Non-nanoscale iron oxide particles, method for preparing same and cosmetic composition containing same

Abstract

The present invention relates to non-nanoscale iron oxide particles, to a method for preparing same, to a cosmetic composition containing same, and to the use thereof as pigments in a cosmetic composition.

Description

[0001] Non-nanometric iron oxide particles, their preparation process and cosmetic composition containing them

[0002] The present invention relates to non-nanometric iron oxide particles, their preparation process, a cosmetic composition containing them, as well as their use as pigments in a cosmetic composition.

[0003] Iron oxide particles are mineral species that are abundant in nature. Examples include goethite or yellow iron oxyhydroxide, composed of hydrated iron (III) oxides with the chemical formula a-FeO(OH), hematite or red iron oxide, composed of iron (III) oxides with the chemical formula a-FeiCh, and brown iron oxide, composed of a mixture of goethite and hematite.

[0004] The present invention aims to synthesize iron oxide particles, for example iron oxide particles consisting of goethite, hematite or a mixture of goethite and hematite, preferably goethite, which are non-nanometric, complying with future European legislation concerning the size of pigments used in cosmetics. This new regulation, which should come into force in 2027, requires that the particles introduced into cosmetic compositions, and in particular pigments, have, for more than 50% by number of the primary particles (corresponding to a D50), a size greater than 100 nm for all dimensions. The pigments of natural or synthetic origin currently used in industry, in particular goethite, comply with the legislation currently in force and are of nanometric size, in the sense that at least one of their dimensions is less than 100 nm.These nanometric pigments will, however, no longer be usable with the constraints imposed by future regulations.

[0005] There is therefore a need to find new synthetic routes allowing the production of non-nanometric iron oxide particles, in particular having a color conforming to the value ranges corresponding to the reference color. Annex IV of Regulation (EC) No 1223 / 2009 on cosmetic products describes, for example, the color index numbers of iron oxide particles.

[0006] Iron oxide particles can be synthesized in several ways, described in the literature, including in particular synthesis by precipitation. The Applicants have now found that the use of at least one iron complexing agent, present either in the form of a counterion of at least one starting iron (III) salt, or in the form of an additive, identical or different from the starting counterion in a basic aqueous solution, promotes the growth of iron oxide particles, and thus the production of non-nanometric iron oxide particles within the meaning of the new regulations. Without wishing to be bound by a theory, it appears that the complexing agent in solution forms one or more complexes, stabilizing the iron in solution. The presence of at least one complexing agent would thus make it possible to influence the dissolution-precipitation balances of the particles, during the formation of iron oxides.These complexes allow a certain amount of iron to be present in solution and available to continue the growth of the iron oxide particles formed. The rate of formation of iron oxides is slowed down and this leads to the increase in particle size in the Ostwald ripening step. According to a particular embodiment, by using complexing agents with high complexation constants, the complexes will be more stable in solution, thus making it possible to maintain a significant concentration of iron in solution, which is favorable to particle growth.

[0007] According to a first aspect, the invention relates to a method for preparing non-nanometric iron oxide particles, said iron oxide particles being goethite particles, hematite particles or a mixture of goethite and hematite particles, comprising the following steps:

[0008] (a) the preparation of a basic aqueous suspension of iron by mixing:

[0009] (i) a basic aqueous solution comprising at least one complexing agent, with a ferric aqueous solution comprising at least one iron (III) salt, said at least one complexing agent being identical to or different from the counterion of said at least one iron (III) salt, or

[0010] (ii) a basic aqueous solution with an aqueous ferric solution comprising an iron (III) salt complex consisting of at least one iron (III) salt and a complexing agent present in the form of a counterion of said at least one iron (III) salt;

[0011] (b) heating the basic aqueous iron suspension obtained in step (a) to a temperature between 50°C and 350°C so as to obtain a precipitate of iron oxides;

[0012] (c) separating, washing and drying the precipitate obtained in step (b).

[0013] According to a second aspect, the invention relates to non-nanometric iron oxide particles obtained by the method according to the invention, said iron oxide particles being goethite particles, hematite particles or a mixture of goethite and hematite particles, preferably goethite particles.

[0014] According to a third aspect, the invention relates to non-nanometric iron oxide particles, characterized in that the iron oxide particles are goethite particles or a mixture of goethite and hematite particles, and that the number median size of the minor dimension and major dimension of the primary particles is greater than 100 nm.

[0015] According to a fourth aspect, the invention relates to a cosmetic composition comprising iron oxide particles according to the invention.

[0016] According to a fifth aspect, the invention relates to a use of iron oxide particles according to the invention, as pigments in a cosmetic composition.

[0017] Any reference to ranges of values ​​in the description and / or claims implies, unless otherwise stated, that the limits of the ranges are included. The use of the term "strictly" means that the value is not included.

[0018] The present invention therefore relates to a process for preparing non-nanometric iron oxide particles, said iron oxide particles being goethite particles, hematite particles or a mixture of goethite and hematite particles, comprising the following steps:

[0019] (a) the preparation of a basic aqueous suspension of iron by mixing:

[0020] (i) a basic aqueous solution comprising at least one complexing agent, with an aqueous ferric solution comprising at least one iron (III) salt, in particular an iron (III) salt, said at least one complexing agent being identical to or different from the counterion of said at least one iron (III) salt, or

[0021] (ii) a basic aqueous solution with an aqueous ferric solution comprising an iron (III) salt complex consisting of at least one iron (III) salt and a complexing agent present in the form of a counterion of said at least one iron (III) salt;

[0022] (b) heating the basic aqueous iron suspension obtained in step (a) to a temperature between 50°C and 350°C so as to obtain a precipitate of iron oxides;

[0023] (c) separating, washing and drying the precipitate obtained in step (b).

[0024] In the context of the invention, the term "non-nanometric particles" refers to solid primary particles whose small and large dimensions are greater than 100 nm for more than 50% of the sample by number (D50 > 100 nm). Preferably, all the dimensions of the particles have a size greater than 100 nm for more than 50% of the sample by number (D50 > 100 nm). Said particles are in the crystalline state.

[0025] In the context of the invention, the term "primary particles" refers to initial source particles of agglomerates or aggregates or mixtures thereof, as defined in ISO 80004-1:2023. Conversely, agglomerates and aggregates are called secondary particles.

[0026] In the context of the invention, the term "complexing agent" refers to a compound capable of forming one or more complexes with iron in solution. A complexing agent is considered to be a ligand which may be mono- or multi-dentate, and whose functions may coordinate with iron.

[0027] In particular, said at least one complexing agent is water-soluble and comprises at least one function chosen from the group consisting of carboxylic acids, thiocarboxylic acids, amines, alcohols, ethers, sulfonic acids, phosphonic acids, phosphoric acids, polymers, their basic forms, and their mixtures.

[0028] Said at least one complexing agent used in step (a)(i) is in particular chosen from the group consisting of acetic acid, lactic acid, oxalic acid, glycine, 2,6-pyridine-dicarboxylic acid, citric acid, nitriletriacetic acid, polyethylene glycol (PEG), hydroxyethylethylenediaminetriacetic acid (HEDTA), ethylenediaminetetraacetic acid (EDTA), their basic forms, and their mixtures.

[0029] Preferably, said at least one complexing agent used in step (a)(i) is chosen from the group consisting of oxalic acid, citric acid, HEDTA, EDTA, their basic forms, and their mixtures, preferably is oxalic acid or citric acid or their basic form.

[0030] In particular, said at least one complexing agent used in step (a)(i) has a log(K) of between 1 and 30, preferably between 3 and 26, in particular between 3 and 25, even more preferably between 19 and 25, this log(K) corresponding to the highest log(K) between log(K1), log(K2) and log(K3).

[0031] In the context of the invention, the term "log(K)" refers to the value of the log of the overall formation constant of iron complexes in solution, i.e. the constants of iron complexes associated with 1, 2 or 3 ligands from iron (III).

[0032] At least two complexing agents may be used in step (a)(i). In particular, two complexing agents are used in step (a)(i), for example a mixture of acetic acid and oxalic acid, as well as their basic forms.

[0033] Alternatively, preferably, a single complexing agent is used in step (a)(i).

[0034] The number of equivalents of said at least one complexing agent used in step (a)(i) may vary between 0.1 and 10 equivalents, preferably is equal to 1 or 3 equivalents, this number of equivalents being a function of the number of functional groups and the complexing power of said at least one complexing agent. A person skilled in the art is able to select the appropriate number of equivalents.

[0035] The concentration of said at least one complexing agent present in the basic aqueous solution is generally between 0.01 mol.L 1 and 1.00 mol.L 1 , preferably between 0.10 mol.L 1 and 0.50 mol.L 1 , more preferably between 0.10 mol.L 1 and 0.30 mol.L 1 .

[0036] Said at least one iron (III) salt used in step (a)(i) is in particular chosen from the group consisting of ferric chloride, ferric nitrate and ferric sulfate, preferably ferric chloride and ferric sulfate.

