Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K23/00—Use of substances as emulsifying, wetting, dispersing, or foam-producing agents
  • C09K23/002—Inorganic compounds
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K23/00—Use of substances as emulsifying, wetting, dispersing, or foam-producing agents
  • C09K23/54—Silicon compounds
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B82—NANOTECHNOLOGY
  • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
  • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K23/00—Use of substances as emulsifying, wetting, dispersing, or foam-producing agents
  • C09K23/42—Ethers, e.g. polyglycol ethers of alcohols or phenols

Definitions

• the present invention relates to emulsifying compositions comprising surfactants formed from surface-modified solid particles, to said surfactants, as well as to methods of preparing such compositions.
• the surfactants currently known are generally molecules or macromolecules of amphiphilic nature, that is to say having on the one hand a hydrophilic region and on the other hand a hydrophobic region. This particular structure induces an orientation of these molecules when they are present at liquid / liquid, liquid / gas or liquid / solid type interfaces.
• surfactants can adsorb at these interfaces. This adsorption causes a lowering of the interfacial tension ⁇ and thus makes it possible to reduce the free energy of the systems which contain a large interfacial area, which induces their stabilization (foams, emulsions ).
• the term surfactant comes from this decrease in the interfacial tension that the phenomenon of orientation of the molecules generates.
• a surfactant is a molecule consisting of one or more ionic or nonionic hydrophilic group (s) and one or more hydrophobic chain (s), most often hydrocarbon (s) ). It is the exact nature of these two groups which determines the surfactant properties of the molecule obtained.
• amphiphilic particles do indeed behave in a particular way at water / oil type interfaces, it cannot however be considered that they can replace the conventional molecular surfactants.
• these particles cannot, for example, be used as emulsifying agents, in particular because of their large size and their weakly marked amphiphilic nature.
• a first object of the present invention is to provide compositions comprising surfactants having, in addition to a marked emulsifying character, interesting physical and / or chemical properties, not linked to this amphiphilic character.
• the invention also aims to provide compositions comprising surfactants having a sufficient size giving them reduced mobility, and nonetheless capable of replacing conventional molecular surfactants, at least in certain applications, and in particular in processes of emulsification.
• Another object of the invention is to provide emulsifying compositions based on surfactants with a solid character which can advantageously replace the emulsifying compositions generally used, for example for the production of emulsions, inverse emulsions or d multiple emulsions, ensuring sufficient stabilization of the emulsion while also benefiting from the solid nature and the physicochemical properties of the surfactants used.
• the subject of the present invention is an emulsifying composition
• an emulsifying composition comprising particles of nanometric dimensions based on a metal oxide, hydroxide and / or oxy-hydroxide, to the surface of which organic chains of hydrophobic nature are linked.
• said composition having specifically an emulsifying character such that it makes it possible to produce an emulsion of the water in oil or oil in stabilized water type, characterized by a content in dispersed phase greater than or equal to 20%, preferably greater than or equal to 30%, and preferably greater than or equal to 40%, and where the average size of the drops forming the dispersed phase is less than or equal to 5 microns, and preferably less than or equal to 3 microns.
• stabilized emulsion is meant, within the meaning of the present invention, a water-in-oil type emulsion (reverse emulsion) or oil in water (direct emulsion), the structure of which remains stable after being subjected to centrifugation carried out at a speed greater than or equal to 4000 revolutions per minute and for a duration of at least twenty minutes.
• the emulsifying compositions of the present invention have an emulsifying character sufficient to allow stabilized emulsions of the water in oil type to be produced (reverse emulsions) characterized by contents in aqueous phase greater than or equal to 40%, and in which the average size of the drops of the dispersed phase is at most 5 microns.
• the particles of nanometric dimensions based on a metal oxide, hydroxide and / or oxy-hydroxide present in the emulsifying compositions of the present invention, to the surface of which organic chains of hydrophobic nature are linked are such that , on the surface of most of these particles, the bonds between said chains and the surface are distributed in a non-homogeneous manner, so that each of the surface particles thus modified has an effective amphiphilic character, that is to say, when it is placed in a two-phase water / oil medium such as a two-phase medium of water / ethyl acetate, water / hexane, or water / octanol type, said particle is localized specifically at the interface between the two phases in presence.
• This amphiphilic character can in particular be demonstrated by using a test of the type of that described by Na ahama et al. in Langmuir, volumel ⁇ , pp. 7882-7886 (2000).
• the surfactants formed by such particles of nanometric surface dimensions modified by organic chains of hydrophobic character, distributed in a non-homogeneous manner on the surface, so that the modified surface particle has an effective amphiphilic character, are new and constitute , according to a particular aspect, another object of the present invention.
• the effective amphiphilic nature of the surfactants present in the compositions of the present invention is explained by the fact that these agents have a structure specifically comprising a zone (1) of generally hydrophilic character. , at least partially due to the hydrophilic nature of the surface of the particle, and an area (2) of generally hydrophobic nature, due to the presence of chains of hydrophobic nature.
• particle of nanometric dimensions is meant, within the meaning of the present invention, an isotropic or anisotropic particle whose average characteristic dimension (s) is or are between 2 and 100 nm.
• the particles of nanometric dimensions of the invention are of isotropic or spherical morphology.
• the average diameter of the particles of nanometric dimensions present in the compositions of the invention is advantageously between 3 and 40 nm, and preferably between 4 and 20 nm.
• said particles of nanometric dimensions are specifically particles based on a metal oxide, hydroxide and / or oxy-hydroxide.
• they are based on an oxide, hydroxide and / or oxy-hydroxide of at least one metal chosen from cerium, aluminum, titanium or silicon.
• the particles present in the compositions of the invention specifically have, intrinsically, a surface of hydrophilic nature.
• This hydrophilic character is generally ensured by the presence, on the surface of the particle, of hydrophilic chemical groups. These groups can be neutral (-OH, COOH, PO 4 H, for example) or preferably loaded, in particular of the type -O (H) ... H ⁇ -OH ... OH " or -CO 3 2" , which then gives the particle a non-zero surface charge.
• the absolute value of the surface charge, expressed relative to the total surface of the particle, is, in the presence of the organic chain (s) linked (s), advantageously greater than 5 micro-coulombs per cm 2 , and preferably greater than 10 micro-coulombs per cm 2 .
• organic chain of hydrophobic nature designates, in general, an organic chain having a hydrophilic / lipophilic balance such that said chain is soluble in a hydrophobic solvent and less soluble, advantageously insoluble, in water.
• the “organic chains of hydrophobic nature” of the invention are chains within which the chemical groups of hydrophobic nature, of the alkylated chain type for example, represent at least 10% by mass, preferably at least 20% by mass and advantageously 30% by mass in said chains.
• organic chains of hydrophobic nature of the invention can in particular be alkyl chains, or alternatively alkyl chains modified by the presence of hydrophilic groups, of ethoxyl type for example, these groups of hydrophilic nature not representing more than 90 % by mass and advantageously representing less than 70%.
