Transparent weakly acidic system containing sodium lauroyl glutamate and application of transparent weakly acidic system

Abstract

The invention discloses a transparent weakly acidic system containing sodium lauroyl glutamate, which comprises the following components in percentage by weight: 5-6% of sodium lauroyl glutamate, 10-20% of second surfactant and water, and the pH value of the system is 6-6.9. The invention also relates to a preparation method of the transparent weakly acidic system containing sodium lauroyl glutamate and an application of the transparent weakly acidic system containing sodium lauroyl glutamate in personal cleaning care products.

Description

Technical Field

[0001] This invention relates to the field of daily chemical products, specifically to a transparent weakly acidic system containing sodium lauroyl glutamate and its applications. Background Technology

[0002] In personal care cosmetics, rinse-off products (such as facial cleansers, shower gels, and shampoos) occupy a significant market share as frequently used daily items. For these rinse-off products, many consumers have developed clear core needs: firstly, they seek a balance between foam texture and moisturizing properties, rejecting low-quality experiences; secondly, they prioritize the gentleness of the formula to minimize potential irritation to the skin barrier; and thirdly, they prefer transparent forms, as this visible appearance complements the excellent foam texture. Based on current market trends, the combination of amino acid surfactants and mildly acidic formulas represents a promising technological direction. Mildly acidic formulas have a pH value closer to the natural pH range of human skin, resulting in less skin irritation compared to alkaline formulas. Amino acid surfactants, containing natural amino acid groups in their molecular structure, exhibit excellent biocompatibility, making them significantly gentler than traditional soap-based and sulfate-based surfactants, thus becoming a core ingredient choice for gentle rinse-off products. The transparent form, through its matching appearance with the skin feel, further reinforces consumers' expectations of the product's refreshing properties.

[0003] Among numerous amino acid surfactants, sodium lauroyl glutamate (SLA) stands out due to its unique dicarboxylic hydrophilic head group and glutamate backbone structure, which endows it with outstanding mildness and moisturizing properties, making it a preferred amino acid surfactant raw material. However, in practical applications, SLA exhibits precipitation, layering, or turbidity in non-alkaline systems, limiting its use in weakly acidic conditions to paste-type products. Its usability for formulating transparent products is very low, making SLA difficult to apply in weakly acidic transparent formulations.

[0004] Some previous technical solutions have also disclosed related applications. For example, Chinese patent application CN202211231592.9 provides an application of a transparent composition with amino acid surfactants, but its compounded components are relatively complex, such as the composition simultaneously containing polyols, nonionic surfactants, and amphoteric surfactants. Achieving transparency is technically easier in this case, and the amino acid surfactant does not contain glutamate. Other technical solutions disclose the application of sodium lauroyl glutamate in facial cleansing products. For example, Chinese patent application CN201611107961.8 provides a preparation and application of a facial cleansing product containing sodium lauroyl glutamate and with a pH adjusted to weakly acidic. However, its application is limited to crystalline products and cannot be used in transparent systems.

[0005] Therefore, researching and finding a sodium lauroyl glutamate surfactant composition that can remain transparent and stable in a weakly acidic system has practical application value. Summary of the Invention

[0006] This application provides a transparent, weakly acidic system containing sodium lauroyl glutamate, comprising: 5-6% by weight of sodium lauroyl glutamate, 10-20% by weight of a second surfactant and water, wherein the pH of the system is 6-6.9.

[0007] In a preferred embodiment, the surfactant in the system has a solid content of 10% by weight.

[0008] In a preferred embodiment, the weight ratio of sodium lauroyl glutamate and the second surfactant is 1:2.2-3.3.

[0009] In a preferred embodiment, the second surfactant is selected from lauramidopropyl betaine or cocamidopropyl hydroxysulfonate.

[0010] In a preferred embodiment, the second surfactant is 13.3-16.7% by weight of cocamidopropyl hydroxysulfonate.

[0011] In a preferred embodiment, the second surfactant is a composition comprising 16.7% by weight of lauramidopropyl betaine.

[0012] In a preferred embodiment, the pH value of the system is 6-6.5.

[0013] This application also provides a method for preparing the above system, including the following steps: 1) Weigh 5-6% by weight of sodium lauroyl glutamate and 10-20% by weight of the second surfactant; 2) Weigh out the deionized water, add the surfactant weighed in step 1) to the deionized water while stirring, heat to 60°C and keep stirring until homogeneous; 3) Cool down to 25°C and add citric acid to adjust the pH.

[0014] This application also provides the application of the above system in personal care products.

[0015] In a preferred embodiment, the personal hygiene product is a wash-off cleaning product composition, which is selected from: shower gel, shampoo, and hand soap. Brief description of the attached figures Figure 1 The image shows the product of Example 4 after a one-month stability test at 25°C. Figure 2This is a photo of the product from Example 29 after a one-month stability test at 4°C. Detailed Implementation

[0016] This invention creatively provides a sodium lauroyl glutamate surfactant composition that can remain transparent and stable in a weakly acidic system, and this composition has practical application value.

