Microparticle composite material based on zinc oxide grafted onto diatomaceous earth, its preparation process and its applications as an anti-UV active ingredient.

Abstract

The invention relates to a method for preparing a composite material comprising zinc oxide crystals grafted onto the surface of diatomaceous earth particles, including a grinding step in the presence of an agent stabilizing electronic charges created during grinding, as well as a composite material comprising zinc oxide crystals grafted onto the surface of diatomaceous earth particles and its use as an active UV protection agent.

Description

Title of the invention: Microparticle composite material based on zinc oxide grafted onto diatomaceous earth, its preparation process and its applications as an anti-UV active ingredient. technical field

[0001] The present invention relates to the field of microparticulate composite materials, in particular those based on zinc oxide. Previous technique

[0002] It is well known that ultraviolet (UV) radiation, emitted naturally by the sun or by artificial sources, is beneficial in small quantities to the human body and essential for the synthesis of vitamin D, which is itself essential for the fixation of calcium to bones and the prevention of osteoporosis. However, overexposure to UV radiation is responsible for damage to the skin (accelerated aging, cancers, etc.), eyes, and immune systems.

[0003] Sunscreen is a cream or lotion used to reduce skin exposure to the sun's ultraviolet radiation. As such, it constitutes a means of passive external photoprotection, functioning as an ultraviolet filter. Such a sunscreen product is composed of ultraviolet filters in a base that can be an oil or, more frequently, an emulsion (cream or lotion). Effective protection must block both UVA and UVB rays: UVB rays (and to a lesser extent UVA rays) can cause sunburn, UVA rays cause premature skin aging, and UVA and especially UVB rays cause skin cancer.

[0004] An ultraviolet filter or UV filter is a chemical compound that blocks or absorbs ultraviolet radiation. All sunscreens contain ultraviolet sunscreens, which fall into two families of molecules: chemical (or organic) filters and mineral (or inorganic) filters.

[0005] Organic filters are easier to use but they pollute the water, are difficult to eliminate, even by wastewater treatment plants, can be allergenic and prove toxic to both humans and the environment, and in particular aquatic biotopes.

[0006] An alternative to organic filters is the use of mineral filters. In cosmetics, only two mineral filters are permitted: titanium dioxide and zinc oxide. These two filters provide immediate protection against UV rays, unlike chemical filters which take up to 25 minutes to guarantee the claimed protection.

[0007] The mineral filters in so-called "organic" sunscreens are hypoallergenic and photostable (making them the recommended sunscreen for allergy sufferers and children). For a long time, they were less popular with consumers because they were more difficult to apply and left users with an unattractive whitish tint. To solve this problem and improve the cosmetic appearance, laboratories reduced these mineral filters to nanoparticles to formulate sunscreens. However, numerous studies have been conducted on nanoparticles and have demonstrated their harmful effects on the environment, particularly on phytoplankton, and their potential health effects, as these particles penetrate the skin. In particular, TiO2 nanoparticles have become the main oxidizing agent entering coastal waters, with direct ecological consequences for the ecosystem.Titanium dioxide nanoparticles disperse in water and end up in filter-feeding organisms (oysters and mussels in particular) or the cells of other marine animals.

[0008] Zinc oxide thus remains a preferred choice due to its numerous qualities as an effective UVB and UVA radiation filter, photostable, and non-allergenic. However, it presents a risk to the environment and potentially to human health in its native nanoparticle form (particles smaller than 100 nm) due to this size and its oxidizing properties under the action of UV radiation.

[0009] Faced with this observation regarding the limits and dangers of the use of organic filters in sunscreens and to take into account the risk of the use of nanoparticulate mineral filters, it is therefore necessary to find an alternative that makes it possible to reconcile protection that is both effective for humans and safe for the environment. General description

[0010] It is to the Applicant's credit that this problem has been solved by developing a process for obtaining a composite material comprising zinc oxide nanoparticles grafted onto natural mineral microparticles of diatomaceous earth, said composite material having a particle size ranging from 30 to 200 nm.