[0037] The concentration of said at least one iron (III) salt present in the aqueous ferric solution is generally between 0.10 mol.L 1 and 1.20 mol.L 1 , preferably between 0.10 mol.L 1 and 0.80 mol.L 1 .

[0038] The iron (III) salt complex used in step (a)(ii) is in particular ferric ammonium oxalate trihydrate or ferric sodium ethylenediaminetetraacetate or ferric citrate.

[0039] Any water-soluble iron (III) salt at the concentrations described above and any complexing agent having a log(K) as described above may be used in the process according to the invention.

[0040] The concentration of said iron (III) salt complex present in the aqueous ferric solution is generally between 0.5 mol.L 1 and 1.7 mol.L 1 .

[0041] The basic aqueous solution used in step (a)(i) or (ii) may comprise an alkaline agent selected from the group consisting of lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide, and a mixture thereof, preferably sodium hydroxide, potassium hydroxide and a mixture thereof.

[0042] The concentration of said alkaline agent present in the basic aqueous solution is generally between 0.7 mol.L 1 and 5.1 mol.L 1 , preferably between 0.8 mol.L 1 and 1.6 mol.L 1 .

[0043] Alternatively, the basic aqueous solution used in step (a)(i) or (ii) may comprise a water-soluble organic base such as 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), ammonia, or 4-dimethylaminopyridine (DMAP).

[0044] Preferably, the pH of said basic aqueous solution used in step (a)(i) or (ii) is between 7 and 14.

[0045] At the end of step (a), a precipitate of iron (III) hydroxide Fe(OH)3 is obtained.

[0046] In particular, in step (b), the heating of the basic aqueous iron suspension is carried out at a temperature between 50°C and strictly less than 200°C, preferably between 100°C and 150°C, or at a temperature above 50°C, preferably between 50°C and 350°C, even more preferably between 100°C and 350°C.

[0047] In particular, in step (b), the heating of the basic aqueous iron suspension is carried out for a minimum duration of 24 hours, preferably between 24 hours and 48 hours, even more preferably between 24 hours and 72 hours.

[0048] Generally, the pressure during step (b) is between 1 and 100 bars, in particular between 1 and 50 bars, preferably between 1 and 10 bars.

[0049] Alternatively, step (b) may be carried out at atmospheric pressure.

[0050] Preferably, step (b) comprises heating said basic aqueous iron suspension to a temperature between 50°C and strictly less than 200°C, preferably between 100°C and 150°C, or to a temperature above 50°C, preferably between 50°C and 350°C, even more preferably between 100°C and 350°C, and at a pressure between 1 and 100 bars, in particular between 1 and 50 bars, preferably between 1 and 10 bars, or at atmospheric pressure.

[0051] The separation in step c) is generally carried out by filtration or centrifugation, preferably by centrifugation, one or more times, for example at 6000 rpm.

[0052] In step c), the washing of the precipitate can be carried out with water, in particular pure water, in particular several times, preferably 3 to 6 times.

[0053] In step c), the drying of the precipitate can be carried out in an oven, for example at 100°C for 1 day.

[0054] A person skilled in the art is able to adjust the pH, temperature and / or pressure ranges in order to obtain the desired iron oxide particles.

[0055] Preferably, the iron oxide particles are goethite particles.

[0056] In a particular embodiment, the non-nanometric iron oxide particles are non-nanometric goethite particles. In particular, the pH of said basic aqueous solution used in step (a)(i) or (ii) is between 12 and 14, preferably 14, and / or the concentration of said alkaline agent present in the basic aqueous solution is generally between 0.7 mol.L 1 and 5.1 mol.L 1 , preferably between 0.8 mol.L 1 and 1.6 mol.L 1; and / or in step (b), the heating of the basic aqueous iron suspension is carried out at a temperature of between 50°C and strictly less than 200°C, preferably between 100°C and 150°C, in particular for a minimum duration of 24 hours, preferably between 24 hours and 48 hours, even more preferably between 24 hours and 72 hours; and / or step (b) is carried out at a pressure of between 1 and 100 bars, in particular between 1 and 50 bars, preferably between 1 and 10 bars, or at atmospheric pressure.

[0057] The expression "strictly less than 200°C" means that the temperature is less than but not equal to 200°C.

[0058] Said non-nanometric goethite particles are in particular in the form of needles or rods, preferably in the form of rods.

[0059] In another particular embodiment, the non-nanometric iron oxide particles are non-nanometric hematite particles. In particular, the pH of said basic aqueous solution used in step (a)(i) or (ii) is between 7 and 14, preferably between 7 and 11.5; and / or the concentration of said alkaline agent present in the basic aqueous solution is generally between 0.7 mol.L 1 and 0.9 mol.L 1 , preferably 0.8 mol.L 1 ; and / or in step (b), the heating of the basic aqueous iron suspension is carried out at a temperature above 50°C, preferably between 100°C and 350°C, in particular for a minimum duration of 24 hours, preferably between 24 hours and 48 hours, even more preferably between 24 hours and 72 hours; and / or step (b) is carried out at a pressure between 1 and 100 bars, in particular between 1 and 50 bars, preferably between 1 and 10 bars, or at atmospheric pressure.

[0060] The present invention also relates to non-nanometric iron oxide particles obtained by the process according to the invention, said iron oxide particles being goethite particles, hematite particles or a mixture of goethite and hematite particles, preferably goethite particles.

[0061] The present invention also relates to non-nanometric iron oxide particles, characterized in that the iron oxide particles are goethite particles or a mixture of goethite and hematite particles, and that the number median size of the minor dimension and major dimension of the primary particles is greater than 100 nm.

[0062] In the context of the invention, the term "number median size" refers to 50% by number of particles having a particular size. For example, a number median size of the primary particles greater than 100 nm means that 50% by number of these particles have a size greater than 100 nm. The number median size of the minor dimension and the major dimension of the primary particles can be measured by electron imaging, for example with a scanning electron microscope (SEM), in particular using a JEOL JSM 7100F microscope with an Oxford Instrument 50mm analysis system. 2 .

[0063] In particular, the number median size of the minor dimension of the primary particles is between 100 nm and 200 nm, preferably between 100 nm and 175 nm, and the ratio between the number median size of the major dimension and the minor dimension of the primary particles is greater than 3.

[0064] In the context of the invention, the term "small dimension of the primary particles" refers to the "width" or "thickness" of the primary particles, for example observed from an SEM image.

[0065] In the context of the invention, the term "large dimension of the primary particles" refers to the "length" of the primary particles, for example observed from an SEM image.

[0066] In particular, the non-nanometric iron oxide particles are goethite particles having the following L*, a* and b* values, measured in CIELAB units, in particular according to ISO / CIE 11664-4:2019, preferably with the Konica Minolta CM-5 spectrophotometer in reflection mode with the parameters “observer 10°” and “illuminant D65”:

[0067] - in full tone, an L* value between 42 and 58, an a* value between 7 and 16, and a b* value between 34 and 53, or

[0068] - in reduced tone in white, an L* value between 64 and 73, an a* value between 2 and 7, and a b* value between 19 and 34.

[0069] The present invention further relates to a cosmetic composition comprising iron oxide particles according to the invention.

[0070] According to a particular embodiment, the composition comprises from 0.1% to 90% by weight of iron oxide particles according to the invention, relative to the total weight of the composition. Said cosmetic composition may in particular be suitable for topical application.

[0071] Said cosmetic composition may comprise other additives customary in the field, such as for example preservatives, pH adjusters, antimicrobial agents, perfumes, sunscreens, and mixtures thereof.

[0072] The invention which is the subject of the present application also relates to the use of iron oxide particles according to the invention, as pigments in a cosmetic composition. By "pigments", it is meant iron oxide particles according to the invention intended to color the composition.

[0073] FIGURES

[0074] Figure 1. Diffraction pattern of iron oxide particles from Comparative Example 1, without complexing agent.

[0075] Figure 2. SEM measurements and particle counting of iron oxides from Comparative Example 1, without complexing agent. 2A. Magnification *20000 with a scale of 1 pm; 2B. Magnification *40000 with a scale of 100 nm. 2C. Distribution of the proportion of particles in number as a function of size for small and large dimensions, based on 100 particles, and value of the median size of the small and large particle dimensions.

[0076] Figure 3. Diffraction pattern of iron oxide particles of Example 3 according to the invention, with 3 equivalents of ammonium oxalate per iron.

[0077] Figure 4. SEM measurements and counting of iron oxide particles of Example 3 according to the invention, with 3 equivalents of ammonium oxalate per iron. 4A. Magnification *20000 with a scale of 1 pm; 4B. Magnification *40000 with a scale of 100 nm. 4C. Distribution of the proportion of particles in number as a function of size for small and large dimensions, based on 100 particles, and value of the median size of the small and large dimensions of the particles.

[0078] Figure 5. Diffraction pattern of iron oxide particles of Example 4 according to the invention, with 3 equivalents of ammonium oxalate per iron.

