, has poor storage stability, and often causes skin discomfort such as tightness, dryness, and even breakouts after use, failing to balance cleansing, skincare, and gentleness.

[0004] Therefore, in response to the problems mentioned above, this invention proposes a plant-based skin-brightening handmade soap and its low-temperature preparation process. Summary of the Invention

[0005] To overcome the problems of herbal powder agglomeration affecting skin feel and safety, high-temperature processing destroying active ingredients, poor product stability, and tightness and discomfort after washing in existing handmade soaps, this invention proposes a plant-based brightening handmade soap and its low-temperature preparation process. This method adds heat-sensitive skin care ingredients in stages under low-temperature conditions throughout the process, while compounding specific nourishing oils and moisturizing systems, thereby obtaining a handmade soap product with a delicate texture, full retention of active ingredients, a gentle washing experience, and good finished product stability.

[0006] The technical solution of this invention is as follows: a plant-based brightening handmade soap, made from the following raw materials in parts by weight: 550-650 parts natural silk protein soap base, 10-20 parts shea butter, 8-12 parts castor oil, 5-10 parts nano pearl powder, 10-20 parts silk protein stock solution, 8-12 parts glycerin, 8-12 parts coconut oil foaming agent, 8-12 parts niacinamide, 2-6 parts panthenol, and 90-115 parts herbal compound powder; The herbal compound powder is made from the following raw materials in parts by weight: honeysuckle 3-7 parts, poria cocos 20-30 parts, atractylodes macrocephala 20-30 parts, bletilla striata 12-18 parts, and angelica sinensis 5-10 parts. In summer, 3-5 parts of sodium lactate can be added to the raw materials.

[0007] As a preferred embodiment, it is made from the following raw materials in parts by weight: 600 parts natural silk protein soap base, 15 parts shea butter, 10 parts castor oil, 7.5 parts nano pearl powder, 15 parts silk protein stock solution, 10 parts glycerin, 10 parts coconut oil foaming agent, 10 parts niacinamide, 4 parts panthenol, and 102.5 parts herbal compound powder. The herbal compound powder is made from the following raw materials in parts by weight: 5 parts honeysuckle, 25 parts white poria cocos, 25 parts atractylodes macrocephala, 15 parts bletilla striata, and 7.5 parts angelica sinensis.

[0008] Preferably, the herbal compound powder has a fineness of not less than 120 mesh, the shea butter is refined natural shea butter, and the glycerin is food-grade glycerin.

[0009] The low-temperature preparation process for this plant-based brightening handmade soap includes the following steps: S1. Honeysuckle, Poria cocos, Atractylodes macrocephala, Bletilla striata and Angelica sinensis are mixed, pulverized and passed through a 180-mesh ultrafine sieve to obtain herbal fine powder.

[0010] S2, place the herbal powder in an extraction container, add a mixture of purified water and a portion of the glycerol in the formula as the extraction medium, wherein the amount of purified water added is 1.5-3 times the weight of the herbal powder, and the amount of the glycerol is 30-60% of the total weight of the glycerol in the formula; seal and let stand at a low temperature of 0-10℃ for 72-96 hours, during which intermittent ultrasonic oscillation is used to assist extraction (200-500W, each oscillation time is 10-20 minutes, oscillation is performed once every 8-12 hours, under nitrogen or inert gas protection), so that the active ingredients of the herbs are fully dissolved and a uniformly dispersed herbal impregnation slurry is formed. After extraction, no filtration is performed, and the obtained whole-component herbal impregnation slurry is directly used for the next step.

[0011] S3 involves melting the natural silk protein soap base at a temperature below 50°C, adding the full-component herbal impregnation slurry, and then sequentially adding shea butter, silk protein stock solution, glycerin, coconut oil foaming agent, castor oil, nano pearl powder, nicotinamide, sodium lactate, and panthenol. The mixture is stirred and mixed evenly at a speed of 30-60 r / min.

[0012] S4. Pour the mixture into the mold at a low temperature and let it stand and cure at room temperature of 20-30℃ for 48-72 hours to allow excess moisture to evaporate slowly and the soap to fully solidify and take shape. Then demold to obtain the product.

[0013] The combination of coconut oil and castor oil optimizes the fineness of the foam, while silk protein and herbal ingredients work together to nourish the skin, gently cleansing, brightening the complexion, and moisturizing.