[0011] EP 2 375 575 describes a cosmetic composition comprising a composite material based on diatomaceous earth and zinc. This composite material is prepared using unmodified diatomaceous earth and therefore has an average particle size of 10 microns, which leads to poor dispersion of the material in a cosmetic composition. Furthermore, the Applicant has observed that, under the zinc chloride concentration conditions described in this patent, the proposed zinc oxide concentration results in only very partial coverage of the diatomaceous earth particles by the zinc crystals and that the zinc oxide concentration of the final product is 10 times lower than indicated. As it stands, the proposed preparation method cannot lead to the production of a material capable of claiming the alleged anti-UV properties.

[0012] On the contrary, within the composite material according to the invention, the modification of diatomaceous earth in the form of microparticles allows for a very significant increase in the specific surface area of ​​the material, leading to a very significant increase in the crystallization surfaces of zinc oxide. This makes it possible to increase, for the same quantity of material, the surface properties and in particular the surface area exposed to light radiation, including UV rays, and the possibility of diffraction and refraction of these rays. This technique allows for the development of large zinc nanocrystal surfaces while greatly limiting the diffusion of the material into the environment, since the zinc oxide nanoparticles are fixed to this non-nanometric support and are therefore not passively diffusible into cells or living organisms.

[0013] A first object of the invention is thus a process for preparing a composite material comprising zinc oxide crystals grafted onto the surface of diatomaceous earth particles, comprising the following steps: 1) preparation of diatomaceous earth microparticles by grinding diatomaceous earth; 2) grafting of zinc salt crystals onto the surface of diatomaceous earth microparticles; 3) transformation of said zinc salt crystals grafted onto the surface of diatomaceous earth microparticles into zinc oxide crystals grafted onto the surface of diatomaceous earth microparticles; 4) grinding of the microparticles obtained in step 3) to an individual particle size ranging from 10 to 300 nm, this grinding being carried out in the presence of a stabilizing agent for electronic charges created during grinding.

[0014] A second object of the invention is a composite material comprising zinc oxide crystals grafted onto the surface of diatomaceous earth particles, said grafted diatomaceous earth particles having an individual particle size ranging from 10 to 300 nm. This composite material is advantageously prepared according to the process of the invention. The invention also relates to the use of the composite material according to the invention or prepared according to the process of the invention as an active ingredient for protection against UV radiation, particularly in cosmetic compositions.

[0015] Another object of the invention is a cosmetic composition comprising the composite material according to the invention or prepared according to the process according to the invention. Detailed description

[0016] A first object of the invention is a process for preparing a composite material comprising zinc oxide crystals grafted onto the surface of diatomaceous earth particles, comprising the following steps: 1) preparation of diatomaceous earth microparticles by grinding diatomaceous earth in an aqueous medium; 2) grafting of zinc salt crystals onto the surface of diatomaceous earth microparticles; 3) transformation of said zinc salt crystals grafted onto the surface of diatomaceous earth microparticles into zinc oxide crystals grafted onto the surface of diatomaceous earth microparticles; 4) grinding of the microparticles obtained in step 3) in aqueous media to an individual particle size ranging from 10 to 300 nm, this grinding being carried out in the presence of a stabilizing agent for electronic charges created during grinding.

[0017] Diatomaceous earth (also called kieselguhr or diatomite) consists of microscopic, single-celled fossilized algae found in large geological deposits located in ancient marine sedimentary basins. This sedimentary rock appears as a protective silica-based coating, called a frustule, which is predominantly silicic in composition and whose shape and size vary according to the age and origin of the sediment. Frustules have a remarkable structure, composed of a large network of macroscopic channels that can represent more than 80% of the total volume of the structure.

[0018] In step 1) of the process according to the invention, the diatomaceous earth is advantageously ground to an individual particle size ranging from 50 nm to 2 pm, preferably from 100 nm to 1 pm, and even more preferably from 150 nm to 500 nm. An "individual particle size" is understood to mean that each particle of the material has a particle size falling within the indicated range. The particle size is determined by scanning electron microscopy (SEM).

[0019] Advantageously, the grinding in the first stage is carried out in such a way as to preserve the silanol groups on the surface of the diatomaceous earth. The Applicant has observed that an excessive increase in the temperature of the material induces an amorphization of the silicic structure, with the disappearance of the surface silanol groups through dehydroxylation of these groups.