[0079] Figure 6. SEM measurements and counting of iron oxide particles of Example 4 according to the invention, with 3 equivalents of ammonium oxalate per iron. 6A. Magnification *20000 with a scale of 1 pm; 6B. Magnification *40000 with a scale of 100 nm. 6C. Distribution of the proportion of particles in number as a function of size for small and large dimensions, based on 100 particles, and value of the median size of the small and large dimensions of the particles.

[0080] Figure 7. Diffraction pattern of iron oxide particles of Example 5 according to the invention, with 1 equivalent of oxalic acid dihydrate per iron.

[0081] Figure 8. SEM measurements and counting of iron oxide particles of Example 5 according to the invention, with 1 equivalent of oxalic acid dihydrate per iron. 8A. Magnification *20000 with a scale of 1 pm; 8B. Magnification *40000 with a scale of 100 nm. 8C. Distribution of the proportion of particles in number as a function of size for small and large dimensions, based on 100 particles, and value of the median size of the small and large dimensions of the particles.

[0082] Figure 9. Diffraction pattern of iron oxide particles of Example 6 according to the invention, with 1 equivalent of citric acid monohydrate per iron.

[0083] Figure 10. SEM measurements and counting of iron oxide particles of Example 6 according to the invention, with 1 equivalent of citric acid monohydrate per iron. 10A. Magnification *20000 with a scale of 1 pm; 10B. Magnification *40000 with a scale of 100 nm. 10C. Distribution of the proportion of particles in number as a function of size for small and large dimensions, based on 100 particles, and value of the median size of the small and large dimensions of the particles.

[0084] Figure 11. Diffraction pattern of iron oxide particles of Example 7 according to the invention, with 1 equivalent of sodium ethylenediaminetetraacetate per iron.

[0085] Figure 12. SEM measurements and counting of iron oxide particles of Example 7 according to the invention, with 1 equivalent of sodium ethylenediaminetetraacetate per iron. 12A. Magnification *20000 with a scale of 1 pm; 12B. Magnification *40000 with a scale of 100 nm. 12C. Distribution of the proportion of particles in number as a function of size for small and large dimensions, based on 100 particles, and value of the median size of the small and large dimensions of the particles.

[0086] Figure 13. Diffraction pattern of iron oxide particles of Example 8 according to the invention, with 1 equivalent of EDTA per iron.

[0087] Figure 14. SEM measurements and counting of iron oxide particles of Example 8 according to the invention, with 1 equivalent of EDTA per iron. 14A. Magnification *20000 with a scale of 1 pm; 14B. Magnification *40000 with a scale of 100 nm. 14C. Distribution of the proportion of particles in number as a function of size for small and large dimensions, based on 100 particles, and value of the median size of the small and large dimensions of the particles.

[0088] Figure 15. Diffraction pattern of iron oxide particles of Example 9 according to the invention, with 1 equivalent of acetic acid and 1 equivalent of oxalic acid dihydrate per iron.

[0089] Figure 16. SEM measurements and counting of iron oxide particles of Example 9 according to the invention, with 1 equivalent of acetic acid and 1 equivalent of oxalic acid dihydrate per iron. 16A. Magnification *20000 with a scale of 1 pm; 16B. Magnification *40000 with a scale of 100 nm. 16C. Distribution of the proportion of particles in number as a function of size for small and large dimensions, based on 100 particles, and value of the median size of the small and large dimensions of the particles.

[0090] Figure 17. Diffraction pattern of iron oxide particles of Example 17 according to the invention, with 1 equivalent of HEDTA per iron.

[0091] Figure 18. SEM measurements and counting of iron oxide particles of Example 17 according to the invention, with 1 equivalent of HEDTA per iron. 18A. Magnification *20000 with a scale of 1 pm; 18B. Magnification *40000 with a scale of 100 nm. 18C. Distribution of the proportion of particles in number as a function of size for small and large dimensions, based on 100 particles, and value of the median size of the small and large dimensions of the particles.

[0092] Figure 19. Diffraction pattern of iron oxide particles of Example 19 according to the invention, with 3 equivalents of oxalic acid dihydrate per iron.

[0093] Figure 20. SEM measurements and counting of iron oxide particles from the example

[0094] 19 according to the invention, with 3 equivalents of oxalic acid dihydrate per iron. 20A. Magnification *20000 with a scale of 1 pm; 20B. Magnification *40000 with a scale of 100 nm. 20C. Distribution of the proportion of particles in number as a function of size for small and large dimensions, referring to 100 particles, and value of the median size of the small and large dimensions of the particles.

[0095] Figure 21. Diffraction pattern of iron oxide particles of Example 20 according to the invention, with 3 equivalents of citric acid monohydrate per iron.

[0096] Figure 22. SEM measurements and counting of iron oxide particles from the example

[0097] 20 according to the invention, with 3 equivalents of citric acid monohydrate per iron. 22A. Magnification *20000 with a scale of 1 pm; 22B. Magnification *43000 with a scale of 100 nm. 22C. Distribution of the proportion of particles in number as a function of size for small and large dimensions, based on 100 particles, and value of the median size of the small and large dimensions of the particles.

[0098] Figure 23. Diffraction pattern of iron oxide particles of Example 21 according to the invention, with 3 equivalents of EDTA per iron.

[0099] Figure 24. SEM measurements and counting of iron oxide particles from the example

[0100] 21 according to the invention, with 3 equivalents of EDTA per iron. 24A. Magnification *20000 with a scale of 1 pm; 24B. Magnification *40000 with a scale of 100 nm. 24C. Distribution of the proportion of particles in number as a function of size for small and large dimensions, referring to 100 particles, and value of the median size of the small and large dimensions of the particles.

[0101] Figure 25. Diffraction pattern of iron oxide particles of Example 22 according to the invention, with 0.1 equivalent of polyethylene glycol per iron.

[0102] Figure 26. SEM measurements and counting of iron oxide particles from the example

[0103] 22 according to the invention, with 0.1 equivalent of polyethylene glycol per iron. 26A. Magnification *20000 with a scale of 1 pm; 26B. Magnification *40000 with a scale of 100 nm. 26C. Distribution of the proportion of particles in number as a function of size for small and large dimensions, referring to 100 particles, and value of the median size of the small and large dimensions of the particles.

[0104] Figure 27. Diffraction pattern of iron oxide particles of Example 23 according to the invention, with 2 equivalents of oxalic acid dihydrate per iron.

[0105] Figure 28. SEM measurements and counting of iron oxide particles from the example

[0106] 23 according to the invention, with 2 equivalents of oxalic acid dihydrate per iron. 28A. Magnification *20000 with a scale of 1 pm; 28B. Magnification *40000 with a scale of 100 nm. 28C. Distribution of the proportion of particles in number as a function of size for small and large dimensions, based on 100 particles, and value of the median size of the small and large dimensions of the particles.

[0107] Figure 29. Diffraction pattern of iron oxide particles from Comparative Example 2, without complexing agent.

[0108] Figure 30. SEM measurements and particle counting of iron oxides from Comparative Example 2, without complexing agent. 30A. Magnification *20000 with a scale of 1 pm; 30B. Magnification *40000 with a scale of 100 nm. 30C. Distribution of the proportion of particles in number as a function of size for small and large dimensions, based on 100 particles, and value of the median size of the small and large particle dimensions.

[0109] EXAMPLES

[0110] The present invention is illustrated in a non-limiting manner by the examples below. Comparative examples are also described below. Materials and methods

[0111] - DRX: The composition of the synthesized iron oxide particles was analyzed by X-ray diffraction (DRX). The measurements were carried out with the presence of a nickel filter. This method quickly provided qualitative information on the composition and crystallinity of the material.

[0112] - Scanning electron microscopy (SEM): The analysis of the morphology and size of iron oxide particles was carried out using the SEM technique. The preparation of the samples to be analyzed was done in a similar way to the protocol generally applied by the National Laboratory of Metrology and Testing (LNE) in the framework of the studies it carries out (Ghomrasni et al., Powder Technology, 2000, 359, 226-237; Delvallée et al., Meas. Sci. Technol. 26, 2015, 085601, 15pp).

[0113] - Preparation of samples for SEM measurements: 10 mg of powder to be analyzed were dispersed in 5 mL of ethanol. The resulting dispersion was placed in an ultrasonic bath for 1 minute. A drop was then spread on a silicon substrate using a spin-coater at a low rotation speed (1000 rpm for 3 seconds) and then at a high rotation speed (3000 rpm for 2 seconds) to quickly dry the plate and remove the ethanol. The plate with the deposited powder was then metallized with palladium gold and passed through a JEOL JSM 7100F microscope with an Oxford Instrument 50mm analysis system. 2 .

[0114] - SEM measurements: Several photographs of the powder were taken over the entire support. 2 photographs were taken at low magnification (*20000 with a scale of 1 micrometer) to observe the distribution of the particles and 4 photographs were taken at high magnification (*40000 with a scale of 100 nanometers) to perform the counting.

