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Boosting SPF with Copolymers and Other Topics: Literature Findings
By: Charles Fox, Independent Consultant
Posted: April 30, 2010, from the May 2010 issue of Cosmetics & Toiletries.
- Formula 1. Skin improvement cream1
- Formula 2. Skin tanning composition2
- Formula 3. Skin lightening cream with anti-inflammatory agent3
- Formula 4. Hair dye6
- Formula 5. Oily hair treatment lotion8
- Formula 6. Permanent wave for bleached hair9
- Formula 7. Lipstick with skin swelling properties10
- Formula 8. Hydrodispersion sunscreen for allergic skin12
- Formula 9. High SPF o/w sunscreen emulsion13
- Formula 10. Solid powder cosmetic composition15
- Formula 11. Skin care emulsion18
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Avobenzone was included at 40.1–48.5% w/w. Release studies indicated that spray congealing enabled a more efficient modulation of avobenzone release from the SLMs—spray congealing released 26% of encapsulated avobenzone after 2 hr, compared with 60% released for the melt dispersion.
The photoprotective efficacy of the SLMs was evaluated after their introduction into a model cream. A statistically significant decrease in the light-induced degradation of avobenzone was obtained by the SLMs prepared via the melt dispersion procedure—the extent of degradation was 38.6 ± 3.6% for nonencapsulated avobenzone and 32.1 ± 4.3% for the microparticle-entrapped sunscreen. In the case of SLMs produced by spray congealing, a more marked reduction in avobenzone photodecomposition was noted, up to 15.4 ± 4.1%. Therefore, the spray congealing technique was found to be superior to the classical melt dispersion method for rapid and solvent free production of SLMs with a high avobenzone loading capacity.
High SPF for allergic skin: Stada Arzneimittel AG has patented a sunscreen hydrodispersion for allergic skin with ≥ SPF 50.12 The described composition is free from emulsifiers, fats, preservatives and perfume oils. An example is shown in Formula 8.
O/W sunscreens with ≥ SPF 50: Stada Arzneimittel also patented o/w sunscreen emulsions with ≥ SPF 50 that contain titanium dioxide, zinc oxide, methylene bis-benzotriazolyl tetramethylbutylphenola and other sunscreens.13 An example is shown in Formula 9.
Boosting SPF with copolymers: Playtex Products Inc. has patented photoprotective compositions with glycol and styrene-acrylate copolymer spheres.14 The compositions described include: one or more photoactive agents such as a UV filter; one or more optimizing agents such as caprylyl glycol; and a styrene-acrylate copolymer such as an SPF booster. Such a composition was reported to provide an unexpected synergistic combination of the optimizing agents and copolymer booster to possibly increase SPF, the UVA/UVB ratio, critical wavelength, the photostability of the UVA absorber and UVA protection factor.