• the organic chains of hydrophobic nature linked to the surface of the particles present in the compositions of the invention are preferably alkyl chains comprising from 6 to 30 carbon atoms, and preferably from 8 to 18 carbon atoms, or polyoxyethylene-monoalkylether chains in which the alkyl chain comprises from 8 to 30 carbon atoms, preferably from 8 to 18 carbon atoms, and in which the polyoxyethylene part comprises from 1 to 10 ethoxy groups -CH 2 CH 2 O-.
• the number of carbon atoms, as well as the number of ethoxyl groups possibly present is to be adapted as a function of the hydrophobic and hydrophilic properties desired respectively for the solid surfactants present in the compositions of the invention.
• the hydrophilic nature is ensured both by the hydrophilic nature of the surface of the particle and by the hydrophilic parts, of the ethoxyl group type, possibly present in the organic chains linked to the particle.
• the hydrophobic nature is ensured by the hydrophobic parts, of the alkyl chain type, of the organic chains.
• the bond between the organic chains and the surface of the particles is ensured by the presence, at one of the ends of each of said chains, of an ionic group inducing a complexing bond with one of the metal cations present. on the surface of the particles.
• the particles present are partially complexed by molecular surfactants of ionic type.
• zone (2) defined above for the solid surfactants present in the compositions of the invention is then ensured by the presence of the hydrophobic chains of the molecular surfactants used, the at least predominantly hydrophilic character of zone (1) being in turn due to the hydrophilic surface of the particle and to the possible residual surface charge does not not participating in the complexation of molecular surfactants of ionic type bound to the surface.
• the coverage rate of the surface of the particles, expressed, for each particle, by the ratio of the number of hydrophilic heads complexed to the surface of said particle on the total surface of this particle is specifically less than 4 heads per nm 2 .
• the coverage rate of the particles present is therefore generally between 0.4 and 3.2 hydrophilic heads per nm 2 , and preferably between 1 and 3.2 hydrophilic heads per nm 2 .
• the charged particles are, where appropriate, particles of positive charge.
• the ionic group inducing the complexing bond is then an anionic group.
• this anionic group is chosen from carboxylate, phosphate, phosphonate, phosphate ester, sulfate, sulfonate or sulfosuccinate groups.
• the organic chain (s) of hydrophobic nature used in this case are ethoxylated or non-ethoxylated alkyl chains comprising from 8 to 30 carbon atoms and from 0 to 10 ethoxyl groups.
• amphoteric surfactant molecules such as the amine propionates, the alkyldimethylbetaines, the imidazoline derivatives, the alkyl amido betaines, or even the alkyglycines.
• the bonds between the organic chains and the surface of the particles present are covalent bonds.
• these covalent bonds are generally established between metal atoms of the particles and the organic chains, via oxygen atoms initially present in a hydroxylated metal group on the surface of the particles.
• the metal atom of these surface hydroxylated metal groups is a silicon, aluminum, or titanium atom.
• the particles present are formed at least partially of silicon oxide, aluminum oxyhydroxide and / or titanium oxide, this or these oxide (s) and / or oxyhydroxide being at least present (s) ) surface.
• the particles can then in particular be formed of oxide (s), hydroxide (s) and / or oxyhydroxide (s) of variable chemical nature, having a surface layer of silicon oxide of oxyhydroxide aluminum and / or titanium oxide, produced for example by surface post-treatment.
• organic chains covalently linked are generally introduced according to this second variant of the invention by condensation of a silanol group SiOH on the particle, according to the general reaction:
• the silanol -SiOH group generally comes from the acid, neutral, or basic hydrolysis of an alkoxysilane group, for example from the acid hydrolysis of a compound of trimethoxyalkysilane or triethoxyalkylsilane type.
• the covalent bond used and the means used to establish it must not be such as to cancel or reduce the hydrophilicity of the surface of the particles present. More precisely, it is preferred, according to this particular variant of the invention, that the rate of coverage of the surface of the particles present, expressed individually by the ratio of the number of bonds established on a particle compared to the total surface of this particle, is between 0.4 and 3.2 bonds per nm 2 , and preferably between 1 and 3.2 bonds per nm 2 .
• chains of predominantly hydrophobic nature used when the bond is of covalent nature are generally alkyl chains comprising from 6 to 30 carbon atoms, and preferably from 8 to 18 carbon atoms.
• connections provided between the surface of the particles and the hydrophobic chains present can in particular be of a different nature within the same surfactant of solid nature according to the invention.
• Next to chains fixed by covalent and / or complexing bond can thus coexist for example hydrophobic chains bound in a less important way to the surface, in particular by electrostatic bonds or by hydrogen bonds.
• the connections between the hydrophobic chains and the particles present in the compositions of the invention are distributed in a non-homogeneous manner over the surface of said particle, so as to define a first zone of generally hydrophilic character and a second zone of generally hydrophobic character.
• the modified surface particles present in the compositions of the invention are such that they can each be divided by a plane of cross section into two surfaces Si and S 2 such that:
• Each of the surfaces Si and S 2 represents at least 20% of the total surface of the particle
• the surface density of organic chains linked to S 2 is greater than at least 5 times the surface density of hydrophobic chains linked to Si.
• compositions of the invention specifically have a pronounced emulsifying character.
• This marked emulsifying character can be demonstrated by the fact that they are capable of emulsifying water / oil systems in the form of stabilized emulsions having a high content of aqueous phase and a small average drop size.
• compositions of the invention are generally capable of emulsifying in the form of stabilized reverse emulsions of water / oil systems, and they can in particular be used in this context to form emulsions of the water in vegetable oil or water in oil type.
• silicone with a high content of dispersed aqueous phase, that is to say having specifically an aqueous phase content at least equal to 40%, advantageously greater than or equal to 50%, or even greater than or equal to 60% in certain cases.
• compositions of the invention for the emulsification of such water / oil systems in the form of reverse emulsions makes it possible, subject to sufficiently pushing the emulsification conditions, to obtain, for these stabilized reverse emulsions, average drop sizes less than or equal to 5 microns.
• average drop sizes of the order of 5 microns are generally difficult to access with conventional emulsifying compositions
• the compositions of the invention make it possible in certain cases to obtain sizes less than or equal to 3 microns, advantageously less than 2 microns and, particularly advantageously, of the order of a micron.
• the emulsifying compositions of the invention generally allow emulsifying water / oil systems in the form of direct emulsions (oil in water) stabilized having a dispersed phase content which can be greater than 40%, preferably greater than 50%, or even greater than 60% or even 70%.
• the size of the drops present in the direct emulsions obtained using the emulsifying compositions of the invention is generally less than or equal to 3 microns, advantageously it can be less than or equal to 2 microns, and preferably less than or equal to 1 micron.