[0115] - Particle counting: For each sample, two counts were performed, one to measure the small dimension of the particles and another to measure the large dimension. The small and large dimensions are considered to be the "width" and "length" of the primary particles seen from a SEM image. Indeed, this only gives a two-dimensional image of the particles. The small dimension is a mixture of particle width and thickness, while the large dimension is a mixture of particle length and width. For both counts, 300 dimensions were measured with Image J software by defining the measurement scale from the SEM image scale. Using the software, a statistical distribution of the measured sizes with the average, smallest and largest sizes were obtained, with a step size of 1 nm.The data were collected by the inventors and processed on Excel to obtain the distribution of the percentage of particles according to the size in number, referring to 100 particles, as well as the value of the median size.

[0116] - Colors: The powder shade is determined using the Müller grinding method. Two grindings of a full tone and a reduced tone in white were carried out to determine the L*, a* and b* values ​​in the CIELab color space as well as the coloring strength of the pigment.

[0117] - Preparation of full and reduced tones in white: The full tone was obtained by grinding 0.050 g of the pigment to be analyzed with 0.450 g of a waxy base for grinding detailed below. The mixture was crushed and ground with 3 times 100 revolutions in a glass plate mill "Müller-Engelsmann Mill". The resulting formulation was placed between two glass plates separated by 1 mm and then passed through a Konica Minolta CM-5 spectrophotometer in reflection mode with the parameters "observer 10°" and "illuminant D65". The reduced tone in white was obtained by grinding 0.215 g of the full tone formulation with 0.285 g of a 30% TiCh grind in the waxy base for grinding. The mixture was crushed and ground 2 times 40 revolutions in a Müller mill. The resulting formulation was also placed between two glass plates separated by 1 mm and then passed through the Konica Minolta CM-5 spectrophotometer in reflection mode with the parameters “observer 10°” and “illuminant D65”.

[0118] - Waxy base for grinding pigments and measuring color in comparison to the internal preferred reference

[0119] Raw material %

[0120] Wax 14.35

[0121] Polymer 22.50

[0122] Oil 30.75

[0123] Gelling agent 32.20

[0124] Antioxidant 0.20 Ton full

[0125] Take 3.6 g of the above wax base and add 0.4 g of pigment. Grind 3 times at 100 rpm using a glass plate mill "Müller-Engelsmann Mill". Measure using a Konica Minolta CM-5 spectrophotometer in reflection mode with the parameters "observer 10°" and "illuminant D65".

[0126] Reduced tone

[0127] Raw material %

[0128] Wax 10.00

[0129] Polymer 15.75

[0130] Oil 21.55

[0131] Gelling agent 22.55

[0132] Antioxidant 0.15

[0133] Titanium dioxide 30.00

[0134] Take 1.72 g of the full-tone preparation and 2.28 g of the waxy preparation containing titanium dioxide. Grind twice at 40 rpm using a glass plate mill "Müller-Engelsmann Mill". Measure using a Konica Minolta CM-5 spectrophotometer in reflection mode with the parameters "observer 10°" and "illuminant D65".

[0135] - Color measurements: The L*, a* and b* values ​​were measured with the Konica Minolta CM-5 spectrophotometer in reflection mode with the parameters "observer 10°" and "illuminant D65" using Spectramagic NX software. These L*, a* and b* values ​​were measured according to the ISO / CIE 11664-4:2019 standard, which refers to the method for calculating the coordinates of the CIE 1976 L*a*b* color space. Five measurements were carried out each time for the two tones. The average value is provided and then compared to the reference. The software then gives the values ​​of L*, a*, b*, C*, h, dL*, da*, db*, dC*, dH*, dE*ab. This allows us to know the deviation from the reference and the coloring strength of the pigment. The reduced tone in white also allows us to know the behavior of the pigment when mixed with other pigments. esis of goethite from FeCh.6H2O without

[0136] Protocol: A 13.8 mL solution was prepared by dissolving 0.764 g of KOH in pure water (0.8 moLL 1 ). Another 1.5 mL solution of ferric chloride hexahydrate (FeCh.ôHzO) was prepared by dissolving 0.465 g in pure water (1.1 mol.L 1 of Fe). The KOH solution was placed in a 23 mL autoclave containing a PTFE chamber and the ferric solution was added dropwise (0.7 moLL 1 of KOH and 0.1 moLL 1 of Fe). The red suspension was mixed for 10 min. The autoclave was placed in an oven and heated at 50°C for 24 h with a temperature ramp of 2 h, then heated to 150°C for 24 h with a temperature ramp of 2 h. A yellow precipitate was formed. The precipitate was centrifuged at 12000 rpm, washed 3 times with pure water, recentrifuged at 12000 rpm and dried in an oven for 1 day at 100°C. A yellow powder was obtained.

[0137] DRX: The peaks of the diffraction pattern obtained (Figure 1) corresponded to the signals of goethite, (upper pattern = experimental diffraction pattern, lower pattern with squares = peaks expected for a goethite sample).

[0138] SEM: The particles measured by SEM were nanometric and had a needle-like morphology. The median size of the small dimension was 94 nm with 55% of nanometric particles by number. The median size of the large dimension was 355 nm with 2% of nanometric particles by number (Figures 2A, 2B and 2C).

[0139] Color measurements: The color obtained in full tone was in the value range corresponding to the reference yellow with a dE*ab = 9.97 and the L*a*b* values ​​were L* = 56.07; a* = 10.45 and b* = 43.24. For the shaded tone in white, the color was also in the reference range with a dE*ab = 4.3 and the L*a*b* values ​​were L* = 71.87; a* = 3.41 and b* = 29.39.

[0140] Comparative example 2: Synthesis of goethite from Fe2(SO4)3.xH2O without complexing agent

[0141] Protocol: A 13.8 mL solution was prepared by dissolving 0.725 g of KOH in pure water (0.80 mol.L 1 ). Another 1.5 mL solution of ferric sulfate hydrate (Fe2(SO4)3.xH2O) was prepared by dissolving 0.633 g in pure water (1.5 mol.L 1 of Fe). The KOH solution was placed in a 23 mL autoclave containing a PTFE chamber and the ferric solution was added dropwise (0.7 moLL 1 of KOH and 0.1 moLL 1of Fe). The red suspension was mixed for 10 min. The autoclave was placed in an oven and heated at 50°C for 24 h with a temperature ramp of 2 h, then heated to 150°C for 24 h with a temperature ramp of 2 h. A yellow precipitate was formed. The precipitate was centrifuged at 12000 rpm, washed 3 times with pure water, recentrifuged at 12000 rpm and dried in an oven for 1 day at 100°C. A yellow powder was obtained.

[0142] DRX: The peaks of the diffraction pattern obtained (Figure 29) corresponded to the signals of goethite.

[0143] SEM: The particles observed by SEM were nanosized and had a needle-like morphology. The median size of the small dimension was 93 nm with 58% of nanosized particles by number. The median size of the large dimension was 419 nm with 3% of nanosized particles by number (Figures 30A, 30B and 30C).

[0144] Color measurements: The color obtained in full tone was in the value range corresponding to the reference yellow with a dE*ab = 7.48 and the L*a*b* values ​​were L* = 57.35; a* = 12.14 and b* = 45.93. For the shaded tone in white, the color was also in the reference range with a dE*ab = 2.99 and the L*a*b* values ​​were L* =

[0145] 72.29; a* = 4.32 and b* = 31.46. èse of aoethite to

[0146] Protocol: A 13.8 mL solution was prepared by dissolving 0.733 g of KOH in pure water (0.8 mol.L 1 ). Another 1.5 mL solution of ferric ammonium oxalate trihydrate (Ee(NH4C2O4)3.3H2O) was prepared by dissolving 0.699 g in pure water (1.1 moLL 1 of Le).

[0147] The KOH solution was placed in a 23 mL autoclave containing a PTEE chamber and the ferric solution was added dropwise (0.7 moLL 1 of KOH and 0.1 moLL1 of Le). The red suspension was mixed for 10 min. The autoclave was placed in an oven and heated at 50°C for 24 h with a temperature ramp of 2 h, then was heated to 150°C for 24 h with a temperature ramp of 2 h. A yellow precipitate was formed. The precipitate was centrifuged at 12000 rpm, washed 3 times with pure water, recentrifuged at 12000 rpm and dried in an oven for 1 day at 100°C. A yellow powder was obtained.

[0148] DRX: The peaks of the diffraction pattern obtained (Figure 3) corresponded to the signals of goethite (upper pattern = experimental diffraction pattern, lower pattern with squares = peaks expected for a goethite sample).

[0149] SEM: The particles measured by SEM were non-nanometric and had a needle-like morphology, as expected for goethite. The study of their dimensions showed that the median size of the small dimension was 146 nm with 20% of nanometric particles by number. The median size of the large dimension was 731 nm with 2% of nanometric particles by number (Figures 4A, 4B and 4C).

[0150] Color measurements: The color obtained in full tone was in the value range corresponding to the reference yellow with a dE*ab = 9.4 and the L*a*b* values ​​were L* = 57.6; a* = 12.02 and b* = 43.81. For the shaded tone in white, the color was also in the reference range with a dE*ab = 3.5 and the L*a*b* values ​​were L* = 72.31; a* = 4.26 and b* = 30.06.

