The Use of Ultramarine Pigments in Cosmetics

Transcription

1 E. Bartholomey* The Use of Ultramarine Pigments in Cosmetics Introduction The natural form of the mineral ultramarine blue is, lapis lazuli, but our discussion focuses upon the synthetic or artificial varieties of ultramarine pigments as used in the cosmetic and personal care industries. The term»ultramarine«must have been in use in Italy by the beginning of the fourteenth century as Antonio Filarete wrote in 1464 that»fine blue is derived from a stone and comes from across the seas and so is called ultramarine«(1). The ultramarine family of colors includes blue, green, pink and violet. Abstract The pinks, violets, and greens are weaker colors than blue. However, they are used in cosmetics and in artist s paints. Green is rarely used. The composition of the ultramarine pigments is very variable and almost never stoichiometric. (Table 1) Ultramarine blues are synthetically produced sodium alumino sulpho- silicates. The major component is a complex sulfur-containing sodium-silicate (Na Al 6 Si 6 O 24 S 2-4 ) which makes ultramarine the most complex of all mineral pigments. Some chloride is often present in the crystal lattice as well. The structure Ultramarine pigments are used within the cosmetic industry primarily in eye make-up products. Eyeshadows, mascaras and eyeliners, and concealers may contain ultramarines that display a wide range of colors. Variants of the ultramarine blue pigment such as»ultramarine pink«,»ultramarine green«,»ultramarine violet«are known, and are based on similar chemistry and crystalline structure. Generally, these pigments are hydrophilic and water-dispersible. Surface treatments can help to improve the dispersion of ultramarine pigments in cosmetics oils and esters. The refractive indices of the surrounding media help to determine the lightness/darkness, opacity, and hue of the pigment. Transparency is increased when the difference in the refractive indices of the pigment and the media are small. Variations of the differences in refractive indices allow for the creation of new and improved pigment mixtures. Translucent ultramarine colors can also synergize with special effects pigments to introduce new products to the consumer. Colors Chemical Composition Blue Na 7 Al 6 Si 6 O 24 S 3 Violet Na 6-10 Al 6 Si 6 O 24 S 2-4 Pink Na 7 Al 6 Si 6 O 24 S 3 Green Na 6.50 Al 6.30 Si 5.70 O 24 S 3.5 Table 1 Chemical composition of ultramarine pigments. consists of an open three-dimensional framework of AlO 4 and SiO 4 tetrahedra and within this framework are found small sulfur-containing anions together with sodium cations which maintain overall electrical neutrality. There are two types of sulfur groups in ultramarine blue, (S 3 ) and (S 2 ). The blue color of the pigment is due to the radical anion (S 3 ) absorbing at (600 nm) and (S 2 ) at 380 nm both containing an unpaired electron (2). This is stabilized within the alumino-silicate framework. Manufacture Different shades of ultramarine blue exist: Cobalt Blue Hue (least violet), Ultramarine Blue (medium violet), and French Ultramarine Blue (most violet). Every one of these colors is simply one pigment, (C. I. Pigment Blue 29: 77007). Variations are due to strength, particle size, processing conditions, formulation, etc. The manufacture of ultramarine blue is described in Patent US A -»Manufacture of ultramarine blue«(3). Green ultramarine (or primary ultramarine) is just an intermediate product in 26 SOFW-Journal

2 Cosmetics Fig. 1 Ultramarine pigments blue, violet, and pink surface treated with ITT prior to grinding. the synthesis of ultramarine blue. It has a limited application as a pigment. After the oxidation process of green ultramarine with atmospheric oxygen at a temperature of about 750 degrees Celsius it turns to ultramarine blue. Ultramarine violet s redness of hue depends on the degree of oxidation. Oxidation of ultramarine blue or ultramarine green with air at 130 to 280 C in the presence of ammonium chloride results in ultramarine violet with the chromophore (S 4 ). Pink ultramarine (also red ultramarine) is obtained by processing the violet form with hydrogen chloride gas in an oxidizing environment at a temperature of about C or greater. An ion exchange reaction with violet produces pink. The nature of the polysulfide dictates the color of the solid. In