• the emulsifying compositions of the invention may be based on several types of particles of nanometric dimensions and / or of chains of hydrophobic nature. Therefore, they can for example comprise a single type of surfactant of solid character as defined above, but they can also comprise a mixture of several types of these surfactants of solid character, and in particular surfactants of solid character having lengths and / or mainly hydrophobic chain natures, or else a mixture of surfactants of solid nature based on solid particles of different chemical natures. In the context of this type of mixture, the association, generally within the same composition, of surfactants formed from solid particles of surface charges of opposite signs, but such an association is not however excluded from the scope of the present invention.
• the emulsifying compositions of the present invention can be formulated in various ways.
• the emulsifying compositions comprising these modified surface particles are advantageously, in the general case, in the form of an emulsion of oil-in-water type, or water in oil, said particles of nanometric dimensions to the surface of which the organic chains of hydrophobic nature are linked being at least partially located at the water / oil type interfaces of said emulsion.
• it may be emulsions stabilized by surfactants of solid character according to the invention.
• these oil-in-water or water-in-oil emulsions have a percentage of dispersed phase relative to the continuous phase of between 2 and 45% by volume, advantageously between 8 and 30% by volume, and particularly preferably between 10 and 25% by volume.
• the average size of the drops present in the emulsifying compositions of the invention in the form of emulsions is generally between 0.1 ⁇ m and 10 ⁇ m, and preferably between 0.5 ⁇ m and 3 ⁇ m, with a distribution of these drops. homodisperse or polydisperse.
• the concentration of modified surface solid particles within this emulsion can be characterized by a rate of recovery of the drops of the emulsion.
• This recovery rate is defined by the ratio of the portion of the total surface of the drops occupied by the particles on the total surface developed by the drops of the emulsion.
• this recovery rate of the drops of the emulsion is between 20% and 100%. Preferably, it is greater than 50%, and particularly preferably, greater than 80%.
• the emulsifying compositions of the invention taking the form of emulsions may also contain surface particles. modified not present at these interfaces, and in particular at interfaces of the water / air or oil / air type.
• the concentration of modified surface particles within the emulsion is such that this theoretical incorporation rate is between 20% and 300% and advantageously between 50 and 200%.
• the presence of these modified surface particles at the liquid / liquid interfaces allows effective stabilization of the emulsifying composition in the form of an emulsion.
• the stability obtained is such that a centrifugation greater than or equal to 4,000 revolutions per minute is not likely to destabilize the emulsion obtained.
• this stabilized emulsion is specifically a stabilizing composition which can be used to stabilize emulsions of the oil in water or water in oil type.
• these compositions emulsifiers in the form of emulsions are, in this case, generally used in high proportions, generally at a rate of 10% to 80% by volume relative to the total volume of the emulsion to be stabilized, and advantageously at a rate of 10 % to 50% by volume.
• the surfactants having a solid character of the invention in the form of a concentrated formulation preferably having a solid content greater than 5% by mass, advantageously greater than 8 % by mass, and preferably greater than 10% by mass.
• This concentrated formulation can for example be formed by an ultracentrifugation pellet obtained for example by ultracentrifugation, or even by concentration by slow evaporation, of an emulsifying composition in the form of an emulsion as defined above.
• the modified surface particles used in this type of concentrated formulations are preferably based on solid particles of cerium oxide, titanium oxide and / or oxy-hydroxide. aluminum, preferably having high surface charges, for which these phenomena of re-agglomeration are minimized.
• the concentrated emulsifying formulations of the invention cannot be limited to these particular compounds.
• the emulsifying compositions of the invention in the form of concentrated formulations generally contain water and liquid compounds which are not very immiscible with water, such as vegetable oils, silicone oils or hydrocarbons. .
• the ratio of the content of water and hydrophobic liquid compounds in these compositions is variable to a large extent.
• the volume ratio of the phase initially corresponding to the dispersed phase to the phase initially corresponding to the continuous phase of the mother emulsion is between 0.01 and 0.5.
• this volume ratio is between 0.01 and 0.25, and preferably between 0.01 and 0.1.
• the concentrated formulations defined above have significant emulsifying properties. They are capable of stabilizing water-in-oil or oil-in-water emulsions, or even multiple emulsions with good stability over time.
• this type of concentrated emulsifying composition is used at a rate of 10 to 200% by mass relative to the mass of the dispersed phase of the emulsion to be stabilized.
• these formulations are used at a rate of 10 to 100% by mass and preferably at a rate of 10 to 50% by mass relative to the mass of the dispersed phase.
• the emulsifying compositions comprising the modified surface particles of the invention can also be in the form of dispersions with a high solid content having, where appropriate, a solid content of between 10 and 90% by mass.
• These concentrated dispersions are generally formed from a dispersion of surface particles modified according to the invention in a continuous phase of hydrophilic or hydrophobic character, where said continuous phase generally represents at least 50% of the volume of the dispersion.
• the stabilized emulsions obtained by using the emulsifying compositions of the invention can use as hydrophobic phase many compounds, such as vegetable oils, mineral oils, aromatic solvents or even non-water-soluble ketones.
• hydrophobic and hydrophilic phases used within the emulsions stabilized by use of an emulsifying composition according to the invention is not necessarily dependent on the nature of the hydrophilic and hydrophobic phases present within the emulsifying composition.
• an emulsifying composition comprising a particular hydrophobic phase may in particular be used to ensure the stabilization of an emulsion comprising another type of oil, insofar as this oil is soluble to that present in the emulsifying composition.
• the emulsifying compositions of the invention can be in the form of a solid powder.
• the present invention also relates to a process for the preparation of emulsifying compositions as defined above.
• This process for preparing an emulsifying composition according to the invention is characterized in that it comprises a step consisting in forming an emulsion from an aqueous phase and a hydrophobic phase in the presence of a molecular surfactant and colloidal particles of metal oxide, hydroxide and / or oxyhydroxide of nanometric dimensions, of hydrophilic surface, and advantageously of non-zero surface charge.
• this step of forming the emulsion must specifically be carried out in such a way as to anchor the colloidal particles associated with the molecular surfactants at the water / oil interfaces of the emulsion, while avoiding the transfer of these colloidal particles associated with the molecular surfactant to the hydrophobic phase.
• This induced anchoring for particles an area oriented towards the hydrophobic phase and an area oriented towards the hydrophilic area.
• the specific anchoring of the particles at the interfaces thus produced can be visualized for example by cryo-transmission microscopy on frozen samples, according to the Dubochet method, consisting in producing a thin film of thickness between 50 and 100 nm by immersing a pierced support in the emulsion, and immersing the film thus obtained in liquid ethane or liquid nitrogen, which preserves a state of dispersion of the particles representative of that present in the initial emulsion.
• the Dubochet method consisting in producing a thin film of thickness between 50 and 100 nm by immersing a pierced support in the emulsion, and immersing the film thus obtained in liquid ethane or liquid nitrogen, which preserves a state of dispersion of the particles representative of that present in the initial emulsion.