[0014] The beneficial effects of this invention are: 1. This invention uses purified water and a partial glycerin mixture as the extraction medium, and performs long-term immersion extraction of herbal compound powder under low-temperature conditions, supplemented by intermittent ultrasonic oscillation. After extraction, no residue is filtered, and the entire material is added to the soap base. This process avoids the use of organic solvents, eliminates the risk of ethanol residue, and ensures that the herbal powder is fully immersed and evenly dispersed in the soap base. It solves the problems of powder agglomeration, coarse soap particles, strong friction during use, and easy clogging of pores leading to acne caused by the direct addition of dry powder in traditional methods. The resulting soap has a delicate texture, a smooth washing feel, and a significantly improved skin feel.

[0015] 2. In this invention, the soap base is melted at a low temperature below 50°C throughout the process, and heat-sensitive active ingredients such as silk protein stock solution and nicotinamide are added in stages. This effectively avoids the decomposition and failure of effective ingredients caused by high-temperature processes. The retention rate of silk protein amino acids and nicotinamide in the finished product is greatly improved, and the tyrosinase inhibition rate reaches 62.4%, so the activity of the effective ingredients is fully preserved.

[0016] 3. This invention combines shea butter, sodium lactate, glycerin, and silk protein soap base to construct a synergistic system for moisturizing and hardening. The resulting soap has a Shore hardness of over 68. After accelerated aging at 40°C and 75% relative humidity for 3 months, the hardness only decreases by 4 units, and the water absorption weight gain rate is less than 8.2%. This effectively solves the problems of soap becoming soft and mushy, turning yellow, and having a short shelf life when exposed to water. The shelf life at room temperature can reach more than 24 months.

[0017] 4. This invention utilizes the synergistic moisturizing effects of shea butter, silk protein extract, and glycerin, combined with the gentle herbal ingredients preserved through a low-temperature process, resulting in a product pH value of 7.2-7.3. Human patch tests showed no irritation, and after use, skin moisture content increased by 28.5%, without any tightness. This avoids breakouts and irritation, achieving a balance between gentle cleansing and brightening / moisturizing. Attached Figure Description

[0018] Figure 1 The diagram shown is a schematic of the low-temperature preparation process of the present invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but 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.

[0020] Example 1: Ingredients (total weight approximately 790g): 600g natural silk protein soap base, 15g refined natural shea butter, 10g castor oil, 7.5g nano pearl powder (particle size ≤100nm), 15g silk protein stock solution (effective protein content ≥5%), 10g food-grade glycerin, 10g coconut oil foaming agent, 10g niacinamide, 4g D-panthenol, 102.5g herbal compound powder (including 5g honeysuckle, 25g poria cocos, 25g atractylodes macrocephala, 15g bletilla striata, and 7.5g angelica sinensis).

[0021] Please see Figure 1 Preparation process: S1. The honeysuckle, poria cocos, atractylodes macrocephala, bletilla striata and angelica sinensis in the above proportions are mixed and put into an ultra-micro pulverizer for low-temperature closed pulverization. Then, the mixture is sieved through a 180-mesh ultrafine sieve. The herbal powder that passes through the sieve is collected, and the part that does not pass through is pulverized again until all of them pass through the sieve. The fineness of the herbal powder obtained is ≥180 mesh and the average particle size is less than 85μm.

[0022] S2, place all the herbal powder obtained in step S1 into a sealed extraction container, add purified water (approximately 205g) twice the weight of the herbal powder and 50% of the total glycerol in the formula (i.e., 5g of glycerol), and mix thoroughly to form a moist slurry. After sealing the container, place it in a constant temperature refrigeration environment at 4℃ for 84 hours to allow it to soak. During this period, turn on an ultrasonic oscillator (300W power, oscillation for 15 minutes) every 10 hours to assist extraction, so that the herbal cell walls are fully broken, and the active ingredients such as flavonoids, coumarins, organic acids, and volatile oils are fully dissolved and evenly dispersed in the liquid phase. The entire extraction process is carried out under nitrogen protection to prevent oxidation of the active ingredients. After extraction, no filtration or separation is performed, and the resulting herbal slurry (containing solid-phase herbal powder and liquid-phase extract) is directly used for the next step.

[0023] S3: Slowly heat and melt the natural silk protein soap base in a water bath below 50℃, keeping the soap base in a flowing liquid state but not exceeding 50℃. First, add all the herbal impregnation slurry obtained in step S2 to the melted soap base, and stir at a low speed of 45 rpm for 5 minutes to initially mix the herbal powder with the soap base. Then, add refined natural shea butter, silk protein stock solution, the remaining 5g of glycerin, coconut oil foaming agent, castor oil, nano pearl powder, niacinamide, and D-panthenol in sequence. After adding each component, stir at a low speed for 2 minutes to ensure all ingredients are evenly dispersed, forming a homogeneous and fine mixture. Throughout the mixing process, the temperature is maintained below 50℃, and the system pH is 7.2 when panthenol is added to avoid hydrolysis of panthenol in an alkaline environment.