violet ultramarine (C.I. Pigment Violet 15:77007) and pink ultramarine (C.I. Pigment Red 259:77007) the chromophore is proposed to be S 3 Cl, S 4 or S 4. Because of their zeolytic structure there is the potential to create other ultramarine colors via ion exchange, such as ultramarine yellow and ultramarine white using soluble salts of metals like silver (yellow), lithium (blue), manganese (gray), calcium, potassium (blue), copper, zinc (violet). Their primary use for cosmetics is in eye products such as eyeshadows, mascaras, eyeliners, and in eye pencils. Ultramarine blue was used significantly in laundry applications in powder detergents and soap bars. It improved the whiteness of white cotton fabrics when washed due to its ability to adhere to fibers and absorb yellow wavelengths (4). By absorbing yellow light it creates»whiter whites«, and in color correction it can help achieve a match. In greys it can create subtle blue undertones. Optical Properties The refractive index of ultramarine blue and similar ultramarine pigments is It has a cubic crystal structure that is isotropic and exhibits no optical activity. The hiding power of ultramarine is greater than would be expected from its low refractive index. In aqueous media it will retain a pure bright blue color due to the difference in refractive indices. However, in oils where that difference is minimal it becomes a much darker blue and translucent. The dominant wavelength is around nm for synthetic ultramarine blue. Ultramarine blue reflects highly in the infrared region and is also used in camouflage and heat-resisting paints. The oil absorption is between 30 and 40 (g/100g). Particle Size The artificial pigment has rounded particles of regular size and shape. Ultramarine blue and green shade particles are about microns in diameter and ultramarine red shade particles are about 5 microns. Ultramarines are hydrophilic and are easily dispersed in aqueous media or polyols. They are easy to grind as a powder. Surface treatments will enhance the dispersibility of these pigments in solvents, oils and esters. Chemical and Physical Properties Ultramarine pigments have good stability to light. Blue is not affected by ammonia or caustic alkalies (ph of 7 or higher) except on very prolonged and drastic treatment. Pink and violet are not as stable within the alkali medium as is blue. Pink is not recommended for toilet soaps because of this instability (5). All ultramarines are very readily decomposed by acids. In ultramarine blue, dilute mineral acids rapidly destroy the blue color with evolution of hydrogen sulfide gas. Hydroxonium ions (H 3 O + ) are small enough to enter the open aluminosilicate framework and react with the enclosed polysulfide ions. Acetic acids will attack the pigment more slowly than mineral acids. So one must be very cognizant of ph levels in the lab, during process scale-up and in manufacturing. Testing long term stability can also reveal changes in the ph. Acid-resistant grades are available in which the particles are coated with silica or silicic acid. They are not completely resistant to mild acids, but are more so than the untreated versions. Grinding these pigments will reduce the effectiveness of the silica surface treatment. Cosmetic surface treatments, such as ITT and silane, will render the ultramarine pigments more dispersible and stable in liquid media. Surface treatments also improve the application of these pigments onto lashes, the eyelid, under eye area, and skin in general. The ultramarine pigments are not permitted in lipsticks, lip glosses or similar cosmetics where there may be some ingestion even though their overall toxicity is low. They are FDA approved for food packaging and other uses, but not for coloring edible foods. Experimental Data & Results Transparency is an advantage for ultramarine pigments when they are combined with effect pigments. You can achieve a combination that can take advantage of the unique hue of ultramarines, as well as their transparency. The blue, violet, and pink ultramarines are excellent for combining with interference pigments, especially in liquid mediums where their refractive indices (R.I.) can be fully optimized. Some pigments that are newer materials to the industry can synergize well with ultramarines, such as borosilicate flakes SOFW-Journal

