Cosmetic emulsion

Several natural surfactants are used in cosmetic formulations, such as those produced from lanolin (wool fat), phytosteroids extracted from various plants and surfactants extracted from beeswax. Unfortunately, these naturally occurring surfactants are not widely used in cosmetics due to their relatively poor physicochemical performance when compared with the synthetic molecules. 

Cosmetic emulsions need to provide several benefits. For example, such systems should deliver a functional benefit such as cleaning (e.g. hair, skin, etc.), provide a protective barrier against water loss from the skin and in some cases they should 

The main physico-chemical characteristics that need to be controlled in cosmetic emulsions are their formation and stability on storage as well as their rheology, which controls spreadability and skin feel. Most cosmetic and toiletry brands have a relatively short life span (3-5 years) and hence development of the product should be rapid. Consequently, accelerated storage testing is needed to predict stability and change of rheology with time. These accelerated tests represent a challenge to the formulation chemist. 

As noted, the main criterion for any cosmetic ingredient should be medical safety (free of allergances, sensitizers and irritants and impurities that have systemic toxic effects). These ingredients should be suitable for producing stable emulsions that can deliver the functional benefit and the aesthetic characteristics. The main components of an emulsion are the water and oil phases and the emulsifier. Several water-soluble ingredients may be incorporated in the aqueous phase and oil-soluble ingredients in the oil phase. Thus, the water phase may contain 

Several emulsifiers, mostly nonionic or polymeric, are used for preparation of 0/W or W/O emulsions and their subsequent stabilization (see Chapter 6). For W/O emulsion, the HLB of the emulsifier is in the range 3-6, whereas for 0/W emulsions this range is 8-18. Clearly, the exact HLB number depends on the nature of the oil. As mentioned in the previous section, sorbitan esters, sorbitan glyceryl ester, silicone copolymers, sucrose esters, orthophosphoric esters, polyglycerol esters, polymeric surfactants, proteins and amine oxides may be used as emulsifiers. 

A number of the above instability problems with suspensions, emulsions and sus-poemulsions can be overcome by using polymeric surfactants that will be discussed later. For example, strong flocculation, coalescence and Ostwald ripening can be reduced or eliminated by the use of specially designed polymeric surfactants. Creaming or sedimentation can be eliminated by the use of thickeners that are sometimes referred to as rheology modifiers . 

Cosmetic emulsions need to satisfy a number of benefits. For example, such systems should deliver a functional benefit such as cleaning (e.g. hair, skin, etc.), provide a protective barrier against water loss from the skin and in some cases they should screen out damaging UV light (in which case a sunscreen agent such as titania is incorporated in the emulsion). As mentioned in the introduction, these systems should also impart a pleasant odor and make the skin feel smooth. Both oil-in-water (0/W) and water-in-oil (W/0) emulsions are used in cosmetic applications. As will be discussed 

The process of emulsion formation is determined by the property of the interface, in particular the interfacial tension which is determined by the concentration and type of the emulsifier. This is illustrated as follows. Consider a system in which an oil is represented by a large drop 2 of euea A1 immersed in a liquid 2, which is now subdivided into a large number of smaller droplets with total area A2 (A2 Al) as shown in Fig. 1.7. The interfacial tension is the same for the large and smaller droplets since the latter are generally in the region of 0.1 to few pm. 

In most cases AAy22 TAS which means that AG is positive, i.e. the formation of emulsions is nonspontaneous and the system is thermodynamically unstable. In the absence of any stabiUzation mechanism, the emulsion will break by flocculation, coalescence, Ostwald ripening or a combination of all these processes. This is illustrated in Fig. 1.8 which shows several paths for emulsion breakdown processes. 