[0024] S4. Slowly pour the mixture obtained in step S3 into a pre-cleaned silicone mold coated with a thin layer of release agent at a temperature below 50℃. After pouring, gently shake the mold to remove any tiny air bubbles. Place the mold in a well-ventilated and clean area at room temperature (24℃) and let it cure for 48 hours. During this process, the moisture introduced into the mixture gradually and slowly evaporates, while the soap slowly solidifies at low temperatures, forming a firm, smooth, and dense solid handmade soap. After curing, remove the handmade soap from the mold and let it air dry in a ventilated place for another 24 hours to obtain the finished plant-based brightening handmade soap. The finished soap is a uniform light beige color, with no cracks or exudates on the surface, a fine cut surface without visible particles, and a faint herbal fragrance.

[0025] Example 2: This embodiment adds 4g of sodium lactate to the soap as described in Example 1. The addition of sodium lactate effectively enhances the soap's hardness and resistance to softening, while also providing moisturizing effects. All other raw material ratios and process parameters remain the same as in Example 1. The resulting product was stored for 3 months in a high-humidity summer environment without significant softening or surface sweating, and the soap's hardness remained excellent.

[0026] The present invention includes the following comparative examples for comparison and verification: Comparative Example 1: According to the raw material formulation of Example 1, the herbal compound powder was added directly to the molten soap base in step S3 in dry powder form without undergoing the low-temperature aqueous phase immersion extraction in step S2, while other steps and parameters remained unchanged. The resulting soap had clearly visible speckled agglomerated particles, a rough cut surface, and a frictional feel on the skin during use. After two weeks of storage, a white powdery precipitate appeared on the surface of the soap, and the hardness of the soap decreased significantly.

[0027] Comparative Example 2: Following the raw material formulation of Example 1, the herbal compound powder was added to 10 times its volume of purified water, heated to 100°C, and refluxed for 2 hours. The residue was then filtered out, retaining only the aqueous extract. The aqueous extract was concentrated and mixed with soap base at 75-80°C. Simultaneously, all other ingredients (including panthenol and niacinamide) were added to the high-temperature system at once, and then the mixture was molded. The resulting soap had a acceptable appearance, but due to the high temperature causing denaturation of silk protein, decomposition of niacinamide, hydrolysis of panthenol, and significant loss of herbal activity, the finished product testing showed a 65% decrease in amino acid content, a 48% decrease in niacinamide content, a 52% decrease in panthenol content, and a 60% decrease in total flavonoid content in the silk protein stock solution. The skin moisturizing effect after use was significantly weaker than in Example 1.

[0028] Comparative Example 3: This comparative example is based on Example 1, but the following key components are removed: Comparative Example 3-1: Shea butter and silk protein stock solution removed; Comparative Example 3-2: Nicotinamide removed; Comparative Example 3-3: Shea butter, silk protein extract and panthenol were removed.

[0029] The remaining formulation and process are the same as in Example 1. Comparative Example 3-1 showed reduced soap hardness, softened easily upon contact with water, and left skin noticeably tight after washing; Comparative Example 3-2 showed no significant brightening effect on skin tone after use, and left skin slightly dry; Comparative Example 3-3 exhibited the worst overall performance, with significant reductions in moisturizing properties, skin feel, and stability, indicating that the synergistic effect of shea butter, silk protein extract, niacinamide, and panthenol is a crucial guarantee for the technical effectiveness of this invention.

[0030] Comparative Example 4: In this comparative example, after step S2, the herbal powder residue was filtered out using a 200-mesh filter cloth, retaining only the extract, which was then added to the soap base. The remaining steps were the same as in Example 1. The resulting soap lacked the physical exfoliation and sustained-release skincare effects of the herbal powder, had an excessively light color, and exhibited significantly reduced skincare effects. The rate of improvement in skin roughness after use was approximately 42% lower than in Example 1.

[0031] To further objectively evaluate the various properties of the plant-based brightening handmade soap of this invention, the finished products of the examples and comparative examples were tested. All tests were conducted in an environment with a temperature of 25±1℃ and a relative humidity of 50±5%. Samples were randomly selected, and each group of tests was repeated 3 times. The average value of the results was taken.

[0032] Comparative Example 5: Following the raw material formula of Example 1, an additional 25g of Angelica dahurica was added, while other steps and parameters remained unchanged. The resulting soap showed a noticeable darkening in appearance.

