Thickening polymer delivers soft, velvety skin feel

Aristoflex Velvet is a highly effective rheology modifier with the ability to thicken and stabilise aqueous systems and O/W emulsions. Moreover it provides an excellent compatibility with organic solvents and facilitates stabilisation of beads. Based on proven Aristoflex technology of copolymerising a polysulfonic acid derivative with various co-monomers, Aristoflex Velvet (now referred to as ‘the new thickener’) is produced as a preneutralised powder. The established process eliminates the subsequent neutralisation required in the case of many acrylic acid based products. The unique properties of the new thickener are determined by the finely tuned composition of its co-monomers. With its superior sensorial profile, the new thickener creates a pleasant and velvety skin feel not just in emulsions, but also in clear gel formulations. Compared to other polymers, it delivers an appealing pampering sensory. This is due to the fact that the new thickener does not immediately break on skin when applied, but instead gently melts to leave skin feeling evenly moisturised. Furthermore, products with the new thickener feature a nice texture, good spreadability, and will not become sticky even at higher glycerol concentrations. Another interesting feature of the new thickener is its excellent compatibility with organic solvents, which enables the possibility of manufacturing clear gels with ethanol contents of up to 70 per cent (see Fig. 1). Other organic solvents, such as acetone, isopropanol or ethyl acetate, can also be used. The viscosity of the polymer gel will remain unaffected over a wide range of solvent concentrations. The new thickener permits the formulation of highly transparent gels with high solvent content (Fig. 2). Its solvent compatibility also lends itself to the formulation of hand sanitisers, always with a pleasant, velvety smooth, non-drying skin feel. The new thickener offers this precise sensorial profile without the need for adding large amounts of emollients (Formulation 1). Other products where the formulation of a highly transparent gel can be of advantage and where the new thickener provides benefits include nail polish removers, facial toners and hair tonics. It is of course possible to develop emulsions with the new thickener that exhibit a particularly nice, smooth texture while at the same time providing an extraordinarily velvety and soothing skin feel during use. With the new thickener, rich and nourishing formulations are just as feasible as light gel creams – always delivering a velvety skin feel.

Emulsion stabilisation

Another favourable property of the new thickener is the stabilisation of different types of emulsions even at elevated temperatures. The temperature stability of an emulsion can be determined by means of rheological tan delta measurement over a temperature sweep from 25°C to 60°C (77°F to 140°F). A cone-plate measuring geometry is used for performing the temperature sweep in an oscillating way. The cone is made to oscillate at a defined frequency while the temperature of the sample is evenly raised within a range from 25°C to 60°C. The rheometer records both the storage modulus G’ and the loss modulus G”, describing the elastic and the liquid contents of the sample, respectively. The tan delta is received by calculating the ratio of the moduli, which then shows whether there is a greater elastic or liquid content in the sample. With a predominantly liquid content, the tan delta will be >1; with a predominantly elastic content, it will be <1. Figure 5 shows that the tan delta of an emulsion without polymer will rise above 1 at approx. 37°C (99°F), so that instability may arise under common stability testing conditions at elevated temperatures e.g. 40°C or 50°C (104°F or 122°F). In contrast, the emulsion sample containing 0.5 % of polymer exhibits a consistent tan delta of <1 over the entire temperature range, offering considerably improved temperature stability. These measured results permit a positive prediction of long-term stability. If the emulsion shows a tan delta below 1 over the entire temperature range from 25°C to 60°C, it very likely will maintain this stability also over a longer period of time. The standard 1% aqueous polymer gel underlines this conclusion with a relatively constant tan delta of approximately 0.35. This indicates that the new thickener will provide a high degree of temperature stability even in aqueous gels. However, the new thickener does not just stabilise the oil droplets in emulsions. It can even provide suspending properties in a variety of products, including clear gels, enabling the stabilisation of colourful beads, pigments, microcapsules, encapsulated particles with actives, sparkling pearls and shimmering particles (Fig. 3). This opens up a wide potential for formulations such as facial tonics with beads or powders and skin care serums. Due to its manufacturing process, the new thickener provides the advantage of being pre-neutralised. As its sulfonic acid groups are completely hydrolysed, it can be used within a wide pH range from 3 to 8 (Fig. 4). This allows formulation with alpha hydroxy acids such as lactic acid, citric acid, malic acid, etc. Additionally, formaldehyde and paraben-free preservation with benzoic acid, salicylic acid and other preservatives is possible. The new thickener can be added to any step of the production process, which greatly facilitates the manufacture of formulations containing this polymer. Both hot and cold processing is possible. The powder can be dispersed directly in the oil phase. If the oil phase is heated, the polymer can simply be dissolved in the hot oil phase. Or if preferred, it can also be added to the water phase, in which it quickly dissolves and builds a gel network. In addition, the new thickener can also be pre-dispersed in a nearly anhydrous polyol phase. Furthermore, the viscosity of the final formulation can be adjusted at the end of the manufacturing process or even thereafter, if necessary. Altogether, these different procedures facilitate the development of an efficient and time saving manufacturing process. This makes the new thickener an extremely friendly ingredient for product developers. The characteristics described above highlight how the new thickener nicely complements Clariant’s existing Aristoflex product range. Each Aristoflex polymer delivers special properties that are beneficial for different cosmetics products. Every Aristoflex polymer also has a unique sensory profile that matches to other benefits for specific cosmetic formulations. Aristoflex AVC was the first innovative development in the Aristoflex polymer line for personal care. Well known all over the world, it is used by many manufacturers globally and features the essential base properties of any polymer in this family, i.e. enhanced stability and emulsifying characteristics as well as thickening capability for emulsions and gels. AVC permits the development of clear gels, O/W emulsions as well as also emulsifierfree formulations. AVS contains the same selection of comonomers as the AVC product, with the only difference in the counter ion of the sulfonic acid group. In AVC, the counter ion is ammonium, in AVS it is sodium. For this reason, AVS can be used for formulations up to a pH of 11, so it is ideal e.g. for selftanning products containing dihydroxyacetone. AVL is a low viscosity, ready-to-use liquid dispersed polymer. It combines the unique properties of AVC with the optimised mixture of the two emulsifiers trilaureth-4 phosphate and polyglyceryl-2- sesquiisostearate in the widely used oil phase caprylic/capric triglyceride. It allows easy formulation of O/W emulsions in a very short time, making it very efficient and user friendly. HMB belongs to the class of hydrophobically modified polymers. It functions as a primary emulsifier and stabiliser in O/W emulsions. As the hydrophobic portion absorbs at the oil-water interface, and the hydrophilic portion swells in the water phase, it provides exceptional emulsion stability to a broad range of oils. HMB can be used to prepare O/W emulsions in both hot and cold processes. HMB is typically added to the oil phase (comprising emollient and emulsifier), where slight agitation facilitates dispersion. In addition, it exhibits high compatibility with surfactants, which also makes it very suitable for formulating rinse-off products. BLV is another hydrophobically modified polymer, with a unique composition particularly suitable for low viscous formulations, like spray-able or liquid lotions. Concentrations of up to 40 per cent of oil can be incorporated into formulations. TAC is a polymer used as a rheology modifier for surfactant based systems. The polymer is pre-neutralised, easy to use and provides formulations with excellent yield force, even at very low polymer concentration and low viscosities. Ideal for stabilisation of beads and shimmering particles in showers, shampoos, perfumes, etc. It also provides a pleasant, soft and slightly nurturing sensation.