3 or synthetic mica that contain multilayers to promote color travel. The interference colors from these pigments are extremely chromatic, with higher transparency, sparkle and clarity due to the substrate and multi-layer design. Many possibilities exist for using the ultramarine series of pigments with these more transparent effect pigments. In order to better understand the ultramarine pigments and their relationship with liquids of varying refractive indices, we set up experiments to measure their transparency and shade differences. We created dispersions using three mediums with a wide difference in R.I. range. (Fig. 2) Dispersions of ultramarines are made at a % concentration by leading manufacturers. We designed the test to measure the lightness/darkness and transparency properties of ultramarine pigments by surrounding the particles with liquids having different refractive indices. For the liquids we selected water (R.I.=1.33), isoamyl laurate (R.I.= 1.44; Radia 7750) and octyl methoxycinnamate (R.I.=1.54; Escalol 557). A small amount of dispersant, 2 % polyglyceryl polyricinoleate (Radiamuls Poly 2253), was added to each of the esters. We added 2 % Lecithin Solec F to the aqueous dispersion along with a small amount of triethanolamine to adjust the ph to the alkaline side. The ultramarine pigments were surface-treated for the oleophilic systems with isopropyl titanium triisostearate to make them more dispersible at high concentrations. The pigments for the aqueous system were used without a coating. Transparency/Opacity Fig. 2 Transparency of ultramarine pigments in refractive index media (dispersions). (Photographs taken at 0.8X magnification.) The overall concentration and transparency/opacity value of the pigments is important for delivering the unique benefits to the consumer. By creating a more transparent or translucent film through the matching of refractive indices, some light is able to pass through some of the particles more easily allowing other surfaces to interplay for complex color effects. The transparency of pigments increases with the following properties: lower refractive index, fineness (until optimal size is reached), lightness of color and in certain cases the topography and complexity of the pigment. We measured the contrast ratio (Black Y/White Y) which translates to transparency/opacity (Fig. 3). As illustrated in the graph for contrast ratios, the series of pigments dispersed in the ester, octyl methoxycinnamate, which has a closely matching refractive index to the pigment provides the most transparency. Water has the lowest refractive index and is most distant from the R.I. of the pigments and therefore provides the most opacity since more light is reflected from the surface of the pigment. 28 SOFW-Journal

4 but not too much chalkiness since its R.I. value is not too distant from the primary blue pigment. The waterproof mascara formulation makes use of ultramarine blue and ultramarine violet along with a small amount of black iron oxide to provide a deep rich blue color with a slight tinge of red. The polymer, hydrogenated polycyclopentadiene, has a high refractive index of which is very close again to that of the ultramarine pigments. This medium provides depth of color because the polymer concentration is significant and helps to surround the ultramarine pigment creating a more optimal interface for a darker shade. Fig. 3 Measurements of contrast ratios for determining transparency and opacity in selected mediums. The isoamyl laurate has an R.I. that is more or less equidistant from the water and octyl methoxycinnamate. The pigments show a balance of transparency and opacity when combined with this ester. Formulation 1 and 2 for eyeshadow and mascara show the relevance of using ultramarine pigments in cosmetic products. The eyeshadow derives its color primarily from ultramarine blue and uses pentaerythritol tetraoctanoate which has a relatively high refractive index of This provides good opacity, Conclusion Though ultramarine pigments remain a small segment of the global market for pigments (<0.5 %) they are widely used within the cosmetic industry. These colors continue to have potential when used in novel ways, especially with newer materials that are available. Surface-treatments and dispersions of ultramarines enable cosmetic formula- Lightness/Darkness The graph for lightness & darkness above shows the