Cosmetic compositions based on Janus particles

Abstract

A cosmetic composition comprising Janus particles, an aqueous phase, and an organic phase employs Janus particles produced by a process comprising preparing hollow particles (1) from a material with a surface energy α, the hollow particles (1) having two discontinuous surfaces: an accessible outer surface (2) and an inaccessible inner surface (3). The surface energy of the outer surface (2) is thereby modified to produce particles (11) with inner surface energies α and β. The modified particles (11) are then milled to obtain particles comprised of small spherical-cap-shaped fragments (21) having an outer surface (12) with the modified energy and an inner surface (13) with an unmodified inner energy. [Selected Figure] Figure 2

Description

[Technical Field]

[0001] The present invention relates to cosmetic compositions based on Janus particles. [Background technology]

[0002] The present invention generally relates to the preparation of amphiphilic particles that can mechanically stabilize the interface between two immiscible liquids to form stable emulsions without the use of molecular emulsifiers. Emulsions stabilized in this way are known in the scientific literature as Pickering emulsions and are known to form thermodynamically stable emulsions.

[0003] It is also known that the stability of Pickering emulsions, when obtained using so-called Janus particles, significantly exceeds that of emulsions obtained with molecular emulsifiers.

[0004] Cosmetics containing water as one of the main ingredients are increasingly popular due to economic and sustainability reasons, as well as the refreshing sensation inherent in such formulations. Most of these consist of water-in-oil (silicone) or oil-in-water (silicone) emulsions. These emulsions are characterized by the presence of two immiscible phases, one dispersed within the other, typically stabilized by emulsifiers and / or co-emulsifiers. Emulsifiers are amphiphilic molecules with varying molecular weights (usually less than 1000 Da) and can be of various natures (ionic or nonionic). The droplet size of the dispersed phase is known to be a fundamental property that influences the appearance, sensory properties, and stability of the emulsion itself.

[0005] On the other hand, Pickering emulsions are based on solid materials that have a contact angle of approximately 90° with the two liquids used in the emulsion. This means that the material is independently wetted by one or the other liquid. When this material is pulverized into a powder, it absorbs and remains sequestered at the interface between the two liquids. Eventually, the particles cover the entire interface, stabilizing the emulsion against aggregation and coalescence. This effect can only be achieved by appropriately selecting the liquid phase and the materials involved. The interfacial energy between a solid and a liquid can be defined as the sum of the energy contributions between the liquid molecules and the chemical functions exposed on the solid's surface. These contributions can be classified as polar, dispersive (van der Waals), acid-base, or hydrogen-bonding mediator. Amphiphilic surfaces have an affinity for both water and oil; that is, they have surface properties that dictate equivalent interfacial energies for water and oil, respectively. Therefore, solids do not have a preference for being wetted by either water or oil. By micronizing this material into a powder, the solid particles can migrate to the water-oil interface and mechanically prevent the dispersed phase from coalescing, thereby acting as an emulsifier. While the surface properties of such materials are uniform, amphiphilic materials are rare and difficult to engineer. Therefore, because powders of certain materials act as solid emulsifiers for a limited range of immiscible liquids (surface tension), it is clear that the method cannot be easily generalized to all types of formulations.

[0006] This problem can be solved by using Janus particles, which are particles that have different faces (e.g., hydrophobic and hydrophilic), each of which preferentially wets one of two phases (e.g., oil and water).

[0007] Janus particles, named after the two-faced Roman god, are an evolution of the amphiphilic particles described above. Janus particles have surfaces with different affinities (surface energies) depending on the region of the particle itself. For example, flake-shaped Janus particles are characterized by hydrophilic and hydrophobic surfaces. Janus particles are superior to powder emulsifiers, which have uniform (undistinguished) surface energies. This is because their interaction with the liquid phase of the emulsion is specific: the hydrophilic surface interacts with the water phase, and the hydrophobic surface interacts with the oil (silicone) phase. As a result, the particles migrate to the liquid-liquid interface and become irreversibly sequestered there. Janus particles can be manufactured using a variety of techniques described in the literature, but these techniques share the commonality of low yields and multiple manufacturing steps.