[0020] The preservation of a maximum of surface silanol groups can be achieved by a grinding technique in aqueous and sequential medium allowing the temperature rise during grinding to be limited below a threshold of 200°C.

[0021] Thus, step 1) of grinding in the process according to the invention is advantageously carried out in aqueous environments using a planetary type grinder.

[0022] This type of mill operates according to the following principle: The grinding bowl is eccentrically positioned on the solar wheel of the planetary ball mill. The solar wheel rotates in the opposite direction to the rotation of the grinding bowl. The grinding balls located in the bowl undergo a deflection resulting from superimposed rotational movements, which are responsible for the Coriolis force. The Coriolis force is a force that deflects the trajectory of a moving object on the surface of a rotating object. It applies particularly to moving masses of air and water. The differences in velocity between the balls and the grinding bowl lead to an interaction between impact and friction forces, releasing significant dynamic energy. The combination of these forces results in the high degree of grinding and very efficient performance of planetary ball mills.

[0023] This grinding step can be carried out by varying one or more of the following parameters: - the volume of grinding charge, namely the volume occupied by the grinding balls in relation to the volume of the grinding bowl; - the particle size of the grinding charge, (the size of the grinding media determines the fineness of the output particle size: the smaller the grinding media, the finer the final particle size can be); - the feed load of product to be ground, and the proportional load of water; - the rotation speed of the crusher, - the number of crushing cycles; - the temperature of the mixture during the process.

[0024] A person skilled in the art knows how to adjust the parameters to obtain the desired particle size. Generally, they will use a grinding media volume of approximately 15% to 25%. The grinding media are advantageously smaller than 1 mm, preferably 0.5 mm. The number of grinding cycles is generally from 1 to 20, preferably from 5 to 15, and even more preferably from 8 to 12. As mentioned previously, the temperature during grinding is advantageously maintained below 200°C, preferably below 150°C. As for the rotational speed of the grinder, it is advantageously in the range of 300 to 800 rpm, for example, 550 rpm.

[0025] Step 2) of the process according to the invention may include the following steps: a) aqueous suspension of diatomaceous earth particles obtained during step 1 with calcium carbonate; b) mixing the mixture obtained at the end of step a) with an aqueous suspension of zinc chloride; c) stirring of the mixture obtained at the end of step b) at a temperature ranging from 5°C at 40°C, preferably 15°C to 25°C, for a period of 24 to 72 hours, preferably 48 hours; d) recovery of the composite material obtained at the end of step c), in particular by sedimentation or centrifugation; e) drying of the composite material at a temperature of 50°C to 90°C, preferably 70°C, for a period of 12 to 48 hours, preferably 24 hours.

[0026] This second step of the process allows the zinc salts to react with the silanol groups on the surface of the diatomaceous earth particles. In particular, this step allows the calcium carbonate present in the diatomaceous earth to solubilize, releasing hydroxyl and carbonate species into the medium, leading to the crystallization of hydrated zinc carbonate hydroxide phases with the chemical formula Zn4(CO3)(OH)6H2O on the surface of the diatomaceous earth particles at the level of the surface silanol groups.

[0027] In particular, the diatomaceous earth particles obtained during step 1 can be suspended in water at a rate of 0.1 to 100 grams of powder per liter of water, preferably 10 grams of powder per liter of water.

[0028] Similarly, calcium carbonate can be suspended in water at a rate of 0.1 to 100 grams of calcium carbonate per liter of water, preferably 10 grams of calcium carbonate per liter of water.

[0029] The aqueous suspension of zinc chloride used in step b) has a concentration of 5.10-3 to 5 mol.L-1, preferably 2 to 3 mol.L-1, in particular about 1 mol.L-1.

[0030] Advantageously, the hydration of the suspension obtained at the end of step a) and of the zinc chloride suspension can be carried out separately for 15 to 60 minutes, preferably 30 minutes before bringing these two suspensions together in step b).

[0031] Step c) of stirring the mixture can be carried out using a paddle mixer at a rotation speed of approximately 100 revolutions per minute.

[0032] Step e) of drying the composite material can be carried out in an oven or a furnace.

[0033] Step 3) of the process according to the invention can be carried out by heat treatment at a temperature ranging from 500°C to 900°C, preferably 700°C, for a period of 1 hour to 4 hours, preferably 2 hours.

