A neutral skin-cleansing soap composition and a method for preparing the same

Abstract

The present application relates to the technical field of neutral soap, and discloses a neutral skin-moistening soap composition and a preparation method thereof, which comprises the following components in percentage by mass: soap particles 10-30%; chelating agent 0.5-5%; SCIA 5-90%; binder 0.5-10%; wherein the SCIA is prepared by heating, co-melting, cooling and forming after sodium cocoyl isethionate, fatty acid and water are added; the SCIA comprises the following components in percentage by mass: sodium cocoyl isethionate 30-70%, fatty acid 20-50%, and water in balance. The sodium cocoyl isethionate with skin-moistening performance is premixed with the fatty acid, the obtained SCIA does not affect the forming of the neutral bath soap, and can greatly reduce the pH of the bath soap system. Meanwhile, the skin-fat reducing effect of the soap base is considered, and the irritability of the soap is greatly reduced, and the skin feeling after washing is improved.

Description

Technical Field

[0001] This invention relates to the technical field of neutral soaps, and in particular to a neutral moisturizing soap composition and its preparation method. Background Technology

[0002] Soap, a traditional detergent, is mainly composed of sodium fatty acids, which are produced by saponifying oils (vegetable or animal oils) with lye. However, traditional high-pH soaps present certain problems when used: 1) Soap has a pH of around 10 and is somewhat alkaline, while the skin's surface pH is around 6.5 and slightly acidic. Therefore, long-term use of soap for washing hands, face, or bathing can significantly increase the skin's pH, potentially causing allergic reactions in highly sensitive skin; 2) When used, soap removes the skin's natural oils, damaging the sebum layer and causing dryness, loss of softness and elasticity, and a feeling of tightness; 3) As soap is alkaline, it easily forms soap scum when it comes into contact with water, clogging pores and causing tightness and dryness, negatively impacting the user experience.

[0003] To overcome the alkalinity of ordinary soap, there are currently two main solutions: First, increase the amount of fatty acids in the formula, but the effect is not significant, and the pH of the soap solution is still greater than 9. If acid is added further, the soap will become soft, difficult to shape, and have a noticeable gritty feel after washing. Second, use anionic / nonionic surfactants as the main washing ingredients, combined with pH adjusters and softeners, to synthesize a "non-soap" synthetic soap. Although this type of soap is weakly acidic, it loses the basic cleaning properties of soap, leaving a slippery feeling after washing. Furthermore, an excessively high water ratio in the formula can cause the soap's performance, including resistance to rotting and cracking, to fail to meet requirements.

[0004] Patent application CN201410674325.8 discloses a neutral moisturizing cleansing soap, proposing to use surfactants as the main ingredient and emphasizing the use of acid agents to adjust the pH of the system to prepare a neutral moisturizing cleansing soap. The resulting cleansing soap has a pH value of approximately 4.5~6.5. Because the pH of the prepared soap is close to the slightly acidic environment of human skin, its degreasing power is low and its cleaning effect is poor. Patent application CN201210238172.3 discloses a multifunctional soap, proposing to prepare a multifunctional soap by replacing most of the soap granules with surfactants and compounding essential oils. The pH value is close to neutral and has low irritation. However, it does not provide specific pH value data for the embodiments involved, and when the sodium cocoyl hydroxyethyl sulfonate content in the formula is ≥60%, the raw material generates a lot of dust during the three-roll milling process, and the three rollers tend to become sticky and soft when heated, making the raw material slippery during milling, resulting in low production efficiency.

[0005] In actual production, the production of neutral soap still faces many problems, such as: 1. Mixing neutral soap requires a long time, often requiring a soap kneader to maintain a certain temperature and knead for about 60 minutes or more, which makes it impossible to continuously produce soap strips, resulting in extremely low production efficiency and consequently high production costs; 2. Formula molding is difficult because lowering the pH of the soap system requires replacing sodium fatty acids with surfactants and adding a large amount of acidifiers. However, most surfactants are liquids, and adding large amounts can cause slippage on the three-roller and make molding difficult. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a neutral moisturizing soap composition and its preparation method. Sodium cocoyl hydroxyethyl sulfonate (SCIA), which possesses moisturizing properties, is premixed with fatty acids (C12-C18), and the resulting SCIA is then used to prepare the soap composition. This method solves the problem of excessive alkalinity in ordinary soaps while also providing gentle skincare, improved cleaning performance, energy efficiency, environmental friendliness, and low production costs.