[0017] To provide a more concise description, some of the quantitative expressions given herein are not modified by the term "approximately". It should be understood that, whether or not the term "approximately" is explicitly used, each quantity given herein is intended to refer to an actual given value, and also to an approximation of such given values ​​that can be reasonably inferred by one of ordinary skill in the art, including approximations of such given values ​​caused by experimental and / or measurement conditions.

[0018] Active The surfactant mentioned in this application is an abbreviation for surfactant.

[0019] weakly acidic system The weakly acidic system described in this application refers to a system with a pH value between 6 and 6.9.

[0020] Second surfactant The second surfactant in this application is a collective term for surfactants other than sodium lauroyl glutamate in a transparent, weakly acidic system containing sodium lauroyl glutamate.

[0021] Solid content The solid content mentioned in this application refers to the actual percentage of surfactant components in the surfactant raw material.

[0022] Example The present invention will be further illustrated below with reference to specific embodiments. However, these embodiments do not constitute any limitation on the present invention and are only used to illustrate the present invention. Any limited modifications made within the scope of the claims of the present invention are still within the scope of the claims of the present invention.

[0023] Unless otherwise stated, percentages and parts are by weight. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as are familiar to those skilled in the art. Furthermore, any methods and materials similar or equivalent to those described herein may be applied to the methods of this invention. The preferred embodiments and materials described herein are for illustrative purposes only.

[0024] Experimental materials: Sodium lauroyl glutamate (100% solid content, Jiujiang Tinci High-Tech Materials Co., Ltd.); Cocamidopropyl hydroxysulfonate (30% solids content, Guangzhou Xingye Technology Co., Ltd.); Lauryl betaine (solid content 30%, Migen Shoji Co., Ltd.); Sodium cocoamphoacetate (30% solids content, Solvay Investment Co., Ltd.); Lauroamide propyl betaine (30% solid content, Dongxiong Chemical Co., Ltd.); Decyl glucoside (55% solids content, BASF (China) Co., Ltd.); Preparation method and stability test of transparent system: 1. Weigh the selected amounts of each component of the surfactant compound. 2. Weigh out the deionized water. Add the weighed components from step 1 to the deionized water while stirring. Heat to 60°C and continue stirring until homogeneous. 3. Cool to 25℃, add citric acid to adjust to the target pH. 4. After placing the prepared sample in a 25℃ constant temperature incubator for 24 hours, remove it and divide it into two equal parts. Place one part in a 25℃ constant temperature incubator and the other part in a 4℃ constant temperature incubator to observe its stability at room temperature and low temperature.

[0025] Examples 1-12 Preparation of Surfactants at Different Concentrations Examples 1-12 describe the preparation of analytes with different solid contents and pH values ​​using sodium lauroyl glutamate as a single surfactant. The sample preparation process described above was used to prepare each sample, as shown in Table 1 below.

[0026] Table 1

[0027] Test Example 1: Stability Test After placing the samples from Examples 1-12 in a 25°C incubator for 24 hours, they were removed and divided into two equal parts. One part was placed in a 25°C incubator, and the other part was placed in a 4°C incubator for one month (M) to observe their stability at room temperature and low temperature. The stability of the surfactant system under different solid contents and different pH values ​​was investigated. In the stability test, √ indicates that the stability test was passed, with clear and transparent appearance as the standard; × indicates that the stability test was not passed, with non-clear and transparent appearance as the standard.

[0028] Table 2

[0029] The results show that regardless of the solid content concentration of sodium lauroyl glutamate (SLG), whether it is 1%, 3%, or 5%, it can only remain transparent and stable at room temperature under weakly alkaline conditions (pH 7.5). Once the pH is adjusted to a weakly acidic range, precipitation occurs. For example... Figure 1This is a photo of Example 4 product after a one-month stability test at 25°C. Figure 1 The product was white and opaque, indicating it failed the stability test. Furthermore, it remained unstable even at low temperatures (4°C) and at pH 7.5. Therefore, the next step is to try a surfactant-based formulation.

[0030] Examples 13-27 Preparation of surfactant compositions with different concentrations Examples 13-27 illustrate the preparation experiments of sodium lauroyl glutamate with a solid content of 5% and compounded with another surfactant at a solid content ratio of 5%:5%. The aim was to select compound surfactants that could better improve stability at low pH and low temperature.

[0031] The sample preparation and processing methods mentioned above were used to prepare each sample, as shown in Table 3 below.

[0032] Table 3

[0033] Test Example 2: Stability Test After placing the samples from Examples 13-27 in a 25°C incubator for 24 hours, they were removed and divided into two equal parts. One part was placed in a 25°C incubator, and the other part was placed in a 4°C incubator for one month (M) to observe their stability at room temperature and low temperature. The stability of the surfactant system under different solid contents and different pH values ​​was investigated. In the stability test, √ indicates that the stability test was passed, with clear and transparent appearance as the standard; × indicates that the stability test was not passed, with non-clear and transparent appearance as the standard.

