Sun Care 2002

Creative Developments (Cosmetics) Limited

Sun Products SPC 2002

John Woodruff

The sunscreen section of the Cosmetic Science Conference 2001, Düsseldorf, was thrown into turmoil by the claims of Margret Schlumpf [Ref 1] that lipophilic chemicals used as UV filters may bioaccumulate in the environment. An investigation into contamination of fish in Meerfelder Maar Lake in the Eifel, Germany and a study on human milk appeared to support her view. Schlumpf said that besides being exposed through the skin to UV screens, humans might also suffer from ecotoxicological exposure resulting from bioaccumulation of these lipophilic chemicals in the food chain. Following the publication of the paper by Schlumpf the Scientific Committee for Cosmetic Products, and Non-food Products intended for Consumers (SCCNFP) was asked to deliver an opinion on the evaluation of potentially estrogenic effects of UV-filters. In summary the SCCNFP came to the conclusion that a number of important technical and scientific shortcomings are present in the study and that, based on the actual scientific knowledge, organic UV-filters used in cosmetic sunscreen products, allowed in the EU market today, have no estrogenic effects that could potentially affect human health [REF 2].

While argument continues as to the safety of organic filters developments in microfine inorganic particles for use as sunscreens continues. Since their introduction in the early nineteen eighties the emphasis has been on combining high SPF with minimal whitening and an elegant skin feel. It was soon realised that pre-dispersed systems simplified the formulator’s task of incorporating the material into either an aqueous or lipid system. Uniqema Solaveil pioneered this technology and produces dispersions in most of the commonly used cosmetic oils, esters and in several silicone compounds. Over time it has narrowed particle size distribution and further reduced whitening and it successfully launched Solaveil Clarus™ at Formulate 2001. This company publishes regular updates for its series, The UV Files, [REF 3] which includes the latest advances in formulating with inorganic oxides.

Many other suppliers of microfine oxides now exist; all claim to provide the optimum size, shape and surface properties, although they do not necessarily agree on what these should be. Nanosun™ Ultrafine Suspensions from Micronisers of Australia are produced in non-aqueous media and claim good transparency by controlling particle size distribution and the refractive index of the surface coating. They are available as oxides of titanium, zinc and iron in paste form containing 70% solids in suitable cosmetic oils and there are no surfactants, dispersants and wetting agents present and hey are said to resist particle agglomeration.

Collaborative Laboratories supply Tio₂sperse™ Ultra; an ethylhexyl hydroxystearate benzoate coated titanium dioxide in a mixture of dimethicone and cyclopentasiloxane. Cardre offer pre-dispersions of zinc oxide and titanium dioxide in octyldodecyl neopentanoate, C12-15 alkyl benzoate, in cyclomethicone or in caprylic/capric triglyceride. Surface treatment with dimethicone allows a co-dispersion of both oxides to be offered.

Merck has added Eusolex™ T-45D to its portfolio of inorganic sunscreens; it is a thixotropic dispersion with 45% solids content in isononyl isononoate. It is coated with alumina and simethicone and polyglyceryl ricinoleate is present as a dispersing aid. Other inorganic sunscreens from Merck include anatase titanium dioxide as a lipophilic powder, a rutile titanium dioxide for aqueous or oil-dispersions and a stearic acid coated titanium dioxide that is said to offer very even particle distribution in the final composition.

Many consumers now realise that sun protection is a daily requirement and sunscreens are added to moisturisers and make up. By coating microfine titanium dioxide with iron oxide pigments Oy Granular Ab, Finland, has produced a number of colour concentrates as semi-solid pastes that when used to impart fashionable colours to makeup, they also give sun protection of approximately SPF20. They are said to be easy to use, to be very stable and to provide improved dispersion when compared with conventional pigments. Further additions of microfine titanium dioxide make it possible to increase the SPF value without unduly affecting the shade if required.

It is well known that the other ingredients present in a sunscreen composition can have a profound effect on product efficacy and none more so than the emollient system [REF 4]. The various dispersions described above are in a selection of different lipids, each with its particular properties and benefits. When formulating with organic sunscreens solubility can be a problem, with inorganic sunscreens it is necessary to obtain good dispersion and in both cases the active needs to be applied as an unbroken film on the skin. There is a wide selection of oils and esters that not only improve solubility but may also enhance the SPF. Finsolv™ TPP from Finetex is C12-15 alkyl benzoate combined with dipropylene glycol dibenzoate and PPG-15 stearyl ether benzoate. It can dissolve up to 30% benzophenone-3 and 16% butyl methoxydibutyl-methane (BMDBM aka Avobenzone).

