Coated colored particles of metal oxides and suboxides and their preparation by flame spray pyrolysis - Patents.com

Abstract

The present invention relates to the use of coated particles of oxides and suboxides of element M for dyeing and / or structuring keratin materials, to a process for the preparation of such coated particles by flame spray pyrolysis technique, to the particles of oxides and suboxides of element M obtained from such a process, to the coated particles of suboxides of element M, and also to compositions comprising such particles.

Description

[Technical field]

[0001] The present invention relates to the use of coated particles of oxides and suboxides of element M for dyeing and / or structuring keratin materials, to a process for the preparation of such coated particles by flame spray pyrolysis technique, to particles of oxides and suboxides of element M obtainable from such a process, to coated particles of suboxides of element M, and to compositions comprising such particles. [Background technology]

[0002] Metal oxides are used in many applications (cosmetics, paints, stains, electronics, rubber, etc.) especially for their coloring properties.

[0003] Currently, the color of formulations, such as cosmetic formulations, is generally obtained by mixing several colored metal oxides.

[0004] However, some oxides exhibit the drawback of being particularly unstable over time, which leads to a loss of their tinting strength and, more particularly, a loss of the intensity and / or chromaticity of the color obtained.

[0005] Thus, it may happen that the color of the formulation changes over time, resulting in a less intense, dull, and / or less desirable color for the user. Differences in the stability of the different metal oxides mixed may even destroy the homogeneity of the colored mixture, for example resulting in migration of the oxides to the surface or bottom of the formulation. This undesirable effect is called the "segregation effect".

[0006] To improve the stability of metal oxides, it has also been envisaged to coat them with silica, in particular by the "sol-gel" method, or to graft fluorinated compounds onto them. However, these solutions are not entirely satisfactory. Metal oxides coated with silica by the sol-gel method generally exhibit poorer colouring properties than uncoated particles. As for the grafting techniques, the use of fluorinated compounds can be harmful to the environment and dangerous for the user.

[0007] It is also known to use the flame spray pyrolysis technique, or FSP method, to prepare metal oxide particles.

[0008] Flame spray pyrolysis, or FSP, is a process that produces single or mixed oxides of various metals with controlled morphologies (e.g., SiO 2 , Al 2 O 3 , B 2 O 3 , ZrO 2 , GeO 2 , WO 3 , Nb 2 O 5 , SnO 2It is a well-known method today that has essentially been developed to synthesize ultrafine powders of metals (such as ZnO, MgO, ZnO) and / or deposit them on various substrates, starting from various metal precursors, generally in the form of an organic or inorganic, preferably flammable, sprayable liquid, which is sprayed into a flame, which, when consumed, releases nanoparticles, in particular of metal oxides, sprayed by the flame itself onto these various substrates. The principles of this method are recalled, for example, in a recent (2011) publication by Johnson Matthey entitled "Flame Spray Pyrolysis: a Unique Facility for the Production of Nanopowders", Platinum Metals Rev., 2011, 55, (2), 149-151. Many alternative forms of FSP methods and reactors are also described in, for example, patents or patent applications WO 2007 / 028267 or U.S. Pat. No. 8,182,573, European Patent Application No. 1,760,043, U.S. Pat. No. 5,958,361, U.S. Pat. No. 2,268,337, WO 01 / 36332 or U.S. Pat. No. 6,887,566, WO 2004 / 005184 or U.S. Pat. No. 7,211,236, WO 2005 / 006,236 or U.S. Pat. No. 7,211,236, WO 2005 / 005 ... These are described in WO 04 / 056927, WO 2005 / 103900, WO 2008 / 049954, or U.S. Pat. No. 8,231,369, WO 2008 / 019905, U.S. Patent Application Publication No. 2009 / 0123357, U.S. Patent Application Publication No. 2009 / 0126604, U.S. Patent Application Publication No. 2010 / 0055340, and WO 2011 / 020204. Summary of the Invention [Problem to be solved by the invention]

[0009] However, the particles prepared by known flame spray pyrolysis methods are not always satisfactory in terms of stability. More specifically, these preparation methods do not allow easy and large amounts of metal oxides or metal suboxides with intermediate oxidation numbers to be obtained. Moreover, the metal oxides and metal suboxides with intermediate oxidation numbers prepared according to these known methods are not stable over time and oxidize to their maximum oxidation number very quickly when in contact with ambient air.

[0010] Additionally, particles prepared by flame spray pyrolysis can still be improved, particularly with respect to the intensity and chromaticity of the color provided.

[0011] There is therefore a real need to develop a method for dyeing and structuring keratinous materials starting from metal oxide particles, which is capable of providing keratinous materials with very intense and chromatic colors.

[0012] In addition, it would be desirable to develop a wide range of these metal oxide particles that exhibit good stability over time and good coloring properties, especially with regard to the intensity and chromaticity of the color imparted, which should make it possible to obtain a rich palette of colors and thus more diverse and finer colorings that are more faithful to the user's wishes.

[0013] It is therefore necessary to develop a method that makes it possible to prepare such particles, and more particularly to prepare particles of metal oxides and metal suboxides with intermediate oxidation numbers that exhibit good stability over time and good properties for dyeing and structuring keratin materials. [Means for solving the problem]

[0014] These objects are achieved with the present invention, the subject of which is the use of at least one particle of an oxide of element M, in particular of the type of oxide M-M' of core / shell structure, for dyeing and / or structuring keratin materials, in particular human keratin fibres and skin, which particle is (i) Formula (I): M m O n-x (I) (1) A core composed of at least one oxide of element M [In the formula, M represents an element selected from the alkali metals of the first column, the alkaline earth metals of the second column and the elements of the third to fourth columns of the periodic table, bismuth, selenium, tellurium and astatine, - m represents an integer equal to or greater than 1; - n represents an integer equal to or greater than 1; - x represents a non-integer number equal to or greater than 0 and strictly less than n; (ii) covering the surface of the core (1) with at least one compound of the formula (II): M' p O q (II) (2) an upper coating layer made of the compound [In the formula, M' is an element other than M, selected from selenium and the elements of columns 4, 13 and 14 of the Periodic Table of the Elements, - p represents an integer equal to or greater than 1; - q represents an integer equal to or greater than 0] Includes.

[0015] It has been found that the particles according to the invention make it possible in particular to obtain very intense and chromatic colorings of keratinous materials.

[0016] Moreover, it has been possible to prepare a large number of particles according to the present invention having a large number of different arbitrary colors (eg, fluorescent colors).

[0017] The particles according to the invention therefore make it possible to obtain a richer palette of colours, which allows for more colouring and therefore colourings closer to the user's wishes, which also makes it possible to reduce the number of metal oxides to be mixed to obtain the desired colour.

[0018] In addition, it has been noted that the coated pigmented particles of oxide of element M according to the invention hardly deteriorate over time, and this is especially true when they are formulated in aqueous compositions.

[0019] In particular, with the particles according to the invention, almost no "segregation effect" is observed.

[0020] It has been observed that cosmetic makeup compositions comprising coated coloring particles of oxide of element M according to the invention also exhibit good masking power (for example of skin imperfections) and also make it possible to obtain colorings that are particularly covering (for example for mascara).

[0021] In addition, the coated particles of oxide of element M according to the invention do not require a hydrophobic coating and can therefore be used across a broad formulation spectrum (e.g. in fully aqueous and / or surfactant-free formulations), further reducing the risk of inappropriate deposition (on the edges of the basin, the walls of the pipes or on rocks) when the formulation thus obtained is finally placed in water (basin drain, lake water or sea water).

[0022] The present invention also relates to particles of a suboxide of element M, (i) Formula (I'): M m O n-x (I') (1) A core composed of at least one oxide of element M [In the formula, M represents an element selected from the alkali metals of the first column, the alkaline earth metals of the second column and the elements of the third to fourth columns of the periodic table, bismuth, selenium, tellurium and astatine, - m represents an integer equal to or greater than 1; - n represents an integer equal to or greater than 1; - x represents a non-integer number greater than 0 and strictly less than n; (ii) covering the surface of the core (1) with at least one compound of the formula (II): M' p O q (II) (2) an upper coating layer made of the compound [In the formula, M' is an element other than M, selected from selenium and the elements of columns 4, 13 and 14 of the Periodic Table of the Elements, - p represents an integer equal to or greater than 1; - q represents an integer equal to or greater than 0] The present invention relates to particles, including

[0023] It has been observed that the particles of suboxides of element M according to the invention are particularly stable over time (i.e. they remain in their suboxidized state) and make it possible to obtain significantly very intense, chromatic and amorphous colorations.

[0024] Another subject of the invention is a process for the preparation of such particles of oxides and suboxides of element M coated with an oxide of element M', in particular with an oxide of the type M-M' oxide of core / shell structure, comprising at least the following steps: a. preparing a composition (A) by adding one or more precursors of element M to a flammable solvent or mixture of flammable solvents, then b. In a flame spray pyrolysis device, a flame is formed by spraying the composition (A) and an oxygen-containing gas (G) until an agglomerate of the oxide of element M is obtained, and then c. spraying, on the surface of said aggregates of oxide of element M, a composition (B) comprising one or more precursors of element M' until a top coating layer (2) composed of element M' or an oxide of element M' is obtained; The aforementioned element M represents an element selected from the alkali metals in the first row of the periodic table, the alkaline earth metals in the second row, and the elements in the third to fourteenth rows of the periodic table, bismuth, selenium, tellurium, and astatine; The element M' is an element other than M selected from selenium and elements in columns 4, 13 and 14 of the Periodic Table; The flame spray pyrolysis apparatus is isolated from the atmosphere so that the amount of oxygen present within the apparatus is controlled.

