A selection of the technical presentations at this year's in-cosmetics paid particular attention to rheology, sun care and hair care
In addition to the exhibition, in-cosmetics offers presentations, workshops and innovations seminars, the latter being free presentations with a commercial bias. However, they are often of great interest to delegates as they introduce new materials and innovative ideas. It is these seminars that form the basis of this review. As always, they are a personal selection by the author, who could not possibly attend them all and was sorry to have missed many that appeared interesting.
Aspects of rheology
The opening presentation was entitled A natural way to rheology by Ross Clark (CP Kelco) who said that he intended to show the relevance of rheological properties to personal care products and that it was his intention to make rheological measurements more approachable and easy to understand. His had three subtitles: Why use a polymer? Why make things thick? Different kinds of thick! Under these Clark introduced the Kelco range of natural carbohydrate polymers, which include thickeners as well as gelling agents. Thickeners can impart a smooth flow like cellulose gum or more structured like xanthan gum. Gelling polymers like carrageenans have textures that range from firm and brittle to soft and elastic. Kelcogel gellan gum is able to gel with added monovalent cations like sodium and potassium as well as divalent cations like calcium or magnesium. Other products like pectin have properties that aid in the protection of skin and film formation.
Clark described the rheological properties of these products from a non-technical and user friendly point of view and showed the different sorts of textures that can be created. A structured liquid tends to pour in an uneven manner while a less structured material will give a smooth and uniform flow. He described the strategy of polymer selection and how sometimes conflicting issues need to be addressed. For example, skin feel is directly related to the viscosity at relatively high shear rates. On the other hand, shelf stability is governed by the viscosity at very low rates of shear. Between these two extremes lie properties such as spread, pouring and most processing operations.
Rheology was a popular subject at in-cosmetics this year. Bernice Ridley (Ciba Specialty Chemicals) said that the development of personal care formulations will necessarily include the consideration of the required product rheology and the correct rheology modifier to provide these effects. Whilst the efficacy of the finished product will depend on the choice and level of active ingredients and excipients, the aesthetics and even the penetration of these actives into the stratum corneum will be affected by the product rheology. Ridley described the use of Tinovis ADE, a rheology modifier that swells in water to form microparticles throughout the aqueous phase. It then shows good suspension properties, easy absorption and efficient thickening combined with good sensorial properties and a reduction in transepidermal water loss (TEWL). A level of 0.125% is sufficient to make a spray-on lotion while 1% will stabilise an emulsion and will impart high gel strength to hydro-alcoholic gels. It is stable over a pH range of 5 - 12.
Olivier Paquette (Laserson) described the development and uses of Gelinnov, a polyacrylate polymer with high charge density stabilised in C18-C21 alkane with trideceth-6. The alkane has a silky feel and the material contains 57% active polymer. It was developed to meet consumer demand for new textures such as illustrated by body butters, gel creams, freshening foams, liquid gels, crackling foams and body sprays. Gelinnov represents a new stage in the technology of thickeners, claimed Paquette, and brings real progress in terms of effectiveness and stability under stressed conditions. Import-antly, when formulated in cosmetic products such as facial creams, Gelinnov displays new sensorial benefits such as freshness and smoothness and it helps create innovative textures. It is stable over the pH range 5.5 - 10 and is suitable for cold processing. The polymer is added to the oil phase but when it comes into contact with water it expands and is an efficient moisturiser for oil contents up to 20%. For higher levels a co-emulsifier is required.
It is not only skin care products that require rheological additives. Keriman Albaha (Cognis) described the use of Arlypon TT [INCI: PEG/PPG-120/10-trimethylolpropane trioleate (&) laureth-2] as a high performance thickening system designed especially for viscosity adjustment in sulphate-free surfactant systems. It synergistically thickens by micelle and associative mechanisms and low levels of Arlypon TT are readily capable of building up the desired viscosity of formulations based on surfactants such as sodium cocoamphoacetate, lauryl glucoside and disodium cococyl glutamate.
