Today’s beauty consumers want it all. The savvy youth market seeks refreshing effects on application and ways to dramatise their appearance – along with perceivable benefits.
Older populations are a driving force for products that bring new life to skin by providing soothing moisturisation and masking the visual effects of ageing. Working populations look for convenience and easy use, along with long-lasting colour. The global marketplace needs a little of everything, from customised products differentiated for gender, age, and ethnicity, as well as those geared for fashion trends and seasonal differences Meanwhile, the growing concept of sustainability brings increased awareness of health, environmental and ethical factors to the forefront.
New materials for market impact
In light of today’s market megatrends, successful personal care products depend on a number of factors, from astute product development to creative marketing. Yet for ultimate impact, innovative material technology is a primary component of consumer acceptance. Emulsions are the foundation for products ranging from skin care and sun protection to hair care and colour cosmetics. Along the way, demand has increased for materials that provide multiple formulation benefits, perhaps combining structure with moisturisation, curl retention with hair shine, or colour intensity with long-lasting wear. Multifunctional waxes that form stable emulsions and also thicken are increasingly used in formulating facial care products. Among the newest materials is an emulsifying soy wax, hydrogenated soy polyglycerides/soyamide DEA (and) C15-23 alkane, (Dow Corning HY-3200 Emulsifying Soy Wax) which forms stable oil-in-water emulsions with a broad range of silicones and cosmetic oils. The off-white or beige coloured wax (Fig. 1) acts as a multifunctional emulsifier and thickener at low use levels. No additional thickener is needed, reducing the number of ingredients and offering a potential cost advantage. The naturally derived soy emulsifying wax is produced using a ‘green chemistry’ approach and renewable feedstock. It was developed for a broad range of oil-in-water applications in skin, hair and sun care as well as colour cosmetics, and joins two related soy materials made by a novel metathesis process.
Hydrogenated soy polyglycerides (and) C15-23 alkane (Dow Corning HY-3050 Soy Wax): This wax adds structure and stiffness to sticks, pomades and creams. It allows for softer sticks with less crystallisation compared to other waxes, and it can be used to build viscosity in water-in-oil formulations.
Hydrogenated soybean oil (and) hydrogenated soy polyglycerides (and) C15-23 alkane (Dow Corning HY-3051 Soy Wax Blend): This blend of wax and oil can serve as a sustainable alternative to petrolatum. It adds shine and helps control frizz in hair conditioning formulations, and it can act as a conditioning agent for moisturisation and emolliency.
The most basic of the soy products, hydrogenated soy polyglycerides (and) C15-23 alkane, is derived from soybean oil. The oil, which contains a large amount of polyunsaturated fatty acid, is metathesised and then hydrogenated to form a soft, plastic-like cosmetic wax useful for structuring a wide range of cosmetic oils. Because of its unique structure and compatibility with other personal care ingredients, the soy wax is less prone to crystallisation compared to other common structuring waxes. Similarly, the soy wax blend is a naturally derived viscous paste formed when the soy wax is blended with partially hydrogenated soybean oil. The process used to form the new emulsifying soy wax takes the metathesis technology a step further. In this case, the soybean oil is metathesised, hydrogenated, and then modified by the addition of polar groups. The result is an emulsifying wax that also has thickening benefits when used in combination with a wide range of cosmetic oils. The three soy materials contain hydrocarbons (C15-23 alkane) that are produced from soybean oil during metathesis. Overall, while standard triglycerides have limited functionality, metathesised triglycerides provide an innovative architecture with the potential for reduced crystallinity, increased malleability and reduced brittleness. The three soy materials also meet consumer desires for sustainable products. The feedstock is renewable and the recognised green chemistry production process focuses on higher reaction efficiency, reduced solvent waste and lower energy consumption when compared to petrochemical technologies.
A new option for thickening and emulsifying
A variety of tests were conducted to assess the performance of the emulsifying soy wax from a perspective of formulation development.
Broad utility with cosmetic ingredients
The soy emulsifying wax was compared with several commercial benchmark emulsifying waxes and evaluated with a variety of commonly used silicones and cosmetic oils. Each test emulsion comprised 5% emulsifying wax, 5% cosmetic oil and 90% water. The wax and oil were heated until the wax was completely melted. The hot water was added, and the sample was mixed until it cooled to approximately 35°C. Results in Figure 2 show the soy emulsifying wax emulsifies and thickens a broad range of common cosmetic oils and silicones more effectively than the commercial benchmark materials.