[0007] The objective of this invention is achieved through the following technical solution: In a first aspect, the present invention provides a neutral moisturizing soap composition comprising, by weight percentage, the following components: soap granules 10-30%; chelating agent 0.5-5%; SCIA 5-90%; binder 0.5-10%; wherein, SCIA is obtained by heating and melting sodium cocoyl hydroxyethanesulfonate, fatty acid and water together, followed by cooling and molding; the SCIA comprises, by weight percentage, the following components: sodium cocoyl hydroxyethanesulfonate 30-70%, fatty acid 20-50%, and water as the balance.

[0008] Sodium cocoyl sulfonate (SCI) is an anionic solid surfactant with a near-neutral pH and low irritation. However, direct addition can lead to excessive dust during three-roll milling, and the heat generated by the mill during continuous operation can cause the material to soften and become sticky, thus affecting production efficiency and molding. Furthermore, directly adding large amounts of acid to adjust the pH can result in a noticeably gritty feel in the soap, negatively impacting the user experience.

[0009] Therefore, this invention premixes sodium cocoyl hydroxyethanesulfonate, which has skin-moisturizing properties, with fatty acids (C12~C18), and then melts the two under certain temperature conditions, cools, and then shapes them. At room temperature, both sodium cocoyl hydroxyethanesulfonate and fatty acids are solids, and the fatty acids are insoluble in water. Adding water during the SCIA preparation process can promote the eutectic reaction of sodium cocoyl hydroxyethanesulfonate and fatty acids and adjust the viscosity of the eutectic.

[0010] Sodium cocoyl ethanesulfonate (SCI) treated with eutectic acid oxidation does not easily soften or slip when heated during milling. This is mainly due to the following reasons: 1. In the molten state, the intensified molecular thermal motion causes the crystal structure of the two substances to change from an ordered long-range arrangement to a disordered liquid state. Under the influence of molecular thermal motion, the two substances co-intercalate, with fatty acids embedding into the interior of SCI, jointly assembling to form mixed micelles. Due to the differences in the length of the hydrophobic chain, the size of the hydrophilic group, and the charge density of the two substances, the formation of mixed micelles enhances the hydrophobic interaction and density of the micelle core, while reducing electrostatic repulsion and the repulsion between micelles. Ultimately, this leads to a more compact and stable micelle structure, thereby improving the hardness of SCI. 2. When fatty acids are embedded in SCI, they "capture" and "pull" the hydrophobic chains of SCI to form a mixed lattice. During cooling, the mixed lattice gradually transforms into a stable β-crystal form, thereby improving the heat resistance of SCI.

[0011] On the other hand, by using mechanical milling, the acidified sodium cocoyl hydroxyethyl sulfonate, sodium fatty acid, and excipients are compounded and then milled through a three-roll mill. This method produces less material dust and prevents slippage, significantly improving production efficiency and making it suitable for continuous production. Simultaneously, the resulting soap is more compact and durable, and possesses both cleansing and moisturizing functions, providing insights for the development of subsequent practical products.

[0012] Preferably, the neutral moisturizing soap composition comprises the following components by mass percentage: soap granules 8.5-15.5%; chelating agent 0.5-5%; SCIA 80-87%; binder 0.5-10%. The neutral moisturizing soap composition contains fatty acids at a mass percentage of 25-36%.

[0013] Preferably, the SCIA comprises the following components by mass percentage: 45-65% sodium cocoyl hydroxyethanesulfonate, 20-40% fatty acids, and 15% water.

[0014] Preferably, the fatty acid includes one or more of lauric acid, myristic acid, palmitic acid, and stearic acid, more preferably palmitic acid and / or stearic acid.

[0015] Preferably, the temperature of the heating and eutectic process is 70~90℃, more preferably 80~85℃; the SCIA is prepared by first heating and eutecticizing sodium cocoyl hydroxyethanesulfonate and water for 10~20 min with a stirring speed of 300~500 rpm, then adding fatty acids and heating and eutecticizing for 5~10 min with a stirring speed of 300~500 rpm, and then cooling and molding.

[0016] The amount of water added to SCIA is small. Heating sodium cocoyl hydroxyethyl sulfonate and water together first can better promote the melting of subsequent fatty acids, so as to form a better embedded stable structure.

[0017] Preferably, the soap granules are obtained by saponifying natural oils, including coconut oil, palm kernel oil, or olive oil; the water content of the soap granules is 10-15%.