[0034] This third step allows the transformation of the zinc salt crystals formed in step 2) into zinc oxide crystals distributed on the surface of the diatomaceous earth particles. The zinc oxide is advantageously covalently bonded to the surface of the diatomaceous earth particles.

[0035] The heat treatment implemented in step 3) can be carried out in a furnace, in Specifically, this involves a temperature increase of 190°C / hour up to 700°C, followed by a plateau at 700°C for 2 hours before cooling to room temperature by switching off the oven. A more gradual temperature increase and a longer plateau could also be used without affecting the result.

[0036] Step 4), grinding the microparticles obtained in step 3 to an individual particle size ranging from 10 to 300 nm, is carried out in aqueous media in the presence of an agent to stabilize the electronic charges created during grinding. The inventors have observed that grinding these microparticles in aqueous media without any additives results in re-agglomeration or recrystallization of the microparticles obtained during and after grinding, and therefore does not allow the desired particle size to be obtained. Quite surprisingly, the inventors found, after extensive research, that grinding in the presence of an agent to stabilize electronic charges created during grinding, such as an aqueous solution of alkali metal silicate, makes it possible to prevent or at least limit this phenomenon of re-agglomeration or recrystallization and thus obtain an individual particle size ranging from 10 to 300 nm.Without wishing to be bound by any particular theory, the inventors believe that during the grinding of zinc crystals, an imbalance of electronic charges is created, and that the phenomenon of re-agglomeration or recrystallization is due to the attraction of the opposite charges created during grinding. According to the inventors' observations, the use of an agent to stabilize the electronic charges created during grinding, such as an aqueous solution of alkali metal silicate, allows the new electronic environment created during grinding to be stabilized by compensating for the charges that appear. Indeed, in the case of an alkali metal silicate, the alkali metal cations would compensate for the negative charges, and the anions resulting from the dissolution of the alkali metal silicate would compensate for the positive charges.

[0037] The alkali metal silicate can be chosen from sodium silicate, lithium silicate and potassium silicate. Preferably, the alkali metal silicate is sodium silicate.

[0038] The alkali metal silicate is used in aqueous solution. The alkali metal silicate is used in a suitable quantity to stabilize the electronic charge imbalance during grinding. In the case of sodium silicate, it is advantageously used in an amount of 3% to 20%, preferably 5% to 15%, particularly 10% to 15%, the percentages being expressed by weight relative to the weight of the microparticles obtained in step 3) of the process according to the invention.

[0039] The grinding in step 4) can be carried out in a manner analogous to that in step 1), using in particular the same type of equipment, more specifically a planetary ball mill. Those skilled in the art know how to adapt the grinding conditions in order to to obtain the desired particle size.

[0040] The microparticles obtained in step 3) are ground in step 4) to an individual particle size ranging from 10 to 300 nm. Preferably, they are ground to an individual particle size ranging from 15 nm to 250 nm. To the inventors' knowledge, such particle sizes were not previously achievable for zinc oxide particles grafted onto the surface of diatomaceous earth particles.

[0041] Thus, a second object of the invention is a composite material comprising zinc oxide particles grafted onto the surface of diatomaceous earth particles, the grafted diatomaceous earth particles having an individual particle size ranging from 10 to 300 nm, preferably from 15 to 250 pm. As stated above, "an individual particle size" means that each particle of the material has a particle size falling within the specified range. The particle size is determined by scanning electron microscopy (SEM).

[0042] Advantageously, the composite material according to the invention comprises zinc oxide present on the surface of diatomaceous earth particles at a concentration of 50% to 80% by weight, preferably 65% ​​to 75% by weight, preferably about 70% by weight.

[0043] The invention also relates to the use of the composite material according to the invention or prepared according to the process according to the invention as an active ingredient for protection against UV radiation, particularly in cosmetic compositions.

[0044] With regard to cosmetic compositions, the composite material according to the invention exhibits both strong anti-UV efficacy and numerous advantages due to its size: a very strong limitation of the diffusion of this material in the environment compared to zinc oxide nanoparticles alone, combined with a very homogeneous diffusion in excipients and a limitation of the effect of reflection of visible light by the particles, which reduces the major disadvantage of whitish surface effects on the skin, compared to a larger size material, such as unground diatomaceous earth.

