Cosmetics Preparation Guidelines and Model Formulations for Target Markets Introduction There is a tendency, in the personal care field, for highly customized products. This might be to specific hair types where the ph and protein levels are unique, or gender-based targets such as male beards. There is also a need to simplify formulations and reduce black- or grey-listed chemicals. Finally, the use of health friendly stabilizers and the bio-delivery of molecules with a presumed medical effect, such as vitamins, are also fields where developments progress. Given this, customized formulations for target markets can be an important complement to brands or personal care products. This application bulletin provides guidelines as to how that is possible. It also attempts to introduce science and technology to a field where formulation has generally been an art. In doing so, highly functional preparations can be made and customized with short lead times, stocking a minimum of raw materials. Types of Cosmetic Products In general, personal care products are either applied topically, to the skin, or on hair. There are various categories and examples of cosmetic products including the following: Health related benefits Protection against external effects such as sunscreen (UV) and sanitizers (bacteria) Protection against an internal effect such as oxidation Delivery of an active ingredient such as a vitamin or analgesic across the skin Hygiene Skin care such as soaps and body washes Hair care including shampoos and 2-in-1 conditioners Refreshing creams which cool after application Sterilizing gels such as sanitizers Cosmetic Applications Creams such for facial, hand and feet applications, all of which have different rheologies Creams which provide protection such as a moisture barrier or against UV Creams which have a specific function (e.g. hydration, make-up removal) Creams designed for a specific time of the day (e.g. morning) or climate (dry, humid) Appearance Nutraceuticals where vitamins/antioxidants are delivered transdermally (anti-aging) Creams such as those which whiten skin or enhance the effect of tanning Therapeutic Creams which provide essential oils to relieve muscle ache Creams delivering an active ingredients (e.g. Aloe Vera, Vitamins)
Table 1 summarizes personal care products according to their function and sensory behaviour, with the key ingredients noted. Table 1. Personal Care Products and their Main Function Product Function Key Ingredients Sensory Aspects Analgesic Suspend Oil for Pain Relief Menthol, Wintergreen Thick, Slow rub-in Anti-Aging Skin Regeneration Provitamin B5 Thick, Creamy Anti-Oxidants Prevent Oxidation/Radicals Oils and Vitamin E Rub-in-Effect Body Wash Remove Grease Soap Thin, Refreshing Conditioner Adsorb on Hair Cationic Polymers Silky Facial Regeneration Cucumber (e.g.) Light, shear thinning Foot Regeneration/ Hydration Salt-tolerant thickener Extremely Thick Hydra-fresh Cooling Mint Evaporation Hydrating Hydration Green Thickener Silky, Film-free Sanitizer Disinfection Ethyl-/isopropyl-alcohol Refreshing Sun Screen Prevent UV Penetration Mineral oxides (zinc) Oily, slightly granular Tanning Enhance UV Penetration Green Tea Extract Thin, rub-in Nutrition Dermal Delivery Vitamins Thick, Odorless Whitening Bleaching Skin Acids Thin, Stay-On
Ingredient Selection Other than some ingredients which are for olfactory reasons, one must functionalize a personal care product by determining what it must include and tolerate. There are five main questions you must ask yourself in selecting a thickener for a personal care product. 1. Must the product be Transparent or Opaque? If the product should be transparent one is typically taught to use a powdered-based thickener. However, one can also apply alkaline swellable emulsions ( ASE ). These are lower in cost by a factor of ten or more and begin as a turbid suspension when added to water, with a ph of approximately 2. When the ph is increased the system becomes viscous and transparent under neutral or near neutral conditions (ph of 6.8 to 7). If the final formulation can be opaque then a traditional inverse-emulsion is the norm. These have a water phase dispersed in a hydrocarbon. They can be made oil-, ethoxylate- and acrylamide-free. These materials are food grade materials with Kosher and Halal certification. They are also Vegan and can have over 95% of bio-based ingredients. One of the key features of inverse emulsions is they hydrate incredibly rapidly, typically in less than ten seconds. Economically they are priced as specialities, in between the ASE and powdered products. Liquid products have the advantage that they can be applied at any part of the process of the formulation of the personal care product. Powders often must be applied to the unmodified water phase. The inverse-emulsions can be tailored to provide sensory applications by the very nature of the terpolymer employed. Given the ingredients, some emulsions can also, without mineral additives, enhance whiteness. Furthermore, they act as emulsifiers themselves, simplifying formulations. They also permit room-temperature preparation. 