[0008] Indeed, Janus particles today (see Non-Patent Documents 1 to 6 listed below) are produced at low yields using sophisticated methods, which cannot be implemented efficiently and cost-effectively. Therefore, to the best of our knowledge, Janus particles are not currently on the market as one of the raw materials used in the cosmetic and other industrial fields. [Prior art documents] [Non-patent literature]

[0009] [Non-Patent Document 1] Chariya Kaewsaneha et al., “Preparation of Janus Colloidal Particles Via Pickering Emulsion: An Overview”, Colloids and Surfaces A: Physiochemical and Engineering Aspects‐Volume 439, 20 December 2013, pages 35-42. [Non-patent document 2] Yunoi Yang et al., “An Overview of Pickering Emulsions: Solid‐Particle Materials, Classification, Morphology, and Applications”, Frontiers in Pharmacology, 1 May 2017, Volume 8, Article 287. [Non-patent document 3] Fuxin Liang et al., “Rational Design and Synthesis of Janus Composites”, Advanced Materials, Volume 26, art 40, 29 October 2014, pages 6944-6949. [Non-patent document 4] Yoshimune Nonomura et al., “Adsorption of Disk Shaped Janus Beads at Liquid-Liquid Interfaces”, Langmuir, 2004, 20, 11821-11823. [Non-Patent Document 5] BPBinks et al., “Particles Adsorbed at the Oil-Water Interface: Theoretical Comparison between Spheres of Uniform Wettability and “Janus” Particles”, Langmuir, 2001, 17, 4708-4710. [Non-patent document 6] Jie Wu et al., “Recent Studies of Pickering Emulsions: Particles Make the Difference”, Small, Volume 12, Part 34, 14 September 2016, pages 4633-4640. Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention provides a specific method for producing Janus particles that can be used in cosmetic applications, and because the material is not nanometer-sized (compared to non-Janus solid emulsifiers on the market), it does not pose safety issues for consumers. [Effects of the Invention]

[0011] According to the present invention, Janus particles are used in the function of "solid emulsifiers" in cosmetic formulations to create emulsions that can have the appearance of standard emulsions or that can feature special visual and sensory effects as a function of the formulation itself, both in the mass state and during application (e.g., stable macroemulsions in which droplets of the dispersed phase are visible to the naked eye). These new product types have significant advantages, one of which is the absence of traditional molecular emulsifiers, which can be irritating to the skin. Indeed, skin care and makeup products are particularly required to improve and in any case respect the physiological functions of the skin. Therefore, emulsions that do not contain traditional emulsifiers represent a significant improvement in the art.

[0012] Furthermore, the exceptional stability of such emulsions may pave the way for new emulsions characterized by low viscosity. DETAILED DESCRIPTION OF THE INVENTION

[0013] The primary objective of the present invention is to provide a cosmetic composition using a new method that allows Janus particles, which can be used in emulsions for making cosmetics, to be easily produced using conventional equipment and at low production costs. Furthermore, the new method for producing Janus particles according to the present invention allows for production of tens of kilograms per hour. Another objective of the present invention is to use such Janus particles in the formulation of cosmetics for face, eye, lip, or body makeup and skin care.

[0014] In the prior art, various techniques can be used to modify the surface energy of materials. When applied to powdered materials, such methods nonspecifically modify the surface, i.e., modify all surfaces accessible to the treatment (chemical or physical). A "physical treatment" is the deposition of a layer of material whose molecules are not covalently bonded to the surface, for example, by deposition or casting from a solvent. On the other hand, a "chemical treatment" is the deposition of a layer of material whose molecules are covalently bonded to the surface. Both of these treatments change the surface energy of the original surface, but physical treatments can be removed by separation methods (e.g., extraction), while chemical treatments are more stable because they require the breaking of covalent bonds formed between the treating agent and the surface itself.