• two cases arise:
• the interactions between particles and molecular surfactants are strong complexing bonds.
• the particles anchored at the interfaces are surfactants of a solid nature within the meaning of the invention and the emulsion obtained is an emulsifying composition within the meaning of the invention.
• the fixing of molecular surfactants by complexing interaction on the surface of the particle is preferably oriented in the direction of the hydrophobic phase, which gives the particles obtained an effective amphiphilic character.
• the method of the invention comprises a second step of fixing the chains by covalent bonding on the surface of the anchored particles thus oriented, and a third step of eliminating the molecular surfactants initially used, thereby an emulsifying composition according to the invention is obtained.
• the process for preparing an emulsifying composition according to the invention comprises the steps consisting in:
• the hydrophobic phase implemented in this first embodiment of the process consists of a liquid or a mixture of organic liquids at least sparingly soluble in water, and advantageously insoluble in water, and which can be extremely varied in nature.
• it may especially be an inert aliphatic and / or cycloaliphatic hydrocarbon, or a mixture of such compounds, such as for example a mineral oil or a petroleum oil which may contain, if necessary, aromatic compounds.
• Mention may also be made, by way of indication, of hexane, heptane, octane, nonane, decane, cyclohexane, cyclopentane, cycloheptane and liquid naphthenes as particularly suitable compounds.
• Aromatic solvents such as benzene, toluene, ethylbenzene and xylenes are also suitable, as well as petroleum fractions of the ISOPAR or SOLVESSO type (trademarks registered by the company EXXON), in particular SOLVESSO 100, which essentially contains a mixture of methylethyl - and trimethyl-benzene, and the SOLVESSO 150 which contains a mixture of alkyl benzenes, in particular dimethylethyl benzene and tetramethyl benzene.
• SOLVESSO 100 which essentially contains a mixture of methylethyl - and trimethyl-benzene
• SOLVESSO 150 which contains a mixture of alkyl benzenes, in particular dimethylethyl benzene and tetramethyl benzene.
• chlorinated hydrocarbons such as chloro- or dichlorobenzene, chlorotoluene, as well as aliphatic and cycloaliphatic ethers such as diisopropyl ether, dibutyl ether or aliphatic and cycloaliphatic ketones such as as methyl isobutyl ketone, dibutyl ketone, or mesityl oxide.
• Ketones immiscible with water can also be used.
• Esters can also be considered. Mention may be made, as esters which can be used, in particular those resulting from the reaction of acids with alcohols having from 1 to 8 carbon atoms, and in particular secondary alcohol palmitates such as isopropanol.
• the acids from which these esters are derived can be aliphatic carboxylic acids, aliphatic sulfonic acids, aliphatic phosphonic acids, alkylarylsulfonic acids, and alkylarylphosphonic acids having about 10 to about 40 carbon atoms, whether natural or synthetic. .
• tall oil fatty acids coconut oil, soybean, tallow, linseed oil, oleic acid, linoleic acid, stearic acid and its isomers , pelargonic acid, capric acid, lauric acid, myristic acid, dodecylbenzenesulfonic acid, 2-ethylhexanoic acid, naphthenic acid, hexoic acid, toluenesulfonic acid , toluene phosphonic acid, lauryl sulfonic acid, lauryl phosphonic acid, palmityl sulfonic acid, and palmityl phosphonic acid.
• Mixtures of these different compounds, and in particular vegetable oils, are particularly suitable hydrophobic phases.
• Silicone oils are also hydrophobic compounds advantageously used.
• the exact nature of the hydrophobic phase used in the process is to be adapted according to the nature of the molecular surfactant used.
• the affinity between the hydrophobic phase and the molecular surfactant used must be sufficiently low for the anchoring of the particles at the interfaces of the emulsion produced.
• the hydrophobic phase and the molecular ionic surfactant used in this first embodiment of the process are generally chosen so that said molecular surfactant does not lead, in the absence of colloidal particles, to a optimal emulsion, especially in terms of stability, of a hydrophilic phase with the hydrophobic phase used.
• hydrophobic phase and the hydrophobic chain of the molecular ionic surfactant used are chosen so that said hydrophobic phase has poor compatibility with the hydrophobic chain of the molecular surfactant used.
• hydrophobic phase and of the molecular surfactant those skilled in the art will therefore be able to use the concept based on the parameters of volume and solubility.
• a hydrophobic phase can be characterized by three solubility parameters ⁇ D, ⁇ P and ⁇ H, defined from the cohesion energy corresponding to the intermolecular attraction forces.
• ⁇ D, ⁇ P and ⁇ H represent respectively the parameters corresponding to the energy of dispersion of London, the energy of polarity of Keesom and to a parameter related to the hydrogen bonding forces.
• J. Hidelbrand in the Journal of the American Chemical Society, volume 38, page 1452, (1916) or to the work by J. Hidelbrand et al., " The solubility of non electrolytes ", 3 rd edition, Reinhold, New York, (1949).
• a hydrophobic chain will be all the less soluble in a hydrophobic phase as the solubility parameters ⁇ D, ⁇ P and ⁇ H of this chain will be different from those of the hydrophobic phase.
• the hydrophobic phase used is preferably a vegetable oil such as a soybean oil, an oil of rapeseed, coconut oil, or linseed oil.
• the hydrophobic phase is advantageously a silicone oil such as for example a silicone oil chosen from the silicone oils sold by Rhodia under the name of Rhodorsil.
• the nature of the molecular surfactant used is for its part to be adapted as a function of the nature of the emulsion (direct or reverse) envisaged and of the nature (size, composition, etc.) of the particles used.
• the molecular surfactants used generally have a molecular mass of 100 g / mol to 10,000 g / mol, and advantageously from 100 g / mol and 5,000 g / mol.
• These molecular surfactants can, for example, be surfactants of the oligomer or block copolymer type.
• the molecular surfactants used specifically have a chemical group capable of complexing the metal cations present on the surface of the particles used.
• the purpose of the method according to this first embodiment is specifically to formulate an emulsifying composition comprising surfactants of solid character within the meaning of the invention where the fixing of the hydrophobic chains on the surface of a particle is ensured by strong complexation.
• the molecular surfactants used according to this first embodiment are preferably molecular surfactants with a complexing polar head which can for example be surfactants with a polar head of carboxylic acid or carboxylate, surfactants with a polar head of phosphoric acid or phosphate, surfactants with a polar head of sulfosuccinic acid or sulfosuccinate , or alternatively surfactants with a sulfonic acid or sulfonate polar head.
• a complexing polar head can for example be surfactants with a polar head of carboxylic acid or carboxylate, surfactants with a polar head of phosphoric acid or phosphate, surfactants with a polar head of sulfosuccinic acid or sulfosuccinate , or alternatively surfactants with a sulfonic acid or sulfonate polar head.
