148 FORMULATING FOR MILDNESS


100000 10000 1000 100 10


4.5 4.6 4.7 4.8 4.9 5.0 pH-Value Figure 3: Surfactant molecular arrangement in Rheo2Green1 diluted solutions at different pH obtained by computer molecular design method. There are other advantages of using


Rheo2Green blends as raw materials. (A) The pure lauryl glucoside is a highly viscous liquid, which usually requires pre- heating before use. Rheo2Green concentrates are low viscous and cold processable that can avoid the necessity of heat boxes in the production process. (B) Compared to the use of separate


Rheo2Green components, these blends simplify logistic aspects such as storage, purchase and dosage during manufacturing.


(C) The price of Rheo2Green raw materials is improved due to production process optimisation. As mentioned previously, this


combination of surfactants entails a natural micellar thickening. Typically most


surfactants form spherical micelles. Only under certain conditions wormlike, cylindrical micelles can be built. On a molecular scale these structures look like long polymer molecules. The interaction between these cylindrical micelles provides the thickening effect in a similar manner (Fig1). With the new products, required viscosity is very easy achievable. The concentrate should be diluted with water and instantaneous thickening takes place when pH is adjusted to 4.6-5.3. Figure 2 shows change of viscosity versus pH for the solutions of Concentrate 1 at different dilutions. It has been found that viscosity of these systems has a maximum. For Concentrate 1 diluted solutions in the absence of further components it is located at constant pH ~4.9. The pH viscosity-


maximum can slightly move between 4.5 and 5.3 when additional ingredients are present.


Micellar thickening phenomenon was further studied using computer molecular design methods. They confirmed that only at a certain pH-value, the interaction of sodium cocoyl glutamate and lauryl glucoside molecules results in the formation of self-assembly of nonspherical micelle structures (Fig 3). Such aggregates, unlike standard spherical micelles, provide the desirable thickening effect/viscosity. As visualised by computer simulation, due to the structural similarity of sodium cocoyl glutamate and lauryl glucoside molecules, they arrange parallel to each other and prefer to form a 1:1 unit together (Fig 4). In the pH range, where the mono


5.1 5.2 5.3


W%product


W%active


 40% 13%  30% 10%  20% 6.6%


5.4


5.5


Figure 4: Computer simulated interaction of sodium cocoyl glutamate and lauryl glucoside molecules in 1:1 blend. PERSONAL CARE EUROPE April 2019


Viscosity (mPa*s)


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