Butyloctyl salicylate is a low viscosity oil that solubilises benzopheneone-3 and BMDBM and also improves its photostability. Hexadecyl benzoate and butyloctyl benzoate have similar solvent properties and diisopropyl sebacate and diisopropyl adipate are also good solvents that form non-occlusive films and are also soluble in ethanol. Octyldodecyl neopentanoate and dicaprylyl maleate are good solubilisers that significantly enhance SPF values and dibutyl adipate and caprylyl carbonate are also good solvents. Phoenix Chemical Inc. promotes butylphthalimide with isopropylphthalimide, trade named Pelemol™ BIP, as a solvent for BMDBM and benzophenone-3. It is a eutectic mixture of two solid materials resulting in a clear colourless liquid. The same company also offers dimethicone PEG-7 phosphate, Pecosil™ PS-100, as a water-soluble silicone phosphate ester that has emulsifying properties and that is also claimed to enhance sunscreen efficacy.

Much work has been done by Cognis [Ref 5], which shows the relationship between organic and inorganic sunscreens with emollients and their influence on SPF factors and sensorial effects. Goldschmidt Personal Care has also published a presentation on the importance of the emollient in suncare products [REF 6]. The basic properties are viscosity, surface tension, pour point, polarity and spreadability and the publication discusses the influence that these properties have on the formulation. Of those discussed, diethylhexyl carbonate, trade named Tegosoft™ DEC, is claimed to provide the optimum properties for sun protection systems.

Craig Bonda of CP Hall has patented many solvent systems for enhancing sun product efficacy and has made a particular study of improving the photostability of organic actives [Ref 7]. Bonda found that diethylhexyl naphthalate (DEHN) significantly improves the photostability of BMDBM. DEHN is a semi-viscous oily liquid with a refractive index of 1.53 and a specific gravity of 1.02. It is insoluble in water, propylene glycol, and glycerin but freely soluble in most cosmetic oils and esters. It is a good solvent for benzophenone-3, BMDBM, MBDC and ethylhexyl triazone. In June 2001 Bonda received an award from the American Chemical Society for innovation and his work with BMDBM.

The silicone ester, diisostearyl trimethylolpropane siloxy silicate, A&E Connock, is a good solubiliser for most organic sunscreens and is substantive to skin so that the active is held in a film that is also water-resistant. There is still no agreement between the main markets of the world on what constitutes water-resistance and how it should be determined but there are materials that improve the compositions resistance to being lost through sweating and bathing. Dermacryl 79 is an acrylates/octylacrylamide copolymer from National Starch & Chemical that is alcohol soluble and may be rendered water-soluble by neutralising the acidic carboxyl groups with a suitable base. If the polymer is neutralised by a long chain amine like stearyl dimethylamine it becomes oil-soluble. It entraps the active within a water-resistant film that is substantive to skin and claims are made for a sustained release effect. Polyols are generally added to cosmetics as humectants so it is somewhat surprising to learn that 1,2 penatenediol has been patented by Dragoco [EP 665 904 51] as an additive to improve water-resistance to sun care formulations but data shows an approximate 50% improvement in resistance to wash-off.

Also with significant influence on SPF are the rheology characteristics of the emulsion [REF 8] and generally a product with a higher yield value will have a higher SPF, particularly in the case of inorganic sunscreens. Polargel™ UV, Amcol Health & Beauty Solutions, USA, is a hydrogel of montmorillonite, titanium dioxide and Picea excelsa (Spruce) extract, which is said to enhance dispersion of organic and inorganic actives and to appreciably improve SPF values. However the trend today is towards spray-on products, which must be thin enough to spray yet still remain stable. Crodafos™ CS-20 Acid from Croda Oleochemicals is a blend of cetearyl alcohol with ceteth-20 phosphate and dicetyl phosphate that needs to be neutralised in-situ and was specially developed to produce light, low viscosity emulsions with high pigment loading and to have excellent dispersing and film-forming properties.