[0151] Example 4 according to the invention: Synthesis of goethite from ferric ammonium oxalate trihydrate, i.e. 3 equivalents of ammonium oxalate relative to iron (150 g)

[0152] Protocol: A 2.5 L solution was prepared by dissolving 834.5 g of KOH in pure water (5.1 mol.L 1 ). Another 3.5 L solution of ferric ammonium oxalate trihydrate (Fe(NH4C2O4)3.3H2O) was prepared by dissolving 812.7 g in pure water (0.5 moLL 1 of Fe). The KOH solution was placed in a 12 L reactor protected by a HALAR lining and the ferric solution was added slowly (2.1 moLL 1 of KOH and 0.3 moLL 1of Fe). The red suspension was mixed for 20 min. The reactor was heated at 50°C for 24 h with a temperature ramp of 5 h, then was heated to 102°C for 22 h with a temperature ramp of 3.5 h. A yellow precipitate was formed and a pH of 14 was measured in the supernatant. The precipitate was filtered through a Büchner funnel, washed with 6.6 L of pure water and dried in an oven for 2 days at 100°C. A yellow powder was obtained.

[0153] DRX: The peaks of the diffraction pattern obtained (Figure 5) corresponded to the signals of goethite (upper pattern = experimental diffraction pattern, lower pattern with squares = peaks expected for a goethite sample).

[0154] SEM: The particles measured by SEM were non-nanometric and had a needle-like morphology, as expected for goethite. The study of their dimensions showed that the median size of the small dimension was 174 nm with 32% of nanometric particles by number. The median size of the large dimension was 1041 nm with 3% of nanometric particles by number (Figures 6A, 6B and 6C).

[0155] Color measurements: The color obtained in full tone was in the value range corresponding to the reference yellow with a dE*ab = 6.98 and the L*a*b* values ​​were L* = 54.6; a* = 13.63 and b* = 45.07. For the shaded tone in white, the color was also in the reference range with a dE*ab = 4.31 and the L*a*b* values ​​were L* = 70.69; a* = 5.75 and b* = 27.61.

[0156] Example 5 according to the invention: Synthesis of goethite from EeCE.ôI EO with 1 equivalent of oxalic acid dihydrate relative to iron.

[0157] Protocol: A 13.3 mL solution was prepared by dissolving 0.700 g of KOH and 0.196 g of oxalic acid dihydrate in pure water (0.8 moLL of KOH and 0.1 moLL of oxalic acid dihydrate). Another 2 mL solution of ferric chloride hexahydrate (FeCl.ôHaO) was prepared by dissolving 0.428 g in pure water (0.8 moLL 1 of Fe). The basic solution was placed in a 23 mL autoclave containing a PTFE chamber and the ferric solution was added dropwise (0.7 moLL 4of KOH, 0.1 moLL of oxalic acid dihydrate and 0.1 moLL of Fe). The red suspension was mixed for 10 min. The autoclave was placed in an oven and heated at 50°C for 24 h with a temperature ramp of 2 h, then was heated to 150°C for 24 h with a temperature ramp of 2 h. A yellow precipitate was formed and a pH of 14 was measured in the supernatant. The precipitate was centrifuged at 6000 rpm, washed 3 times with pure water, recentrifuged at 6000 rpm and dried in an oven for 1 day at 100°C. A yellow powder was obtained.

[0158] DRX: The peaks of the diffraction pattern obtained (Figure 7) corresponded to the signals of goethite (upper pattern = experimental diffraction pattern, lower pattern with squares = peaks expected for a goethite sample).

[0159] SEM: The particles observed by SEM were non-nanometric and had a needle-like morphology, as expected for goethite. The median size of the small dimension was 115 nm with 36% of nanometric particles by number. The median size of the large dimension was 569 nm with 3% of nanometric particles by number (Figures 8A, 8B and 8C).

[0160] Color measurements: The color obtained in full tone was in the value range corresponding to the reference yellow with a dE*ab = 12.67 and the L*a*b* values ​​were L* = 56.04; a* = 10.19 and b* = 40.32. For the shaded tone in white, the color was also in the reference range with a dE*ab = 3.77 and the L*a*b* values ​​were L* = 71.49; a* = 3.81 and b* = 29.59. Example 6 according to the invention: Synthesis of goethite from FeCh.61 LO with 1 equivalent of citric acid monohydrate relative to iron.

[0161] Protocol: A 13.3 mL solution was prepared by dissolving 0.758 g of KOH and 0.325 g of citric acid monohydrate in pure water (0.9 moLL 1 of KOH and 0.1 mol.L 1 citric acid monohydrate). Another 2 mE solution of ferric chloride hexahydrate (FeCF.6HzO) was prepared by dissolving 0.427 g in pure water (0.8 moLL 1 of Fe). The basic solution was placed in a 23 mL autoclave containing a PTFE chamber and the ferric solution was added dropwise (0.7 moLL 1 of KOH, 0.1 mol.L 1 of citric acid monohydrate and 0.1 moLL 1of Fe). The red suspension was mixed for 10 min. The autoclave was placed in an oven and heated at 50°C for 24 h with a temperature ramp of 2 h, then was heated to 150°C for 24 h with a temperature ramp of 2 h. A yellow precipitate was formed and a pH of 14 was measured in the supernatant. The precipitate was centrifuged at 6000 rpm, washed 3 times with pure water, recentrifuged at 6000 rpm and dried in an oven for 1 day at 100°C. A yellow powder was obtained.

[0162] DRX: The peaks of the diffraction pattern obtained (Figure 9) corresponded to the signals of goethite (upper pattern = experimental diffraction pattern, lower pattern with squares = peaks expected for a goethite sample).

[0163] SEM: The particles observed by SEM were non-nanometric and had a needle-like morphology. The median size of the small dimension was 109 nm with 41% of nanometric particles by number. The median size of the large dimension was 850 nm with 3% of nanometric particles by number (Figures 10A, 10B and 10C).

[0164] Color measurements: The color obtained in full tone was in the value range corresponding to the reference yellow with a dE*ab = 7.61 and the L*a*b* values ​​were L* = 55.96; a* = 11.19 and b* = 45.58. For the shaded tone in white, the color was also in the reference range with a dE*ab = 3.15 and the L*a*b* values ​​were L* = 70.73; a* = 4.45 and b* = 29.59.

[0165] Example 7: Synthesis of goethite from ferric sodium EDTA, i.e. 1 equivalent of sodium EDTA relative to iron

[0166] Protocol: A 10 mL solution was prepared by dissolving 0.550 g of KOH in pure water (0.8 mol.L 1 ). Another 1 mL solution of ferric sodium ethylenediaminetetraacetate (Fe-EDTA-Na) was prepared by dissolving 0.440 g in pure water (1.2 moLL' 1 of Fe). The KOH solution was placed in a 16 mL autoclave containing a PTFE chamber and the ferric solution was added dropwise (0.7 mol.L 1 of KOH and 0.1 moLL 1 of Fe). The red suspension was mixed for 10 min. The autoclave was placed in an oven and heated at 50°C for 24 h with a temperature ramp of 2 h, then heated at 150°C for 24 h with a temperature ramp of 2 h. A yellow precipitate was formed. The precipitate was centrifuged at 12000 rpm, washed 3 times with pure water, recentrifuged at 12000 rpm and dried in an oven for 1 day at 100°C. A yellow powder was obtained.

[0167] DRX: The peaks of the diffraction pattern obtained (Figure 11) corresponded to the signals of goethite (upper pattern = experimental diffraction pattern, lower pattern with squares = peaks expected for a goethite sample).

[0168] SEM: The particles observed by SEM were non-nanometric and had a rod-like morphology. The median size of the small dimension was 147 nm with 30% of nanometric particles by number. The median size of the large dimension was 505 nm with 9% of nanometric particles by number (Figures 12A, 12B and 12C).

[0169] Color measurements: The color obtained in full tone was in the value range corresponding to the reference yellow with a dE*ab = 1.56 and the L*a*b* values ​​were L* = 54.95; a* = 15.28 and b* = 52.66. For the shaded tone in white, the color was also in the reference range with a dE*ab = 3.07 and the L*a*b* values ​​were L* = 71.32; a* = 5.41 and b* = 29.15.

[0170] Example 8 according to the invention: Synthesis of goethite from LO with 1 equivalent of EDTA compared to iron.

[0171] Protocol: A 13.3 mL solution was prepared by dissolving 0.731 g of KOH and 0.448 g of ethylenediaminetetraacetic acid in pure water (0.8 moLL 1 of KOH and 0.1 mol.L 1 of ethylenediaminetetraacetic acid). Another 2 mL solution of ferric chloride hexahydrate (FeCF.ôHaO) was prepared by dissolving 0.426 g in pure water (0.8 moLL 1of Fe). The basic solution was placed in a 23 mL autoclave containing a PTFE chamber and the ferric solution was added dropwise (0.7 moLL 1 of KOH, 0.1 mol.L 1 of ethylenediaminetetraacetic acid and 0.1 moLL 1 of Fe). The red suspension was mixed for 10 min. The autoclave was placed in an oven and heated at 50°C for 24 h with a temperature ramp of 2 h, then was heated to 150°C for 24 h with a temperature ramp of 2 h. A yellow precipitate was formed and a pH of 14 was measured in the supernatant. The precipitate was centrifuged at 6000 rpm, washed 3 times with pure water and 1 time with ethanol, recentrifuged at 6000 rpm and dried in an oven for 1 day at 100°C. A yellow powder was obtained.