2. What is the intended ph of the formulation? No formulation or ingredient is completely polyvalent. Some function better in acidic conditions and others thrive with alkalinity. Owing to their permanent charge, cationic polymers can work at extremely low, even negative, phs. The later would be an acid gel for industrial applications. Overall, one might practically say that cationic polymers are operative at phs from 2 to 9. Anionics are generally based on acrylates. These have charges which depend on the alkalinity. Therefore, the thickest rheology is obtained at ph of 5-12. Highly basic gels, with a ph of 13, used for straightening hair, can be prepared. In general hair care uses transparent products at elevated ph. Cationics have the advantage that they adhere to the silica. Skin care products tend to be opaque creams, meaning they are formulated with inverse-emulsions, as described in the previous section. 3. What must be put inside the Gel? Polyelectrolytes swell in water. If the polymer is housed inside a particle typically of 100 nm, this sphere also expands. Such materials, therefore, function very well in suspending solid particles. This is a fashion in transparent systems where sparkles or colored beads are part of the appeal of the final product, though have little or no functional role. An exception might be industrial cleaning formulations where the suspended micro-particles result in abrasion and can remove grease from hands more effectively and less expensively than soap alone. Such gels would be very reasonably formulated with an alkaline swellable emulsion, which is anionic in nature. Cationic polymers prepared in inverse-emulsions are generally branched, though not crosslinked. This gives them a high charge density. They can suspend acids very well, even at levels of 5-10%. They can also incorporate low polarity oils (e.g. polydecanes) as well as highly polar liquids (e.g. sunflower oil) up to 20%. As an example, an analgesic cream will have to be able to stabilize over ten percent of oils such as menthol or wintergreen. In some formulations one may wish to include an alcohol. For example, sanitizers have 50% or more of ethanol. These tend to be well tolerated in gels made from powdered polymers where there is an intra-and inter-molecular network on the 1-10 nm scale.
4. Is the absence of Grey-Listed Ingredients Necessary? In some cases there are materials which should be avoided. These grey listed ingredients can include paraben, ethoxylates, mineral oils (skin irritants), as well as acrylamide (suspected carcinogen). Some consumer groups advocate against fatty acids, silica and salts. There have been published health concerns in relation to silicones and endocrine disrupters (e.g. benzopehnone, a UV protector). While most formulations include many of these chemicals, some new generation products have a health friendly perspective and avoid the aforementioned products as well as any animal-derived products. Many of the grey-listed materials can be replaced by natural or health-friendly alternatives. For example, vitamins are good preservatives. They also deliver across the skin more extensively than they do via oral or gut absorption. Some formulations have very high electrolyte levels. This might be the case for a cream used for hydration, repair and protection. These usually contain botanical extracts. The new generation of health-friendly emulsion thickeners (aquacharm 100) provide very good salt tolerance; the original products were designed to swell in water, which is not a very reasonable continuous phase. The issue of salt sensitivity is important for any product applied to the skin as the salinity of the epidermis is sufficient to break the viscosity of many products and render them fluid. 5. Which Quality-Related Aspects Are Needed? Quality is not merely batch-to-batch reproducibility. Many formulations involve specifications which do not exist on the market. This can include the following, which either can be tuned for a given client, or must be selected: Particle size control, which may be necessary to provide a glossy, textureless, gel Simple, cold, formulations are preferred to hot processes employing emulsifiers Ability to formulate without homogenization or high pressure injections Ability to incorporate molecules with different solubilities and volatilities (perfumes) Vegan or animal-free formulations Origin of the material and regional standards such as REACH or.