Goldschmidt suggest Teginacid H, a mixture of glyceryl stearate with ceteath-20 for traditional spray-on emulsions and Abil Care™ 85 (Bis-PEG/PPG-16/16 PEG/PPG-16/16 dimethicone; caprylic/capric triglyceride) for cold-process systems. Cognis has done much to promote Phase Inversion Technology (PIT) for the preparation of emulsions and it appears a particularly suitable process for the low viscosity compositions required for sun protection sprays. Its recommended emulsifier is Emulgade™ SE-PF, a propriety mixture of glyceryl stearate, ceteareth-20, ceteareth-12 and cetearyl alcohol with cetyl palmitate. Dermacryl 79 is said to be an excellent additive to spray-type formulations as it confers water-resistance without affecting spray characteristics. It is also suitable for the formulation of foaming sun protection formulations; a product form also advocated by Goldschmidt and both companies will provide starting formulations.

Particulate organics appear to offer the safety of inorganic sunscreens allied to the efficacy of organic types. Collaborative Laboratories supplies Solarease™ II, a combination of butyl methoxydibenzoylmethane and ethylhexyl methoxycinnamate encapsulated in lecithin and dispersed in cyclopentasiloxane. A Diglycol/CHDM/isophthalates/SIP copolymer from Eastman Chemical Products, Inc. is a water-dispersible polyester that is strongly substantive to skin as a water-resistant film. If incorporated in a sun protection product the organic actives are dissolved within this film, which also enhances SPF values by increasing the path length through scattering effects. A styrene/acrylates copolymer from ISP has a similar action; the copolymer is in the form of microscopic hollow spheres filled with water but as these dry in the cosmetic film on the skin water is lost by evaporation and is replaced by air. The microscopic air bubbles deflect radiation and the effective path length of the photons is therefore increased.

1. Schlumpf, M., Estrogen Active UV Screens, Cosmetic Science Conference, Düsseldorf 2001

2. Scientific Committee for Cosmetic Products, and Non-food Products intended for Consumers - Opinion on the Evaluation of Potentially Estrogenic Effects of UV-filters adopted by the SCCNFP during the 17th Plenary meeting of 12 June 2001

3. The UV Files; Uniqema Solaveil publications 1995 – 2002

4. Hewitt J., Woodruff J., Factors Influencing Efficacy of Oil-dispersed Physical Sunscreens, IFSCC Magazine, Vol.3 No.1, pp.18-23 (Jan/Mar 2000)

5. Synergistic Sun Systems, Cognis, January 2001,

6. Basic Properties of Cosmetic Oils, Goldschmidt Personal Care, January 2002.

7. The Photochemistry of Sunscreen Photostability, Craig Bonda & Pete Marinelli, The UV & Sunfilters Conference, Paris 1999

8. Hewitt J., Woodruff J., Rheology Modifiers & Inorganic Sunscreens, In-Cosmetics Conference, 1998

British Agents for Companies mentioned in the text.

q Amcol Health & Beauty Solutions; Paroxite Ltd.

q Cardre; Adina Chemicals Ltd.

q Collaborative Laboratories; Optima Chemicals Ltd.

q Finetex; Cornelius Produce Company

q Mel-co; Optima Chemicals Ltd.

q Merck; S. Black

q Micronisers; Chemlink

q National Starch & Chemical; S. Black

q Phoenix Chemical Inc; Cornelius Produce Company

Formula for Sun Spray with SPF 30, courtesy of Cognis

INCI / CTFA	% ^w/_w

Glyceryl Stearate, Ceteareth-20, Ceteareth-12, Cetearyl Alcohol, Cetyl Palmitate (Emulgade SE-PF)	7.8
Ceteareth-30	5.2
Dicaprylyl Ether	2.0
Cetearyl Isononanoate	2,0
Benzophenone-3	4.0
Ethylhexyl Methoxycinnamate	7.5
Homomenthyl Salicylate	7.0
Octyl Salicylate	5,0
Glycerin	5.0
Aqua	54.5

Melt the oily components at 80 - 85°C and stir. Heat the water phase to 80- 85°C and add to the oil phase while stirring. Cool down while stirring. Avoid incorporation of air. Add perfume and preservatives to suit at 40°C. Continue cooling to 30°C.