SUN CARE
What is an inversion emulsion? Inverse emulsion polymerisation is an effective manufacturing technology for producing high- performance liquid thickeners. Pre-neutralised and ready to use, these polymers can be used cold during the formulation of end-products. These products are composed of an oily
continuous phase and an aqueous dispersed phase. The monomers are polymerised in the water droplets which are stabilized by a non- ionic surfactant.
When the emulsion comes in contact with an aqueous phase, then the inversion is immediate and the continuous phase becomes water with an optimum viscosity development. The best solution offered by SNF to achieve
high SPF formulation with mineral filters is Natursol™ EMI 132 (INCI: Sodium Acrylate/ Sodium Acryloyldimethyl Taurate (ATBS) copolymer and C15-19 Alkane and Lauryl Glucoside). This is a multifunctional rheology modifier for oil-in-water formulations that provides viscosity, stabilization texture, and sensory to formulations. In addition, it is a multifunctional rheology
modifier that is 67% naturally-derived according to ISO 16128. This allows formulators to design systems with up to 99% naturality.
Steps to stable formulation development The formulations were developed using a standard mixer at room temperature. None of the formulation trials used heat. Each trial
followed the same procedure, except in trial 2 when the xanthan gum was removed. Procedure Phase A: Glycerin and xanthan gum were premixed and added to the mixing vessel with water. One the mixture was uniform, the remaining ingredients in Phase A were added in sequential order. Phase B: In a separate vessel, the ingredients in Phase B were added and homogenised until Phase B was smooth and creamy. Next, Phase A was slowly added to Phase B while mixing until Phase AB was well emulsified, homogeneous and free from any lumps. Phase C: Finally, Phase C was added to Phase AB and continued mixing until the product was uniform.
Observations In each trial, observations were made
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and used to determine the next steps to developing a successful formulation. Each ingredient plays an important role in the overall performance of SNF’s cold process mineral SPF 50+ formulation. Since the goal was to develop a sunscreen product that was better for the environment, raw materials with a natural index close to one were selected. Trial 1 Sodium Stearoyl Glutamate is a 100% natural emulsifier. It is effective at low concentrations and compatible with mineral UV filters. The product showed signs of separation in 24 hours in 40°C incubation. There was a visible liquid separation. Trial 2
The amount of Sodium Stearoyl Glutamate was increased and xanthan gum was removed. The sensory of the formulation improved with the additional Sodium Stearoyl Glutamate. The formulation had velvety feel, increased play time and cushion. The formulation was stable initially.
However, after incubation for 24 hours at 40°C, the sunscreen had a cheesy appearance. This indicated that there was not enough emulsification in the formulation for it to remain stable. Trial 3 Xanthan gum was added back with an increased percentage. Also, Sodium Acrylate/ Sodium Acryloyldimethyl Taurate Copolymer (and) C15-19 Alkane (and) Lauryl Glucoside percentage was increased.
www.personalcaremagazine.com
October 2022 PERSONAL CARE
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