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Conventional cosmetic emulsions (macroemulsions) normally contain about 70% or more of the external phase, which may be a mixture of components. The internal phase is routiaely iatroduced iato the external phase at an elevated temperature with vigorous agitation. The emulsifiers are distributed according to their solubility between the two phases. The level of emulsifiers (rarely more than about 10%) is kept low siace excessive amounts may destabilize emulsions or form a clear solubilizate. Auxiliary emulsifiers and other components are iacluded ia the phases ia which they are soluble. 

The formation of nitrosamines in aprotic solvents has applicability to many practical lipophilic systems including foods (particularly bacon), cigarette smoke, cosmetics, and some drugs. The very rapid kinetics of nitrosation reactions in lipid solution indicates that the lipid phase of emulsions or analogous multiphase systems can act as "catalyst" to facilitate nitrosation reactions that may be far slower in purely aqueous media (41, 53, 54). This is apparently true in some cosmetic emulsion systems and may have important applicability to nitrosation reactions in vivo, particularly in the GI tract. In these multiphase systems, the pH of the aqueous phase may be poor for nitrosation in aqueous media (e.g., neutral or alkaline pH) because of the very small concentration of HONO or that can exist at these pH ranges. 

Significance of Partition Coefficient of a Preservative in Cosmetic Emulsion, by H S Bean et all, American Perfumer and Cosmetics, Vol. 85, March, 1970... 

R Clark. Cosmetic emulsions. In HW Hibbott, ed. Handbook of Cosmetic Science. New York Pergamon Press, 1963, pp 175-204. 

Cosmetic applications, lactic acid in, 14 125 Cosmetic emulsions, 10 129 Cosmetic formulations, interaction with skin, 24 158... 

The physicochemical nature of the oil phase components in a cosmetic emulsion, the emollients, determines the skin-care effects, such as smoothing, spreading, sensorial appearance. Test methods have been developed to characterize and classify the numerous emollients available on the market, such as silicones, paraffins, and oleochemical-based products. The latter include glycerides, esters, alcohols, ethers, and carbonates with tailor-made structures, depending on the performance needed (Table 4.8). However, especially with regard to additional effects, there is still a demand for new products with unique performance properties. 

A material that is added to a formulation that increases the quantity of formulation required for a process without actually changing the formulation s reactivity. Example Barium sulfate is sometimes added during processing to increase the density of polyurethane (solid) foam. (CAPICO) A system in which potential cosmetic emulsion ingredients are numerically categorized so that one may calculate their influence on the phase inversion temperature of a formulated emulsion. 

The breakdown of emulsions can either be desirable or unwanted. Of course, cosmetic emulsions such as creams or cleansers have to be stable and become useless if separated. On the other hand, in processes such as enhanced oil recovery emulsions may be formed that are considerably stable and a notable effort is necessary for their separation. 

Mapstone, G. E. (1974), Crystalization of cetyl alcohol from cosmetic emulsions, Cosmet. Perfum., 89(11), 31-33. 

Oil oil-sand separation Viscous oil transportation Cosmetic emulsions... 

Acetylated lecithins have improved fluid properties, improved water dispersibility, and are effective oil-in-water emulsifiers for a wide variety of food formulations (56, 58). Moderately and highly acetylated lecithins are resistant to heat and can be repeatedly heated and cooled without darkening. The intended uses for minimally acetylated products are in infant foods, coffee whiteners, meat sauces, and gravies, and for oil-in-water cosmetic emulsions. Moderately and maximally acetylated products are used in cheese sauces, release agents in pumpable and aerosol formulations, and shortenings. 

Schambil F, Jost F, Schwuger MJ. Interfacial and colloidal properties of cosmetic emulsions containing fatty alcohol and fatty alcohol polygylcol ethers. Progr Colloid Polym Sci 1987 73 37 7. 

Fukushim S, Yamaguchi M. The effect of cetostearyl alcohol in cosmetic emulsions. Cosmet Toilet 1983 98 89-102. 

