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Pickering Emulsions – A New Approach for Technical Relevant Emulsions

IP.com Disclosure Number: IPCOM000030408D
Publication Date: 2004-Aug-12
Document File: 3 page(s) / 28K

Publishing Venue

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Abstract

The preparation of stable emulsions requires the stabilization of the water-oil interface in order to prevent coalescence of the dispersed droplets, which can be oil for oil-in-water (o/w) emulsions or water for water-in-oil (w/o) emulsions. Currently, mainly organic emulsifiers such as non-ionic or anionic emulsifiers are used. However, due to their amphiphilic properties such emulsifiers are also able to adsorb at the surface of solid substrates, which significantly influences the wetting properties of the substrate. This effect can negatively influence the application properties of emulsions. Emulsifiers used for cosmetic applications can be irritating for the human skin. In order to overcome the mentioned shortcomings emulsions without organic surfactants are of interest.

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Pickering Emulsions – A New Approach for Technical Relevant Emulsions

The preparation of stable emulsions requires the stabilization of the water-oil interface in order to prevent coalescence of the dispersed droplets, which can be oil for oil-in-water (o/w) emulsions or water for water-in-oil (w/o) emulsions.

Currently, mainly organic emulsifiers such as non-ionic or anionic emulsifiers are used. However, due to their amphiphilic properties such emulsifiers are also able to adsorb at the surface of solid substrates, which significantly influences the wetting properties of the substrate. This effect can negatively influence the application properties of emulsions. Emulsifiers used for cosmetic applications can be irritating for the human skin.

In order to overcome the mentioned shortcomings emulsions without organic surfactants are of interest.

Recently, the use of finely divided particles for the stabilization of o/w or w/o emulsions becomes more and more popular.

Typical examples for these kinds of particles are silicates, aluminates, titanates, alumosilicates such as bentonites, montmorillonates, smektites, and hectorites, metal oxides such as aluminum, silicon, titanium, nickel, cobalt, iron, manganese, chromium, or vanadium oxides, carbon blacks, or nitrides or carbides, such as boron nitride, boron carbide, silicon nitride, or silicon carbide. Of special interest are fine SiO2 based particles, such as precipitated silica, colloidal silica, and pyrogenic silica particles. However, it turned out that the particles have to meet several requirements in order to effectively stabilize emulsions. Most importantly, the particles should not be completely wetted by water for stabilization of o/w emulsions and not be completely wetted by oil when used for the stabilization of w/o emulsions. The wetting properties of pyrogenic silica particles can be readily tuned by the degree of surface modification, which can be monitored by the residual silanol content of the silica. In general particles suited for the stabilization of o/w emulsion exhibit a residual silanol content between 95% and 50%. Particles used for the stabilization of w/o emulsion should show a residual silanol content between 50% and 5%. The silanol content can be determined by means of an acid-base titration and the residual silanol content is defined as (silanol content of treated silica / silanol content of untreated base silica) * 100. Organosilicon compounds, such as chloroalkylsilanes, alkoxyalkylsilanes, HMDZ, or PDMS fluids are usually employed for surface modification.

Particle stabilized emulsions can be used for water-borne coatings, adhesives, or sealants containing e.g. organopolysiloxanes, saturated or unsaturated polyester, epoxy resins, polyurethanes, polyacrylates, polysulfides, or their precursors.

Particle stabilized emulsions can also be used in cosmetic applications for shampoos, conditioning shampoos, conditioners, after dye treatment and hair relaxer treatments...