• these surfactants can be chosen from alkylcarboxylates or carboxylic acids containing from 6 to 18 carbon atoms or alkylphosphates containing from 6 to 18 carbon atoms.
• molecular surfactants can also be chosen from polyoxyethylenated alkyl ethers of carboxylic acids of formula Ra- (OC 2 H 4 ) n -0-Rb, where Ra is a linear or branched alkyl having 4 to 20 carbon atoms, n is an integer between 1 and 12 and R is a carboxylic acid group such as CH 2 -COOH, or mixtures of such compounds, such as those marketed under the brand AKIPO ® by the company Kao Chemicals.
• the molecular surfactant can also be chosen from polyoxyethylenated alkyl ethers phosphates.
• polyoxyethylenated alkyl ethers phosphates is meant the polyoxyethylenated alkyl phosphates of formula:
• R c , R d . R e represent a linear or branched alkyl radical having from 2 to 20 carbon atoms; a phenyl radical; an alkylaryl radical, more particularly an alkylphenyl radical, with in particular an alkyl chain having from 8 to 12 carbon atoms; an arylalkyl radical, more particularly a phenylaryl radical; n represents an integer which can vary from 2 to 12; Mi represents a hydrogen, sodium or potassium atom.
• the radicals R c , R d and R e can in particular be hexyl, octyl, decyl, dodecyl, oleyl or nonylphenyl radicals.
• the molecular surfactant can also be chosen from diakylsulfosuccinates, that is to say the compounds of formula R 6 -0-C (0) -CH 2 - CH (S0 3 M 2 ) -C (0) -0-R 7 in which R 6 and R 7 , which are identical or different, represent an alkyl radical from C 4 to C- ⁇ for example and M 2 is an alkali metal or hydrogen.
• R 6 and R 7 which are identical or different, represent an alkyl radical from C 4 to C- ⁇ for example and M 2 is an alkali metal or hydrogen.
• R 6 and R 7 which are identical or different, represent an alkyl radical from C 4 to C- ⁇ for example and M 2 is an alkali metal or hydrogen.
• R 6 and R 7 which are identical or different, represent an alkyl radical from C 4 to C- ⁇ for example and M 2 is an alkali metal or hydrogen.
• R 6 and R 7 which are identical or different, represent an alkyl radical from C 4 to C- ⁇
• the molecular surfactants used are advantageously surfactants whose polar head is a group complexing agent chosen by a carboxylate group or a phosphate group.
• the polar head of the molecular surfactant used is preferably a phosphate group.
• the total concentration of molecular ionic surfactant within the hydrophobic or hydrophilic phase is generally such that the quantity of molecular ionic surfactant is used in an amount of 0.2 to 20% by mass relative to the weight of the dispersed phase of the emulsion obtained, and preferably in an amount of 0.5 to 10% by mass.
• the colloidal particles are used in this first embodiment of the process in the form of colloidal dispersions generally having heterodisperse or monodisperse particle size distributions, and preferably monodisperse distributions characterized by an interparticle agglomeration rate of less than 20% by number, preferably less than 5%, within which the average hydrodynamic diameter of the particles is advantageously between 2 and 100 nm and preferably between 3 and 20 nm.
• the particles preferably formed at least partially of an oxide, a hydroxide and / or an oxy-hydroxide of a metal chosen from cerium, titanium or aluminum, can present on the surface various chemical groups, advantageously -OH groups, acetate, nitrate, chloride, acetyl-acetonate or even citrate groups.
• colloidal dispersions can be produced according to various methods known to those skilled in the art, such as high temperature cracking, followed by acid peptization, thermohydroiysis of aqueous solutions, or aqueous precipitation followed by peptization, described in particular in patent applications EP-A-208580, FR 99 16786, or FR 99 14728.
• a hydrophobic phase a molecular surfactant or specific colloidal particles.
• a first parameter for example the chemical nature of the colloidal particle used, it is the skill of the person skilled in the art to adapt the other parameters, in particular the nature of the hydrophobic phase and of the molecular surfactants used , as well as the different concentrations and the hydrophobic phase / hydrophilic phase ratio used.
• the concentration of the colloidal dispersion used is generally such that it corresponds to a theoretical coverage rate of the drops in the emulsion obtained at the end of step (c), defined by the ratio of the surface that are theoretically capable of covering the colloidal particles used on the total surface developed by the drops of the emulsion, between 100 and 600%, preferably located between 100 and 400%, and advantageously between 100 and 300%.
• an excess of particles of nanometric dimensions is therefore generally implemented according to this first method.
• the concentration of colloidal particles in the colloidal dispersions used is generally between 10 20 and 4.10 21 particles per liter and preferably between 2.10 20 and 10 21 particles per liter.
• the ratio of the volume of the dispersed phase to the total volume of the emulsion used according to this first process is generally between 5 and 40%, preferably between 10 and 30%, and particularly advantageously between 15 and 25%.
• Step (c) leading to the formation of the emulsion from the hydrophobic and aqueous phases is generally carried out by dispersing or microfluidization at room temperature, in particular by implementation of a rapid disperser type Ultraturrax ®.
• the emulsion is generally obtained by subjecting the mixture resulting from step (b) to a dispersion under shear, generally carried out for a period of 15 seconds to 1 hour, and preferably for a period of 30 seconds to 2 minutes, with a stirring speed advantageously between 5,000 and 20,000 revolutions per minute.
• This emulsification step (c) leads to a so-called "raw" emulsion, where, taking into account the preferential implementation of an excess of colloidal particles, a possibly large portion of the colloidal particles may not be located at the interfaces of water / oil type of emulsion.
• the raw emulsion obtained at the end of step (c) can be subjected to a subsequent centrifugation step (d). Where appropriate, this centrifugation is carried out at a speed advantageously between
• this centrifugation leads to obtaining 3 phases: the upper phase of the continuous phase type of the raw emulsion of step (c), the lower phase constituting the centrifugation pellet and generally comprising the colloidal particles put in excess, and an intermediate phase consisting of a stabilized emulsion of improved quality. It is this stabilized emulsion constituting the intermediate phase which is, if necessary, recovered at the end of step (d).
• the emulsion obtained can then be subjected to a step (e) of heat treatment aimed at strengthening the interactions between particles and molecular surfactants.
• this heat treatment step is carried out by wearing the emulsion obtained at the end of the preceding steps at a temperature between 40 ° C and 100 ° C, and preferably between 50 ° C and 90 ° C, for a period ranging from 30 minutes to 24 hours, and advantageously included between 2 a.m. and 5 a.m.
• the emulsion can be brought to said temperature, either directly, or by a gradual rise in temperature ranging, if necessary, from 4 ° C. per minute to 0.2 ° C. per minute.
• step (c) The emulsion obtained at the end of step (c) and any steps (d) and / or (e) can be used as an emulsifying composition according to the invention.