Cationic systems may also present rheological difficulties and overcoming these with the use of Carbopol Aqua CC Polymer [INCI: Poly-acrylate-1 crosspolymer] was the subject of the presentation by Alan Suares (Noveon). Suares said that high performance formulations are designed to deliver enhanced benefits for hair and skin through the use of cationic ingredients and the delivery of actives with improved efficacy at low pH. Traditionally, these challenging applications have limited the range of rheology modifiers used. Typical anionic thickeners may not be well suited in a low pH or cationic containing environment, and nonionic options may provide undesirable aesthetics. Carbopol Aqua CC polymer overcomes these limitations and allows the formulator to create these systems with confidence, said Suares. It is designed for use in low pH personal care applications, where low to medium viscosities are desired, and offers low pH formulations a smooth flow and feel, good suspension capability and excellent stability.
Sun analysis
Sun protection was another major subject, and was also the topic for a one-day scientific conference that ran concurrently with the innovations seminars. Current EU recommendations are that UVA protection be proportional to UVB protection and that the UVA protection factor should be at least one third of the SPF value. Christine-Mendrok-Edinger (DSM) described how this could be achieved, even for high SPF products that consumers now expect under the title of high SPF formulations, with low filters content compliant with new EU recommendations on the efficacy of sunscreen products.
It is well known that for the majority of UV filters, SPF does not increase linearly with increasing concentration so the formulator’s challenge is to find synergy between filters to maximise efficacy. The speaker described how combinations that included Parsol SLX [INCI: Polysilicone-15] showed synergistic properties with phenyl benzimidazol sulfonic acid, butyl methoxydibenzoylmethane, octocrylene and titanium dioxide. It was possible to achieve in-vivo SPF 45 and an in-vivo UVA factor of 15 with 14.5% actives.
How to fulfil the new UVA protection standards was the title of the presentation by Uli Osterwalder (Ciba) who described the new European sunscreen recommendation, the various ways of assessing UVA acceptable in Europe and elsewhere, the role of photostability and then how to comply with the EU recommendation. Osterwalder described the different restrictions on sunscreens in Europe, North America, Australia and Japan and the use of the Ciba sunscreen simulator to calculate expected SPF for any combination of permitted filters.
Achieving photostability is a known problem, said Osterwalder, and obtaining sufficient UVA protection for a product claiming SPF 30 using the traditional mixture of ethylhexyl methoxycinnamate (EHMC), octocrylene and butyl methoxydibenzoylmethane (BMDBM) is not possible. The answer is to eliminate EHMC and introduce either of the two new broadband filters available from Ciba: Tinosorb M [INCI: Methylene-bis-benzotriazolyl tetramethylbutylphenol (MBBT)] and Tinosorb S [INCI: Bis-ethylhexyloxyphenol methoxyphenyltriazine (BEMT)]. Ciba also supplies a new photostabiliser trade named Tinogard TL [INCI: Benzotriazolyl dodecyl p-cresol] that inhibits photodegradation of BMDBM. A photostable formulation returning SPF 30 and a UVA factor >14 can thus be achieved using 1.5% ethylhexyl triazone with 2% Tinosorb S and 14% Tinosorb M.
Julian Hewitt (Croda) described methods of improving compatibility and photostability of mixed organic and inorganic sunscreen formulations. For optimum results a combination of sunscreens is necessary and it is preferable that they be in both the aqueous and oil phase for a more even distribution on the skin. Work by Hewitt and Woodruff showed that there was synergy between EHMC and TiO2 with in-vivo SPF of 33 possible with a combination of 6% TiO2 and 5% EHMC.
Problems when formulating sunscreens include the propensity of some organic UV filters to crystallise within the formulation and the development of yellow discolouration when avobenzone and oxybenzone are incorporated with TiO2 in a formulation. Optimising the emollient content can prevent crystallisation, said Hewitt, and the use of a pre-dispersed TiO2 can keep the inorganic separate from the organic filter and thus inhibit yellowing.
The whitening effect, at one time a problem with TiO2 formulations, can be overcome by using Solaveil CT-100W, an aqueous dispersion of hydrophobically coated fine particle TiO2 and Hewitt presented formulations that achieved 5* on the Boots’ Star Rating System using relatively low levels of actives. Hewitt also described the use of Optisol, a novel UV filter that incorporates manganese ions in the TiO2 crystal lattice structure. This combination minimises free radical generation and also enhances the photostability of organic filters such as BMDBM in the presence of EHMC.