relationship between the ultramarine pigments and their ability to appear either light or dark in surrounding media (Fig. 4). The pigments are very dark in the bulk dispersion in the octyl methoxycinnamate as light is not reflected from the pigment interface as it is in aqueous vehicles. The ultramarine pigments are lighter and brighter when dispersed in aqueous media as the light gets reflected at the interface of the pigment and liquid. Again, the isoamyl laurate creates a nice balance between the two extreme refractive indices and provides a balance of benefits. Formulations Fig. 4 Measurements of (L.) values for determining lightness and darkness of the pigment in different mediums. 30 SOFW-Journal

5 Ultra Blue Natural Matte Eye Shadow % Ingredients INCI Name MICA S/MM3 Mica (And) Magnesium Myristate TALC N/MM3 Talc (And) Magnesium Myristate BEUB/MM3 Ultramarines (And) Magnesium Myristate FLORITE R Calcium Silicate 4.00 BRO/MM3 Iron Oxides (And) Magnesium Myristate 2.00 BTD/MM3 Titanium Dioxide (And) Magnesium Myristate 0.05 Methyl Paraben NF Methylparaben 0.04 Propyl Paraben NF Propylparaben PE-48 Pentaerythritol Tetraoctanoate 100 Procedure: 1. Premix all powders including the parabens and then pass them through a micro-pulverizer. 2. Add the liquid binder, PE-48 pentaerythritol tetraoctanoate, and blend well. Do not overheat. 3. Press at 500 psi. Formulation 1 Ultra Blue Natural Matte Eye Shadow. Ultramarine Waterproof Mascara % Ingredients INCI Name Soltrol 130 C10-13 Isoparaffin KOBOGUARD 5400 IDD Hydrogenated Polycyclopentadiene (and) Isododecane 5.75 Bentone 38V Quaternium-18 Hectorite 0.95 Phenoxyethanol Phenoxyethanol 0.05 Methyl Paraben NF Methylparaben 0.04 Propyl Paraben NF Propylparaben 1.75 Carnauba Wax, NF Copernicia Cerifera (Carnauba) Wax 1.75 Candelilla Wax, NF Euphorbia Cerifera (Candelilla) Wax 6.35 Asensa SC 210 Polyethylene 1.75 Thixcin R Trihydroxystearin 6.25 BEUB-11S2 Ultramarines (And) Triethoxycaprylylsilane 1.25 BUV CG-11S2 Ultramarines (And) Triethoxycaprylylsilane 2.15 BLACK NF-11S2 Iron Oxides (C.I ) (And) Triethoxycaprylylsilane 1.25 KOBOPEARL PERPETUAL BlueViolet Synthetic Fluorphlogopite (And) Silica (And) Titanium Dioxide Procedure: 1. Dissolve the Koboguard 5400 IDD in the Soltrol 130 at room temperature in a stainless steel beaker. Using a water bath on a hot plate heat the solution to 85 C under a fume hood using a dispersator for stirring. 2. Add the Bentone 38V and stir at high speed for minutes. Add the phenoxyethanol and parabens; stir 10 minutes. 3. Add the carnauba, candelilla, polyethylene and thixcin. Stir minutes or until melted. 4. Add the three pigments, BEUB-11S2, BUV CG-11S2 and BLACK NF-11S2; Stir for 45 minutes at high speed. 5. Add the KOBOPEARL PERPETUAL BlueViolet and begin cooling. Cool and stir to C using an ice bath Formulation 2 Ultramarine Waterproof Mascara. tors to provide new benefits to consumers. We created dispersions in media that tested these pigments for their transparency and opacity in addition to the effects of lightness and darkness with respect to their refractive indices. The results helped to show that all three of the ultramarine pigments behave similarly for these two physical properties. They also demonstrate that one can vary the surrounding media for ultramarines to create special effects. With regards to transparency, the ultramarine pigments are a distinct class of pigments as the R.I. of many cosmetic liquids and polymers are in the same range. Therefore, the combinations are many and can produce excellent results especially when combined with the more recent introductions of special effect pigments based upon borosilicate flakes or synthetic mica. Bibliography (1) Ashok Roy, Artists Pigments, A Handbook of their History and Characteristics Volume 2, National Gallery of Art (1993) (2) Gunter Buxbaum, Ullmann s Encyclopedia of Industrial Chemistry Pigments, 3. Colored Pigments, Wiley-VCH (2002) (3) Robert Henry Hill, Robert Bruce Order, U.S. Patent A -»Manufacture of ultramarine blue«. Sept. 17, 1957 (4) Nubiola USA, PCI Magazine (Paint and Coatings Industry), 2006 (5) Gunter Bauxham, Industrial Inorganic Pigments p.125, John Wiley & Sonds (2008) p.130 *Author s address: Edward Bartholomey Principal Research Scientist Kobo Products Inc., 3474 South Plainfield, New Jersey, U.S.A. Tel: [email protected] n 32 SOFW-Journal