[0018] Preferably, the chelating agent includes one or more of tetrasodium hydroxyethyl phosphate, tetrasodium glutamate diacetate, and tetrasodium ethylenediaminetetraacetate.

[0019] Preferably, the binder includes one or more of starch, polyethylene glycol, and polyvinylpyrrolidone.

[0020] Preferably, the neutral moisturizing soap composition further includes, by weight percentage, the following component: 0.05-1% plant essential oil.

[0021] Preferably, the plant essential oil includes one or more of shea butter, lavender essential oil, jojoba seed oil, grape seed oil, olive fruit oil, and rose essential oil.

[0022] Secondly, the present invention also provides a method for preparing a neutral moisturizing soap composition, comprising the following steps: S1. Weigh each component according to the proportion and knead until evenly mixed; S2. The kneaded material is then subjected to a three-roll mill to obtain soap flakes. S3. Vacuum press the ground soap sheets into strips; S4. Cut the strip into pieces and then print them into shapes.

[0023] Preferably, during vacuum pressing, the outlet temperature of the barrel is controlled at 50~60℃, and the cooling water temperature of the pressing machine is controlled at 2~10℃.

[0024] Preferably, the temperature of the mold is set to -15~-5℃ during the printing process.

[0025] Compared with existing technologies, the present invention has the following beneficial effects: The present invention selects a suitable ratio of sodium fatty acid to sodium cocoyl ethanesulfonate, and further selects suitable fatty acids and a reasonable process temperature, which not only does not affect the molding of neutral bath soap, but also greatly reduces the pH of the bath soap system. Furthermore, in the technical solution of the present invention, the neutral bath soap simultaneously takes into account the degreasing effect of the soap base, and also greatly reduces the irritation of the soap, improving the skin feel after washing. Detailed Implementation

[0026] The technical solution of the present invention will be illustrated below with specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0027] The soap granules used in the following examples and comparative examples were obtained by saponifying natural oils, specifically coconut oil, and the water content of the soap granules was 13%.

[0028] The chelating agent used in the following examples and comparative examples is tetrasodium ethylenediaminetetraacetate.

[0029] The plant essential oil used in the following examples and comparative examples is lavender essential oil.

[0030] Examples 1-8

[0031] The preparation of surfactant SCIA includes the following steps: (1) Sodium cocoyl hydroxyethyl sulfonate and water are stirred evenly until completely melted under certain temperature conditions. The stirring temperature is 70~90℃, the stirring speed is 400rpm, and the stirring time is 20min. (2) Under heat preservation conditions, slowly add fatty acids (lauric acid, myristic acid, palmitic acid or stearic acid) to step (1) for co-melting. The stirring temperature is 70~90℃, the stirring speed is 400rpm, and the stirring time is 10min. (3) The mixture in the mixing container is fed into the rolling mill to form a sheet. After cooling and solidification, it is scraped off by a scraper to obtain SCIA sheets.

[0032] Examples 9-16 and Comparative Examples 1-5 The preparation of the soap composition includes the following steps: S1. Kneading and mixing: After accurately weighing each component according to the required proportions, add it to the soap kneader and mix the materials. The kneading time is 5 minutes until the materials are evenly mixed. S2. Three-roll mill: Add the kneaded and mixed material to a three-roll mill and mill it into soap flakes. S3. Vacuum pressing: The ground soap flakes are put into a vacuum pressing machine for vacuum pressing. The temperature of the pressing head outlet is controlled at 55℃, and the temperature of the cooling water in the pressing machine is controlled at 4℃. S4. Printing and Shaping: The long strips of soap pressed by the pressing machine are cut into blocks and directly fed into the printer for printing. The temperature of the mold is set to -10℃ during printing to obtain the shaped soap.

[0033] Table 1. Formulation composition of SCIA in Examples 1-4 As shown in Table 1, comparing the molding conditions of SCIA in Examples 1 to 4, it can be seen that the SCIA obtained when the fatty acid is palmitic acid or stearic acid has better hardness and can better meet the subsequent soap molding requirements.

[0034] Table 2. Formulation composition of SCIA in Examples 5-8 As shown in Table 2, comparative examples 4-6 show that an excessively high proportion of fatty acids in SCIA results in a material that is too thin and cannot be molded, thus affecting subsequent soap molding. Comparative examples 6-8 show that a low stirring temperature during SCIA preparation prevents the material from completely melting, hindering the formation of a good co-intercalation state between sodium cocoyl hydroxyacetate and fatty acids. A high stirring temperature during SCIA preparation affects the stability of SCI, leading to yellowing and consequently impacting product quality.