[0025] It has been observed that the method according to the invention makes it possible to obtain particles of oxides and suboxides of element M coated with a layer of an inorganic material based on element M' which are particularly stable over time and exhibit good water resistance.

[0026] Moreover, unlike conventional coating methods, the method according to the invention has the advantage of preserving good intrinsic performance qualities of the core despite the presence of the top coating layer, since, due to the specific properties of the top coating layer, for a given particle mass, it is possible to reduce the proportion of oxides or suboxides of element M, without nevertheless reducing and / or adversely affecting the properties of said oxides or suboxides of element M.

[0027] The process of the invention therefore makes it possible to produce stable zinc oxide particles of an oxide or suboxide of element M, while avoiding the inconvenience of increasing the amount of particles previously required to maintain good colouring properties of the oxide or suboxide of element M.

[0028] According to another aspect, the present invention also relates to a specific flame spray pyrolysis apparatus for carrying out the preparation method of the present invention, comprising a first chamber, a second chamber in communication or fluidly connected with the first chamber, a first feed, e.g. a first tube, appearing in the first chamber and capable of delivering a first composition (A) and a first oxygen-containing gas (G), and an injection system comprising a second feed, e.g. a second tube, appearing in the first chamber and capable of delivering a mixture (P) comprising oxygen and one or more combustible gases, the first and second feeds being separate from each other.

[0029] The apparatus further comprises a third feed capable of delivering a second composition (B) comprising one or more precursors of element (M') to the second chamber.

[0030] The first and second chambers of said device are isolated from the outside air so that the amount of oxygen present in said device is controlled, more preferentially so that the oxygen present in said first and second chambers originates exclusively from said first gas (G) and optionally from said mixture (P).

[0031] For example, and in no way limiting, the second chamber may be coaxial with the first chamber, eg, positioned in extension of said first chamber.

[0032] Advantageously, the first and second feeds are coaxial, the second feed at least partially surrounding the first feed.

[0033] According to one embodiment, the first chamber comprises two separate compartments, the first compartment comprising a first opening through which the injection system emerges and a second opening opposite the first opening, the second compartment at least partially surrounding the first compartment and isolated from the outside air, said second compartment being separated from the first compartment by a first partition.

[0034] For example, the first partition is porous to allow the passage of gas into the first compartment, and the second compartment is pressurized, for example with a gas selected from nitrogen, methane, argon, hydrogen, hydrogen sulfide, and ammonia, or by heating.

[0035] For example, the device comprises an injector configured to inject a second gas into a second compartment of the first chamber, thus pressurizing said second compartment.

[0036] According to one embodiment, the second chamber comprises two separate compartments, the first compartment comprising a first opening in fluid communication or connection with the second opening of the first chamber and a second opening opposite the first opening, the second compartment at least partially surrounding the first compartment and isolated from the outside air, said second compartment being separated from the first compartment by a second partition and having a feed for supplying the second composition (B) to the second chamber.

[0037] For example, the apparatus comprises an additional feed configured to inject a third gas into the second compartment of the second chamber, thus pressurizing said second compartment.

[0038] For example, the second partition is porous or perforated to allow the second composition (B) to pass into the first compartment of the second chamber. The second compartment is pressurized, for example, by a third gas (G3) selected from nitrogen, methane, argon, hydrogen, hydrogen sulfide and ammonia, or by heating.

[0039] For example, the apparatus further comprises a collection system, for example coaxial with the two chambers, positioned above the second chamber and configured to stop particles while allowing gas to pass through. In other words, the collection system is gas permeable. For example, the collection system includes a filtration system mounted inside the aforementioned collection system and a pressure reduction system configured to generate a negative pressure inside the collection system.

[0040] The injection system, the first chamber, the second chamber and the collection system are assembled, for example by screwing or welding, in a manner that makes it possible to prevent access of outside air to the interior of said device, in order to ensure a complete leak-proofness of the device.

[0041] Without being in any way limiting, the injection system, the first chamber, the second chamber and the collection system are positioned within an enclosure, making it possible to prevent the access of outside air to the inside of said enclosure, the interior of which is placed under negative pressure by a vacuum system, in order to ensure a total leak-proofness of the device.

[0042] The present invention also relates to a composition, in particular a cosmetic composition, comprising one or more particles of an oxide of element M according to the invention.

[0043] A better understanding of the invention may be obtained by studying the detailed description of the embodiments, which are presented by way of example only and are not limiting in any way and are illustrated by the accompanying drawings, which are not necessarily to scale. [Brief description of the drawings]

[0044] [Figure 1] FIG. 2 represents a cross-sectional view of a particle of an oxide of element M of formula (I) coated with a compound of formula (II) according to one embodiment of the present invention. [Diagram 2] 1 is a schematic diagram of a flame spray pyrolysis apparatus according to one embodiment of the present invention. [Diagram 3] FIG. 2 is a schematic diagram of a flame spray pyrolysis apparatus according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0045] Other characteristics, aspects and advantages of the invention will become even more apparent on reading the description and examples which follow.

[0046] In this specification, unless otherwise indicated, - the term "at least one" is equivalent to and interchangeable with the term "one or more"; - the use of the term "to" is equivalent to and can be substituted for the term "to the extent of" and indicates that a limit is included; - the expression "strictly to" is equivalent to and can be substituted for the expression "strictly to the extent of" and indicates that no limit is included; - The expression "strictly less than" means exclusive of the limit point; - the expression "keratinous materials" denotes in particular human keratinous fibres such as skin, hair etc.; the upper coating layer 2, also called the "outer layer", "casing", "coating" or "shell"; - the term "elements of the third column of the periodic table of the elements" is understood within the meaning of the present invention to mean scandium and yttrium, in other words the elements of the lanthanides and actinides do not belong to the elements of the third column of the periodic table of the elements within the meaning of the present invention. - The term "alkyl" refers to an "alkyl group", i.e. a straight or branched C 1 ~C 10 , especially C 1 ~C 8 , more specifically C 1 ~C 6 , with priority given to C 1 ~C 4 is understood to mean a hydrocarbon radical, for example methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl or tert-butyl, an "aryl" group is understood to mean a monocyclic or fused or non-fused polycyclic carbon-based group containing 6 to 22 carbon atoms, at least one ring of which is aromatic, preferentially an aryl group is phenyl, biphenyl, naphthyl, indenyl, anthracenyl or tetrahydronaphthyl, preferably phenyl; - The term "arylate" group refers to one or more carboxylate -C(O)O - is understood to mean an aryl group containing a group, for example naphthalate or naphthenate, - the term "complexed metal" is understood to mean that a metal atom forms a "metal complex" or "coordination compound" in which the metal ion corresponding to the central atom, i.e. M, is chemically bound to one or more electron donors (ligands); - the term "ligand" is understood to mean a coordinating organic chemical group or compound, i.e. which comprises at least one carbon atom, is capable of coordinating to the metal M and which, once coordinated or complexed, results in a metal compound (unique complex or chelate) which corresponds to the principle of a coordination sphere with a given number of electrons - see Ullmann's Encyclopedia of Industrial Chemistry, "Metal-Complex Dyes", 2005, pp. 1-42. More specifically, the ligand is an organic group which comprises at least one group which is electron donating via inductive and / or mesomeric effects, more specifically an organic group carrying at least one amino, phosphino, hydroxy or thiol electron donating group, or the ligand is a persistent carbene, in particular of the "argengo" type (imidazol-2-ylidene) or which comprises at least one carbonyl group. In particular, the ligands may include: i) those containing at least one phosphorus atom -P< (i.e. phosphines, for example triphenylphosphine); ii) bidentate ligands of formula RC(X)-CR'R''-C(X)-R''', where R and R''' are the same or different and may be linear or branched (C 1 ~C 6 ) alkyl group, and R′ and R″ are the same or different and are a hydrogen atom or a linear or branched (C 1 ~C 6 Preferentially, R' and R'' represent a hydrogen atom and X represents an oxygen atom or a sulfur atom or an N(R) group, where R represents a hydrogen atom or a linear or branched (C 1 ~C 6 iii) a group having the formula [HO-C(O)], such as acetylacetone or a β-diketone; n-AC(O)-OH and their deprotonated forms, in which A represents a monovalent radical when n has the value zero or a polyvalent radical when n is 1 or more, which is a saturated or unsaturated, cyclic or acyclic, aromatic or non-aromatic, based on a hydrocarbon containing 1 to 20 carbon atoms, optionally interrupted by one or more heteroatoms and / or optionally substituted, inter alia, by one or more hydroxyl groups, preferably A is a monovalent (C 1 ~C 6 ) alkyl group or polyvalent (C 1 ~C 6 ) an alkylene group and n is an integer from 0 to 10 (inclusive), preferably n is 0 to 5, e.g., 0, 1 or 2; iv) (poly)hydroxycarboxylic acid ligands, such as lactic acid, glycolic acid, tartaric acid, citric acid, maleic acid and arylate groups, e.g., naphthalate; and iv) C containing 2 to 5 hydroxyl groups. 2 ~C 10 Polyol ligands, especially ethylene glycol, glycerol, even more particularly, the ligands have carboxy groups, carboxylate groups or amino groups, in particular, the ligands have acetate groups, (C 1 ~C 6 )alkoxylate group, (di)(C 1 ~C 6 ) alkylamino groups, and arylate groups, such as naphthalate or naphthenate groups. - the term "flammable" is understood to mean a liquid compound or gas that, together with oxygen and energy, is consumed in an exothermic chemical reaction: combustion. In particular, flammable liquids are selected from protic solvents, in particular alcohols such as methanol, ethanol, isopropanol or n-butanol, esters such as those obtained from methyl esters and acetates (such as 2-ethylhexyl acetate), acids (such as 2-ethylhexanoic acid (EHA)), acyclic ethers (such as ethyl ether, methyl tert-butyl ether (MTBE), methyl tert-amyl ether (MTAE), methyl tert-hexyl ether (MTHE), ethyl tert-butyl ether (ETBE) or ether tert-amyl ether (ETAE), diisopropyl ether (DIPE)), cyclic ethers (such as tetrahydrofuran (THF)), aromatic hydrocarbons or arenes (such as xylene), aprotic solvents, in particular selected from non-aromatic hydrocarbons, and mixtures thereof. The combustible may optionally be selected from liquefied hydrocarbons such as acetylene, methane, propane or butane, and mixtures thereof.