• this emulsion can also be subjected in certain cases to a step (f) of ultracentrifugation so as to obtain a concentrated emulsifying formulation in the form of an ultracentrifugation pellet.
• the ultracentrifugation of step (f) is carried out at the rate of 5,000 to 30,000 revolutions per minute, advantageously at the rate of 3,000 to 25,000 revolutions per minute, for a period generally ranging from 1 to 8 hours. , and preferably for a period ranging from 2 to 6 hours.
• the ultracentrifugation pellet obtained is then generally characterized by a solid content greater than 5% by mass, and preferably greater than 8% by mass.
• the water and oil contents vary as a function of the nature of the emulsion subjected to the ultracentrifugation.
• the volume ratio of the phase corresponding to the dispersed phase of the original emulsion to the volume of the phase corresponding to the continuous phase of the original emulsion varies between 0.01 and 0.5 , advantageously between 0.01 and 0.25 and preferably between 0.01 and 0.1.
• this ultracentrifugation stage can lead, within the framework of the use of certain colloidal particles, to phenomena interparticle agglomerations liable to harm the emulsifying properties of the ultracentrifugation pellet obtained.
• colloidal particles used in this variant of the process are preferably, but not limited to, particles of oxide, hydroxide or oxy-hydroxide of cerium, titanium or aluminum.
• step (f) of ultracentrifugation can also be subjected to a step (g) comprising the steps consisting in: (gi) adding a solvent to the concentrated formulation, the mass of the solvent added being between 0.1 and 10 times the mass of the concentrated formulation used; and
• this step (g) is carried out several times with successive solvents of increasing polarities, whereby a concentrated dispersion of modified surface particles of the surfactant type solid type is obtained in an essentially hydrophilic phase.
• solvents of low polarity such as heptane or hexane
• solvents of greater polarity such as chloroform
• solvents of even greater polarity such as water-methanol mixtures.
• step (g) can be carried out several times with successive solvents of increasing hydrophobicities, whereby a concentrated dispersion of surface-modified particles of surfactant type having a solid character is obtained in an essentially hydrophobic phase. .
• obtaining a phase enriched in solid can be carried out, in the stages of type (g 2 ), by filtration, or even by any other solid / liquid separation means known from the skilled in the art.
• the content of continuous phase in the concentrated dispersion obtained is at least 50% by volume.
• the solid content is generally between 10 and 90% by mass.
• the emulsion obtained at the end of step (c) and any steps (d) and / or (e) can also be subjected to a step (f) of drying to low temperature, that is to say below 150 ° C., whereby the emulsifying composition is obtained in the form of a solid.
• This step f is generally carried out at a temperature of between 20 and 120 ° C., and it advantageously comprises a step of prior dilution of the emulsion obtained at the end of step (c) and any steps (d) and / or (e), by adding an aqueous phase and / or a hydrophobic phase.
• an oil having a low boiling point advantageously less than 180 ° C., preferably less than 150 ° and even more preferentially less at 120 ° C.
• the particles of nanometric dimensions used to form compositions in the form of a redispersible solid are generally particles having in themselves a redispersible character, such as particles based on cerium or titanium oxide of the type of those described in patent applications FR 99 01939 or FR 99 16786.
• the process for preparing an emulsifying composition according to the invention is characterized in that it comprises the steps consisting in:
• step ( ⁇ ) at least partially eliminating the molecular surfactants present at the end of step ( ⁇ ).
• the emulsion of step ( ⁇ ) of this second embodiment of the process can be an oil-in-water or water-in-oil emulsion.
• the aqueous phase advantageously consists of a water-ethanol mixture preferably comprising from 20 to 50% ethanol by volume, this ratio being expressed on the basis of the volumes of water and alcohol measured before mixing.
• the volume of the dispersed phase generally represents from 5 to 50%, and preferably from 10 to 40%, relative to the total volume of the emulsion.
• the hydrophobic phase of the emulsion of step ( ⁇ ) can in general consist of one or more organic liquids not or only slightly soluble in water, such as those used according to the first method .
• this hydrophobic phase consists at least partially of a mixture of aliphatic hydrocarbons preferably having from 8 to 18 carbon atoms.
• the hydrophobic phase can advantageously be an oil cut of the type of ISOPAR oil cuts sold by Exxon (aliphatic C 12 -C oil cuts).
• ( ⁇ ) is above all characterized by the presence of molecular surfactants.
• molecular surfactants play the role of transient emulsifying agents and are generally used at a rate of 0.5 to 10% by mass relative to the mass of the dispersed phase.
• these molecular surfactants playing the role of transient emulsifying agents are preferably used in the form of the combination of at least one molecular surfactant of nonionic type and of minus an ionic type molecular surfactant. Furthermore, it should also be noted that these molecular surfactants must be chosen so that they can be eliminated relatively easily during the subsequent step ( ⁇ ).
• the non-ionic molecular surfactant (s) used are, where appropriate, preferably ethoxyl alcohols comprising from 2 to 10 ethoxyl groups and from 8 to 18 carbon atoms at the level of their alkyl chain, such as those sold under the brand names Brij 30, Brij 35, Brij 52, Brij 56, Brij 58, Brij 72, Brij 76, or Brij 78, by the company Fluka, or even the surfactants sold by Sigma under the brand name of Tergitol, non-ionic surfactants with Sorbitane head, or surfactants marketed under the brand Span by the company Fluka.
• the ionic surfactant (s) molecular (s) used depend at least partially on the nature of the particles used.
• the molecular ionic surfactants used are preferably mono-, di- or tri-alkylamines in their protonated form.
• the molecular ionic surfactants are generally surfactants with a carboxylate polar head, advantageously alkylethoxylated carboxylates comprising from 2 to 10 ethoxy groups and from 8 to 18 carbon atoms at the level of their alkyl chain.
• the molar ratio (ionic surfactants) / (ionic and nonionic surfactants) is in this case generally between 5 and 50%, preferably between 10 and 30%.
• the colloidal particles of nanometric dimensions used according to the second embodiment of the process of the invention are colloidal particles comprising, at least at the surface, a silicon oxide, an oxyhydroxide aluminum or a titanium oxide.
• the colloidal particles can be used in particular marketed under the trade name Ludox ® by Dupont de Nemours.
• these particles are preferably used in the form of a colloidal dispersion in an aqueous or hydroalcoholic medium within which the average hydrodynamic diameter of the particles is generally between 2 and 50 nm, and preferably between 3 and 40 nm.
• the concentration of colloidal particles within this dispersion is advantageously between 10 21 and 4.10 21 particles per liter, and preferably between 10 21 and 4.10 21 particles per liter.
• these aqueous colloidal dispersions preferably have either a clearly acidic pH, generally less than 3, and advantageously less than 2, or a clearly basic pH, generally greater than 8, and preferably greater than 8.5.