[0035] Table 3. Formulation composition of the soap compositions in Examples 9-16 Table 4. Formulation composition of soap compositions in Comparative Examples 1-5 Performance evaluation of the SCIA and soap composition in this invention: 1. pH determination: The pH value of the above embodiment was determined according to the potentiometric method for determining the pH value of surfactant aqueous solution in GB / T 6368-2008.

[0036] Table 5. pH results of surfactant SCIA in Examples 1-8 Table 6. pH results of the soap compositions in Examples 9-16 Table 7. pH results of soap compositions in Comparative Examples 1-5 2. Stability Test High temperature stability: Place the test sample open or in a bag with holes punched in it at 45±2℃ for 2 / 4 weeks, then return it to room temperature (25±2℃) and observe its appearance and odor.

[0037] High temperature and high humidity stability: Place the test sample open or in a bag with holes punched in it at 45±2℃ and 70% humidity for 2 / 4 weeks, then return it to room temperature (25±2℃) and observe its appearance and odor.

[0038] Room temperature stability: Place the test sample open or in a bag with holes punched in it at 25±2℃ for 2 / 4 weeks and observe it directly with the naked eye.

[0039] A "-" indicates that the sample has no obvious changes in odor and appearance, which is within the acceptable range and the stability is qualified; a "+" indicates that the sample has severe discoloration or produces an unpleasant odor, and the stability is unqualified. The number of "+" indicates the severity of discoloration and odor. The more "+" signs, the more obvious the abnormality and the more unstable the sample.

[0040] Table 8. Stability results of surfactant SCIA in Examples 1-8 Table 9. Stability results of the soap compositions in Examples 9-16 Table 10. Stability results of soap compositions in Comparative Examples 1-5 3. Anti-scrambling test Suspend one end of the soap in a 500 mL beaker, add deionized water to the beaker so that 2 / 3 of the test sample is submerged in the water, and soak for 5 hours. After soaking, remove the sample and let the water droplets drain. Place the sample on its side on a smooth and flat table, cut the sample horizontally with a thin blade, and measure the thickness of the three mushy surfaces with a ruler. Take the average value and express it in mm.

[0041] Table 11 Results of anti-smudging test of soap compositions in Examples 9-12 and Example 15 Table 12 Results of anti-smudging test for soap compositions in Comparative Examples 1-5 4. Crack resistance test Hang one end of the soap in a 500mL beaker, add deionized water to the beaker so that 2 / 3 of the test sample can be immersed in the water, soak for 1 hour, take it out, drain the water overnight, and observe the cracks on the soap surface.

[0042] Table 13. Cracking resistance results of the soap compositions in Examples 9-12 and Example 15 Table 14. Cracking resistance results of soap compositions in Comparative Examples 1-5 5. Gravel Sensation Test 1) Reagents and instruments: water, thermometer, water basin (minimum diameter 200mm, maximum diameter 325mm, height 120mm) 2) Measurement steps: ① Pour 2L of water into a basin and adjust the water temperature to 30°C. ② Soak the soap in the water for 30 seconds. Apply the soaked soap to your arm 5 times, then soak it again. Repeat this process 10 times. ③ Feel for any gritty feeling during the application.

[0043] Thirty test subjects (15 males and 15 females) were selected according to the prescribed method for detecting gritty textures to score the gritty textures of the above samples (5 - obvious gritty texture, 4 - some gritty texture, 3 - slight gritty texture, 2 - almost no gritty texture, 1 - no gritty texture). The lower the score, the lower the degree of gritty texture. The results were recorded.

[0044] Table 15. Grittiness of the soap compositions in Examples 9-12 and Example 15 Table 16. Grittiness of the soap compositions in Comparative Examples 1-5 6. Stratum corneum moisture content test The CM 825 skin moisture meter was used to measure the moisture content of the stratum corneum using the capacitance method. Changes in skin capacitance value reflected changes in moisture content. The main procedures were as follows: a) After cleaning the inner forearm of the subject, a 3cm × 3cm test area was marked. b) The CM 825 skin moisture meter was used to measure the moisture content of the designated area three times consecutively, and the average value was taken as the initial moisture content. c) Moisturizing soap was evenly applied to the test area 20 times, then rubbed and washed. After washing, residual moisture was patted dry with a paper towel, and the area was left to stand for 5 minutes before testing the moisture content of the designated area again, which was taken as the post-use moisture content. d) The changes in moisture content before and after using the moisturizing soap were compared among 30 subjects (15 males and 15 females) to evaluate the moisturizing effect. (Note: All procedures were performed with the consent of the subjects.) The stratum corneum moisture growth rate = (stratum corneum moisture content after washing - stratum corneum moisture content before washing) / stratum corneum moisture content before washing. It is mainly related to the difference in stratum corneum moisture content before and after washing. A positive growth indicates that it has a moisturizing effect, while a negative growth indicates that it does not have a moisturizing effect.