[0172] DRX: The peaks of the diffraction pattern obtained (Figure 13) corresponded to the signals of goethite (upper pattern = experimental diffraction pattern, lower pattern with squares = peaks expected for a goethite sample).

[0173] SEM: The particles observed by SEM were non-nanometric and had a needle-like morphology. The median size of the small dimension was 105 nm with 44% of nanometric particles by number. The median size of the large dimension was 662 nm with 4% of nanometric particles by number (Figures 14A, 14B and 14C).

[0174] Color measurements: The color obtained in full tone was in the value range corresponding to the reference yellow with a dE*ab = 13.29 and the L*a*b* values ​​were L* = 57.3; a* = 9.88 and b* = 40.09. For the shaded tone in white, the color was also in the reference range with a dE*ab = 3.67 and the L*a*b* values ​​were L* = 71.81; a* = 3.77 and b* = 30.01.

[0175] Example 9 according to the invention: Synthesis of goethite from EeCL.ôI I2O with 1 equivalent of acetic acid and 1 equivalent of oxalic acid dihydrate relative to iron.

[0176] Protocol: A 13.3 rnL solution was prepared by dissolving 0.707 g of KOH, 0.088 rnL of acetic acid and 0.214 g of oxalic acid dihydrate in pure water (0.8 moLL 1 of KOH, 0.1 mol.L 1 of acetic acid and 0.1 moLL 1of oxalic acid dihydrate). Another 2 rnL solution of ferric chloride hexahydrate (FeC.l3.6H2O) was prepared by dissolving 0.427 g in pure water (0.8 mol.L 1 of Fe). The basic solution was placed in a 23 rnL autoclave containing a PTFE chamber and the ferric solution was added dropwise (0.7 mol.L 1 of KOH, 0.1 mol.L 1 acetic acid, 0.1 moLL 1 of oxalic acid dihydrate and 0.1 moLL 1of Fe). The red suspension was mixed for 10 min. The autoclave was placed in an oven and heated at 50°C for 24 h with a temperature ramp of 2 h, then was heated to 150°C for 24 h with a temperature ramp of 2 h. A yellow precipitate was formed and a pH of 14 was measured in the supernatant. The precipitate was centrifuged at 6000 rpm, washed 3 times with pure water and 1 time with ethanol, recentrifuged at 6000 rpm and dried in an oven for 1 day at 100°C. A yellow powder was obtained.

[0177] DRX: The peaks of the diffraction pattern obtained (Figure 15) corresponded to the signals of goethite (upper pattern = experimental diffraction pattern, lower pattern with squares = peaks expected for a goethite sample).

[0178] SEM: The particles observed by SEM were non-nanometric and had a needle-like morphology. The median size of the small dimension was 127 nm with 27% of nanometric particles by number. The median size of the large dimension was 557 nm with 4% of nanometric particles by number (Figures 16A, 16B and 16C).

[0179] Color measurements The color obtained in full tone was in the value range corresponding to the reference yellow with a dE*ab = 12.87 and the L*a*b* values ​​were L* = 56.71; a* = 10.14 and b* = 40.28. For the shaded tone in white, the color was also in the reference range with a dE*ab = 3.89 and the L*a*b* values ​​were L* = 71.98; a* = 3.84 and b* = 29.61.

[0180] Table I below summarizes the results obtained from the examples according to the invention and the comparative examples mentioned above.

[0181] Table L Characterizations of iron (III) oxides obtained from different iron (III) salts (0.1 moLL 1 ) in the presence of KOH (0.7 moLL 1 ), except for example 4 where ferric ammonium oxalate trihydrate is present at a concentration of 0.3 moLL 1 and KOH has a concentration of 2.1 moLL 1 (1** corresponds to the small dimension of the to the large dimension of the particle; the concentrations

[0182]

[0183] with 1 e( of steel to the iron.

[0184] Protocol: The synthesis of goethite from FeCh.ôFFO with 1 equivalent of acetic acid per iron was carried out in a manner analogous to the protocol of Example 5. The results obtained are reported in Table II below.

[0185] DRX: the peaks of the diffraction pattern obtained corresponded to the signals of goethite.

[0186] SEM: The particles observed by SEM were non-nanometric and had a needle-like morphology. The median size of the small dimension was 105 nm with 43% of nanometric particles by number. The median size of the large dimension was 450 nm with 5% of nanometric particles by number.

[0187] Color measurements The color obtained in full tone was in the value range corresponding to the reference yellow with a dE*ab = 12.3 and the L*a*b* values ​​were

[0188] L* = 56.34; a* = 10.05 and b* = 40.86. For the gradient tone in white, the color was also within the reference range with a dE*ab = 4.11 and the L*a*b* values ​​were L* = 71.98; a* = 3.68 and b* = 29.45. of steel to the iron.

[0189] Protocol: The synthesis of goethite from FeCh.ôFFO with 1 equivalent of lactic acid per iron was carried out in a manner analogous to the protocol of Example 5. The results obtained are reported in Table II below.

[0190] DRX: the peaks of the diffraction pattern obtained corresponded to the signals of goethite.

[0191] SEM: The particles observed by SEM were non-nanometric and had a needle-like morphology. The median size of the small dimension was 111 nm with 39% of nanometric particles by number. The median size of the large dimension was 426 nm with 1% of nanometric particles by number.

[0192] Color measurements The color obtained in full tone was in the value range corresponding to the reference yellow with a dE*ab = 9.64 and the L*a*b* values ​​were L* = 55.17; a* = 10.91 and b* = 43.2. For the shaded tone in white, the color was also in the reference range with a dE*ab = 6.8 and the L*a*b* values ​​were L* = 72.28; a* = 2.9 and b* = 26.45.

[0193] Example 12 according to the invention: Synthesis of goethite from FeCh.6112O with 1 equivalent of glycine relative to iron.

[0194] Protocol: The synthesis of goethite from FeCh.ôFFO with 1 equivalent of glycine per iron was carried out in a manner analogous to the protocol of Example 5. The results obtained are reported in Table II below.

[0195] DRX: the peaks of the diffraction pattern obtained corresponded to the signals of goethite.

[0196] SEM: The particles observed by SEM were non-nanometric and had a needle-like morphology. The median size of the small dimension was 104 nm with 47% of nanometric particles by number. The median size of the large dimension was 402 nm with 5% of nanometric particles by number.

[0197] Color measurements: The color obtained in full tone was in the value range corresponding to the reference yellow with a dE*ab = 12.22 and the L*a*b* values ​​were L* = 55.36; a* = 10.06 and b* = 40.76. For the shaded tone in white, the color was also in the reference range with a dE*ab = 4.81 and the L*a*b* values ​​were L* = 72.12; a* = 3.35 and b* = 28.75.

[0198] Example 13 according to the invention: Synthesis of goethite from FeCh.6H2O with 1 equivalent of 2,6-pyridinedicarboxylic acid relative to iron.

[0199] Protocol: The synthesis of goethite from FeCh.ôFFO with 1 equivalent of 2,6-pyridinedicarboxylic acid per iron was carried out in a manner analogous to the protocol of Example 5. The results obtained are reported in Table II below.

[0200] DRX: the peaks of the diffraction pattern obtained corresponded to the signals of goethite.

[0201] SEM: The particles observed by SEM were non-nanometric and had a needle-like morphology. The median size of the small dimension was 117 nm with 35% of nanometric particles by number. The median size of the large dimension was 513 nm with 6% of nanometric particles by number.

[0202] Color measurements: The color obtained in full tone was in the value range corresponding to the reference yellow with a dE*ab = 13.95 and the L*a*b* values ​​were L* = 55.69; a* = 9.69 and b* = 39.06. For the shaded tone in white, the color was also in the reference range with a dE*ab = 5.43 and the L*a*b* values ​​were L* = 72.08; a* = 3.26 and b* = 27.91. from FeCh.61 EO with 1 to the iron.

[0203] Protocol: The synthesis of goethite from FeCh.ôFFO with 1 equivalent of 5-sulfosalicylic acid dihydrate per iron was carried out analogously to the protocol of Example 5.

[0204] The results obtained are reported in Table II below.

[0205] DRX: the peaks of the diffraction pattern obtained corresponded to the signals of goethite.

[0206] SEM: The particles observed by SEM were nanometric and had a needle-like morphology. The median size of the small dimension was 90 nm with 66% of nanometric particles by number. The median size of the large dimension was 276 nm with 1% of nanometric particles by number.