Case Studies The thickeners made by permit the formulation of personal care products which are based on health friendly formulations. These are simple to make and can be prepared in minutes. They have few ingredients and can be preserved with natural products, such as Vitamin E. They are available, in bulk, made in Switzerland. Though the recipes are secret, one example, using aquacharm 100, is provided for a hydrating hypoallergenic cream. Hydrating Hypoallergenic Cream Formulation Deionized Water at 95.6% aquacharm 100 at 4% Vitamin E from Sunflower at 0.4% Preparation In preparing a personal care formulation there are two important mechanical elements. The selection of the appropriate equipment, including the reservoir for mixing/reacting, is key. Often something off the shelf is used and this provides inadequate mixing, perhaps due to its shape. The consequences can be a lower functional cream (e.g. less active ingredient suspended). One may also require more material to have the appropriate rheological characteristics. The conditions of agitation are also as critical as the formulation itself, and can contribute to skin feel, for example. These are both discussed in the following section. The procedure demonstrates how, on a lab preparation/qc scale, one could optimize preparations Equipment Figure 1 is a photo of an appropriate mixing system for thick gels. If a non-marine impeller is applied it is critical that the alternative system results in circulation of the air-fluid interface. Figure 1. Photo of an appropriate reactor and impeller. The vortex, reaching the bottom of the reservoir, is evident.
Agitation Conditions If a liquid phase is not well mixed the hydration will be slow. In such cases the thickening polymer may, indeed, fight against the full incorporation of material, influencing the tolerance to ingredients (e.g. salt, oil, solvents) as well as the final texture. Figure 2 is an example of a preformulation after mixing under recommended agitation conditions. Figure 2. Photo of a well mixed pre-formulation as well as the product, itself, hanging off a spatula. The well distributed polymer results in a viscosity of approximately 70,000 cps (Brookfield RV, Spindle 7, 20 RPM, 25C) Conclusions Traditionally, the function of a personal care product has been provided by a mixture of ingredients. In the late 20 th century the influence of mechanical modifications on rheology provided another parameter. Furthermore, we have, as a society, grown accustomed to gels which are visually pleasing (e.g. with their smell, colour or suspended materials). Some ingredients, however, will not mix. Oil and water are incompatible. Antioxidants, which are oil soluble, therefore, do not mix easily in skin creams. One can use a soap to emulsify the organic phase into the water, much as garlic and mustard function in salad dressing. However, if one needs to suspend solids in a gel, these will settle over time. Pierre-Gilles de Gennes won a Nobel prize for the concept of reptation*. Molecules wiggle and behave like snakes. Therefore, a gel of polymers is not like an entangled bunch of wool or hangers, but rather individual molecules which can move independently. If there is a pressure, such as from a suspended material, or molecule of different density, this can push apart the gel and lead to sedimentation or floatation. Basically, the smaller molecules are pushed out of the way. If all molecules had the same size and were large enough that diffusion is minimal, even over the period of years, such separation would be avoided or minimized. has process technology which permits uniform molecular synthesis, even from branched polymers. This permits one to formulate seemingly incompatible materials, much as soap does for oil and water.
About provides pre-made skin and hair care products in bulk which can be packaged locally. Ready-to-use formulations, to which the final active ingredients can be added, are also available. Based in Geneva, Switzerland, is a renowned firm, with accolades from important international firms such as the Wall Street Journal Europe and Dow Jones. These include prizes for our technology and the entrepreneurs themselves (Swiss Economic Award). Our Director has also been on the Nobel Prize nominating committee. We develop, produce and market products for personal care and in water treatment. Figure 3 shows some of the ready made cosmetics prepared in Geneva. Figure 4 is an aerial photo of the production facility. Figure 3. Hypoallergenic, Hydra-fresh, Facial, Morning, Whitening and Anti-Aging Creams. Figure 4. production facility outside of Geneva, Switzerland