[0015] The conversion of a hydrophilic surface to a hydrophobic surface is possible, for example, by using well-known chemical functionalization techniques (chemical sol-gel). The techniques used in the prior art do not allow for precise localization of the particle's modified regions, and the entire surface is usually modified. It is necessary to protect part of the particle's surface from surface modification. This protection method is described in the literature, but it employs wet techniques and has low yields.

[0016] Powdered materials in the form of hollow spheres (spherical bubbles) are inherently self-protective: each particle can be divided into two surfaces: an inner surface that is inaccessible to treatments, and an outer surface that is accessible to treatments.

[0017] The method according to the present invention involves functionalizing the outer surface of the particles by any method known in the art. After functionalization, the particles have a "protected" non-functionalized surface and an exposed functionalized surface. The material is then crushed to expose the non-functionalized surface, ultimately resulting in Janus particles. If the original material has the morphology of a hollow sphere, spherical cap-shaped particles can be obtained after processing and crushing.

[0018] There are many different materials on the market that have microbubble morphology. One category consists of glass (e.g., Glass Microbubbles from 3M). Another example consists of hollow microspheres made of plastic materials (e.g., Expancel from Akzo Nobel). However, any powdered material characterized by an inner surface and an outer surface (bubble or shell) can be used in the present invention. This type of material is becoming increasingly available on the market. Indeed, this type of material has the function of a functional excipient and allows for very low specific weight formulations.

[0019] The cosmetic composition according to the present invention is defined in claim 1.

[0020] The method for producing Janus particles that can be used in the cosmetic composition of the present invention involves the following series of steps, as shown in the accompanying Figures 1 and 2:

[0021] 1) Hollow particle 1 (e.g., a spherical bubble shape as shown on the left side of Figure 1) is a material with surface energy α (e.g., a contact angle with water W CA -Hydrophilic material with α<90° or W CA The hollow particle 1 is made of a hydrophobic material (with a surface energy β greater than or equal to α) and is characterized by two discontinuous surfaces: an outer (accessible) surface 2 and an inner (inaccessible) surface 3. The surface energy of the outer surface of such a hollow particle 1 is modified chemically or physically (e.g., by chemical coating) to produce a modified particle 11, as shown on the right side of Figure 1. The resulting hollow particle 11 has a modified surface energy β (larger or smaller than α) and a modified contact angle with water (W CA -β>W CA -α or W CA -β <W CAThe surface is characterized by an outer surface 12 (α) and an inner surface 13 that has not been modified by the modification treatment and has an original surface energy α. The surface treatment agent can be, for example, a copolymer of polymethylhydrosiloxane, or triethoxysilane and / or trimethoxysilane. In the case of physical modification, the modifying material can be deposited by evaporating a volatile solvent or by depositing a molten material followed by solidification.

[0022] 2) The particles 11 (shown on the left side of Figure 2) are then crushed (center of Figure 2) using any crushing technique capable of breaking down the particles 11, resulting in small spherical-crown-shaped fragments (particles 21). The smaller the solid angle subtended by the spherical cap, the more closely it resembles a flat shape. By breaking down the treated hollow spheres, the unmodified inner surface 13 becomes accessible, thereby creating Janus particles (right side of Figure 2).

[0023] By using Janus particles produced in this manner, a cosmetic composition can be obtained that comprises an aqueous phase and an organic phase, contains 0.01% to 99.99% by weight of Janus particles, and has a total of 0.01% to 99.99% by weight of the aqueous phase and the organic phase.

[0024] In particular, cosmetic compositions can be obtained that contain 10% to 90% by weight of an organic phase. The aqueous phase can be 90% to 10% by weight, and Janus particles can be 20% to 0.01% by weight, with the aqueous phase dispersed in the organic phase (water-in-oil (silicone) emulsion) or vice versa (oil-in-water / silicone emulsion). Cosmetic compositions can also be obtained that contain 0.01% to 10% by weight of an organic phase, 10% to 70% by weight of an aqueous phase, and 10% to 90% by weight of Janus particles.