[0047] Coated particles of oxide of element M Particles of oxides of element M, in particular of the type M-M' oxides with a core / shell structure, (i) Formula (I): M m O n-x (I) (1) A core composed of at least one oxide of element M [In the formula, M represents an element selected from the alkali metals of the first column, the alkaline earth metals of the second column and the elements of the third to fourth columns of the periodic table, bismuth, selenium, tellurium and astatine, - m represents an integer equal to or greater than 1; - n represents an integer equal to or greater than 1; - x represents a non-integer number equal to or greater than 0 and strictly less than n; (ii) covering the surface of the core 1, and at least one compound represented by the formula (II): M' p O q(II) The upper coating layer 2 is made of the compound [In the formula, M' is an element other than M, selected from selenium and the elements of columns 4, 13 and 14 of the Periodic Table of the Elements, - p represents an integer equal to or greater than 1; - q represents an integer equal to or greater than 0] Includes.

[0048] Preferably, the element M represents an element selected from the alkali metals of the first row, the alkaline earth metals of the second row and the elements of the fourth to fourteenth rows of the periodic table, bismuth, selenium, tellurium and astatine.

[0049] Advantageously, element M is other than gold, silver, iridium, platinum, palladium, rhodium, ruthenium, osmium and carbon.

[0050] More preferentially, the element M is chosen from iron, zinc, aluminium, silicon, selenium, sodium, potassium, magnesium and calcium.

[0051] Even more preferentially, the element M is chosen from iron, zinc and aluminium.

[0052] Very particularly preferably, the element M is selected from iron and zinc.

[0053] Preferably, the integer m ranges from 1 to 10, more preferentially from 1 to 5.

[0054] Preferably, the integer n ranges from 1 to 20, more preferentially from 2 to 10.

[0055] In particular, x is equal to 0 or strictly less than n and represents a non-integer number between 0 and 20.

[0056] According to a preferred embodiment of the present invention, x is equal to 0.

[0057] According to another embodiment of the invention, x represents a non-integer number greater than 0 and strictly less than n, preferably strictly less than n and between 0 and 20, and more preferentially strictly less than n and between 0 and 10.

[0058] Preferably, the oxide of element M in formula (I) is FeO, Fe 2 O 3 , Fe 3 O 4 , where x is a strictly non-integer between 0 and 1, and the formula FeO 1-x Compounds of formula Fe, where x is strictly a non-integer between 0 and 4. 3 O 4-x Compounds of formula Fe, where x is strictly a non-integer between 0 and 3. 2 O 3-x and compounds of the formula ZnO, where x is a strictly non-integer between 0 and 1. 1-x The compound is selected from the group consisting of

[0059] More preferentially, the oxide of element M of formula (I) is FeO, Fe 3 O 4 , where x is a strictly non-integer between 0 and 1, and the formula FeO 1-x Compounds of formula Fe, where x is strictly a non-integer between 0 and 4. 3 O 4-x Compounds of formula Fe, where x is strictly a non-integer between 0 and 3. 2 O 3-x and compounds of the formula ZnO, where x is a strictly non-integer between 0 and 1. 1-x The compound is selected from the group consisting of

[0060] According to the invention, an element M in a particle is different from an element M' in this same particle.

[0061] Preferably, the core is in a crystalline state.

[0062] The crystalline state of Core 1 and its composition can be determined, for example, by conventional X-ray diffraction methods.

[0063] Advantageously, the core 1 of the particle according to the invention is composed of one or more aggregates of crystalline primary particles of an oxide of element M. In other words, the core 1 is composed of several crystallites of an oxide of element M.

[0064] The coated particles of the oxide of element M according to FIG. 1 have an average diameter D m Includes Core 1.

[0065] The coated particles of oxide of element M according to FIG. 1 are composed of a compound of formula (II) and completely cover the surface of the core 1 with an average thickness d m It also includes a top coating layer 2 which is

[0066] Number average diameter D of core 1 m can be determined, for example, by transmission electron microscopy (abbreviated as TEM). Preferably, the number-average diameter D m is in the range spanning from 3 to 5000 nm, more preferentially from 10 to 3000 nm, even more preferentially from 30 to 1000 nm.

[0067] The coated particle of oxide of element M according to the invention comprises an upper coating layer 2 coating the surface of a core 1, composed of a compound of formula (II).

[0068] Advantageously, the top coating layer 2 covers at least 90% of the surface of the core 1. More preferentially, the top coating layer 2 covers the entire surface of the core 1.

[0069] The degree of coverage of the core by the top coat layer can be determined, for example, using a visual analysis of the TEM-BF or STEM-HAADF type coupled with a STEM-EDX analysis.

[0070] Each of the analyses is carried out on a statistical particle count, in particular at least 20 particles. The particles are deposited on a metal grid made of a metal other than any metal that forms part of the particle, whether in the core or in the top coating layer. For example, the grid is made of copper (unless it is desired to use copper in the manufacture of the particles).

[0071] By visual analysis of the TEM-BF and STEM-HAADF images, it is possible to infer, based on contrast, whether the coating completely surrounds the core of the particle. By analyzing each of the 20 (or more) images, it is possible to infer from them the degree of core coverage, and then to determine the average degree of coverage by taking the average.

[0072] By STEM-EDX analysis it is possible to verify that the coating indeed contains predominantly or exclusively the element M'. For this purpose it is necessary to carry out pointings at the edges of the particles (for at least 20 particles). These pointings reveal the element M'.

[0073] STEM-EDX analysis also allows to verify that the core really contains element M. To do this, it is necessary to perform pointings at the centre of the particles (for at least 20 particles). These pointings reveal the elements M and M'.

[0074] According to the invention, element M' is other than element M and is selected from selenium and elements of columns 4, 13 and 14 of the Periodic Table of the Elements.

[0075] Preferably, element M' is selected from selenium, titanium, aluminum and the elements of column 14 of the periodic table of the elements.

[0076] More preferentially, the element M' is selected from selenium, titanium, aluminium, carbon and silicon.

[0077] Very particularly preferably, the element M' is selected from carbon and silicon.

[0078] According to a preferred embodiment, the element M' is silicon.

[0079] According to another embodiment of the invention, the element M' is carbon.

[0080] Preferably, the integer p ranges from 1 to 4. More preferentially, the integer p is equal to 1 or 2, and even better still, p is equal to 1.

[0081] Preferably, the integer q ranges from 0 to 4. More preferentially, the integer q is strictly greater than 0. Even more preferentially, the integer q ranges from 1 to 4.

[0082] Preferably, the compound of formula (II) is carbon, SiO 2 , SnO 2 and Al 2 O 3 is selected from.

[0083] More preferentially, the compound of formula (II) is composed of carbon and SiO 2 is selected from.

[0084] Advantageously, element M exhibits intermediate oxidation numbers, either stoichiometric or non-stoichiometric.

[0085] Within the meaning of the present invention, the term "intermediate oxidation numbers" is understood to mean oxidation numbers between 0 (not included) and the maximum oxidation number of element M (not included).

[0086] When the oxidation number is an integer, the expression "stoichiometric intermediate oxidation number" is used. For example, when the element M exhibiting the stoichiometric intermediate oxidation number is iron, the oxide of element M in formula (I) is FeO and Fe 3 O 4 In another example, when the element M exhibiting the intermediate oxidation state in the stoichiometric range is copper, the oxide of element M in formula (I) can be selected from Cu 2 It can be O.

[0087] When the oxidation number is a non-integer, the expression "non-stoichiometric intermediate oxidation number" is used. When element M exhibits a non-stoichiometric intermediate oxidation number, the expression "suboxide of element M" is used. For example, when element M exhibits a non-stoichiometric intermediate oxidation number is iron, the suboxide of element M in formula (I) has the formula FeO1-x The compound of formula Fe 3 O 4-x and compounds of formula Fe 2 O 3-x In another example, when the element M exhibiting a non-stoichiometric intermediate oxidation state is copper, the suboxide of element M in formula (I) can be selected from the compounds of formula CuO 1-x and compounds of formula Cu 2 O 1-x The compound can be selected from the following compounds:

[0088] In particular, it has been observed that particles in which the element M exhibits intermediate oxidation numbers make it possible to obtain colorations of the keratin material that are more intense and more chromatic. In addition, these particles make it possible to obtain novel colorations.

