22 SUN CARE
(Penetol GE-IS) as an emulsifier that forms liquid crystals in W/O emulsions with higher internal phase content, thereby affording a lighter and non-oily feel of the skin.
Lauryl Lactate: a natural solubilizer and dispersing agent of UV filters Lauryl Lactate is a clear, colourless liquid with a 100% natural origin (ISO 16128). It is a fatty alcohol and fatty acid ester, and so has properties of both molecules, providing moisture or improving the lipid content of the skin. It offers viscosity builder action in aqueous
cleansing systems, and can also be used as a solubilizer and dispersing agent for hydrophobic molecules, such as some UV filters. Proper dispersion of inorganic UV filters
is crucial for the stability, UV protection, transparency and physical properties of solar products. In this study we used two inorganic UV filters (Zinc Oxide and Titanium Dioxide) combined with Lauryl Lactate or C12-15 Alkyl Benzoate used as reference. The evaluation of dispersion was carried out
taking into account three factors: the interaction of the emollients with the powder of the mineral filters; the minimum level of emollient required to wet the powder; and the viscosity of the dispersion. The optimum selection would be to identify
an oil-powder combination which can produce relatively low viscosity dispersion, with fast interaction, but without too fast a rate of sedimentation, in order to balance between dispersibility and stability.1 The use of Lauryl Lactate with mineral
UV filters shows a good balance between dispersibility and stability, requiring less emollient to wet the UV filters powders. This is positive, because it affords ‘free’ emollient left available for the emulsification or solubilization of other UV filters. Moreover, low dispersion viscosity is obtained, related to better handling and providing an indication of potential viscosity addition to the final sunscreen product.
Lauryl Lactate also has good solubilizer
properties for organic UV filters, allowing the solubilization of greater quantities of some common UV filters than standard solubilizers
35 30 25 20 15 5 0
DHHB BEMT
DHHB: Diethylamino Hydroxybenzoyl Hexyl Benzoate EHT: Ethylhexyl Triazone
EHT AB
BEMT: Bis-Ethylhexyloxyphenol Methoxyphenyl Triazine AB: Avobenzone
Figure 2: UV-filter solubility of Lauryl Lactate versus C12-15 Alkyl Benzoate PERSONAL CARE June 2024
Power dispersion factors:
Emollient interaction 0.7g of powder to 45g of oil
Minimum emollient required to wet
UV filter ZnO TiO2 ZnO TiO2 25% ZnO Viscosity of dispersions 35% TiO2 51200 cP INORGANIC UV FILTER 11102cP
C12-15 Alkyl Benzoate Fast Slow 65mL/100g 110mL/100g 10000 cP
Lauryl Lactate Medium Slow 35mL/100g 90 mL/100g 247 cP
Fast
Medium Figure 1: Summary of the dispersion evaluation of two emollients with TiO2
such as C12-15 Alkyl Benzoate. The solubility properties of Lauryl Lactate
from solid organic UV filters was characterized in terms of the % of solid organic UV filters soluble in 100 ml of emollient at 20 °C, and in terms of the UV absorbance characteristics. Figure 2 illustrates that Lauryl Lactate versus the reference exhibits greater solubility in the Diethylamino Hydroxybenzoyl Hexyl Benzoate (DHHB) and Ethylhexyl Triazone (EHT) UV filters. In Figure 3, the absorbance curves of the UV
Exceparl LM-LC ■ C12-15 AlkylBenzoate ■
Slow and ZnO UV filters
filters combination (Bis-Ethylhexyloxyphenol Methoxyphenyl Triazine (BEMT) + 2-Ethylhexyloxyphenol Methoxyphenyl Triazine (EHMC) + Titanium Dioxide (TiO2
) at 3:3:1 ratio
and 14% total active) dissolved in Lauryl Lactate or in C12-15 Alkyl Benzoate show that the combination of UV filters dissolved in Lauryl Lactate exhibits a hyperchromic effect, which allows greater efficiency, especially in the UVB region.
These results demonstrate that Lauryl
Lactate is a good candidate for solubilizing and/or dispersing UV filters, which could have a positive impact upon UV protection efficacy and SPF.
Isostearyl Glyceryl Ether: emulsifier for W/O emulsions with high water content The emulsifier selected for re-designed sun protection products is crucial for defining the type of emulsion. The present study selected Isostearyl Glyceryl Ether (GE) with a very low HLB number, i.e. 2, which allows us to formulate water-in-oil emulsions. It is known to Kao Chemicals that Isostearyl
Glyceryl Ether forms a stable transparent liquid crystalline phase of a reversed hexagonal type with water. This was confirmed by small angle X-ray scattering (SAXS) measurements on the emulsifying characteristics of GE, investigated by Yuji Suzuki and Hisao Tsutsumi.2
www.personalcaremagazine.com
% of organic UV-filter soluble in emollients
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80