[0207] Color measurements The color obtained in full tone was in the value range corresponding to the reference yellow with a dE*ab = 7.95 and the L*a*b* values ​​were L* = 55; a* = 10.94 and b* = 45.06. For the shaded tone in white, the color was also in the reference range with a dE*ab = 4.52 and the L*a*b* values ​​were L* = 72.31; a* = 3.57 and b* = 29.09. with 1 e( of steel to the iron.

[0208] The synthesis of goethite from FeCh.ôFFO with 1 equivalent of nitrilotriacetic acid per iron was carried out in a manner analogous to the protocol of Example 5. The results obtained are reported in Table II below.

[0209] DRX: the peaks of the diffraction pattern obtained corresponded to the signals of goethite.

[0210] The particles observed by SEM were non-nanometric and had a needle-like morphology. The median size of the small dimension was 102 nm with 48% of nanometric particles by number. The median size of the large dimension was 732 nm with 3% of nanometric particles by number. Color measurements The color obtained in full tone was in the value range corresponding to the reference yellow with a dE*ab = 15.08 and the L*a*b* values ​​were L* = 57.78; a* = 9.3 and b* = 38.46. For the shaded tone in white, the color was also in the reference range with a dE*ab = 4.88 and the L*a*b* values ​​were L* = 72.06; a* = 3.38 and b* = 28.58. of steel to the iron.

[0211] Protocol: The synthesis of goethite from FeCh.ôFFO with 1 equivalent of sahcylic acid per iron was carried out in a manner analogous to the protocol of Example 5. The results obtained are reported in Table II below.

[0212] DRX: the peaks of the diffraction pattern obtained corresponded to the signals of goethite.

[0213] SEM: The particles observed by SEM were nanometric and had a ball-shaped morphology. The median size of the small dimension was 61 nm with 94% of nanometric particles by number. The median size of the large dimension was 134 nm with 12% of nanometric particles by number. The color obtained in full tone was in the value range corresponding to the reference yellow with a dE*ab = 11.58 and the L*a*b* values ​​were L* = 57.87; a* = 10.05 and b* = 41.36. For the shaded tone in white, the color was also in the reference range with a dE*ab = 5.26 and the L*a*b* values ​​were

[0214] L* = 72.18; a* = 3.02 and b* = 28.43. of steel to the iron.

[0215] Protocol: The synthesis of goethite from FeCh.ôFFO with 1 equivalent of hydroxyethylethylenediaminetriacetic acid (HEDTA) per iron was carried out in a manner analogous to the protocol of Example 5. The results obtained are reported in Table II below.

[0216] XRD: The peaks in the diffraction pattern obtained (Figure 17) corresponded to the signals of goethite (upper pattern = experimental diffraction pattern, lower pattern with squares = expected peaks for a goethite sample). SEM: The particles observed by SEM were non-nanometric and had a rod-like morphology. The median size of the small dimension was 149 nm with 19% of nanometric particles by number. The median size of the large dimension was 863 nm with 6% of nanometric particles by number (Figures 18A, 18B and 18C). The color obtained in full tone was in the value range corresponding to the reference yellow with a dE*ab = 13.23 and the L*a*b* values ​​were L* = 56.1; a* = 9.98 and b* = 39.8. For the shaded tone in white, the color was also in the reference range with a dE*ab = 4.12 and the L*a*b* values ​​were

[0217] L* = 70.85; a* = 3.88 and b* = 28.82. 4,5-dil acid disodium to the iron.

[0218] The synthesis of goethite from FeCh.ôHiO with 1 equivalent of 4,5-dihydroxy-1,3-benzenedisulfonic acid disodium monohydrate (Tiron) per iron was carried out in a manner analogous to the protocol of Example 5. The results obtained are reported in Table II below.

[0219] DRX: the peaks of the diffraction pattern obtained corresponded to the signals of goethite.

[0220] The particles observed by SEM were nanometric and had a needle-like morphology. The median size of the small dimension was 96 nm with 56% of nanometric particles by number. The median size of the large dimension was 322 nm with 3% of nanometric particles by number. The color obtained in full tone was in the value range corresponding to the reference yellow with a dE*ab = 19.1 and the L*a*b* values ​​were

[0221] L* = 53.1; a* = 7.27 and b* = 34.34. For the gradient tone in white, the color was also within the reference range with a dE*ab = 5.81 and the L*a*b* values ​​were L* = 70.61; a* = 2.81 and b* = 27.48. goethite from FeCh.6Ü2O with 3 to the iron.

[0222] Protocol: A 13.3 mL solution was prepared by dissolving 1.405 g of KOH and 0.586 g of oxalic acid dihydrate in pure water (1.6 mol.L 4 of KOH and 0.3 mol.L4 of oxalic acid dihydrate). Another 2 mL solution of ferric chloride hexahydrate (FeCh.ôlUO) was prepared by dissolving 0.429 g in pure water (0.8 mol.L 4 of Fe). The basic solution was placed in a 23 mL autoclave containing a PTFE chamber and the ferric solution was added dropwise (1.4 mol.L 4 of KOH, 0.3 mol.L 4 of oxalic acid dihydrate and 0.1 mol.L 4 of Fe). The red suspension was mixed for 10 min. The autoclave was placed in an oven and heated at 50°C for 24 h with a temperature ramp of 2 h, then was heated to 150°C for 24 h with a temperature ramp of 2 h. A yellow precipitate was formed and a pH of 14 was measured in the supernatant. The precipitate was centrifuged at 6000 rpm, washed 3 times with pure water, recentrifuged at 6000 rpm and dried in an oven for 1 day at 100°C. A yellow powder was obtained.

[0223] DRX: The peaks of the diffraction pattern obtained (Figure 19) corresponded to the signals of goethite (upper pattern = experimental diffraction pattern, lower pattern with squares = peaks expected for a goethite sample).

[0224] SEM: The particles observed by SEM were non-nanometric and had a needle-like morphology. The median size of the small dimension was 124 nm with 37% of nanometric particles by number. The median size of the large dimension was 521 nm with 2% of nanometric particles by number (Figures 20A, 20B and 20C). The color obtained in full tone was in the value range corresponding to the reference yellow with a dE*ab = 11.83 and the L*a*b* values ​​were

[0225] L* = 57.65; a* = 10.12 and b* = 41.78. For the gradient tone in white, the color was also within the reference range with a dE*ab = 3.31 and the L*a*b* values ​​were L* = 71.98; a* = 4.02 and b* = 30.51. goethite from FeCh.6H2O with 3 to the iron.

[0226] Protocol: The synthesis of goethite from FeCF.ôHiO with 3 equivalents of citric acid monohydrate per iron was carried out in a manner analogous to the protocol of Example 19. The results obtained are reported in Table II below.

[0227] DRX: The peaks of the diffraction pattern obtained (Figure 21) corresponded to the signals of goethite (upper pattern = experimental diffraction pattern, lower pattern with squares = peaks expected for a goethite sample).

[0228] SEM: The particles observed by SEM were non-nanometric and had a rod-shaped morphology. The median size of the small dimension was 155 nm with 26% of nanometric particles by number. The median size of the large dimension was 701 nm with 11% of nanometric particles by number (Figures 22A, 22B and 22C). color The color obtained in full tone was in the value range corresponding to the reference yellow with a dE*ab = 20.44 and the L*a*b* values ​​were

[0229] L* = 42.17; a* = 15.54 and b* = 35.02. For the gradient tone in white, the color was also in the reference range with a dE*ab = 13.43 and the L*a*b* values ​​were L* = 64.9; a* = 6.9 and b* = 19.6. èse of goethite from eCh.ôILO with 3 er.

[0230] Protocol: The synthesis of goethite from FeCh.ôHiO with 3 equivalents of EDTA per iron was carried out in a similar manner to the protocol of Example 19. The results obtained are reported in Table II below.

[0231] DRX: The peaks of the diffraction pattern obtained (Figure 23) corresponded to the signals of goethite (upper pattern = experimental diffraction pattern, lower pattern with squares = peaks expected for a goethite sample).

[0232] SEM: The particles observed by SEM were non-nanometric and had a needle-like morphology. The median size of the small dimension was 137 nm with 33% of nanometric particles by number. The median size of the large dimension was 502 nm with 6% of nanometric particles by number (Figures 24A, 24B and 24C).

[0233] Color measurements The color obtained in full tone was in the value range corresponding to the reference yellow with a dE*ab = 13.5 and the L*a*b* values ​​were L* = 56.91; a* = 9.87 and b* = 39.74. For the shaded tone in white, the color was also in the reference range with a dE*ab = 4.06 and the L*a*b* values ​​were

[0234] L* = 71.97; a* = 3.87 and b* = 29.28. ese of aoethite from FeCh.6112O with 0.1 to the iron.