• step ( ⁇ ) is specifically to obtain an emulsion where particles of nanometric dimensions with non-zero surface charge are anchored at the water / oil type interfaces.
• This arrangement of the particles schematically induces for each of the particles thus located at the interfaces a zone oriented towards the hydrophobic phase and a zone oriented towards the hydrophilic phase.
• step ( ⁇ ) of a reagent soluble in the continuous phase leads to a preferred fixation in the zone oriented towards the continuous phase.
• the fixing of chains of predominantly hydrophobic character by covalent bond carried out during step ( ⁇ ) is carried out by condensation of a silanol on the surface of the particle.
• the reagent used is a silane, which, by hydrolysis on contact with the aqueous phase, forms the corresponding silanol.
• the hydrophilic phase used in the emulsion of step ( ⁇ ) is advantageously an aqueous or hydroalcoholic phase of pH less than 3 or greater than 8 , so as to ensure acid or basic hydrolysis of the silane used.
• the condensation reaction of the silanol at the surface of the particle is carried out by progressive addition of a silane to the emulsion, with stirring, at a temperature ranging from 15 ° C to 95 ° C, and preferably from 25 ° C to 80 ° C, and preferably in the form of a solution in a hydrophobic solvent, advantageously in solution in a solvent of the type of the hydrophobic phase used in the emulsion.
• the silane used is a compound of formula R-Si (OR ') 3 , where OR' denotes a group chosen from methoxy or ethoxy groups, and R denotes an ethoxylated alkyl chain R 4 - (CH 2 -CH 2 -0) n , where R 4 represents a linear or branched alkyl chain comprising from 8 to 30 carbon atoms, and n represents an integer ranging from 1 to 10.
• the amount of said reagent used depends on the coverage rate of the particle sought in fine.
• this quantity is to be adapted as a function of the physicochemical nature (size, surface, composition) of the colloidal particles used and the nature of the reagent.
• the quantity used, expressed relative to the total surface of the particles used in step ( ⁇ ) is generally between 0.1 and 10 molecules of silane per nm 2 .
• This amount is generally added gradually, advantageously at a constant flow rate and for a duration ranging from 5 minutes to 6 hours and preferably between 15 minutes and 2 hours.
• the addition is generally followed by ripening, advantageously for a period ranging from 2 to 16 hours, and preferably at a temperature ranging from 15 ° C to 25 ° C.
• the emulsion obtained at the end of step ( ⁇ ) contains molecular surfactants and any excess reagents which it is necessary to remove at least partially so as to obtain an emulsifying composition according to the invention.
• the step ( ⁇ ) of elimination of the molecular surfactants playing the role of transient emulsifying agents generally comprises at least a first centrifugation step, generally carried out at the rate of 500 to 5,000 revolutions per minute for a period ranging from from 3 to 60 minutes.
• the centrifugation carried out generally leads to the production of a phase with a high solid content.
• the phase with a high solid content obtained at the end of each centrifugation step is generally washed by redispersion in a water / oil type mixture, advantageously comprising the same hydrophobic phase as that used in the emulsion. from step ( ⁇ ).
• the pH of the aqueous phase of the washing mixture of water / oil type used is modified so as to obtain the neutral form of the molecular ionic surfactant to be eliminated.
• the aqueous phase will be advantageously acidified, for example by adding a strong acid such as HCl or HN0 3 .
• a base such as ammonia will advantageously be added to the aqueous phase.
• the choice of the base or of the acid used in this case is naturally to be adapted according to the 01/85 3?
• the last washing step is generally in a water / oil mixture of neutral pH.
• steps ( ⁇ ), ( ⁇ ) and ( ⁇ ) of this second implementation of the method generally lead to the formation of emulsifying compositions in the form of more concentrated emulsions than those obtained at the end of steps ( c), (d) and / or (e) of the first process.
• the emulsion obtained at the end of step () can be used as an emulsifying composition according to the invention.
• this emulsion can also be subjected in certain cases to a subsequent ultracentrifugation stage ( ⁇ ) so as to obtain a concentrated emulsifying formulation in the form of an ultracentrifugation pellet.
• the ultracentrifugation of step ( ⁇ ) is then carried out at the rate of 5,000 to 25,000 revolutions per minute, advantageously at the rate of 3,000 to 20,000 revolutions per minute, for a period generally ranging from 1 to 8 hours, and preferably for a period ranging from 2 to 5 hours.
• the ultracentrifugation pellet obtained is then generally characterized by a solid content greater than 5% by mass.
• the water and oil contents vary as a function of the nature of the emulsion resulting from step ( ⁇ ).
• the volume ratio of the phase corresponding to the dispersed phase of the original emulsion to the volume of the phase corresponding to the continuous phase of the original emulsion varies between 0.01 and 0.5 .
• the concentrated formulations obtained at the end of the ultracentrifugation step ( ⁇ ) can advantageously be subjected to a step ( ⁇ ) comprising the steps consisting in: ( ⁇ -i) adding a solvent to the concentrated formulation, the mass of the added solvent being between 0.1 and 10 times the mass of the concentrated formulation used; and
• this step ( ⁇ ) is carried out several times with successive solvents of increasing polarity, whereby a concentrated dispersion of particles of modified surface of the surfactant type with a solid character is obtained, in an essentially hydrophilic phase.
• Step ( ⁇ ) can also be carried out several times with successive solvents of increasing hydrophobicity, whereby a concentrated dispersion of modified surface particles of surfactant type having a solid character is obtained in an essentially hydrophobic phase.
• the content of continuous phase in the concentrated dispersions obtained is greater than 50% by volume.
• the solid content is generally between 10 and 80% by mass.
• the emulsifying compositions of the invention can be used in many areas of application.
• the emulsifying compositions of the invention can in particular be used for the formulation of detergent compositions especially suitable for cleaning hard surfaces, where the combination of the emulsifying character and the presence of solid particles induces both mechanical abrasion and a emulsification of hydrophobic stains. Furthermore, the emulsifying compositions of the invention can have interesting physicochemical properties due to the presence of solid particles.
• the emulsifying compositions of the invention can in particular be used for the production of films and materials, in particular packaging films, having anti-UV or anti-corrosion properties, for example by using particles based on cerium oxide.
• the use of solid particles of amphiphilic nature of the invention can also allow the manufacture of films with high mechanical resistance, or even opacifying films, for example using particles based on titanium oxide.
• the solid particle of amphiphilic nature originating from the emulsifying composition plays both a role linked to its intrinsic physicochemical properties and a role of surfactant linked to its amphiphilic character.
• the surface-modified particles of the surfactant type of the invention also have the advantage, by their solid nature, of not leading to migration phenomena. generally observed on the surface.
• Figures 1 and 2 attached are photographs obtained by subjecting emulsifying compositions according to the invention in the form of emulsions to an analysis by transmission electron cryomicroscopy.