[0033] Experiment 1: Take fresh soap from each example and comparative example, and cut the soap into 1cm pieces. 3 Small pieces were prepared into a 10% aqueous solution with distilled water at 25℃, and the pH was measured using a pH meter. The results are shown in Table 1: Table 1. pH value measurement results As shown in Table 1, the pH value of the embodiments of the present invention is between 7.2 and 7.3, which is weakly alkaline but close to neutral, and is gentle on the skin. Comparative Example 2 has a higher pH due to excessive saponification of the soap base caused by high temperature; Comparative Example 1 has excessively high local alkalinity due to powder agglomeration; Comparative Examples 3-3 have a pH of 7.9 due to the lack of a moisturizing oil system, resulting in increased skin irritation; Comparative Example 5 is the same as Example 1.

[0034] Experiment 2: In this experiment, soap was prepared into a 0.2% aqueous solution using distilled water. The instantaneous foam height and the foam height after 5 minutes were measured using a Roche foam meter at 40℃. The results are shown in Table 2. Table 2. Results of foam performance tests As shown in Table 2, the foam height and persistence of Example 1 are better than those of Comparative Examples 1 and 2, indicating that the process of the present invention helps to achieve uniform distribution of the foaming agent and foam stability. Sensory evaluation also shows that the foam of Example 1 and Comparative Example 5 is as delicate as cream and leaves no residue after rinsing.

[0035] Experiment 3: In this experiment, each sample was cut into soap blocks of 3cm × 3cm × 2cm, weighed, and placed in a constant temperature and humidity chamber at 23℃ and 80% relative humidity. Every 24 hours, the soap was removed, the surface moisture was gently absorbed with absorbent paper, and the weight gain was calculated. Simultaneously, the hardness of the soap was measured using a Shore A hardness tester. The tests were conducted continuously for 7 days, and the results are shown in Table 3. Table 3. Soap body hardness and resistance to softening / rotting tests As shown in Table 3, the soaps in Examples 1 and 2 of this invention have high hardness and low water absorption, exhibiting good resistance to softening and crumbling, especially after the addition of sodium lactate. In contrast, the comparative examples, due to the lack of shea butter and sodium lactate, or improper processing, showed a significant decrease in soap stability.

[0036] Experiment 4: This experiment selected 30 healthy volunteers (aged 25-55 years, half male and half female) with no history of skin diseases. The sample was prepared as a 10% aqueous solution, and 0.02 mL was placed in a patch applicator and applied to the inner forearm of the subjects. The patch applicator was removed after 24 hours, and skin reactions were observed at 0.5 h and 24 h, and a closed patch test was performed. Simultaneously, the change in the stratum corneum moisture content of the inner forearm was measured using a skin moisture meter 2 hours after application. The results are shown in Table 4. Table 4 Skin Moisturizing and Irritation Tests (Human Patch Test) As shown in Table 4, Example 1 showed no irritation and increased skin moisture content by 28.5%, demonstrating excellent moisturizing effects. The comparative examples, due to coarse powder, high pH, ​​or lack of moisturizing components, exhibited varying degrees of irritation and lower moisturizing rates. This indicates that the formulation and process of the present invention significantly reduce irritation and improve skin affinity.

[0037] Experiment 5: This experiment used an in vitro method to test the inhibition of tyrosinase activity. Each soap sample was prepared into a 1% aqueous solution using pH 6.8 phosphate buffer. L-tyrosine was used as the substrate, and mushroom tyrosinase (200 U / mL) was added. The mixture was incubated at 37°C for 20 minutes, and the absorbance at 475 nm was measured to calculate the inhibition rate. This experiment objectively reflects the product's potential to inhibit melanin production. The results are shown in Table 5. Table 5. Determination of in vitro tyrosinase inhibition rate As shown in Table 5, the inhibition rate of Example 1 was as high as 62.4%, indicating that nicotinamide and the flavonoids and coumarins contained in the herbal compound powder, such as Poria cocos and Bletilla striata, have a synergistic effect and a good ability to inhibit tyrosinase activity. The inhibition rate of the comparative example was significantly reduced due to process or component deficiencies.

[0038] Experiment 6: In this experiment, each soap sample was sealed in an aluminum-plastic composite bag and stored in a constant temperature and humidity chamber at 40℃ and 75% relative humidity for 3 months (simulating 18 months of storage at room temperature). Changes in appearance, odor, and physicochemical properties were observed, and the results are shown in Table 6. Table 6 Stability Tests (Accelerated Aging) As shown in Table 6, the stability results indicate that the soap in the embodiments of the present invention maintained excellent stability under accelerated conditions, while the comparative example showed obvious deterioration. This is because the low-temperature process retains the natural antioxidant components, along with the effects of stabilizers such as shea butter and sodium lactate.

