Surfactant-free emulsions from clay-based particles

In addition to these properties some clay-based products (e.g. Laponite XLG, Mineral Colloid BP and Tixogel MPZ) also offer several less well-known benefits that can be utilised in many different formulations alongside traditional rheology modification. One example is their use as Pickering emulsion stabilisers and this aspect is described in more detail in this article.

 Rockwood Additives’ range of clay-based rheology modifiers for personal care and cosmetics applications for aqueous systems include synthetic layered silicates (Laponite range, INCI name: Lithium Magnesium Sodium Silicate) and high purity natural clays such as sodium/calcium bentonite (Mineral Colloid range, INCI name: Bentonite). For solvent/oil-based formulations, organically-modified bentonite (Tixogel range, INCI names: Stearalkonium Bentonite and Quaternium-90 Bentonite) is also available. Laponite is one of the most versatile thickeners across the range of water-based rheology modifiers and some of the key benefits are that it rapidly disperses in water without the need for high shear, to give colourless dispersions; it offers a high degree of shear-thinning compared with other thickeners (Fig. 1); high viscosity at low shear rates which produces very effective anti-settling properties (Figs. 2 and 3); low viscosity at high shear rate and therefore can be easily sprayed or applied; it has a non-elastic texture, and is nonstringy; progressive and controllable thixotropic restructuring after shear; synergistic interactions with some polymeric thickeners – tuneable rheology profiles, particularly useful for ‘harsh conditions’ i.e. high surfactant/electrolyte formulations; it is a film-former and emulsion stabiliser – keeping actives or phases apart; it is inorganic, non-yellowing, non-toxic, stable at high temperatures and cannot support microbial growth. Some of these properties also apply to formulations containing the natural bentonite products, both aqueous and solvent-based. In particular, recent research into the stabilisation of emulsions using clay-based particles has led to the discovery that several clay-based particles traditionally used for rheology modification are excellent emulsion stabilisers when incorporated using a unique, fast, novel process developed as a result of this research. These emulsions are termed Pickering emulsions. In addition to stabilisation against creaming and coalescence, these products also simultaneously impart their rheological properties to the Pickering emulsions, resulting in a two-in-one benefit for the formulator.

 Emulsion stabilisation