SUN CARE 95
Tinosorb (now referred to as ‘TSB’) S Lite Aqua is unique as a dispersion of the oil- soluble UV filter active BEMT. Figure 1 shows the absorbance spectra of several UV filters, including BEMT.
Incorporating BEMT into both the water and the oil phase boosts the SPF of a formulation while allowing manufacturers to reduce the oil phase, thus keeping the formulation light. This helps manufacturers avoid solubility issues due to an oil phase overload. Incorporated into the water phase, the aqueous dispersion forms a homogeneous film on the skin. The insolubility of BEMT in water ensures water resistance while supporting effective sun protection.
Tests and results Formulations containing the new BEMT- based cosmetic UV filter formulation have proven their performance and the formulation’s effect on water resistance in a series of in vivo and in vitro tests: SPF in vivo test ISO24444, UVA-PF in vitro test ISO24443, WR in vitro test according to internal BASF method No. 50, and WR in vivo test according to the Cosmetic Europe Water Resistance Guideline, Dec 2005. As a reference, a sunscreen formulation
(UV-DE-16-123-1-8) was prepared containing the UV-B filters Ethylhexyl Triazone (EHT, e.g. Uvinul®
T 150) at 2.0%
and Ethylhexyl Salicylate (EHS) at 5.0% as well the UV-A filter Diethylamino Hydroxybenzoyl Hexyl Benzoate (DHHB, Uvinul A Plus) at 3.0% in the oil phase. Two further formulations were prepared containing an additional 2% BEMT (TSB S) in the oil phase (UV-DE-16-123-1-1) and an additional 2% BEMT (10% TSB S Lite Aqua equals 2% BEMT active) in the water phase (UV-DE-16-123-1-2), respectively. The respective protection factors that were achieved are given in Table 1, SPF in vivo and UVA-PF in vitro. The formulation containing no broad- spectrum UV filter (UV-DE-16-123-1-8)
1.6 1.4 1.2 1
0.8 0.6 0.4 0.2 0
290 Figure 2: Tinosorb® November 2019 320 S Lite Aqua boosts sun protection. PERSONAL CARE ASIA PACIFIC 350 Wavelenght (nm) 380
achieved an SPF in vivo of around 10 (12) and a UVA-PF in vitro of 5.1. By contrast, the formulation containing 2% BEMT (TSB S) in the oil phase (UV-DE-16-123-1-1) achieved an SPF in vivo of around 15 (13) and a UVA-PF in vitro of 7.3, while the one containing 10% TSB S Lite Aqua (equals 2% BEMT active) in the water phase (UV-DE-16- 123-1-2) reached an SPF in vivo of around 25 (23) and a UVA-PF in vitro of 11.2. The addition of 2% BEMT to the water phase effectively increased the sun protection values SPF and UVA-PF compared with adding 2% BEMT to the already loaded oil phase (Fig 2).
Selection of emollients To dissolve 4% BEMT (TSB S) in the oil phase, a large volume of polar oils is needed (Table 2, formulation UV-DE-16- 123-2-5). If just half of the BEMT can be transferred to the water phase (UV-DE-16- 123-2-9), formulators will have more flexibility to choose light emollients with high spreadability values, for lighter sensory properties (Table 2).
Enhancing water resistance To assess the effects of water-phase UV filters on a sunscreen’s water resistance (WR), three SPF 50+ formulations were prepared with
n UV-16-123-1-2 Tinosorb®
S Lite Aqua
Base + 10% Tinosorb® (2% BEMT in water phase)
n UV-16-123-1-1 BEMT
Base + 2% BEMT (Tinosorb® S)
n UV-16-123-1-8 Base 2.0% Ethylhexyl Triazone (EHT) 5.0% Ethylhexyl Salicylate (EHS) 3.0% Diethylamino Hydroxybenzoyl Hexyl Benzoate (DHHB)
S Lite Aqua
Table 2: SPF in vivo and UVA-PF in vitro results UV filters
UVB filters Ethylhexyl Triazone (EHT, e.g. Uvinul®
T 150) Ethylhexyl Salicylate (EHS) UVA filter
Diethylamino Hydroxybenzoyl Hexyl Benzoate (DHHB, Uvinul®
A Plus)
Broad- spectrum BEMT (Tinosorb®
Tinosorb® SPF in vivo
S) S Lite Aqua UVA-PF in vitro
– –
12 5.1
2.0% –
13 7.3 –
10.0% 23
11.2 % by weight 2.0% 5.0% 3.0% % by weight UV-DE-16-123-1-8 UV-DE-16-123-1-1 2.0% 5.0% 3.0% % by weight UV-DE-16-123-1-2 2.0% 5.0% 3.0%
Absorbance
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