[0235] Protocol: A 13.3 mL solution was prepared by dissolving 0.698 g of KOH and 0.919 g of polyethylene glycol having a molar mass of 6000 g. mol' 1 in pure water (0.80 moLL' 1 of KOH and 0.01 mol.L 1 of polyethylene glycol). Another 2 mL solution of ferric chloride hexahydrate (FeC.l3.6H2O) was prepared by dissolving 0.428 g in pure water (0.77 mol.L' 1 of

[0236] Fe). The basic solution was placed in a 23 mL autoclave containing a PTFE chamber and the ferric solution was added dropwise (0.69 moLL' 1 of KOH, 0.01 moLL' 1 of polyethylene glycol and 0.10 moLL' 1 of Fe). The red suspension was mixed for 10 min. The autoclave was placed in an oven and heated at 50°C for 24 h with a temperature ramp of 2 h, then was heated to 150°C for 24 h with a temperature ramp of 2 h. A yellow precipitate was formed and a pH of 14 was measured in the supernatant. The precipitate was centrifuged at 6000 rpm, washed 3 times with pure water and 1 time with ethanol, recentrifuged at 6000 rpm and dried in an oven for 1 day at 100°C. A yellow powder was obtained.

[0237] DRX: The peaks of the diffraction pattern obtained (Figure 25) corresponded to the signals of goethite (upper pattern = experimental diffraction pattern, lower pattern with squares = peaks expected for a goethite sample).

[0238] SEM: The particles observed by SEM were non-nanometric and had a needle-like morphology. The median size of the small dimension was 103 nm with 47% of nanometric particles by number. The median size of the large dimension was 463 nm with 4% of nanometric particles by number (Figures 26A, 26B and 26C).

[0239] The strength of the complexing agent can be measured by looking at the value of the overall formation constant Kf of the complex in solution following the following reaction (M = metal; L = ligand):

[0240] M + nL = ML n (1)

[0241] Kf„ = [ML n ] / [M].[L]" (2)

[0242] Log(Kfn ) = log ([ML n ] / [M].[L]") (3)

[0243] For a complex containing n ligands, we can determine its Kf n from the concentration values ​​of the species involved and thus obtain the log(Kf n ). The inventors based themselves on the values ​​of log(Kf n ) of complexing agents present in the literature (eg, Lange's Handbook of Chemistry; 15th Edition; Section 8 Electrolytes, Electromotive Force, and Chemical Equilibrium, section 8.2.2)

[0244] The inventors observed that the strength of the complexing agent as well as its nature impacted the size but also the morphology of the goethite particles formed. Some complexing agents such as salicylic acid or 5-sulphosalicylic acid inhibited the growth of goethite along its large dimension while, conversely, nitrilotriacetic acid or ethylenediaminetetraacetic acid (EDTA) promoted growth along this dimension. Too high a complexation constant value could also severely limit or even prevent the precipitation of goethite, leaving the iron in solution. This was the case, for example, with 4,5-dihydroxy-1,3-benzenedisulfonic acid disodium monohydrate (Tiron). There is therefore a range of values ​​of log(Kf n) for which the complexing agents promote the growth of non-nanometric particles. Preferred agents according to the invention are oxalic acid, citric acid, ethylenediaminetetraacetic acid (EDTA) and hydroxyethylethylenediaminetriacetic acid (HEDTA).

[0245] Table II Characterizations of goethites obtained from different complexing agents (L* corresponds to the large particle size, 1** corresponds to the small particle size, G corresponds to goethite; the concentrations correspond to the values ​​of the species present in the basic aqueous ferric suspension of step a).

[0246] Example 23 according to the invention: Synthesis of hematite from FeCF.ôILO with 2 equivalents of oxalic acid dihydrate relative to iron.

[0247] Protocol: A 9.2 mL solution was prepared by dissolving 0.502 g of KOH and 0.282 g of oxalic acid dihydrate in pure water (0.8 moLL of KOH and 0.2 moLL of oxalic acid dihydrate). Another 1.4 mE solution of ferric chloride hexahydrate (FeC.l3.6H2O) was prepared by dissolving 0.307 g in pure water (0.8 moLL 4 of Fe). The KOH solution was placed in a 16 mL autoclave containing a PTFE chamber and the ferric solution was added dropwise (0.7 moLL 4of KOH, 0.2 moLL of oxalic acid dihydrate and 0.1 moLL of Fe). The red suspension was mixed for 10 min. The autoclave was placed in an oven and heated at 50°C for 24 h with a temperature ramp of 2 h, then was heated to 150°C for 24 h with a temperature ramp of 2 h. A red precipitate was formed and a pH of 11.06 was measured in the supernatant. The precipitate was centrifuged at 6000 rpm, washed 3 times with pure water and 1 time with ethanol, recentrifuged at 6000 rpm and dried in an oven for 1 day at 100°C. A red powder was obtained.

[0248] DRX: The peaks of the diffraction pattern obtained (Figure 27) corresponded to the signals of hematite (upper pattern = experimental diffraction pattern, lower pattern with squares = peaks expected for a hematite sample).

[0249] SEM: The particles observed by SEM were non-nanometric and had a spherical morphology. The median size of the small dimension was 187 nm with 7% of nanometric particles by number. The median size of the large dimension was 250 nm with 2% of nanometric particles by number (Figures 28A, 28B and 28C).

Claims

CLAIMS 1. A method for preparing non-nanometric iron oxide particles, said iron oxide particles being goethite particles, hematite particles or a mixture of goethite and hematite particles, comprising the following steps: (a) the preparation of a basic aqueous suspension of iron by mixing: (i) a basic aqueous solution comprising at least one complexing agent, with a ferric aqueous solution comprising at least one iron (III) salt, said at least one complexing agent being identical to or different from the counterion of said at least one iron (III) salt, or (ii) a basic aqueous solution with an aqueous ferric solution comprising an iron (III) salt complex consisting of at least one iron (III) salt and a complexing agent present in the form of a counterion of said at least one iron (III) salt; (b) heating the basic aqueous iron suspension obtained in step (a) to a temperature between 50°C and 350°C so as to obtain a precipitate of iron oxides; (c) separating, washing and drying the precipitate obtained in step (b).

2. Method according to claim 1, characterized in that said at least one complexing agent is water-soluble and comprises at least one function chosen from the group consisting of carboxylic acid, thiocarboxylic acid, amine, alcohol, ether, sulfonic acid, phosphonic acid, phosphoric acid, polymer functions, their basic forms, and their mixtures.

3. Method according to claim 1 or 2, characterized in that said at least one complexing agent used in step (a)(i) is chosen from the group consisting of acetic acid, lactic acid, oxalic acid, glycine, 2,6-pyridine-dicarboxylic acid, citric acid, nitriletriacetic acid, polyethylene glycol (PEG), hydroxyethylethylenediaminetriacetic acid (HEDTA), ethylenediaminetetraacetic acid (EDTA), their basic forms, and their mixtures.

4. Method according to any one of claims 1 to 3, characterized in that said at least one complexing agent used in step (a)(i) is chosen from the group consisting of oxalic acid, citric acid, HEDTA, EDTA, their basic forms, and their mixtures, preferably is oxalic acid or citric acid or their basic form.

5. Method according to any one of claims 1 to 4, characterized in that said at least one complexing agent used in step (a)(i) has a log(K) of between 1 and 30, preferably between 3 and 26, even more preferably between 19 and 25, this log(K) corresponding to the highest log(K) between log(K1), log(K2) and log(K3).

6. Method according to any one of claims 1 to 5, characterized in that said at least one iron (III) salt used in step (a)(i) is chosen from the group consisting of ferric chloride, ferric nitrate and ferric sulfate.

7. Process according to any one of claims 1 to 5, characterized in that the iron (III) salt complex used in step (a)(ii) is ferric ammonium oxalate trihydrate or ferric sodium ethylenediaminetetraacetate or ferric citrate.

8. Method according to any one of claims 1 to 7, characterized in that the basic aqueous solution comprises an alkaline agent chosen from the group consisting of lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide, and a mixture of the latter, preferably sodium hydroxide, potassium hydroxide and a mixture of the latter.

9. Method according to any one of claims 1 to 8, characterized in that the iron oxide particles are goethite particles.

10. Non-nanometric iron oxide particles obtained by the method according to any one of claims 1 to 9, said iron oxide particles being goethite particles, hematite particles or a mixture of goethite and hematite particles, preferably goethite particles.

11. Non-nanometric iron oxide particles, characterized in that the iron oxide particles are goethite particles or a mixture of goethite and hematite particles, and the number median size of the minor dimension and major dimension of the primary particles is greater than 100 nm.

12. Iron oxide particles according to claim 11, characterized in that the number median size of the small dimension of the primary particles is between 100 nm and 200 nm, and the ratio between the number median size of the large dimension and the small dimension of the primary particles is greater than 3.

13. Iron oxide particles according to claim 11 or 12, characterized in that the iron oxide particles are goethite particles having the following L*, a* and b* values, measured in CIELAB units: - in full tone, an L* value between 42 and 58, an a* value between 7 and 16, and a b* value between 34 and 53, or - in reduced tone in white, an L* value between 64 and 73, an a* value between 2 and 7, and a b* value between 19 and 34.

14. Cosmetic composition comprising iron oxide particles according to any one of claims 10 to 13.

15. Use of iron oxide particles according to any one of claims 10 to 13, as pigments in a cosmetic composition.

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