[0039] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments that can be applied to other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A plant-based brightening handmade soap, characterized in that, Made from the following raw materials in parts by weight: 550-650 parts natural silk protein soap base, 10-20 parts shea butter, 8-12 parts castor oil, 5-10 parts nano pearl powder, 10-20 parts silk protein stock solution, 8-12 parts glycerin, 8-12 parts coconut oil foaming agent, 8-12 parts niacinamide, 2-6 parts panthenol, and 90-115 parts herbal compound powder; The herbal compound powder is made from the following raw materials in parts by weight: honeysuckle 3-7 parts, poria cocos 20-30 parts, atractylodes macrocephala 20-30 parts, bletilla striata 12-18 parts, and angelica sinensis 5-10 parts.

2. The plant-based brightening handmade soap according to claim 1, characterized in that... Made from the following ingredients in parts by weight: 600 parts natural silk protein soap base, 15 parts shea butter, 10 parts castor oil, 7.5 parts nano pearl powder, 15 parts silk protein stock solution, 10 parts glycerin, 10 parts coconut oil foaming agent, 10 parts niacinamide, 4 parts panthenol, and 102.5 parts herbal compound powder. The herbal compound powder is made from the following raw materials in parts by weight: 5 parts honeysuckle, 25 parts white poria cocos, 25 parts atractylodes macrocephala, 15 parts bletilla striata, and 7.5 parts angelica sinensis.

3. The plant-based brightening handmade soap according to claim 1, characterized in that: The herbal compound powder has a fineness of not less than 120 mesh, the shea butter is refined natural shea butter, the glycerin is food-grade glycerin, and the panthenol is D-panthenol.

4. The plant-based brightening handmade soap according to claim 1, characterized in that: In summer, the raw materials also include 3-5 parts of sodium lactate.

5. A low-temperature preparation process for a plant-based brightening handmade soap, comprising the preparation of the plant-based brightening handmade soap according to any one of claims 1-4, characterized in that, Includes the following steps: S1, mix honeysuckle, white poria, atractylodes macrocephala, bletilla striata and angelica sinensis, grind them into powder, and sieve to obtain fine herbal powder; S2, place the herbal powder in an extraction container, add a mixture of purified water and a portion of the glycerol in the formula as the extraction medium, wherein the amount of purified water added is 1.5-3 times the weight of the herbal powder, and the amount of the glycerol is 30-60% of the total weight of the glycerol in the formula; seal and let it stand for 72-96 hours at a low temperature of 0-10℃, during which intermittent ultrasonic oscillation is used to assist extraction, so that the active ingredients of the herbs are fully dissolved and form a uniformly dispersed herbal impregnation slurry. After extraction, no filtration is performed, and the obtained whole-component herbal impregnation slurry is directly used for the next step; S3 involves melting natural silk protein soap base at low temperature, adding all-component herbal impregnation slurry, and then sequentially adding shea butter, silk protein stock solution, glycerin, coconut oil foaming agent, castor oil, nano pearl powder, nicotinamide, sodium lactate and panthenol, and stirring until well mixed. S4. Pour the mixture into the mold at a low temperature and let it stand for 48-72 hours to allow excess moisture to evaporate slowly and the soap to fully solidify and solidify. Then, demold the soap to obtain the final product.

6. The low-temperature preparation process of a plant-based brightening handmade soap according to claim 5, characterized in that: In step S1, the sieving is performed through an 180-mesh sieve.

7. The low-temperature preparation process of a plant-based brightening handmade soap according to claim 5, characterized in that: The purified water in step S2 is deionized water or distilled water.

8. The low-temperature preparation process of a plant-based brightening handmade soap according to claim 5, characterized in that: In step S2, the power of the ultrasonic oscillation is 200-500W, the oscillation time is 10-20 minutes, and the oscillation is performed once every 8-12 hours; the entire extraction process is carried out under the protection of nitrogen or inert gas.

9. The low-temperature preparation process of a plant-based brightening handmade soap according to claim 5, characterized in that: In step S3, the low-temperature melting temperature is below 50°C, and the stirring speed is 30-60 r / min.

10. The low-temperature preparation process of a plant-based brightening handmade soap according to claim 5, characterized in that: The static curing in step S4 is carried out at room temperature, 20-30℃.

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