[0045] Another object of the invention is a cosmetic composition comprising the composite material according to the invention or prepared according to the process according to the invention. Cosmetic compositions according to the invention include, but are not limited to, formulations for topical application, such as creams, oils, milks, suspensions, sprays, lotions, balms, and serums.

[0046] The invention will be better understood with the aid of the figures and examples that follow. Figures

[0047] [Fig. 1] is a scanning electron microscopy image of ground diatomaceous earth particles.

[0048] [Fig.2] is a scanning electron microscopy image of a material composite according to the invention in an embodiment using 5% by weight of sodium silicate.

[0049] [Fig.3] is a scanning electron microscopy image of a material composite according to the invention in an embodiment using 10% by weight of sodium silicate.

[0050] [Fig.4] is a scanning electron microscopy image of a material composite obtained by grinding in the absence of an electronic charge stabilizing agent.

[0051] [Fig. 5] shows the in vivo anti-UV effect of a composite material according to a method of lisation implementing 10% by weight of sodium silicate 24h after exposure of the volunteer to sunlight. Examples

[0052] Example 1: Preparation of the composite material comprising zinc oxide crystals grafted onto the surface of diatomaceous earth microparticles (steps 1) to 3) of the process according to the invention) 40 grams of diatomaceous earth were ground in a planetary type mill (Retsch PM100) equipped with a 50 mL bowl with the following parameters: - Volume of grinding material: 60% of the grinding bowl capacity; - Granulometry of the grinding media. Grinding balls with a diameter of 0.5mm; - Product feed load: 16% of the bowl volume; - Water content: 24% of the bowl volume; - Rotation speed: 550 rpm; - Number of grinding cycles. 8 cycles of 10 minutes with 10-minute pause periods between each grinding phase.

[0053] Several 40-gram batches of diatomaceous earth were ground in this manner to recover 1000 grams of diatomaceous earth powder. Scanning electron microscopy analyses of this powder show a fairly homogeneous grinding of the diatomaceous earth particles below 500 nm (see [Fig. 1]). The recovered powder was suspended in tap water at a mass concentration of 10 g of powder per liter of water, and then 1000 grams of calcium carbonate were added at a mass concentration of 10 g per liter of water.

[0054] In parallel, 13,600 grams of ZnCl2 were dissolved in tap water to prepare a solution with a concentration of 1 mole / litre. The two suspensions were hydrated separately for 30 minutes before being mixed. The two resulting aqueous phases were then mixed in a suitable tank. The resulting aqueous mixture was agitated carried out using a paddle mixer at a rotation speed of approximately 100 revolutions / minute and at a temperature between 15°C and 25°C, for a period of 48 hours.

[0055] The composite obtained after mixing the two aqueous phases was then recovered by first emptying the mixing tank by gravity into a collection container with a plastic bag. Several settling phases were carried out to remove surface water, and the material thus recovered in the form of a cream was then dried by placing the cream in trays which were then dried in an oven at 90°C for 24 hours.

[0056] The powder from this drying was then transferred into calcination gauzes which were finally placed in the oven for calcination with a temperature rise programmed from 190°C / hour up to 700°C then a plateau at 700°C for 2 hours before a return to ambient temperature by stopping the oven. At the end of this step, approximately 10 kg of the composite material according to the invention were recovered.

[0057] Example 2: Grinding of the composite material obtained in Example 1 in the presence of sodium silicate

[0058] 10 g of composite material obtained according to Example 1 was subjected to grinding in The presence of tap water and an aqueous solution of sodium silicate (Arcane Industries 40% Sodium Silicate, CAS No. 1344-09-8) in a planetary mill equipped with a 50 mL bowl and 0.5 mm grinding media at a ratio of 1 / 100 of the available quantity, i.e., approximately 100 g. The grinding parameters were as follows: - Total cycle duration: 8 hours - Settings: 32 cycles of 10 minutes of grinding separated by 5-minute pauses (i.e., 5 hours and 20 minutes of effective grinding) - Rotation speed: # 500 rpm - Wait for the cycle to finish and for the bowl to cool down - Rinse with a new Retsch 250pm sieve using water and a brush to collect the beads. Weigh the water added. - Recovery and preservation of the different creams obtained: approximately 10 g of dry equivalent recovered per trial.