Sun not only affects the skin, it also affects hair colour and hair condition. Holger Leidreiter (Degussa) des-cribed a study whereby the appearance of hair tresses was evaluated by colour measurements, fibre tensile strength and a keratin degradation parameter. The type of damage selected was irradiation by a sunlight simulator. The hair tresses were pre-treated by perming and oxidative bleaching. Two types of cosmetic treatments were applied as model systems. One was a standard shampoo with sodium laureth sulfate (SLES) and cocamidopropyl betaine (CAPB) as the surfactant system and the other one a rinse conditioner based on fatty alcohol and cetrimonium chloride. The test compounds were incorporated into these base formulations.
The UV absorber investigated in this study was Abil UV Quat 50, a siloxane copolymer grafted with methoxycinnamic acid ester and cationic alkoylamidopropyl dimethyl ammonium groups. This was compared with other cationic UV screens and a nonionic, silicone based material. All were selected from the group of ingredients offered for hair protection against UV irradiation. The use of Abil UV Quat 50 in both shampoo and rinse led to a maximum protection of 50% reduced colour change. Polyamide-2 performed well in the shampoo application while polyquaternium-59 provided a good performance in the conditioner formulation.
The tensile strength of hair fibres was reduced by sunlight irradiation. Some of the UV filters provided protection when used in a conditioner formulation. The best effect observed was 40% less reduction in tensile strength change when using either Abil UV Quat 50 or polyamide-2. The best protection of the keratinous structure according to DSC measurement was provided by both Abil UV Quat 50 and polysilicone-15. The DSC signal is shifted by irradiation from about 154°C to 142°C. In hair fibres, pre-treated by formulations containing one of the silicone derivatives, this shift was reduced by about 10 - 15%. In conclusion Leidreiter stated that sunlight induced hair damage can be inhibited and fastness of hair dyes against sunlight fading can be improved by using UV screens in shampoos and conditioners, provided they are sufficiently substantive to hair.
Hair specifics
Various aspects of hair styling and conditioning were covered by a number of speakers. Raymond Rigoletto (ISP) described a new polymer [INCI: Polyquaternium-69]. It is hydrophobic yet water soluble and predominantly non-ionic with a weakly cationic nature, providing a broad range of compatibility with cosmetic ingredients including anionic gellants. Improved water resistance for increased hold was demonstrated by high humidity curl retention test results and the product is suitable for various styling products such as clear and cream gels, aerosol and non-aerosol mousses, and styling lotions and sprays. Marie-Laure Breton (Rohm and Haas Co) presented the properties and uses of Acudyne SCP, a hair styling polymer for use in hair gels and other styling products where it delivers long-lasting hold performance associated with conditioning benefits and a light, smooth feel.
Dorina Ghirardi (Noveon) introduced Fixate Superhold polymer, a branched anionic acrylate copolymer. It provides stiff hold and superior humidity resistance, and enables the creation of cost effective, low-to-high viscosity styling products with high clarity, shine, flake resistance, superior texture and aesthetics. The polymer structure offers an optimised balance of properties such as: stiff hold without stickiness; superior humidity resistance with easy wash-out; clear, uniform films with good adhesion and no flaking; and easy distribution through hair. It can be used in a wide range of styling applications, such as gels, creams and pump sprays, said Ghirardi.
Sylvie Doulut-Mislin (Rohm and Haas) gave a detailed presentation on the interactions of styrene-based polymers used as opacifiers with cationic ingredients, amphoteric compounds and salt in typical personal care formulations. After a brief overview on colloidal stability and phenomena such as creaming, sedimentation, flocculation and coalescence, Doulet-Mislin discussed the stability of formulations containing PQ-7, PQ-10 and guar derivatives using Turbiscan equipment. Critical parameters for opacifier stability in the presence of cationics are pH, the type of cationic used and its concentration and the nature, design and particle size of the opacifier.
There were presentations describing anti-ageing ingredients, plant-based ingredients, new delivery systems, a cosmetic approach to slimming, pigment wetting and dispersing. In fact, about every aspect of cosmetic formulation and design got a look in.