[0025] The aqueous phase may consist of water and water-soluble and / or water-dispersible substances, and the organic phase may consist of oils from the class of triglycerides, and / or esters, and / or glyceryl esters, and / or silicones, and / or other cosmetically acceptable oils, and mixtures of each of these, and may contain one or more oils and oil-soluble and / or oil-dispersible substances. [Example]

[0026] Below are some examples of the preparation of Janus particles according to the present invention and their use in forming emulsions and other preparations suitable for cosmetic applications.

[0027] Example 1 - Preparation of Janus particles (hydrophilic silicone) by functionalizing hollow hydrophilic glass particles with dimethicone 200 g of hollow glass particles with an average diameter of 100 μm were added to a powder mixer and gently mixed at 100 rpm for 5 minutes. After adding 4 g of a surface treatment agent (polymethylhydrosiloxane-polydimethylsiloxane copolymer), the mixture was stirred for an additional 5 minutes. The resulting mixture was heat-treated in air at 150°C for 24 hours. After heat treatment, the mixture was allowed to cool. The coated hollow particles had a surface energy of less than 0.00033 N (33 dyn) / cm. These particles were then milled using an air jet mill at a feed rate of 10 g / min and 700 kPa (7 bar) (feeding and milling chamber). The final particle size distribution, measured by a laser diffraction particle sizer, was between 0.1 μm and 20 μm.

[0028] Example 2 - Preparation of Janus particles (hydrophilic aliphatic compounds) by functionalizing hydrophilic glass hollow particles with benzylcarbamoylpropyl polysilsesquioxane Add 200 g of hollow glass particles with an average diameter of 200 μm to a heated powder mixer and gently mix at 60 rpm for 5 minutes. Add 4 g of phenylcarbamoylpropyltriethoxysilane as a surface treatment agent, then heat the mixture to 80°C and mix thoroughly for 1 hour. Add 1 g of a dilute acid solution as a catalyst to the mixer and continue mixing at 80°C for 2 hours. Allow the mixture to cool. The coated hollow particles have a surface energy of less than 0.00033 N (33 dyn) / cm. Then, vigorously mix the particles at 3000 rpm to break the hollow shells in situ, ensuring a final particle size distribution between 0.1 μm and 20 μm.

[0029] Example 3 - Preparation of Janus particles (hydrophilic aliphatic compounds) by functionalizing hollow hydrophilic glass particles with triethoxycaprylylsilane Add 200 g of hollow glass particles with an average diameter of 200 μm to a heated powder mixer and gently mix at 60 rpm for 5 minutes. Add 4 g of triethoxycaprylylsilane as a surface treatment agent, then heat the mixture to 80°C and mix thoroughly for 1 hour. Add 1 g of a dilute acid solution as a catalyst to the mixer and continue mixing at 80°C for 2 hours. Allow the mixture to cool. The coated hollow particles have a surface energy of less than 0.00033 N (33 dyn) / cm. These particles are then milled using an air jet mill at a feed rate of 10 g / min and 700 kPa (7 bar) (feed and milling chamber). The final particle size distribution is between 0.1 μm and 10 μm.

[0030] Example 4 - Preparation of Janus particles (hydrophobic and hydrophilic) by functionalizing hydrophobic polymer hollow particles with atmospheric plasma 200 g of hollow spheres of a hydrophobic polymer (polyacrylonitrile / crosslinked polymethyl methacrylate) with an average particle size of 80 μm were added to an atmospheric plasma reactor and treated for 2 hours. The treated powder had a surface energy of greater than 0.00072 N (72 dyn) / cm, making it hydrophilic. The powder was then crushed at low temperatures (below the glass transition point of the material) using an air jet mill to break the shell and generate Janus particles. The final particle size distribution was between 0.1 μm and 10 μm.

