All that glitters

C&I Issue 7, 2010

Innovation has always been vital in the swift-moving world of personal care, and the eye-popping pigments and shimmering special effects seen in colour cosmetics are no exception. Helen Carmichael reports

According to US speciality chemicals industry consultant, Neil A. Burns, some key effects now increasingly engineered into cosmetics are refraction, reflection, luminescence, pearlescence, colour shifting and light interference. ‘These tend to drive demand for micronised titanium dioxide and some specialty surfactants,’ he adds.

Suppliers like Germany’s Merck offer typical examples. The company’s ingredients portfolio is based on substrates such as natural and synthetic mica, SiO2, Al2O3, Ca-Al-borosilicate and bismuth oxychloride. As well as providing intense colours and special effects, the company also promotes other properties that assist with formulation. For instance, Merck’s Timiron, a silver-white pearlescent pigment, contains small amounts of silver oxide which, if used at the right concentration in colour cosmetics and personal care products, also acts as a stabiliser and can keep microorganisms found naturally on the skin from over-production – and accompanying breakouts.

Dark or intense colours are increasingly popular, particularly for eye shadows and nail colours. Merck uses silicon dioxide flake technology or special coatings with a mica substrate to create colour travel effects – where colours appear a different hue when seen from varying angles.

Its interference pigments consist of various substrates coated with titanium dioxide. The characteristic single reflection colour of each interference pigment is an optical effect caused by light interference with the titanium dioxide layer. Through controlled thickness of the titanium dioxide layer, all colours of the rainbow can be achieved. The effect is best observed when the pigment particles are oriented in parallel to maximise reflection. Interference pigments exhibiting different lustre effects are obtained by using different particle size mica as a base.

Global business

The global recession has not had a major impact on demand for pigments and other colour cosmetic raw materials, which Burns says has ‘held up pretty well along with other personal care products’. In particular, China’s growing wealth, especially among middle classes, is fuelling huge growth both as a market for cosmetic sales, and as a source of home-grown ingredients and competition. Retail cosmetic sales grew at 16.9% in China in 2009, to $10.8bn, according to the National Bureau of Statistics of China. In terms of sales of special ingredients destined for cosmetics, Burns says that the impact of Chinese competition is ‘huge - but that is no different from the rest of the fine and specialty chemicals market’.

Mergers and acquisitions among specialty chemical companies are continuing and Burns suggests that there are more to come. Dow Chemical's acquisition of Rohm & Haas is to go ahead after hitting some financial difficulties earlier this year. Sun Chemical, the world's largest producer of printing inks and pigments and a major supplier of cosmetic pigments is ‘on the acquisition path’, and BASF just finished absorbing Engelhard after swallowing Ciba last year.

Back to the future

Not all the colours used today are the latest inventions – many popular since antiquity are still in demand. For instance ultramarine blue, originally derived from the precious stone, Lapis Lazuli, featured on Tutankhamun’s funeral mask, was also used to decorate the Taj Mahal. French scientist Jean Baptiste Guimet and Germany’s Christian Gmelin separately discovered synthetic routes to ultramarine in the late 1820s, prompting a wave of factories in Europe. Ultramarine’s blue colour is based on sulfur (SIII), although this is readily oxidised and so is stabilised in a protective kaolin (clay) lattice, produced by heating sulfur, clay and sodium carbonate to almost 800oC in a kiln, followed by slow cooling, oxidation and purification processes.

The synthetic pigment was particularly popular for taking a yellow tone out of white laundry during washing. James Reckitt built an ultramarine factory in Hull, UK, in 1884 to extend his range of existing laundry products. This eventually became Holliday Pigments. Still a leading supplier of ultramarine pigments today, Holliday became part of Rockwood Holdings’ Colour Pigments and Services Division in 2008. The company’s pigments are widely used in eye shadows, mascara, eyeliners, blushers, lipsticks, body and face paints. Ultramarine blue is also often utilised as a shading component in black mascaras and eyeliners.

The colour purple

Spring makeup trends often feature either bold, punchy colours or soft pastels. The mix of lighter and bright shades in 2010 is no exception. In the last two years, purples have been extremely popular – including dark, gothic-inspired lip colours, metallic effect eye shadows and deep violet nail polish. This season, however, colour picks are lightening up, towards softer lilac shades.

Dave Masterman, technical support manager for Holliday Pigments, explains the chemistry behind both the pastel and more vibrant shades of violet currently so fashionable: ‘Manganese violet (MnV) is a synthetic, inorganic pigment which was first introduced around 1900,’ he says. It is essentially a covalent combination of ammonia, manganese and phosphate. The standard chemical description is ammonium manganese pyrophosphate. ‘The chromophore which gives the pigment its bright violet colour is trivalent manganese, which is stabilised within the compound structure by strong coordination with the phosphate and ammonia ions.’

Manufacturers create MnV with a manganese salt slurried with di-ammonium hydrogen phosphate and some form of phosphoric acid. As well as using a very clean process, Masterman says that correct raw material selection is important, because the exact shade and purity of the MnV pigment is determined by the ratio of initial reactants and the initial source of manganese. ‘In practice, a blue-shade violet and a red-shade violet are the two ends of the MnV colour range,’ he says. ‘Intermediate shades can be obtained by blending these two.’

MnV is mainly produced for cosmetics, which account for between 70 and 80% of global production of around 200t/year. Its high demand is thanks to the red tone it achieves, and delicate tints that can be created using blends of talc.

Eyeliner, mascara and eye shadow are principal uses, while rouges, blushers, nail lacquers and toners are other products typically containing the pigment. Its high light fastness, non-migrating characteristics and stability, with good transparency and purity of shade, make it an ideal choice, and its heat stability and good dispersal characteristics should also aid manufacture.

Although unlikely to cause issues at the levels used in makeup, Environment Canada has flagged MnV for further attention due to its suspected aquatic toxicity and persistence.

Lighten up

According to Peter D. Bohm, president and ceo of Ariel Laboratories, based in New Jersey, US, when it comes to the cosmetic industry, most companies focus on imitation, not innovation. ‘It's the classic case of catching up with the competition in order to maintain one's position in the marketplace,’ he says.

Ariel thinks it is onto something truly innovative in the large and growing market for ‘skin lightening’ products. The company does not divulge much about its new raw material, Luminera an ingredient that it says increases the skin’s apparent luminosity when added to base formulas, giving a youthful effect.

Where Bohm believes the product differs is that most facial formulas use opaque pigments, which mask imperfections, but fail to capture the youthful ‘glow’. ‘Aging skin, which has been subjected to sunlight, loses its youthful appearance due to an inability to fluoresce blue and green light,’ according to the company. ‘This lack of fluorescence often produces an uneven skin tone, discoloration and an overall unhealthy appearance.’

The new Luminera particles are transparent, containing a ‘diamond core complex’ that transforms UV light into blue light, which the company says recreates the youthful glow effect.

Helen Carmichael is a freelance science writer, based in Vancouver, Canada

1. Jianping Ge et al, JACS, 2009, 131, 15687

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