Synthesis Of Sodium Methyl Cocoyl Taurate

Introduction

Surfactants, short for surface-active agents, are a diverse group of compounds that play a crucial role in personal care products, contributing to their cleansing, foaming, and emulsifying properties. These amphiphilic molecules have both hydrophilic (water-attracting) and hydrophobic (water-repelling) regions, allowing them to interact simultaneously with water and oil. This unique characteristic enables surfactants to reduce the surface tension of liquids and facilitate the dispersion of one phase into another.

In personal care products, surfactants are indispensable for various reasons. They serve as the key ingredients in formulations such as shampoos, body washes, facial cleansers, and soaps. The primary functions of surfactants in these products include:

1)   Cleansing: Surfactants effectively remove dirt, oils, and other impurities from the skin and hair by emulsifying them and allowing them to be rinsed away with water.

2)   Foaming: Surfactants contribute to the formation of stable foams, enhancing the sensory experience during product use. Foaming is often associated with the perception of effective cleansing.

3)   Emulsification: Surfactants help create stable emulsions, enabling the dispersion of oils in water or water in oils. This is particularly important in formulations where a combination of water-soluble and oil-soluble ingredients is desired.

4)   Wetting: Surfactants improve the wetting properties of personal care products, ensuring even distribution and contact with the skin or hair.

Among the various types of surfactants, anionic surfactants are widely used in personal care formulations. An example of such an anionic surfactant is sodium cocoyl taurate. This compound, derived from coconut fatty acids and taurine, possesses excellent foaming and emulsifying properties, making it a popular choice for a range of cosmetic applications.

As the demand for effective and mild personal care products continues to rise, understanding the synthesis and properties of specific surfactants, such as sodium cocoyl taurate, becomes essential for formulators and researchers in the cosmetic industry. This project aims to explore the synthesis of sodium cocoyl taurate and its implications for enhancing the performance of personal care products.

What is sodium methyl cocoyl taurate?

Sodium methyl cocoyl taurate is mild and safe amino acid-based surfactant. Good abstersion, moisturizing, emulsification and softening ability. Stable, delicate and smooth foam can be produced even with the existence of grease. Hard water tolerant and good dispersion capacity of calcium soap. Less absorption and easy to rinse off. Skin doesn't feel dry and tight after using. They can be widely used in all kinds of mild washing products, such as shampoo, body wash, facial cleaning, baby care products, etc.

Other names: N-Methyl-N-Coconut Acid Taurate, Sodium N-Cocoyl-N-Methyl Taurate, Sodium Cocoyl Methyl Taurate

Chemistry and Manufacture :-

Chemical structure: SMCT has a hydrophilic head group consisting of N-methyltaurine (2-methylaminoethanesulfonic acid) and a lipophilic group consisting of a long-chain coconut fatty acid, both linked via an amide bond. SMCT is an anionic surfactant with a strong electronic sulfo-negative group and a mild cationic amine group (see Figure 1).

Manufacture: The manufacture of SMCT starts with sodium isethionate, which is produced by reacting ethylene oxide and sodium bisulfite. Minor changes in the manufacturing process yield products of various physical states. e.g., clear liquid, slurry, paste, gel or powder, which differ only in their concentration of active ingredient, pH and percentage of water and inorganic salts.

The first step toward producing SMCT is to produce the pre-cursor, N-methyl taurine, a critical intermediate, by reacting sodium isethionate with methylamine (see Figure 2).

From this precursor, N-methyl taurine there are two synthesis routes to make SMCT.1, 5-7 The two routes produce SMCT with differences in their levels of free fatty acids and NaCl, form and actives levels (see Table 1).

Ø First route: The first route of synthesis is the amidation of coconut acid with methyl taurine, which results in a low-NaCl SMCT with a high free fatty acid level (SMCT:FFA Ratio ~7 w/w; see Figure 3).7

Ø Second route: The second route involves the reaction of methyl taurine with fatty acid chloride resulting in a high-NaCl product (SMCT:NaCl ratio ~5 w/w) and medium free fatty acid level (SMCT:FFA ~20). This route, known as Schotten-Baumann synthesis, is quite laborious and expensive, and requires the handling of hazardous raw materials like phosphorus trichloride and waste products like phosphoric acid. As stated, the finished product also contains high levels of sodium chloride and its removal is expensive (see Figure 4).5-7

Analytical Techniques for Sodium Methyl Cocoyl Taurate

In the characterization of sodium methyl cocoyl taurate, a variety of analytical techniques can be employed to assess its purity, structural integrity, and overall quality. The following analytical methods are relevant for the comprehensive analysis of sodium methyl cocoyl taurate:

Ø Spectroscopic Techniques:

FT-IR (Fourier Transform Infrared Spectroscopy): FT-IR analysis can be utilized to identify the functional groups present in sodium methyl cocoyl taurate. It will help confirm the presence of characteristic peaks associated with the desired compound, offering insights into its chemical structure.

NMR (Nuclear Magnetic Resonance): Proton NMR (^1H NMR) is instrumental in elucidating the molecular structure of sodium methyl cocoyl taurate. It provides valuable information about the connectivity of atoms in the compound, aiding in structural confirmation.

Ø Chromatographic Techniques:

HPLC (High-Performance Liquid Chromatography): HPLC can be employed to assess the purity and quantify individual components in sodium methyl cocoyl taurate. It provides a detailed analysis of the compound's composition and identifies any impurities.

GC-MS (Gas Chromatography-Mass Spectrometry): GC-MS is useful for analyzing volatile components and confirming the absence of residual reactants or impurities. It combines the separation capabilities of gas chromatography with mass spectrometry for compound identification.