[0089] Preferably, the oxide of element M of formula (I) has the formula (I′): M m O n-x (I') [In the formula, M represents an element selected from the alkali metals of the first column, the alkaline earth metals of the second column and the elements of the third to fourth columns of the periodic table, bismuth, selenium, tellurium and astatine, - m represents an integer equal to or greater than 1; - n represents an integer equal to or greater than 1; - x represents a non-integer greater than 0 and strictly less than n].

[0090] The preferences and properties of element M and numbers m and n of formula (I) described above also apply to element M and numbers m and n of formula (I').

[0091] Preferably, x is strictly less than n and represents a non-integer number from 0 to 20, and more preferentially x is strictly less than n and represents a non-integer number from 0 to 10.

[0092] Preferably, the suboxide of element M of formula (I') has the formula FeO 1-x Compounds of formula Fe, where x is strictly a non-integer between 0 and 4.3 O 4-x Compounds of formula Fe, where x is strictly a non-integer between 0 and 3. 2 O 3-x and compounds of the formula ZnO, where x is a strictly non-integer between 0 and 1. 1-x The compound is selected from the group consisting of

[0093] According to a particularly preferred embodiment of the invention, the particles are - FeO, Fe 2 O 3 , Fe 3 O 4 , where x is a strictly non-integer between 0 and 1, and the formula FeO 1-x Compounds of formula Fe, where x is strictly a non-integer between 0 and 4. 3 O 4-x Compounds of formula Fe, where x is strictly a non-integer between 0 and 3. 2 O 3-x and compounds of the formula ZnO, where x is a strictly non-integer between 0 and 1. 1-x a core 1 composed of an oxide of element M of formula (I) or (I') selected from the compounds - Carbon, SiO 2 , SnO 2 and Al 2 O 3 An upper coating layer 2 covering the surface of the core 1, which is composed of a compound of formula (II) selected from the following: Includes.

[0094] According to a particularly preferred embodiment of the invention, the particles are - FeO, Fe 2 O 3 , Fe 3 O 4 , where x is a strictly non-integer between 0 and 1, and the formula FeO 1-x Compounds of formula Fe, where x is strictly a non-integer between 0 and 4. 3 O 4-x Compounds of formula Fe, where x is strictly a non-integer between 0 and 3. 2 O 3-x and compounds of the formula ZnO, where x is a strictly non-integer between 0 and 1. 1-x a core 1 composed of an oxide of element M of formula (I) or (I') selected from the compounds - Carbon and SiO2 An upper coating layer 2 covering the surface of the core 1, which is composed of a compound of formula (II) selected from the following: Includes.

[0095] Number average thickness of the upper coating layer d m can also be determined by transmission electron microscopy.

[0096] Preferably, the number average thickness d m is in the range spanning from 1 to 20 nm, more preferentially from 1 to 10 nm, even more preferentially from 2 to 6 nm.

[0097] Advantageously, the top cladding layer 2 is amorphous.

[0098] Advantageously, the top coating layer 2 is transparent.

[0099] Advantageously, the particles according to the invention comprise the elements M and M' in a specific (M / M') molar atomic ratio.

[0100] This ratio corresponds to the ratio, on the one hand, of the amount in molar units of element M present in the particles according to the invention and, on the other hand, of the amount in molar units of element M' present in the particles according to the invention.

[0101] This ratio can be determined by spectroscopic measurements according to one of the following two methods. According to the first method, the powder is spread and an X-ray fluorescence quantitative study is carried out using an X-ray spectrometer, from which the metal ratio is deduced. According to another method, the particles of the invention are dissolved in acid beforehand. Then, an elemental analysis is carried out on the obtained material by ICP-MS (Inductively Coupled Plasma Mass Spectroscopy), from which the metal ratio is deduced.

[0102] Preferably, the (M / M') molar atomic ratio of the particles according to the invention is strictly greater than 0.3, more preferentially greater than or equal to 1, even more preferentially greater than or equal to 3, and even better still in the range ranging from 3 to 100, and even better still in the range ranging from 3 to 10.

[0103] The number average diameter of the particles according to the invention can also be determined by transmission electron microscopy. Preferably, the number average diameter of the particles according to the invention is in the range ranging from 4 to 5000 nm, more preferentially from 10 to 3000 nm, even more preferentially from 30 to 1000 nm.

[0104] Preferably, the particles according to the invention have a BET specific surface area of ​​1 m 2 / g~200m 2 / g, more preferentially 30-100m 2 / g.

[0105] According to a particular embodiment of the invention, the coated particles according to the invention may optionally further comprise an additional coating layer covering the upper coating layer 2 and comprising at least one hydrophobic organic compound.

[0106] The hydrophobic organic compound contained in the additional coating layer is more preferentially chosen from silicones, in particular silicones containing at least one fatty chain, carbon-based derivatives containing at least 6 carbon atoms, in particular fatty acid esters, and mixtures thereof.

[0107] The additional coating layer can be produced by the liquid route or by the solid route. By the liquid route, the hydroxyl functional groups react with the reactive functional groups of the compound forming the coating (typically the silanol functional groups of silicones or the acid functional groups of carbon-based fatty substances). By the solid route, the particles are contacted with a liquid or pasty compound that contains a hydrophobic substance.

[0108] Preferably, the coated particles according to the invention are obtained by the inventive preparation method described below.

[0109] Method for preparing coated particles Another subject of the invention relates to a process for the preparation of particles of an oxide of element M of formula (I) coated with a compound of formula (II), in particular particles of the type of oxide M-M' of core / shell structure, comprising at least one of the steps a. of preparing a composition (A), then b. of forming a flame and c. of spraying a composition (B).

[0110] Step a of the method according to the invention consists of the preparation of composition (A) by adding one or more precursors of element M to a combustible solvent or a mixture of combustible solvents.

[0111] According to the invention, the element M represents an element selected from the alkali metals of the first row, the alkaline earth metals of the second row and the elements of the third to fourteenth rows of the periodic table, bismuth, selenium, tellurium and astatine.

[0112] Preferably, the element M represents an element selected from the alkali metals of the first row, the alkaline earth metals of the second row and the elements of the fourth to fourteenth rows of the periodic table, bismuth, selenium, tellurium and astatine.

[0113] Advantageously, element M is other than gold, silver, iridium, platinum, palladium, rhodium, ruthenium, osmium and carbon.

[0114] More preferentially, the element M is chosen from iron, zinc, aluminium, silicon, selenium, sodium, potassium, magnesium and calcium.

[0115] Even more preferentially, the element M is chosen from iron, zinc and aluminium.

[0116] Very particularly preferably, the element M is selected from iron and zinc.

[0117] According to the present invention, element M is other than element M'.

[0118] The precursors of element M and the combustible solvents that can be used according to the invention can be selected from the precursors of element M and the combustible solvents conventionally used in flame spray pyrolysis.

[0119] Preferably, the precursor of element M contained in composition (A) is - nitrates of elements M, e.g. iron nitrate, - sulfates of elements M, e.g. iron sulfate, - compounds comprising one or more elements M, complexed or uncomplexed with one or more ligands containing at least one carbon atom, such as carbonate, acetate and citrate, - and mixtures thereof is selected from.

[0120] More preferentially, said ligand is acetate, (C 1 ~C 6 ) alkoxylates, (C 2 ~C 10 ) alkyl carboxylate, (di)(C 1 ~C 6 ) alkylamino, and arylate, such as naphthalate or naphthenate, groups.

[0121] More preferentially, the precursors of element M contained in composition (A) are chosen from nitrates of element M.

[0122] Preferably, the flammable solvent is selected from protic flammable solvents, aprotic flammable solvents and mixtures thereof, more preferentially from alcohols, esters, acids, acyclic ethers, cyclic ethers, aromatic hydrocarbons or arenes, non-aromatic hydrocarbons, such as liquefied hydrocarbons, for example acetylene, methane, propane or butane, and mixtures thereof, and better still from 2-ethylhexyl acetate, 2-ethylhexanoic acid (EHA), ethyl ether, methyl tert-butyl ether (MTBE), methyl tert-amyl ether (MTAE), methyl tert-hexyl ether (MTHE), ethyl tert-butyl ether (ETBE), ether tert-amyl ether (ETAE), diisopropyl ether (DIPE), tetrahydrofuran (THF), xylene, and mixtures thereof.

[0123] Particularly preferably, the flammable solvent is selected from aprotic flammable solvents containing at least 3 carbon atoms and mixtures thereof, and better still from xylene, tetrahydrofuran, 2-ethylhexyl acetate, 2-ethylhexanoic acid (EHA), and mixtures thereof.

[0124] According to a particular embodiment of the invention, composition (A) comprises a mixture of flammable solvents, preferably at least two of the following flammable solvents: 2-ethylhexanoic acid (EHA), toluene, anhydrous ethanol and diethylene glycol monobutyl ether.

[0125] Even better, composition (A) comprises a mixture of flammable solvents composed of 2-ethylhexanoic acid (EHA), toluene, absolute ethanol and diethylene glycol monobutyl ether.

[0126] Even better, composition (A) comprises a mixture of flammable solvents composed of at least 5% by volume of 2-ethylhexanoic acid (EHA), at least 5% by volume of toluene, at least 5% by volume of anhydrous ethanol and at least 5% by volume of diethylene glycol monobutyl ether, based on the total volume of the mixture of flammable solvents.

[0127] Advantageously, the content of precursor of element M in composition (A) is between 1% and 60% by weight, preferably between 15% and 30% by weight, relative to the total weight of composition (A).