Viscosity versus concentration
Two test formulations were used to evaluate emulsion viscosity versus concentration of the soy emulsifying wax. The basic test formulation for natural oil moisturiser contained 4% emulsifying soy wax, 9% sunflower oil, 3% ultra high viscosity dimethiconol in a low viscosity dimethicone fluid, 0.2% preservative, and water. The basic test formulation for a natural butter moisturiser contained 4% emulsifying soy wax, 9% shea butter, 3% phenyl trimethicone, 0.2% preservative, and water. For the purposes of the evaluations, the concentration of soy wax was varied from 4.0 wt% to 6.0 wt%, with a corresponding adjustment for water. Figure 3 illustrates how it is possible to achieve a wide range of viscosities by varying a low level of emulsifying soy wax. Whether in need of a thick cream or a light lotion, formulators have increased flexibility to achieve the desired thickness of the final product without extensive alterations to the formulation.
pH tolerance and stability
A test moisturising lotion formulation containing 6% soy wax emulsifier, 4% dimethicone (and) dimethiconol, 3% phenyl trimethicone, 5% glycerin and 0.2% preservative was used to assess variability of the emulsion viscosity with changing pH. Glycolic acid or a 10% solution of sodium hydroxide was used to vary the pH in the samples. Figure 4 illustrates viscosity of the test formulation over a broad pH range. Viscosity remained relatively unchanged between pH 4 and pH 7, and also between pH 10 and pH 12, although it increased significantly at levels higher than pH 7. This acceptance of varying pH allows for the use of the soy wax emulsifier in personal care applications requiring a high or low pH level, which may lead to immediate emulsion failure with other emulsifiers. To evaluate pH stability over three months, the same basic test lotion was prepared with 5% emulsifying soy wax. Figure 5 illustrates the stability of samples at three pH levels. Over the course of this study, the viscosities of all three samples remained relatively unchanged, with no noticeable emulsion instability.
The moisturising lotion formulation, this time with 5% emulsifying soy wax, was used to establish the effects of varying salt concentration on viscosity. As typically seen with many formulations, the viscosity of the emulsion initially increases with the addition of NaCl. For this study, the viscosity of the emulsion peaks around 0.75% NaCl and decreases around 1.25%, where it then begins to stabilise until at least 2.5% NaCl.
The role of sensory characteristics
Consumers of beauty and skin care products not only look for pleasant sensory effects upon application and during wear, but they also expect comfort, which includes an absence of inflammation, tenderness or itchiness.
Lack of skin irritation
Repeat insult patch testing was used to assess the irritation potential of the emulsifying soy wax. The wax was dispersed in water at levels of 5% and 10%. The higher level represents what might be expected as the top range of concentration used in a typical formulation. The samples were compared with distilled water and a solution of 0.2% sodium lauryl sulfate, a recognised skin irritant. Figure 7 shows there was no evidence of significant skin irritation at either level of soy emulsifying wax. In addition to its broad potential for use in skin care products, the emulsifying soy wax demonstrated beneficial sensory effects in an oil-in-water formulation for rinse-off hair conditioner, as tested on Caucasian hair tresses. The test formulation for these evaluations contained 3% emulsifier, 0.5% cetrimonium chloride, 1.2% hydroxyethylcellulose, and 0.2% preservative. For the second series of evaluations, 5% cyclopentasiloxane (and) dimethiconol was added, with a corresponding adjustment in the amount of water. As Figure 8 shows, use of the emulsifying soy wax gave nearly identical sensory properties when compared with two industry benchmark emulsifying waxes. When a blend of ultra high viscosity dimethiconol in cyclopentasiloxane was added to the test formula, the sensory characteristics were essentially equal, suggesting the use of additional components to create consumerperceivable sensory effects may not be required. The ability to use fewer ingredients or those having multifunctional properties may result in lower formulation cost.
Formulators in today’s beauty and personal care market strive to create products that fulfil evolving global megatrends, whether related to ageing populations, a fashionforward youth market, or environmental sustainability. Multifunctional materials with broad ingredient compatibility and the ability to form stable formulations with novel sensory and textural characteristics are in the best position to have an impact in today’s marketplace. The new emulsifying soy wax and its related materials suggest opportunities for nextgeneration skin and hair care products.
Credit: Dow Corning Corporation
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