[0031] Example 5 - Preparation of a water-in-silicone emulsion using Janus particles from Example 1

[0032] [Table 1]

[0033] This water-in-silicone emulsion is prepared by mechanically stirring phase A in a beaker at room temperature and then adding phase B while generating the emulsion using a high-shear rotor-stator device at 10,000 rpm for 5 minutes. The final water droplet size distribution, as detected by optical microscopy, is between 10 μm and 150 μm. The resulting emulsion is stable against coalescence for more than 6 months at room temperature.

[0034] Example 6 - Preparation of water-in-oil emulsions using Janus particles from Example 2

[0035] [Table 2]

[0036] This water-in-oil emulsion is prepared by mechanically stirring phase A in a beaker at room temperature and then adding phase B while generating the emulsion using a high-shear rotor-stator device at 10,000 rpm for 5 minutes. The final water droplet size distribution, as detected by optical microscopy, is between 10 μm and 170 μm. The resulting emulsion is stable against coalescence for more than 6 months at room temperature.

[0037] Example 7 - Preparation of silicone-in-oil emulsion using Janus particles from Example 4

[0038] [Table 3]

[0039] This water-in-oil emulsion is prepared by mechanically stirring phase A in a beaker at room temperature and then adding phase B while generating the emulsion using a high-shear rotor-stator device at 10,000 rpm for 5 minutes. The final water droplet size distribution, as detected by optical microscopy, is between 30 μm and 200 μm. The resulting emulsion is stable against coalescence for more than 6 months at room temperature.

[0040] Example 8 - Preparation of water-in-silicone emulsions using in situ generation (wet milling) of Janus particles

[0041] [Table 4]

[0042] This example demonstrates the in situ generation of Janus particles during emulsion formation. Silicone-treated glass microbubbles from Example 1 were used in their pre-milled state. Phase A was prepared in a beaker and the mixture was passed through a three-cylinder calender, which produced silicone-dispersed Janus particles. Phase A was then added to Phase B at room temperature, followed by Phase C, which was then added while the emulsion was formed at 10,000 rpm for 5 minutes using a high-shear rotor-stator device. The final water droplet size distribution, as detected by optical microscopy, was between 10 μm and 150 μm. The resulting emulsion was stable against coalescence for over 6 months at room temperature.

[0043] Example 9 - Preparation of a water-in-oil emulsion foundation

[0044] [Table 5]

[0045] A water-in-oil emulsion foundation is prepared as follows: Phase A is heated to 80°C to melt the wax. Phase B is then added with mechanical stirring. Phase C is heated to 80°C and added to Phase A + Phase B using a high shear rotor-stator device at 10,000 rpm for 5 minutes to form an emulsion. Phase D is then added to the mixture while stirring. The mixture is then cooled to ambient temperature with mechanical stirring.

[0046] Example 10 - Preparation of a "powder cream" cosmetic product

[0047] [Table 6]

[0048] A "powder cream" cosmetic product is prepared as follows: Phase A is mixed in a powder mixer (2500 rpm for 5 minutes) at ambient temperature. Phase B is added to Phase A and mixed until homogenous (2 cycles of 5 minutes at 2500 rpm). Phase C is then added to Phase A + Phase B and mixed until the mixture has the appearance of a free-flowing dry powder. Such a powder has the ability to transform into a cream when applied (rubbed) to the skin and return to a dry state when the water evaporates.

[0049] Example 11 - Preparation of oil-in-water emulsion for skin care

[0050] [Table 7]

[0051] An oil-in-water emulsion for skin care is prepared as follows: Phase A is brought to 50°C and homogenized, and Phase C is heated to 50°C. Phase B is added to Phase A using a high shear rotor-stator device to form an emulsion at 10,000 rpm for 5 minutes. The emulsion is then allowed to cool and Phases C and D are added with mechanical stirring (200 rpm).

[0052] Comparative Example Below are comparative examples that demonstrate the failure of attempts to form water-in-silicone emulsions using particles obtained by alternative manufacturing methods (no treatment, no grinding, or a different sequence of treatment and grinding).