[0128] The preparation method according to the present invention further comprises a step b. of injecting the composition (A) and an oxygen-containing gas into a flame spray pyrolysis (FSP) device 10 to form a flame.

[0129] The flame spray pyrolysis apparatus 10 is more particularly described below with reference to FIGS.

[0130] During this step b., the composition (A) and the oxygen-containing gas (G) are advantageously injected into the flame spray pyrolysis device 10 .

[0131] Preferably, the frame formed during step b. is at a temperature of 2000° C. or greater in at least a portion of the frame.

[0132] Step b. may optionally further comprise the additional injection of a "premix" mixture (P) comprising oxygen and one or more combustible gases. This "premix" mixture (also called "supported flame oxygen") allows the generation of a support flame intended to ignite and maintain the flame obtained from composition A and an oxygen-containing gas (i.e. "dispersed oxygen"). On the one hand, the mixture of composition (A) and gas (G) and, on the other hand, the premix (P) are injected separately, i.e. the mixture of composition (A) and oxygen-containing gas (G) is injected by one tube and the premix (P) by another tube.

[0133] Preferably, during step b., composition (A), the oxygen-containing gas and the optional "premix" mixture, if present, are injected into a reaction tube (also called "filling tube"). Preferably, this reaction tube is made of metal or quartz. Advantageously, the reaction tube exhibits a height of at least 30 cm, preferably at least 40 cm and more preferentially at least 50 cm. Preferentially, the length of said reaction tube is between 30 cm and 300 cm, in particular between 40 cm and 200 cm, more particularly between 45 cm and 100 cm, for example 50 cm.

[0134] The mass ratio between the mass of solvent present in the composition (A), on the one hand, and the mass of the oxygen-containing gas (G), on the other hand, is defined as follows:

[0135] First, the amount of oxygen-containing gas (also called oxidizer compound) is calculated so that the aggregates formed by composition (A), i.e., on the one hand, the combustible solvent and the precursor of element M, and on the other hand, the oxygen-containing gas, can react together in a combustion reaction in a stoichiometric ratio (so that there is neither too much nor too little oxidizer compound).

[0136] Starting from this calculated amount of oxygen-containing gas (also called "calculated oxidizer"), a new calculation is carried out according to the following formula to derive from it the amount of oxygen-containing gas to be injected (also called "injected oxidizer"): Injected oxidizer = calculated oxidizer / φ In the formula, φ is a correction factor preferably between 1 and 2.5, more preferentially between 1.2 and 2, even more preferentially between 1.3 and 1.8, and better still between 1.4 and 1.6.

[0137] This method is defined, inter alia, by Turns, S. R. in An Introduction to Combustion: Concepts and Applications, 3rd ed.; McGraw-Hill: New York, 2012.

[0138] Preferably, the molar amount of oxygen-containing gas (G) injected during step b. is strictly less than the molar amount of oxygen-containing gas required to react composition (A) with oxygen in the stoichiometric ratio.

[0139] The flame spray pyrolysis device 10 that can be used in the preparation method according to the invention can comprise one or more chambers. Preferably, the flame spray pyrolysis device 10 that can be used in the preparation method according to the invention comprises several chambers, more preferentially two chambers.

[0140] Preferably, the aforementioned flame spray pyrolysis apparatus 10 is pressurized with an inert gas (G2) selected, for example, from nitrogen, methane, argon, hydrogen, hydrogen sulfide and ammonia, more preferentially from nitrogen, methane, hydrogen and argon, even more preferentially from nitrogen and argon, and better still by nitrogen.

[0141] According to a preferred embodiment of the present invention, when the flame spray pyrolysis apparatus 10 comprises only a single chamber, the chamber of said flame spray pyrolysis apparatus 10 is pressurized by an inert gas (G2) selected, for example, from nitrogen, methane, argon, hydrogen, hydrogen sulfide and ammonia, preferably from nitrogen, methane, hydrogen and argon, more preferentially from nitrogen and argon, and better still by nitrogen.

[0142] According to another preferred embodiment of the invention, when the flame spray pyrolysis apparatus 10 comprises several chambers, the first chamber 20 of said flame spray pyrolysis apparatus 10 is pressurized by an inert gas (G2), for example selected from nitrogen, methane, argon, hydrogen, hydrogen sulfide and ammonia, preferably selected from nitrogen, methane, hydrogen and argon, more preferentially from nitrogen and argon, and even better still by nitrogen.

[0143] Preferably, the flow rate of the inert gas (G2) injected into the flame spray pyrolysis apparatus 10 ranges from 5 l / min to 70 l / min, more preferentially from 10 l / min to 50 l / min.

[0144] More preferentially, the flow rate of nitrogen (G2) injected into the flame spray pyrolysis device 10 ranges from 5 l / min to 70 l / min, more preferentially from 10 l / min to 50 l / min.

[0145] According to a particularly preferred embodiment of the present invention, the correction factor φ is between 1 and 2.5, more preferentially between 1.2 and 2, even more preferentially between 1.3 and 1.8, and even better between 1.4 and 1.6, and the flow rate of the inert gas (G2), more particularly nitrogen, injected into the flame spray pyrolysis apparatus 10 is in the range of 5 l / min to 70 l / min, more preferentially between 10 l / min and 50 l / min.

[0146] The preparation method according to the invention further comprises a step c. which comprises spraying, on the surface of said aggregates of oxide of element M, a composition (B) comprising one or more precursors of element M' until a top coating layer 2 composed of element M' or an oxide of element M' is obtained.

[0147] As stated above, according to the present invention, element M' is other than element M and is selected from selenium and elements of columns 4, 13 and 14 of the Periodic Table of the Elements.

[0148] Preferably, element M' is selected from selenium, titanium, aluminum and the elements of column 14 of the periodic table of the elements.

[0149] More preferentially, the element M' is selected from selenium, titanium, aluminium, carbon and silicon.

[0150] Very particularly preferably, the element M' is selected from carbon and silicon.

[0151] According to a preferred embodiment, the element M' is silicon.

[0152] According to another embodiment of the invention, the element M' is carbon.

[0153] Preferably, the precursor of element M' comprises at least two M' atoms and several M'-carbon covalent bonds. More preferentially, the precursor of element M' comprises at least three M atoms and several M-carbon covalent bonds.

[0154] More preferentially, the precursor of element M' is hexa(di)(C 1 ~C 4 Alkyldisiloxanes, such as hexadimethyldisiloxane, (di)(tri)(tetra)(C 1 ~C 4 ) Alkoxysilanes, such as tetraethoxysilane, bis[(di)(tri)alkoxysilyl](C 1 ~C 4 ) alkanes, such as 1,2-bis(triethoxysilyl)ethane or 1,2-bis(trimethoxysilyl)ethane, (C 1 ~C 4 )Alkoxy(di)(tri)(C 1 ~C 4) alkylsilanes, such as methoxytrimethylsilane, hydrocarbon gases, such as acetylene, aluminum(di)(C 1 ~C 6 ) alkoxylate, aluminum (di) (C 1 ~C 6 ) alkyl carboxylates, such as aluminum hydroxide diacetate, (poly)(C 1 ~C 6 ) alkoxylate stannates, (poly)(C 1 ~C 6 ) alkyl carboxylate stannates, such as tetraacetate stannate, and mixtures thereof.

[0155] Even more preferentially, the precursor of element M' is chosen from hexadimethyldisiloxane, tetraethoxysilane, 1,2-bis(triethoxysilyl)ethane, 1,2-bis(trimethoxysilyl)ethane, methoxytrimethylsilane and mixtures thereof.

[0156] According to a particular embodiment of the invention, composition (B) can be injected with an inert gas (G3), for example chosen from nitrogen, methane, argon, hydrogen, hydrogen sulphide and ammonia, preferably chosen from nitrogen, methane, hydrogen and argon, more preferentially from nitrogen and argon.

[0157] For example, nitrogen can be bubbled into composition (B) before injection during step c. The injection flow rate of composition (B) can then be controlled by known pressure determinations by those skilled in the art, for example, the method set out by Scott, DW; Messerly, JF; Todd, SS; Guthrie, GB; Hossenlopp, IA; Moore, RT; Osborn, AG; Berg, WT; McCullough, JP, Hexamethyldisiloxane: Chemical Thermodynamic Properties and Internal Rotation about the Siloxane Linkage, J.Phys.Chem., 1961, 65, 1320-6.

[0158] Preferably, the content of precursor of element M' in composition (B) injected during step c. of the method according to the invention is between 1% and 60% by volume, more preferentially between 5% and 30% by volume, relative to the total volume of composition (B).

[0159] Advantageously, composition (B) may further comprise one or more solvents. Preferably, the solvent present in composition (B) is a polar protic solvent other than water, more preferentially (C 1 ~C 8 ) alkanols. Even more preferentially, composition (B) comprises ethanol.

[0160] Preferably, the solvent present in composition (B) is chosen from solvents that are flammable at the flame temperature of step c., preferably at temperatures between 200° C. and 600° C., more preferentially between 300° C. and 400° C. Better still, the solvent present in composition (B) has a boiling point above room temperature (25° C.), more preferentially between 50° C. and 120° C.

[0161] During the method according to the invention, (M / M') 噴射A molar atomic ratio can be calculated, which corresponds to the ratio, on the one hand, of the amount in molar of element M injected during step b., and, on the other hand, of the amount in molar of element M' injected during step c.

[0162] Preferably, (M / M') 噴射 The molar atomic ratio is greater than or equal to 0.25, more preferentially in the range from 0.25 to 120, even more preferentially in the range spanning from 0.25 to 99, better still in the range spanning from 1 to 80, and even better still in the range spanning from 3 to 20.