[0045] Table 17 Results of stratum corneum moisture content of soap compositions in Examples 9-12 and Example 15 Table 18. Test results of stratum corneum moisture content of soap compositions in Comparative Examples 1-5 7. Evaluation of hand-washing feel on the skin A questionnaire was used to allow participants to self-assess their skin hydration before and after using the product. Forty volunteers (20 men and 20 women) who regularly use soap were selected to rate their skin's moisturizing effect before and after using the soap, on a 7-point scale. The specific rating criteria were: 7 - Very satisfied, 6 - Satisfied, 5 - Somewhat satisfied, 4 - Average, 3 - Not very satisfied, 2 - Dissatisfied, 1 - Very dissatisfied. Moisturizing performance was evaluated based on the participants' ratings; higher scores indicated better moisturizing performance.

[0046] Table 19. Handwashing test results of the soap compositions in Examples 9-12, Example 15, and Comparative Examples 1-5 As shown in Table 5, the pH of the soap after SCI and stearic acid are acidified to form SCIA is weakly acidic. As shown in Table 7, comparing Comparative Example 4 with Example 11, the pH of the soap did not change significantly, indicating that applying SCIA to soap can reduce the alkalinity of the product. However, the gritty feel of Example 11 was significantly reduced, and the moisturizing and skin-softening effects were improved. As shown in Table 6, comparing Examples 9-11, 15, and 16, it can be seen that when the amount of SCIA added is ≥80%, the pH of the soap can be adjusted to neutral. This is mainly because when the amount of SCIA added is ≥80%, the amount of sodium fatty acid used can be greatly reduced, resulting in a more significant pH reduction effect on the soap system. However, the soap compositions in Examples 12-14 still have a relatively strong alkalinity. This is because the proportion of fatty acids added to the soap in Example 12 is relatively low, and when lauric acid and myristic acid are used as fatty acids in Examples 13-14, the effect of acid in adjusting pH is not significant, resulting in insufficient pH adjustment to neutral.

[0047] As shown in Tables 8-10, the SCIA obtained in Examples 1 and 2 and the soaps obtained in Examples 13 and 14 exhibited poor stability. This was mainly because when lauric acid and myristic acid were used as acid regulators in Examples 1 and 2, the fatty acid structure was looser than that of stearic acid. When acidified with SCI, the crystal support force embedded in its structure was weaker, resulting in lower strength and softer SCIA. Therefore, the stability of the SCIA added to the soap was poor.

[0048] As shown in Tables 11-14, SCIA prepared by pre-acidification and added to soaps such as Examples 9-12 exhibited good anti-smudging and anti-cracking properties. However, SCI without pre-acidification, directly mixed with fatty acids and added to soaps such as Comparative Examples 2-5, showed poor anti-smudging properties and all exhibited cracking. This is mainly because SCIA is formed by acidifying SCI and stearic acid under high-temperature melting conditions. At high temperatures, the structure of stearic acid and SCI changes from ordered crystals to disordered crystalline liquids. Under the action of molecular thermal motion, the two undergo co-intercalation. After complete melting and subsequent cooling, the internal crystals reorganize. The highly ordered and strong supporting framework of stearic acid promotes an increase in the hardness of the cooled SCIA. Therefore, when SCIA is used in soap, its wear resistance is improved by three-roll milling during the preparation process, solving the problem of material slippage. This ensures that all materials in the soap formula are fully milled and mixed, improving the overall hardness of the soap, thus enhancing its anti-smudging and anti-cracking properties. In contrast, Comparative Example 1 showed slight cracking due to the absence of polyethylene glycol 800. Polyethylene glycol 800, as a binder, can tightly bind the various raw materials inside the soap together, increasing the hardness and structural stability of the soap, making it less prone to softening and cracking during use, and improving its durability.

[0049] As shown in Tables 15-16, the soaps of Examples 9-12 had a significantly better gritty feel after washing than those of Comparative Examples 2-5. This is mainly because Comparative Examples 2-5 were prepared by simply stirring SCI and stearic acid with other raw materials. The stearic acid in these examples was not completely kneaded and mixed with the other materials, resulting in a noticeable gritty feel.