[0053] The comparative powders are as follows:

[0054] Comparative Example I (hydrophilic microbubbles) - Hydrophilic hollow glass spherical powder was used as is (no coating, no crushing) Comparative Example II (hydrophilic flakes) - Hydrophilic flakes were obtained in the same manner as in Example 1, except for the coating step (no coating, crushed). Comparative Example III (Hydrophobic Microbubbles) - Hollow hydrophobic glass spheres were obtained in the same manner as in Example 1, except for the air jet milling step (coated, no milling). Comparative Example IV (Hydrophobic Flakes) - Hydrophobic flakes were obtained in the same manner as in Example 1, except that the order of coating and grinding was reversed (with grinding and coating).

[0055] Emulsions are prepared according to Example 5 using the different powders (Comparative Examples I-IV) as Phase A. Phase B (aqueous phase) is added along with 0.1% of the water-soluble dye FD&C Blue 1 to add color to the droplets.

[0056] Visual and optical microscopic evaluations show that only the Janus particles described in this invention produce Pickering emulsions with improved stability. No emulsions are formed when the particles are completely hydrophilic (hollow spheres or flakes) or when hydrophobic hollow spheres are used (Comparative Example I, Comparative Example II, and Comparative Example III, respectively). While hydrophobic flakes (Comparative Example IV) produce Pickering emulsions based on intermediate average wetting between the water and silicone phases, these emulsions have larger droplet sizes and less stability against coalescence compared to the Janus particle-based Pickering emulsions that are the subject of this invention, as shown by accelerated stability tests (centrifugation at 4000 rpm for 2 minutes or 2500 rpm for 10 minutes). [Explanation of symbols]

[0057] 1 hollow particle 2 Outer surface 3 Inner surface 11 Modified particles 12 Outer surface 13 Inner surface 21 Fragments

Claims

1. A cosmetic composition comprising Janus particles, an aqueous phase, and an organic phase, wherein the Janus particles are present in an amount of 0.01% to 99.99% by weight, and the total amount of the aqueous phase and the organic phase is 0.01% to 99.99% by weight, characterized in that the Janus particles are composed of fragments (21) of hollow spherical particles (11) having an inner concave surface with a surface energy α and a chemically treated outer convex surface with a modified surface energy β, and the fragments (21) have a concave surface (13) with an unmodified surface energy α and a convex surface (12) with the modified surface energy β.

2. 2. The cosmetic composition of claim 1, wherein the aqueous phase comprises water and a water-soluble and / or water-dispersible substance.

3. 2. The cosmetic composition according to claim 1, wherein the organic phase comprises oils from the class of triglycerides, and / or esters, and / or glyceryl esters, and / or silicones, and / or other cosmetically acceptable oils, and mixtures of each of these.

4. 4. The cosmetic composition of claim 3, wherein the organic phase contains one or more oils and oil-soluble and / or oil-dispersible substances.

5. The Janus particles are contained in an amount of 20% by weight to 0.01% by weight, 5. The cosmetic composition according to claim 1, wherein the aqueous phase is dispersed in the organic phase as a water-in-oil emulsion / water-in-silicone emulsion, or the organic phase is dispersed in the aqueous phase as an oil-in-water emulsion / silicone-in-water emulsion.

6. The cosmetic composition according to any one of claims 1 to 4, characterized in that the Janus particles are contained in an amount of 10% to 90% by weight.

7. 2. The cosmetic composition according to claim 1, wherein the surface energy α is greater than the surface energy β.

8. 2. The cosmetic composition according to claim 1, wherein the surface energy α is smaller than the surface energy β.

9. 2. The cosmetic composition according to claim 1, wherein said convex surface (12) is a surface chemically treated with a copolymer of polymethylhydrosiloxane.

10. 2. The cosmetic composition according to claim 1, wherein said convex surface (12) is a surface chemically treated with triethoxysilane and / or trimethoxysilane.

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