[0163] According to the invention, the flame spray pyrolysis apparatus 10 is isolated from the outside air so that the amount of oxygen present in said apparatus 10 is controlled, and more preferentially so that the oxygen present in said apparatus 10 comes only from said gas (G) and optionally from the mixture (P). In other words, the oxygen of the air cannot enter the combustion chamber and react with the composition (A) and the solvent.

[0164] Preferably, step b. is carried out in a first chamber of a flame spray pyrolysis apparatus 10 and step c. is carried out in a second chamber of said apparatus 10.

[0165] 2 and 3, the second chamber 30 is continuous with and extends through the first chamber 20. In an alternative embodiment, the two chambers may be connected by a pipe.

[0166] The present invention also relates to coated particles of oxide of element M of formula (I) or (I') obtainable according to the preparation process according to the invention described above.

[0167] Flame Spray Pyrolysis Equipment An example of a flame spray pyrolysis apparatus 10 is shown in FIG.

[0168] The flame spray pyrolysis apparatus 10 comprises a first chamber 20 that uses a composition (A) and an oxygen-containing gas (G), and a second chamber 30 that uses a composition (B) that includes one or more precursors of element M'.

[0169] The flame spray pyrolysis device 10 further comprises an injection system 40 comprising a first tube 42 emerging in the first chamber 20 and delivering the composition (A) and an oxygen-containing gas (G), and a second tube 44 emerging in the first chamber 20 and delivering a "premix" mixture (P) comprising oxygen and one or more combustible gases, for example methane. The second tube 44 makes it possible to guarantee the flame necessary for the ignition of the compounds emerging from the first tube 42.

[0170] The first and second tubes 42, 44 are separate from each other.

[0171] As shown, the first and second tubes 42, 44 are coaxial, with the second tube 44 at least partially surrounding the first tube 42.

[0172] Without being limiting in any way, the injection system 40 of the apparatus 10 further comprises an additional feed 46 of an inert gas, such as nitrogen, to the first chamber 20. The additional feed 46 may be at a pressure between 2 and 20 bar (i.e., 2×10 5 ~20×10 5 The inert gas may be provided in the form of a porous portion through which the inert gas can emerge under a pressure of 1000 MPa (10 Pa).

[0173] The composition (A), the oxygen-containing gas (G) and the combustibles (P) obtained from the injection system 40 are incinerated in the first chamber 20 .

[0174] As shown, the first chamber 20 includes two separate compartments 22, 24. The first compartment 22 includes a first lower opening 22a through which the injection system 40 emerges and a second upper opening 22b opposite the first opening 22a.

[0175] The second compartment 24 surrounds the first compartment 22 and is isolated from the outside air. The second compartment 24 is separated from the first compartment 22 by a gas permeable partition 26.

[0176] The second compartment 24 includes a top wall, a bottom wall and a side wall (not referenced) that form an enclosed housing isolated from the outside atmosphere.

[0177] The second compartment 24 is pressurized with a gas (G2) selected from, for example, nitrogen, methane, argon, hydrogen, hydrogen sulfide, and ammonia. The gas (G2) is injected into the second compartment 24 via an injector 28. For example, the injector 28 includes a single tube that emerges into the second compartment 24. In an alternative form, the injector 28 can include two or more tubes that emerge into the second compartment 24. The tubes may or may not be evenly spaced around the circumference of the second compartment 24.

[0178] The partition 26 for separating the two compartments 22, 24 is configured to allow the passage of the gas (G2) to the first compartment 22. For example, the partition 26 is made of a porous material. The porosity of the partition 26 is, for example, 10 μm to 100 μm.

[0179] The first chamber 20 exhibits a height H1 of, for example, 10 cm to 1 m.

[0180] The second chamber 30 is configured to use a composition (B) that includes one or more precursors of element M'.

[0181] As shown, the second chamber 30 includes two separate compartments 32, 34. The first compartment 32 includes a first lower opening 32a that coincides with the second opening 22b of the first chamber 20 and a second upper opening 32b opposite the first opening 32a.

[0182] In an alternative form, the first lower opening 32a may be laterally offset from the second opening 22b of the first chamber 20. The first chamber 20 may be connected to the second chamber 30 by a pipe.

[0183] The second compartment 34 surrounds the first compartment 32 and is isolated from the outside air. The second compartment 34 is separated from the first compartment 32 by a gas permeable partition 36.

[0184] The second compartment 34 comprises a top wall, a bottom wall and a side wall (not referenced) which form a closed housing isolated from the outside atmosphere.

[0185] The second compartment 34 has a feed 38 for supplying composition (B) to the second chamber 30 .

[0186] The feed 38 is pressurized, for example, by a gas (G3) selected from nitrogen, methane, argon or hydrogen, or by heating the composition (B). For example, the feed 38 comprises a single tube emerging into the second compartment 34. In an alternative form, the feed 38 comprises two or more tubes emerging into the second compartment 34. The tubes may or may not be evenly spaced around the circumference of the second compartment 34.

[0187] The partition 36 for separating the two compartments 32, 34 is configured to allow the passage of the composition (B) from the second compartment 34 to the first compartment 32. For example, the partition 36 may be configured to have a width of 1 cm of the separating partition 36. 2 It contains multiple perforations (not shown) of about 0.1 mm to 0.5 mm, with 1 to 10 perforations per hole.

[0188] The second chamber 30 exhibits a height H2 of, for example, 10 cm to 1 m.

[0189] Preferably, the height H1 of the first chamber 20 is equal to plus or minus 10% of the height H2 of the second chamber 30. Preferably, the dimensions of the first chamber 20 are equal to the dimensions of the second chamber 30.

[0190] The flame spray pyrolysis apparatus 10 further includes a collection system 50 configured to stop particles while allowing gases to pass therethrough.

[0191] In this case, the collection system 50 is coaxial with the two chambers 20, 30 and positioned above the second chamber 30. In an alternative configuration, the collection system 50 may be laterally offset from the chambers 20, 30.

[0192] The collection system 50 is radially defined by one or more side partitions 52 and axially defined by a lower wall 54 including an opening 54a emerging into the second chamber 30, and an upper wall 55 opposite the lower wall 54.

[0193] Collection system 50 further includes a filtration system 56 mounted inside said collection system between side walls 52 and a vacuum system 58 , such as a pump, mounted on a top wall 55 of said system 50 .

[0194] The pump 58 is configured to generate a negative pressure within the collection system 50 to isolate the chambers 20, 30 from the outside air. Advantageously, the negative pressure within the collection system 50 is between 0.5 and 0.8 bar (i.e., 5×10 4 ~8×10 4 The order of magnitude of this is 100 Pa.

[0195] Although not by any means limiting, the collection system 50 is axially spaced from the second chamber 30 by a spacer 60 .

[0196] As shown in FIG. 2, the injection system 40, the first chamber 20, the second chamber 30 and the collection system 50, indeed even the spacer 60, if present, are assembled, for example by screwing or welding, so as to ensure complete leak-proofing of the device 10, in particular the chambers 20, 30, making it possible to prevent access of outside air to the interior of said device 10.

[0197] 3, in which the same elements have the same reference numbers, differs from the embodiment shown in Fig. 2 only in that the injection system 40, the first chamber 20, the second chamber 30 and the collection system 50, indeed even the spacer 60, if present, are positioned in an enclosure 70 so as to guarantee a perfect leakproofness of the device 10, in particular of the chambers 20, 30, making it possible to prevent the access of external air to the interior of said enclosure 70. The interior of the enclosure 70 is put under negative pressure by a pump 58.

[0198] According to a preferred embodiment of the device, said device exhibits an axis of symmetry Δ passing through the center / centre of the injection system 40 and the center / centre of the collection system 50. More preferentially, the device is symmetrical, in particular cylindrical, passing through said axis of symmetry Δ.

[0199] composition Another subject of the present invention relates to a composition, preferably a cosmetic composition, comprising one or more coated particles of an oxide of element M of formula (I) or (I') above and / or preferably obtained by the preparation process according to the invention.

[0200] The compositions according to the invention are intended to be applied to keratinous materials, preferably to the skin (in particular the face) and / or to the hair, in order to dye and / or structure the keratinous materials. An optional step of drying the keratinous materials can be carried out.

[0201] The composition according to the invention can be in various presentation forms: it can thus be in the form of a powder (pulverulent) composition, or a liquid composition, or in the form of a milk, cream, paste or aerosol composition.

[0202] The composition according to the invention is in particular a cosmetic composition, i.e. the material of the invention is in a cosmetically acceptable carrier. The term "cosmetically acceptable carrier" means a medium that is suitable for application to keratinous materials, in particular human keratinous materials such as the skin, said cosmetically acceptable carrier generally being composed of water or a mixture of water and one or more organic solvents or a mixture of organic solvents.

[0203] The composition according to the invention is advantageously an aqueous composition.

[0204] Preferably, the composition comprises water in a content ranging from 5% to 95% (both ends included), in particular relative to the total weight of the composition.

[0205] Within the meaning of the present invention, the term "organic solvent" is intended to mean an organic substance capable of dissolving another substance without chemically modifying it.

[0206] As the organic solvent, for example, lower C 2 ~C 6 Mention may be made of alkanols, such as ethanol and isopropanol; polyols and polyol ethers, such as 2-butoxyethanol, propylene glycol, propylene glycol monomethyl ether and diethylene glycol monoethyl ether and diethylene glycol monomethyl ether, as well as aromatic alcohols, such as benzyl alcohol or phenoxyethanol, and mixtures thereof.

