Formation of nano-emulsions has been studied in the system water/Brij 30/decane at 25 °C by three low-energy emulsification methods:  (A) stepwise addition of oil to a water−surfactant mixture, (B) stepwise addition of water to a solution of the surfactant in oil, and (C) mixing all the components in the final composition. Nano-emulsions with average droplet size of 50 nm and high kinetic stability have been obtained only at oil weight fractions, R, lower than 0.3 by emulsification method B. Independent of the oil weight fraction, R, emulsions obtained by method B have lower polydispersity than those obtained by methods A and C. Phase behavior studies have revealed that compositions giving rise to nano-emulsions consist of Wm, (O/W microemulsion), Lα (lamellar liquid crystalline), and O (oil) phases, at equilibrium. It has been shown that equilibrium properties cannot fully explain nano-emulsion formation. Low values of equilibrium interfacial tensions and phase equilibrium involving a lamellar liquid cry...

Formation of Nano-emulsions by Low-Energy Emulsification Methods at Constant Temperature

Oil-in-water nanoemulsions for pesticide formulations.

A hydroalcoholic lotion is disclosed which comprises (a) a lower alcohol and water in a weight ratio of about 35:65 to 100:0, and (b) between at least 0.5% and 8% by weight thickener system comprised of at least one emulsifier present in at least 0.05% by weight wherein the composition in a polymer free state has a viscosity of at least 4,000 centipoise at 23 degrees C. and wherein the emulsifier is comprised of at least one hydrophobic group and at least one hydrophilic group. The hydroalcoholic composition is useful as a hand preparation such as a lotion or as a presurgical scrub replacement.

Stable hydroalcoholic compositions

A hair cosmetic composition including (a) at least one compound selected from fatty acids containing a linear or branched alkyl or alkenyl group having 12-40 carbon atoms, salts thereof and fatty acid esters composed of one of the fatty acids and a polyhydric alcohol; (b) at least one aromatic alcohol represented by general formula (1), wherein R1 means a hydrogen atom or a methyl or methoxy group, Y denotes a single bond or a linear or branched alkylene or alkenylene group having 1-3 carbon atoms, Z is a hydrogen atom or a hydroxyl group, and p and q stand individually for a number of 0-5; and (c) at least one cationic surfactant. The hair cosmetic composition has neither sticky nor oily feel to the touch, is excellent in hair-conditioning effects of, for example, giving users a moistured feel of the hair and imparting softness and smoothness to the hair, gives resilience to the hair and is superb in effects of preventing damage to the hair and of keeping the waves or curls of the hair beautiful.

Hair cosmetic composition

The low-energy emulsification method Emulsion Inversion Point (EIP) was used to prepare O/W nano-emulsions in the W/potassium oleate−oleic acid−C12E10/hexadecane ionic system. This method had not practically been used in ionic systems up to now. The resulting droplet sizes, much smaller than those obtained with the high-energy emulsification methods, depend on the composition (formulation variables) and preparation variables (addition and mixing rate). Phase diagrams, rheology measurements, and experimental designs applied to nano-emulsion droplet sizes obtained were combined to study the formation of these nano-emulsions. To obtain small droplet sizes, it is necessary to cross a direct cubic liquid crystal phase along the emulsification path, and it is also crucial to remain in this phase long enough to incorporate all of the oil into the liquid crystal. When nano-emulsion forms, the oil is already intimately mixed with all of the components, and it only has to be redistributed. Results show that the sma...

Optimization of nano-emulsion preparation by low-energy methods in an ionic surfactant system.

An oil-in-water type emulsion composition comprising: an amphiphile and a surfactant selected from the substances which can form a gel in an amphiphatic substance-surfactant-water system at a temperature of not lower than ordinary temperatures; oil and water, wherein substantially the total amount of amphiphile and surfactant exist on the boundary surfaces of emulsion particles. The emulsion composition has both the physical properties close to those of an aqueous solution and a creamy feel at the time of use.

Oil-in-water type emulsion composition

Physicochemical properties of oil-in-water (O/W) emulsions containing fatty alcohols and surfactants have been investigated with the aim of developing new formulations that are less viscous and more transparent than conventional milky lotions, as well as for providing greater skin-improving effects. O/W-based creams can be converted to low viscosity milky lotions following their emulsification with a homogenizer at temperatures greater than the transition temperatures of their molecular assemblies (α-gel). The stability of the O/W emulsions evaluated in the current study increased as the transition temperatures of the molecular assemblies formed from their fatty alcohol and surfactant constituents increased. A decrease in the emulsion droplet size led to the formation of a new formulation, which was transparent in appearance and showed a very low viscosity. The absence of a molecular assembly (α-gel) formed by the fatty alcohol and surfactant molecules in the aqueous phase allowed for the formation of a stable transparent and low viscosity nanoemulsion. Furthermore, this decrease in droplet size led to an increase in the interfacial area of the emulsion droplets, with almost all of the fatty alcohol and surfactant molecules being adsorbed on the surfaces of the emulsion droplets. This was found to be important for preparing a stable transparent formulation. Notably, this new formulation exhibited high occlusivity, which was equivalent to that of an ordinary cosmetic milky lotion, and consequently provided high skin hydration. The nanoemulsion was destroyed following its application to the skin, which led to the release of the fatty alcohol and surfactant molecules from the surface of the nanoemulsion into the aqueous phase. These results therefore suggest that the fatty alcohol and surfactant molecules organized the molecular assembly (α-gel) and allowed for the reconstruction of the network structure.