[0034] Table 4

[0035] The results show that within the pH range of 6.0-6.9, glycoside nonionic surfactants cannot maintain a transparent and stable state at 4°C. The same applies to amphoteric surfactants sodium cocoamphoacetate and lauryl betaine; therefore, these three were excluded from further testing. Of the remaining compound surfactants, cocamidopropyl hydroxysulfonate performed best. The cocamidopropyl hydroxysulfonate composition maintained the system's transparency and stability at room temperature at pH 6.0 and at 4°C at pH 6.5. Lauryl propyl betaine, on the other hand, maintained stability at 4°C at pH 6.9. In other words, Examples 19, 25, and 26 have achieved the technical application of sodium lauroyl glutamate exhibiting low-temperature stability and transparent form under weakly acidic conditions. Further experiments will be conducted with different ratios of sodium lauroyl glutamate with lauryl propyl betaine and cocamidopropyl hydroxysulfonate to observe whether increasing the proportion of sodium lauroyl glutamate can improve the product's foam texture.

[0036] Examples 28-39 Preparation of surfactant compositions with different concentrations Examples 28-39 are surfactant compositions with a total solids content of 10%, tested at a solids content ratio of sodium lauroyl glutamate to compound surfactants of 6:4 and 7:3.

[0037] The sample preparation and processing methods mentioned above were used to prepare each sample, as shown in Table 5 below.

[0038] Table 5

[0039] Test Example 3: Stability Test After placing the samples from Examples 28-39 in a 25°C incubator for 24 hours, they were removed and divided into two equal parts. One part was placed in a 25°C incubator, and the other part was placed in a 4°C incubator for one month (M) to observe their stability at room temperature and low temperature. The stability of the surfactant system under different solid contents and different pH values ​​was investigated. In the stability test, √ indicates that the stability test was passed, with clear and transparent appearance as the standard; × indicates that the stability test was not passed, with non-clear and transparent appearance as the standard.

[0040]

[0041] The results show that when sodium lauroyl glutamate and the compound surfactant are mixed at a ratio of 6%:4%, cocamidopropyl hydroxysulfonate remains stable at 4°C and pH 6.5 and 6.9, demonstrating certain practicality. However, lauroamide propyl betaine loses its original stability at 4°C and pH 6.9 at a ratio of 5%:5%. Furthermore, when sodium lauroyl glutamate and the compound surfactant are mixed at a ratio of 7%:3%, stability under all conditions is lost. Therefore, through experiments, Examples 28 and 29 also meet the technical requirements for sodium lauroyl glutamate to achieve low-temperature stability and transparent form under weakly acidic conditions. For example... Figure 2 This is a photo of Example 29, showing the product after a one-month stability test at 4°C. Figure 2 The product exhibits a clear and transparent appearance, indicating that it passed the stability test. Furthermore, due to the higher proportion of sodium lauroyl glutamate, its foam texture is better than that of Examples 19, 25, and 26, demonstrating practical application value. Therefore, this invention researches and finds a sodium lauroyl glutamate surfactant composition that can maintain transparency and stability in a weakly acidic system.

[0042] Application examples The compositions described in this invention can be used as intermediate raw materials in the preparation of corresponding personal care products. These personal care products are preferably wash-off cleaning product compositions, including but not limited to the preparation of formulations such as children's or adults' shower gels, shampoos, and hand sanitizers. The following are specific examples of the application of the compositions obtained through examples in personal care products, as well as the formulations and preparation methods of these formulations. Specific applications are as follows: Application Example 1: Preparation of Mild Baby Bath

[0043] Application Example 2: Preparation of a Mild Shampoo for Children

[0044] Application Example 3: Preparation of Adult Moisturizing Shower Gel

[0045] Application Example 4: Preparation of Adult Moisturizing Hand Sanitizer

Claims

1. A transparent, weakly acidic system containing sodium lauroyl glutamate, comprising: 5-6% by weight sodium lauroyl glutamate, 10-20% by weight a second surfactant and water, wherein the pH of the system is 6-6.

9.

2. The system as described in claim 1, characterized in that, The surfactant in the system has a solid content of 10% by weight.

3. The system as described in claim 1, characterized in that, The weight ratio of sodium lauroyl glutamate and the second surfactant is 1:2.2-3.

3.

4. The system as described in claim 1, characterized in that, The second surfactant is selected from lauramidopropyl betaine or cocamidopropyl hydroxysulfonate betaine.

5. The system as described in claim 4, characterized in that, The second surfactant is 13.3-16.7% by weight of cocamidopropyl hydroxysulfonate betaine.

6. The system as described in claim 4, characterized in that, The second surfactant is a composition comprising 16.7% by weight of lauramidopropyl betaine.

7. The system as described in claim 1, characterized in that, The pH value of the system is 6-6.

5.

8. A method for preparing the system according to any one of claims 1-7, comprising the following steps: 1) Weigh 5-6% by weight of sodium lauroyl glutamate and 10-20% by weight of the second surfactant; 2) Weigh deionized water, add the surfactant weighed in step 1) to the deionized water while stirring, heat to 60°C and keep stirring until uniform; 3) Cool down to 25°C and add citric acid to adjust the pH.

9. The application of the system as described in any one of claims 1-7 in personal care products.

10. The application as described in claim 9, characterized in that, The personal hygiene product is a wash-off cleaning product composition, which is selected from: shower gel, shampoo, and hand soap.

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