[0207] Preferably, the organic solvent is present in the composition according to the invention in a content of from about 0.1% to 40% by weight (both end values ​​inclusive) relative to the total weight of the composition, more preferentially from about 1% to 30% by weight and even more particularly from 5% to 25% by weight (both end values ​​inclusive) relative to the total weight of the composition.

[0208] The compositions of the invention may comprise a fatty phase and may be in the form of a direct or inverse emulsion.

[0209] The compositions according to the invention may be prepared in the form of simple or multiple emulsions (abbreviated as oil-in-water or O / W, water-in-oil or W / O, oil-in-water-in-oil or O / W / O, or water-in-oil-in-water or W / O / W), such as creams, milky or creamy gels, according to techniques well known to those skilled in the art.

[0210] According to a particular embodiment of the present invention, the composition according to the present invention can also be provided in the form of anhydrous composition, for example in the form of oil.The term "anhydrous composition" is understood to mean a composition that contains less than 2% by weight of water, preferably less than 1% by weight of water, and even more preferentially less than 0.5% by weight of water relative to the total weight of the composition, and even a composition that does not actually contain water.In this type of composition, the water that may be present is not added during the preparation of the composition, but corresponds to the residual water brought by the mixed components.

[0211] The particles according to the invention may be in dry form (powder, flakes, plates), as a dispersion, or as a liquid suspension, or as an aerosol. The particles according to the invention may be used as such or in admixture with other components.

[0212] Preferably, the composition of the invention comprises from 0.1% to 40% by weight, more preferentially from 0.5% to 20% by weight, even more preferentially from 1% to 10% by weight and even more preferentially from 1.5% to 5% by weight of particles according to the invention relative to the total weight of the composition.

[0213] The composition of the present invention can be used for single or multiple applications. When the composition of the present invention is intended for multiple applications, the content of the particles of the present invention is usually lower than in compositions intended for single applications.

[0214] Within the meaning of the present invention, the term "single application" is understood to mean exactly one application of the composition, which application is optionally repeated several times a day, each application being optionally separated from the next by more than one hour, or a single application per day.

[0215] Within the meaning of the present invention, the term "multiple applications" is understood to mean the application of the composition repeated multiple times, usually 2 to 5 times, each application being separated from the next by a few seconds to a few minutes. Each multiple application can be repeated multiple times a day, separated from the next by one hour or more, or even once a day, if necessary.

[0216] The following examples are illustrative of the present invention but are not intended to be limiting. EXAMPLES

[0217] Example 1: 1.1 In a first step, composition (A) was prepared from manganese nitrate (200 mm) in a mixture of flammable solvents: acetonitrile and ethyl hexanoate.

[0218] Subsequently, uncoated manganese oxide MnO particles P1 were prepared using a conventional FSP preparation method Prep 1 using a previously prepared composition (A) (not according to the present invention).

[0219] The parameters for the Prep 1 method are as follows: - Ratio (composition (A) / O 2 ) = 5 ml / min of composition (A) and 5 l / min of gas (O 2 ), - a gas mixture for providing a flame of 1 l / min methane and 2 l / min oxygen, An inert gas flow (G2) of 10 l / min of nitrogen is injected into the FSP device.

[0220] 1.2 Particles of manganese oxide MnO coated with silicon dioxide P2 are then prepared by the preparation method Prep 2 according to the invention to produce Mn / Si 粒子 A dual chamber FSP apparatus was prepared having composition (A) containing manganese nitrate (200 mm) in a mixture of flammable solvents (acetonitrile + ethylhexanoate) in such proportions that the molar atomic ratio of manganese nitrate to manganese nitrate was 0.49, and gas composition (B) containing hexadimethyldisiloxane and nitrogen.

[0221] The parameters for the Prep 2 method are as follows: - The composition (A) and the oxygen-containing gas (G) are mixed together in a mixture of (composition (A) / O 2 ) ratio = 5 ml / min of composition (A) and 5 l / min of gas (O 2 ) was injected into the first chamber of the FSP device. - a gas mixture for providing a flame of 1 l / min methane and 2 l / min oxygen, - Injecting a flow of 10 l / min of nitrogen inert gas (G2) into the first chamber of the dual chamber FSP device; - Composition (B) is injected into the second chamber of the FSP device by means of a nitrogen flow of 5 l / min.

[0222] The coefficient φ for adjusting the oxygen flow rate is the same for preparation method Prep 1 and preparation method Prep 2.

[0223] 1.3 The obtained manganese oxide particles were observed to be crystalline. It was also observed that the uncoated manganese oxide particles P1 (outside the scope of the invention) had a green-grey colour. The particles P1 according to method Prep 1 have a number average diameter equal to 50 nm.

[0224] Moreover, the particles P2 obtained according to the method Prep 2 according to the invention have a dark green color and are covered with an upper layer of silicon dioxide having a thickness of about 20 nm and a (Mn / Si) of 0.49. 粒子 The atomic ratios are shown.

[0225] The particles P2 according to method Prep 2 have a number average diameter equal to 70 nm.

[0226] 1.4 The colorimetric data of particles P1 and P2 are then measured in a CIELab system with a Data Color SF600X spectrophotometer (illuminant D65, angle 10°, and specular reflection component). In this L*a*b* system, L* represents lightness, a* indicates the green / red axis, and b* indicates the blue / yellow axis. The higher the value of L, the lighter or less intense the color. Conversely, the lower the value of L*, the darker or more intense the color. The higher the value of a*, the redder the color tone, and the higher the value of b*, the more yellow the color tone.

[0227] The results are collated in Table 1 below:

[0228] [Table 1]

[0229] It was observed that the green color of the coated manganese oxide particles P2 according to method Prep 2 (invention) was more intense than the green-gray color of the uncoated manganese oxide particles P1 according to method Prep 1 (outside the scope of the invention).

[0230] It was also observed that after storage for three months in open air and at ambient temperature and ambient light, the color of the coated manganese oxide particles P2 according to method Prep 2 (invention) did not change over time, unlike the color of the uncoated manganese oxide particles P1 according to method Prep 1 (outside the scope of the invention), which changed to dark gray over time.

[0231] Example 2: According to the above-described method Prep 2, a composition C1 (invention) was prepared containing 0.45 g of manganese oxide particles P2 coated with silicon dioxide and 9 ml of isododecane.

[0232] Composition C2 (outside the invention) was prepared containing 0.45 g of commercial pigment PG-7 (based on copper phthalocyanine), 0.25 g of commercial pigment PY-42 and 9 ml of isododecane. The color of composition C1 is similar to that of composition C2.

[0233] The following protocol is then repeated 10 times for each of compositions C1 and C2: - Stir the composition for 15 seconds, then application of 0.4 g of the composition to a surface equivalent to the skin, followed by - Dry in the open air.

[0234] Each of the 10 coatings thus prepared for each composition was then visually compared.

[0235] The green colour was observed to be identical for each of the 10 coatings obtained with composition C1 according to the invention.

[0236] In contrast, for the 10 coatings obtained with comparative composition C2, a change in color from bluish green to gray was observed.

[0237] The colour reproduction of the coating obtained with the composition C1 according to the invention is therefore much better than that of the coating obtained with the comparative composition C2.

Claims

1. For dyeing and / or structuring keratin materials, (i) Formula (I): M ｍ O ｎ－ｘ (I) A core (1) composed of at least one oxide of element M of During the ceremony, M represents an element selected from the alkali metals of column 1, the alkaline earth metals of column 2 and the elements of columns 3 to 14 of the Periodic Table of the Elements, bismuth, selenium, tellurium and astatine, m represents an integer of 1 or more; n represents an integer equal to or greater than 1; a core (1), where x is equal to 0 or represents a non-integer number greater than 0 and strictly less than n; (ii) covering the surface of the core (1), and having at least one compound represented by the formula (II): M' ｐ O ｑ (II) A top coating layer (2) made of a compound of During the ceremony, M' is an element other than M, selected from selenium and the elements of columns 4, 13 and 14 of the Periodic Table of the Elements, p represents an integer of 1 or more, - q represents an integer of 0 or more, an upper coating layer (2); The use of at least one particle comprising:

2. 2. Use according to claim 1, characterised in that the element M is selected from iron, zinc, aluminium, silicon, selenium, sodium, potassium, magnesium and calcium, preferably from iron, zinc and aluminium and more preferentially from iron and zinc.

3. Together or separately, m represents an integer ranging from 1 to 10, preferably from 1 to 5, and / or n represents an integer ranging from 1 to 20, preferably from 2 to 10, and / or -p represents an integer ranging from 1 to 4, preferably equal to 1 or 2 and more preferentially equal to 1, and / or Use according to claim 1 or 2, characterized in that q represents an integer ranging from 0 to 4.

4. The oxide of element M of formula (I) is FeO, Fe ２ O ３ , Fe ３ O ４ , where x is a strictly non-integer between 0 and 1; １－ｘ and a compound of formula Fe, where x is strictly a non-integer between 0 and 4. ３ O ４－ｘ and a compound of formula Fe, where x is strictly a non-integer between 0 and 3. ２ O ３－ｘ and compounds of the formula ZnO, where x is a non-integer strictly between 0 and 1. １－ｘ Use according to any one of claims 1 to 3, characterized in that the compound is selected from the group consisting of

5. Use according to any one of claims 1 to 4, characterized in that the element M' is selected from selenium, titanium, aluminium and the elements of column 14 of the periodic table of the elements, preferably from selenium, titanium, aluminium, carbon and silicon, more preferentially from carbon and silicon.