Eccleston GM. Properties of fatty alcohol mixed emulsifiers and emulsifying waxes. In Florence AT, ed. Materials Used in Pharmaceutical Formulation Critical Reports on Applied Chemistry, volume 6. Oxford Blackwell Scientific, 1984 124-156. Mapstone GE. Crystallization of cetyl alcohol from cosmetic emulsions. Cosmet Perfum 1974 89(11) 31-33. 

Kostenbauder HB. Physical chemical aspects of preservative selection for pharmaceutical and cosmetic emulsions. Dev Ind Microbiol 1962 1 286-296. 

Use Food products (margarine, hydrogenated shortenings) synthetic cocoa butter soaps cosmetics emulsions cotton dyeing synthetic detergents source of fatty acids, fatty alcohols, and methyl esters base for laundering and cleaning preparations for soft leathers. 

Use Emulsifying agent, drycleaning soaps, soluble textile oils, wax removers, metal-cutting oils, cosmetics, emulsion paints, plasticizers, insecticides. 

Several industrial systems involve emulsions, of which the following are worthy of mention. Food emulsions include mayonnaise, salad creams, deserts, and beverages, while personal care and cosmetics emulsions include hand creams, lotions, hair sprays, and sunscreens. Agrochemical emulsions include self-emulsifiable oils that produce emulsions on dilution with water, emulsion concentrates with water as the continuous phase, and crop oil sprays. Pharmaceutical emulsions include anaesthetics (O/W emulsions), hpid emulsions, and double and multiple emulsions, while paints may involve emulsions of alkyd resins and latex. Some dry-cleaning formulations may contain water droplets emulsified in the dry cleaning oil that is necessary to remove soils and clays, while bitumen emulsions are prepared stable in their containers but coalesce to form a uniform fihn of bitumen when apphed with road chippings. In the oil industry, many crude oils (e.g.. North sea oil) contain water droplets that must be removed by coalescence followed by separation. In oil slick dispersion, the oil spilled from tankers must be emulsified and then separated, while the emulsification of waste oils is an important process for pollution control. 

Lochhead RY, Hemker WJ, Castaneda JY, Garlen D. Novel cosmetic emulsions. Cosmetics Toiletries 1986 101 125-138. 

Neumann P, Tiefensee K. A new liquid thickener for all kind of cosmetic emulsions. SOFW J 1999 125 8-10. 

Aminoi. [Finetex] Fatfy add alkanol-amides softening agent, emulsifier, soap active, foam boosier/stabilizo , thickener cosmetic emulsions, household cleaners, industrial tqiplics. 

HD-Ocenol . enkel/Emery/Cospha Henkel KGaA] Linear primary alcohols intermediates for surfactant mfg., emollient superfatting agent carrier for cosmetics, emulsions. 

Hydrofol. [Procter Gamble] Fatty acids or glycerides used in cosmetic emulsions. 

Llpdan. (Lion] alpha-Olefln sulfonate emulsifier for cosmetics, emulsion polymerization d ergent base. 

QO-33-F. [Hefti Ltd.] Sorbitan sesqui-deate emulsitia for cosmetic emulsions. 

Rewomat [Rewo GmbH] Sulfosuc-cinamides detergent, foaming agent/ stabilizer, enuilsifier, solubilizer, dispersant for cosmetics, emulsion polymerization, latexes. 

Rhodapon. [Rhone-Poulenc Surf. Rhone-Poulenc France] Sidfates wetting s ent, emulsifier, detergent for cosmetics, emulsion ptdymerkation, rug shanqxx), latex stabilization. 

Special Oil. [Hals Am.] Glyceryl triesters tracer additive to other fats such as dairy butler. rdease agent lubricant in cosmetic emulsions, lipsticks, hair care prods. pigment dispersant for sticks and liners. 

Manro. fanro Prods. Ltd.] Si actants foam booster, wetting agent, thickener used in cosmetics, emulsion polymerization, cleaning ptods fire fighting foams, industtial prods. 

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