• FIG. 1 is a photograph obtained by cryomicroscopy of an emulsion characterized by the following elements: - dispersed phase: water
• FIG. 2 is also a photograph obtained by cryomicroscopy of an emulsion, characterized in turn by the following elements:
• cerium oxide particles Ce0 with a surface modified by the presence of Akipo R020 V6 (KaO Chemicals GmbH).
• Example 1 Preparation of a concentrated emulsifying composition comprising cerium oxide particles of amphiphilic nature as surfactants.
• aqueous colloidal dispersion D of perfectly individualized Ce0 2 cerium oxide particles, with an average diameter of 5 nm, was obtained by redispersion in water of synthesized cerium hydrate, as described in the application for Patent EP 208 580 by thermo-hydrolysis at 10 ° C. of a partially neutralized ceric nitrate solution. More specifically, 583.5 g of cerium hydrate at 58.95% Ce02 were redispersed in water demineralized, the volume being adjusted to 2000 ml. After stirring at room temperature, a colloidal dispersion with a concentration equal to 1.0 M in CeO 2 was obtained. 10 g of the colloidal dispersion of CeO 2 particles thus obtained were incorporated into the silicone oil phase prepared in step (a).
• step (d) The crude emulsion obtained at the end of step (c) was centrifuged at 4400 rpm for 10 minutes. Three phases were then collected:
• step (g) To another aliquot of the ultracentrifugation pellet obtained at the end of step (f), a volume of heptane was added representing five times the volume of said aliquot. The mixture obtained was then stirred at room temperature for 30 minutes, then filtered.
• the enriched solid phase filter cake was recovered.
• the filter cake obtained was redispersed in a volume of chloroform equal to the volume of heptane from the previous step.
• the mixture obtained was stirred for 30 minutes and then filtered.
• the new filter cake was collected.
• the recovered cake was redispersed in a volume of a water / methanol mixture (50:50 by volume) equal to the volume of chloroform from the previous step.
• the mixture obtained was stirred for 30 minutes, then filtered, whereby a dispersion with a high solid content was obtained.
• the product obtained was then dried at room temperature.
• the carbon content of the solid product obtained is 4% by mass, relative to the total mass of the solid product.
• Example 2 Preparation of an emulsifying composition comprising cerium oxide particles of amphiphilic nature as surfactants.
• An emulsion was obtained according to steps (a) to (d) of Example 1. After step (d) of centrifugation at 4400 rpm and recovery of the central emulsion, the emulsion was subjected to an additional heat treatment step consisting in placing the emulsion in a closed enclosure at 80 ° C. for 5 hours.
• Example 3 Preparation of a concentrated emulsifying composition comprising particles of cerium oxide of amphiphilic nature as surfactants.
• the wet pellet thus obtained constitutes a concentrated emulsifying composition comprising surfactants based on solid particles of modified surface cerium oxide.
• the emulsifying properties of this pellet were demonstrated in the following test.
• step (f) A last aliquot of the central emulsion obtained at the end of step (d) was subjected to an ultracentrifugation step, at a rate of 3.15 g per ultracentrifugation tube. After ultracentrifugation at 20,000 rpm for 3 hours, an average of 0.87 g of wet pellet was collected per tube.
• Example 4 Preparation of an emulsifying composition comprising cerium oxide particles of amphiphilic nature as surfactants.
• the emulsion obtained was subjected to an additional stage of thermal treatment consisting in placing the emulsion in a closed enclosure at 80 ° C for 5 hours. Following this heat treatment, a stable emulsion was obtained, the drop size of which, determined by optical microscopy, is of the order of 1 micron.
• the stability of the emulsion obtained is such that centrifugation at the rate of 4,400 revolutions per minute does not affect its stability.
• Example 5 Preparation of an emulsifying composition comprising cerium oxide particles of amphiphilic nature as surfactants.
• This anionic surfactant consists of a mixture of monoesters of formula R- ⁇ O- (OC 2 H 4 ) 3 -P0 3 " and diesters of formula (R 2 0- (OC 2 H 4 ) 3 ) 2 (P0 2 " ), where R- ⁇ and R 2 represent alkyl chains having 13 carbon atoms.
• step (b) 10 g of the colloidal dispersion of particles D of CeO 2 from Example 1 were incorporated into the rapeseed oil phase prepared in step (a).
• step (c) The mixture thus obtained was then emulsified using a rapid disperser (Ultraturax) for 2 minutes at the rate of 20,000 revolutions per minute.
• step (d) The crude emulsion obtained at the end of step (c) was centrifuged at 4400 rpm for 10 minutes. Three phases were then collected:
• the stability of this emulsion is such that no centrifugation at 4,400 revolutions per minute does not affect its stability.
• Example 6 Preparation of an emulsifying composition comprising cerium oxide particles of amphiphilic nature as surfactants.
• step (b) 10 g of the colloidal dispersion D of CeO 2 particles of Example 1 were then incorporated into the rapeseed oil phase prepared in step (a).
• step (c) An emulsion was obtained at the end of step (c) which has a drop size of the order of 1 micron, while the implementation of Akipo
• RO 20 VG used alone as a surfactant is not capable of ensuring a emuisification of a water / rapeseed oil type mixture with such a reduced drop size.
• Example 7 Preparation of an emulsifying composition comprising cerium oxide particles of amphiphilic nature as surfactants.
• Example 8 Preparation of an emulsifying composition comprising particles of titanium oxide of amphiphilic nature as surfactants.
• a colloidal dispersion of titanium oxide Ti0 2 was obtained by thermo-hydrolysis of a TiOCI 2 solution in the presence of Ti0 2 seeds and citrate anions with a citrate / Ti0 2 molar ratio within the dispersion of 3% under the following conditions: Was added successively to 394.7 g of a solution of titanium oxychloride at 1.9 mole / kg:
• the mixture obtained was brought to the boil and kept there for 3 hours. The solution was left to settle and the supernatant was drawn off by siphoning.
• This supernatant was dispersed in demineralized water so as to obtain a dispersion having a dry extract of 6% by mass. A perfectly stable soil was thus obtained.
• the mean hydrodynamic diameter of the colloids within this soil has been summarized equal to 22nm.
• phase enriched in solid obtained after these various washes was redispersed in a mixture (Water: Isopar) (50:50) by volume, and centrifugation was carried out for 15 min at a rate of 4500 rpm.
• This emulsion recovered by centrifugation can be diluted with water.
• an assay by plasma emission spectrometry indicates a Si / Ti mass ratio of the order of 2%.
• the residual concentration of AKIPO RO20 in the recovered emulsion was moreover determined by infrared analysis of a solution resulting from the solid / liquid extraction with chloroform.
• the amount collected indicates a very low residual content of the order of 10 ⁇ 4 moles / liter within the emulsion, which confirms an effective removal of the surfactant introduced, during successive washes in acidic medium. step ( ⁇ ).

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