Preparation and Thermal Properties of Fatty Alcohol/Surfactant/Oil/Water Nanoemulsions and Their Cosmetic Applications.

We prepared a thermodynamically unstable microemulsions in which a droplet does not change in size for over one year. The phase diagram showed these microemulsions to exist in the two-phase region. These microemulsions may be regarded as microemulsions in a broad sense by Rosano. They were obtained by the rapid cooling of the homogeneous phase in nonionic surfactant-oil-water systems, to room temperature. The droplet mean radius was related to the ratio of oil to surfactant by a linear function. The droplet size of these microemulsions can thus be controlled by changing this ratio.The stability of the microemulsions depends on the nature of the oil and surfactant. The stability rises dramatically with increase in the carbon number of the oil. The droplet having liquid paraffin (Lp) or squalane (Sq) undergoes no appreciable change in size for over a year at 25°C.Small quantities of Lp or Sq increase the stability of the unstable microemulsions containing a short chain hydrocarbon oii, The stability of the microemulsions increases with the size of the surfactant molecule. The main cause of instability in such systems thus appears to be related to Ostwald ripening rather than droplet coalescence.

Micraemulsion Formation in Two-phase Region

A new method for preparation of ultrafine emulsions was developed. The ultrafine emulsions can be obtained easily by rapid cooling of the high temperature microemulsions, i.e., the swollen micellar solutions in the oil-water-nonionic surfactant systems, to room temperature. They are the thermodynamically unstable dispersions of which the mean droplet diameters are bellow 100nm, and look like so-called microemulsions, i.e., transparent or translucent. The droplet diameter was related to the ratio of oil to surfactant by a linear function. The droplet size of the ultrafine emulsions can thus be controlled by changing this ratio.The stability of the ultrafine emulsions depends on the chemical nature of the oil and surfactant. The stability rises dramatically with increase in the carbon number of the oil, and decreases with increase in the polarity of the oil. The droplets of the liquid paraffin (Lp) and squalane (Sq) ultrafine emulsions do not practically change in size for over a year at 25°C. The addition of small quantities of a long-chain alkane to the disperse phase can have a profound effect on ultrafine emulshion stability. The unstable ultrafine emulsions of short-chain alkanes such as dodecane can be stabilized by added Lp or Sq. The results suggest that the main cause of instability in the ultrafine emulsions may be molecular diffusion (Ostwald ripening) rather than droplet coalesence. The stability of the ultrafine emulsions increases with the size of the surfactant molecule.The ultrafine emulsions were prepared by using the commercial materials for the purpose of applying to the products of cosmetics. The transparent or translucent lotions containing oil components were obtained by using small quantities of the surfactants, and were very stable. Since this method can keep the droplet size under precise controll, the turbidity of the products can be controlled easily.

https://www.jstage.jst.go.jp/article/sccj1979/23/4/23_4_288/_pdf

Ultrafine Emulsions and Application to Cosmetics

Phase transition phenomena in the water-potassium stearate-polyol (glycerol, propylene glycol, 1, 3-butanediol) systems were studied by differential scanning calorimetry and X-ray diffraction. In the absence of polyols, suitable annealing treatment for the samples was necessary to the gel-to-coagel transition. In the presence of polyols, in the temperature range where the coagel phase is stable state, the gel phase was transformed into the coagel phase without annealing. With increasing polyol content, the transition temperature for the gel-isotropic solution or liquid crystal (Tc) decreased and that for the coagel-gel (Tgel) increased. Therefore, Tc and Tgel coincided with each other at a certain polyol content, and above this content the stable gel phase disappeared and the coagel phase was directly transformed into the isotropic solution. The order of reducing the area of the gel region in the phase diagram was following; 1, 3-butanediol> propylene glycol> glycerol.

Satoshi Tomomasa

Papers

Oil-in-water type emulsion composition

Preparation and Thermal Properties of Fatty Alcohol/Surfactant/Oil/Water Nanoemulsions and Their Cosmetic Applications.

Micraemulsion Formation in Two-phase Region

Ultrafine Emulsions and Application to Cosmetics

Phase Transitions of the Potassium Stearate-Water-Polyol Systems