[0050] As shown in Tables 17-19, based on the stratum corneum moisture test results and hand-wash evaluation, the following conclusions can be drawn: 1. Pre-acidifying SCI and stearic acid into SCIA before adding it to soap can greatly improve the skin feel after washing. Furthermore, as the amount of SCIA added increases, the rate of increase in stratum corneum moisture content and the hand-wash score also increase (Examples 11 and 15). 2. When the amount of SCIA added is ≥80% (Examples 11 and 15), the rate of increase in stratum corneum moisture content and the hand-wash score after soap washing are better. When the amount of SCIA added is >87% (Example 16), the resulting soap has lower hardness, and the soap softens during high-temperature testing, affecting its usability. The above results are mainly due to: 1. SCIA is made by acidifying and melting SCI and stearic acid. Its pH is weakly acidic. Adding it to soap can lower the pH. Furthermore, as the amount of SCIA added increases, the amount of sodium fatty acids in the soap will decrease, further reducing the soap's pH to neutral, thus solving the problem of tightness after washing with traditional high-alkaline soaps. However, when the amount of SCIA added is too high, the amount of sodium cocoamide isoflavone added also increases, and conversely, the amount of soap granules added decreases. Sodium fatty acids in soap granules form a tight, regular crystalline network, playing a supporting role in the soap formula. If the amount added is too low, it will affect the internal crystal structure of the soap, resulting in lower hardness and softening at high temperatures. 2. Because the pH of SCIA in Example 6 is lower than that in Example 4, the pH of Example 11 added to the soap is lower than that of Example 12, resulting in a better skin feel after washing.

[0051] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made using the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A neutral skin-cleansing soap composition, characterized by comprising: It includes the following components by mass percentage: Soap granules 10-30%; Chelating agent 0.5-5%; SCIA 5~90%; Adhesive 0.5~10%; SCIA is prepared by heating sodium cocoyl hydroxyethanesulfonate, fatty acids and water together and then cooling and molding it. The SCIA comprises the following components by mass percentage: 30-70% sodium cocoyl hydroxyethanesulfonate, 20-50% fatty acids and water as the balance.

2. The neutral moisturizing soap composition according to claim 1, characterized in that, The fatty acids include one or more of lauric acid, myristic acid, palmitic acid, and stearic acid.

3. The neutral moisturizing soap composition according to claim 1 or 2, characterized in that, The temperature for the heating and eutectic process is 70~90℃; the SCIA is prepared by first heating and eutecticizing sodium cocoyl hydroxyethanesulfonate and water, then adding fatty acids and heating and eutecticizing, followed by cooling and molding.

4. The neutral moisturizing soap composition according to claim 1, characterized in that, The soap granules are obtained by saponifying natural oils, including coconut oil, palm kernel oil, or olive oil; the water content of the soap granules is 10-15%.

5. The neutral moisturizing soap composition according to claim 1, characterized in that, The chelating agent includes one or more of tetrasodium hydroxyethyl phosphate, tetrasodium glutamate diacetate, and tetrasodium ethylenediaminetetraacetate.

6. The neutral moisturizing soap composition according to claim 1, characterized in that, The adhesive includes one or more of starch, polyethylene glycol, and polyvinylpyrrolidone.

7. The neutral moisturizing soap composition according to claim 1, 4, 5, or 6, characterized in that, The neutral moisturizing soap composition further includes, by weight percentage, the following component: 0.05-1% plant essential oil.

8. The neutral moisturizing soap composition according to claim 7, characterized in that, The plant essential oils include one or more of shea butter, lavender essential oil, jojoba seed oil, grapeseed oil, olive fruit oil, and rose essential oil.

9. A method for preparing a neutral moisturizing soap composition as described in any one of claims 1-8, characterized in that, Includes the following steps: S1. Weigh each component according to the proportion and knead until evenly mixed; S2. The kneaded material is then subjected to a three-roll mill to obtain soap flakes. S3. Vacuum press the ground soap sheets into strips; S4. Cut the strip into pieces and then print them into shapes.

10. The method for preparing the neutral moisturizing soap composition according to claim 9, characterized in that, During vacuum pressing, the nozzle outlet temperature is controlled at 50~60℃, and the cooling water temperature of the pressing machine is controlled at 2~10℃; during printing, the mold temperature is set to -15~-5℃.

Images