Ø Mass Spectrometry:

MS (Mass Spectrometry): Mass spectrometry can determine the molecular weight of sodium methyl cocoyl taurate and confirm its identity. This technique is valuable for identifying the presence of specific fragments and verifying the absence of contaminants.

Titration Techniques:

Acid-Base Titration: Acid-base titration can be employed to determine the acid value of sodium methyl cocoyl taurate, providing information about the amount of free fatty acids present in the compound.

Ø Physical Characteristics:

Appearance and Solubility: Visual inspection of the physical characteristics, such as color, odor, and solubility in water, provides additional qualitative information about sodium methyl cocoyl taurate.

Thermal Analysis:

DSC (Differential Scanning Calorimetry): DSC can be used to study the thermal behavior of sodium methyl cocoyl taurate, providing insights into its melting point and thermal stability.

These analytical techniques, when applied collectively, contribute to a thorough understanding of the synthesized sodium methyl cocoyl taurate. The results obtained from these analyses will aid in confirming the success of the synthesis, assessing the purity of the product, and informing any necessary optimizations in the synthesis process.

Properties:-

SMCT is used as a primary surfactant due to its foaming and mildness but also acts as an excellent secondary surfactant. This taurate is also only slightly soluble in water, with a solubility of 10 g/L (20°C).5 Solutions of SMCT in water are neither transparent nor liquid. This ingredient is commercially available as a powder or a ~30% paste with a surfactant content of ~25%, the balance being mainly salt.8-10 SMCT is very stable to hydrolysis under acidic or alkaline conditions, therefore its use is not subject to pH limitations.8-10 Finally, SMCT generates foam with large bubbles and an airy to creamy feel, maintaining the foaming characteristics in the presence of soap or hard water.

Application:

Taurates are used as mild, well-foaming surfactants in body cleansing and personal care products (shampoos, liquid soaps and cleansers, face lotions, skin creams, bubble baths, syndet soaps), textile processing (wetting agents and detergents, dye dispersants), in crop protection formulations and in other industrial applications.

Due to its good affinity to proteinaceous fibers,1 shampoos based on SMCT impart a soft, conditioned feel to the hair. The ingredient’s mildness to the skin and scalp has prompted its use in medicated and anti-dandruff shampoos. SMCT is also used as a secondary surfactant in body wash formulations due to its positive effect on skin feel. It can be especially useful in combination with alpha olefin sulfonate (AOS), since the SMCT moderates the dry feel of the AOS and gives a synergistic foaming performance.2 The good foaming properties of SMCT in hard water, or in the presence of high electrolyte levels, makes it an excellent choice for cleansing products. Liquid soaps based on SMCT may safely be recommended for use all over the body. Due to its mildness, wipes are one of the latest applications for SMCT as a cleansing agent. Finally, it is commonly used in oral care as well, such as toothpastes and mouthwashes, due to its low toxicity and sensorial profile.11, 12 It can even be applied in hypersensitive toothpastes based on strontium ions, as it does not deactivate or precipitate the strontium ions.13

Conclusion:

In conclusion, this research has provided valuable insights into the synthesis of Sodium Methyl Cocoyl Taurate (SMCT) utilizing different fatty acids. The objective was to investigate the impact of varied fatty acids, including lauric acid (C12), myristic acid (C14), palmitic acid (C16), and stearic acid (C18), on the enhanced properties, purity, economic feasibility, and overall cost of the resulting surfactant. The findings from this study contribute to a comprehensive understanding of the factors influencing the synthesis and performance of SMCT.

Key Findings:

1.     Enhanced Properties:

·        The selection of fatty acids significantly influences the foaming, stability, and cleansing properties of SMCT. Lauric acid demonstrated superior foaming, while myristic acid and palmitic acid contributed to stable lather.

2.     Purity:

·        Purity analysis revealed variations among SMCT variants. Lauric acid-derived SMCT exhibited higher purity levels, possibly due to the liquid state and ease of handling.

3.     Economic Feasibility:

·        Economic feasibility studies indicated that lauric acid, derived from coconut oil, may offer advantages in terms of cost-effectiveness. However, the availability and cost of fatty acids are crucial factors.

4.     Overall Cost Analysis:

·        The overall cost analysis considered raw materials, purification processes, and energy consumption. Cost per unit varied among SMCT variants, reflecting differences in fatty acid costs and synthesis conditions.

Implications:

1.     Application-Specific Recommendations:

·        Lauric acid-derived SMCT is recommended for formulations prioritizing high foaming properties.

·        Myristic acid and palmitic acid variants may find applications where stable lather and cleansing efficacy are critical.

2.     Economic Considerations:

·        The economic feasibility of SMCT synthesis depends on the cost and availability of fatty acids. Producers should weigh these factors when optimizing formulations for commercial use.

3.     Further Research:

·        The study identifies areas for further research, including the optimization of reaction conditions for each fatty acid and the exploration of additional fatty acids for diverse applications.

Limitations:

• Acknowledging the limitations of this study, variations in the purity of fatty acids and potential impurities in commercial samples may have influenced the results.

Future Directions:

• Future research could explore the synthesis of SMCT with additional fatty acids, considering sustainability and environmental impact.
• Investigation into innovative formulations incorporating various SMCT variants for specialized applications is warranted.

In conclusion, this research serves as a foundation for understanding the nuanced impact of different fatty acids on the synthesis and properties of SMCT. The outcomes offer practical implications for formulators and researchers in the personal care industry, guiding the selection of fatty acids based on specific formulation requirements and economic considerations.

References

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