6. The compound of formula (II) is selected from the group consisting of carbon, SiO ２ , SnO ２ , and Al ２ O ３ From the above, preferably carbon and SiO ２ The use according to any one of claims 1 to 5, characterized in that it is selected from:

7. The particles are (i) a core (1) composed of an oxide of element M of formula (I), such as FeO, Fe ２ O ３ , Fe ３ O ４ , where x is a strictly non-integer between 0 and 1; １－ｘ and a compound of formula Fe, where x is strictly a non-integer between 0 and 4. ３ O ４－ｘ and a compound of formula Fe, where x is strictly a non-integer between 0 and 3. ２ O ３－ｘ and compounds of the formula ZnO, where x is a non-integer strictly between 0 and 1. １－ｘ A core (1) selected from the compounds (ii) Carbon, SiO ２ , SnO ２ and Al ２ O ３ An upper coating layer (2) covering the surface of the core (1), which is composed of a compound of formula (II) selected from the following: Use according to any one of claims 1 to 6, characterized in that it comprises

8. Use according to any one of claims 1 to 7, characterized in that the (M / M') molar atomic ratio of said particles is strictly greater than 0.3, preferably greater than or equal to 1, more preferentially greater than or equal to 3 and more preferentially comprised in the range spanning from 3 to 10.

9. The number average thickness d of the upper coating layer (2) measured by transmission electron microscopy (TEM) ｍ Use according to any one of claims 1 to 8, characterized in that is comprised within the range of 1 to 20 nm, preferably 1 to 10 nm and more preferentially 2 to 6 nm.

10. Use according to any one of claims 1 to 9, characterized in that the number average diameter of the particles, determined by transmission electron microscopy (TEM), is comprised within the range of from 4 to 5000 nm, preferably from 10 to 3000 nm and more preferentially from 30 to 1000 nm.

11. Use according to any one of the preceding claims, characterized in that the upper coating layer (2) of the particle covers at least 90% of the surface of the core (1), preferably covering the entire surface of the core (1).

12. A particle, (i) Formula (I'): M ｍ O ｎ－ｘ (I’) A core (1) composed of at least one suboxide of element M of During the ceremony, M represents an element selected from the alkali metals of column 1, the alkaline earth metals of column 2 and the elements of columns 3 to 14 of the Periodic Table of the Elements, bismuth, selenium, tellurium and astatine, preferably M is selected from iron, zinc, aluminium, silicon, selenium, sodium, potassium, magnesium and calcium, more preferentially from iron, zinc and aluminium and even more preferentially from iron and zinc, m represents an integer of 1 or more; n represents an integer equal to or greater than 1; a core (1), where x represents a non-integer greater than 0 and strictly less than n; (ii) covering the surface of the core (1), and having at least one compound represented by the formula (II): M' ｐ O ｑ (II) A top coating layer (2) made of a compound of During the ceremony, M' is an element other than M, selected from selenium and the elements of columns 4, 13 and 14 of the Periodic Table of the Elements, preferably M' is selected from selenium, titanium, aluminum and the elements of column 14 of the Periodic Table of the Elements, more preferentially from selenium, titanium, aluminum, carbon and silicon, even more preferentially from carbon and silicon, p represents an integer of 1 or more, - q represents an integer of 0 or more, an upper coating layer (2); Including, particles.

13. The suboxide of element M of formula (I') has the formula FeO １－ｘ and a compound of formula Fe, where x is strictly a non-integer between 0 and 4. ３ O ４－ｘ and a compound of formula Fe, where x is strictly a non-integer between 0 and 3. ２ O ３－ｘ and compounds of the formula ZnO, where x is a non-integer strictly between 0 and 1. １－ｘ 13. The particle according to claim 12, characterized in that it is selected from the compounds of the formula:

14. 14. Particles according to claim 12 or 13, characterized in that the (M / M') molar atomic ratio of said particles is strictly greater than 0.3, preferably greater than or equal to 1, more preferentially greater than or equal to 3 and more preferentially comprised in the range extending from 3 to 10.

15. Particle according to any one of claims 12 to 14, characterized in that the upper coating layer (2) of the particle covers at least 90% of the surface of the core (1), preferably covering the entire surface of the core (1).

16. A composition, preferably a cosmetic product, comprising one or more particles as defined in any one of claims 12 to 15.

17. A method for the preparation of one or more particles as defined in any one of claims 1 to 15, comprising at least the following steps: a. preparing a composition (A) by adding one or more precursors of element M to a flammable solvent or mixture of flammable solvents, then b. In a flame spray pyrolysis device (10), a flame is formed by spraying the composition (A) and an oxygen-containing gas (G) until an agglomerate of the oxide of element M is obtained, and then c) spraying, on the surface of said aggregates of oxide of element M, a composition (B) comprising one or more precursors of element M' until a top coating layer (2) composed of element M' or an oxide of element M' is obtained; said element M is selected from the alkali metals of row 1, the alkaline earth metals of row 2 and the elements of rows 3 to 14 of the Periodic Table of the Elements, bismuth, selenium, tellurium and astatine, preferably M is selected from iron, zinc, aluminum, silicon, selenium, sodium, potassium, magnesium and calcium, more preferentially from iron, zinc and aluminum, even more preferentially from iron and zinc; said element M' is other than M and is selected from selenium and elements of the 4th, 13th and 14th columns of the Periodic Table of the Elements, preferably M' is selected from selenium, titanium, aluminum and elements of the 14th column of the Periodic Table of the Elements, more preferentially from selenium, titanium, aluminum, carbon and silicon, even more preferentially from carbon and silicon; The method of claim 1, wherein the flame spray pyrolysis apparatus (10) is isolated from the outside atmosphere such that the amount of oxygen present within the apparatus is controlled.

18. Together or separately, - (M / M') 噴射 a molar atomic ratio equal to or greater than 0.25, preferably falling within the range extending from 0.25 to 120, more preferentially from 0.25 to 99, even more preferentially from 1 to 80 and better still from 3 to 20; and / or step b. is carried out in a first chamber (20) of a flame spray pyrolysis apparatus (10) and step c. is carried out in a second chamber (30) of said apparatus (10) in fluid communication with said first chamber (20); and / or said composition (B) contains one or more solvents, preferably said solvents being selected from polar protic solvents other than water, more preferentially from (C １ ~C ８ ) alkanols, better still, said solvent is ethanol, and / or 18. The method according to claim 17, characterized in that the molar amount of oxygen-containing gas (G) injected during step b. is strictly less than the molar amount of oxygen-containing gas necessary to react said composition (A) with said oxygen in stoichiometric ratio.

19. 19. The method according to claim 17 or 18, characterized in that the flame spray pyrolysis device (10) is pressurized with an inert gas (G2) preferably selected from nitrogen, methane, argon, hydrogen, hydrogen sulfide and ammonia, more preferentially from nitrogen, methane, hydrogen and argon, even more preferentially from nitrogen and argon, and better still by nitrogen.

20. Particles according to any one of claims 1 to 15, characterized in that they are obtained by a process as defined in any one of claims 17 to 19.

21. A flame spray pyrolysis apparatus (10) comprising a first chamber (20), a second chamber (30) fluidly connected to the first chamber, an injection system (40) including a first feed (42) emerging from the first chamber (20) and capable of delivering a first composition (A) and a first oxygen-containing gas (G), and a second feed (44) emerging from the first chamber (20) and capable of delivering a mixture (P) comprising oxygen and one or more combustible gases. a third feed (38) capable of delivering a second composition (B) comprising one or more precursors of element M' to the second chamber (30), the first and second chambers (20, 30) of the apparatus (10) being isolated from the outside air such that the amount of oxygen present in the first and second chambers (20, 30) is controlled.

22. 22. The apparatus (10) of claim 21, wherein the first and second feeds (42, 44) are coaxial, and the second feed (44) at least partially surrounds the first feed (42).

23. 23. The device (10) according to claim 21 or 22, wherein the first chamber (20) comprises two separate compartments (22, 24), the first compartment (22) comprising a first opening (22a) through which the injection system (40) emerges and a second opening (22b) opposite the first opening (22a), the second compartment (24) surrounding the first compartment (22) and isolated from the outside air, the second compartment (24) being separated from the first compartment (22) by a first partition (26).

24. 24. The apparatus (10) of claim 23, further comprising an injector (28) configured to inject a second gas (G2) into the second compartment (24) of the first chamber (20), and the first partition (26) is permeable to the second gas (G2).

25. 25. The apparatus (10) according to claim 23 or 24, wherein the second chamber (30) comprises two separate compartments (32, 34), the first compartment (32) comprises a first opening (32a) in fluid communication with the second opening (22b) of the first chamber (20) and a second opening (32b) opposite the first opening (32a), the second compartment (34) surrounds the first compartment (32) and is isolated from the outside air, the second compartment (34) is separated from the first compartment (32) by a second partition (36), and has a feed (38) for supplying the second composition (B) to the second chamber (30).

26. 26. The apparatus (10) of claim 25, further comprising an additional feed (38) configured to inject a third gas (G3) into the second compartment (34) of the second chamber (30), the second partition (36) being permeable to the third gas (G3).

27. The apparatus (10) of any one of claims 21 to 26, further comprising a gas-permeable collection system (50) positioned above the second chamber (30).

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