[0059] Two tests with different concentrations of sodium silicate were carried out: - Test 2-1: 5% by weight of sodium silicate relative to the weight of the composite material, i.e. 1250 mg of 40% sodium silicate solution for 10 g of composite material used; - Test 2-2: 10% by weight of sodium silicate relative to the weight of the composite material, i.e. 2500 mg of 40% sodium silicate solution for 10 g of composite material used.

[0060] For both tests, the individual particle size is within the range ranging from 10 to 300 nm, as shown in figures 1 and 2.

[0061] Example 3: Grinding of the composite material obtained in Example 1 without the addition of sodium silicate (Comparative example)

[0062] 10 g of composite material obtained according to Example 1 was subjected to grinding in The presence of 20 g of tap water in a planetary grinder equipped with a 50 mL bowl and 0.5 mm grinding balls at a rate of 1 / 10th of the available quantity, i.e., approximately 100 g. The grinding parameters were as follows: - Total cycle duration: 8 hours - Settings: 32 cycles of 10 minutes of grinding separated by 5-minute pauses (i.e., 5 hours and 20 minutes of effective grinding) - Rotation speed: # 500 rpm - Wait for the cycle to finish and for the bowl to cool down - Rinse with a new Retsch 250pm sieve using water and a brush to collect the beads. Weigh the water added. - Recovery and storage of the resulting cream: approximately 10g of dry equivalent recovered. Example 4: Evaluation of the in vivo anti-UV effect of the material from Example 2 prepared with 10% sodium silicate

[0063] The material of Example 2, prepared with 10% sodium silicate, was tested to evaluate its ability to protect human skin against UV radiation (anti-UV effect). The test was carried out on a healthy human volunteer with no photosensitivity problems and type I skin, i.e., skin that always reddens and never tans.

[0064] Approximately 1 g of the cream recovered at the end of example 2 with implementation 10% sodium silicate was applied in a V shape on the torso of the volunteer and he then exposed himself to the sun from 1 p.m. to 3 p.m. at the end of May in Brittany (France).

[0065] After exposure, the unprotected skin had become very red while the V-shaped area protected by the material according to the invention remained unchanged. After 24 hours, the unprotected skin was still very red and the protected area unchanged, as can be seen in [Fig. 4].

[0066] .

Claims

Demands

1. A method for preparing a composite material comprising zinc oxide crystals grafted onto the surface of diatomaceous earth particles, comprising the following steps: 1) preparing diatomaceous earth microparticles by grinding diatomaceous earth in aqueous medium; 2) grafting zinc salt crystals onto the surface of the diatomaceous earth microparticles; 3) transforming said zinc salt crystals grafted onto the surface of the diatomaceous earth microparticles into zinc oxide crystals grafted onto the surface of the diatomaceous earth microparticles; 4) grinding the microparticles obtained in step 3) in aqueous media to an individual particle size ranging from 10 to 300 nm, this grinding being carried out in the presence of an agent stabilizing electronic charges created during grinding.

2. A method according to claim 1, wherein step 1 of grinding is carried out using a planetary type mill.

3. A process according to claim 1 or 2, wherein step 2 comprises the following steps: a) aqueous suspension of diatomaceous earth particles obtained in step 1) with calcium carbonate; b) mixing the mixture obtained at the end of step a) with an aqueous suspension of zinc chloride; c) stirring the mixture obtained at the end of step b) at a temperature of 5°C to 40°C, preferably 15°C to 25°C, for a period of 24 to 72 hours, preferably 48 hours; d) recovery of the composite material obtained at the end of step c), in particular by sedimentation or centrifugation; e) drying of the composite material at a temperature of 50°C to 90°C, preferably 70°C, for a period of 12 to 48 hours, preferably 24 hours.

4. A method according to any one of claims 1 to 3, wherein step 3 is carried out by heat treatment at a temperature of 500°C to 900°C, preferably 700°C, for a period of 1 to 4 hours, preferably 2 hours.

5. A method according to any one of claims 1 to 4, wherein the agent stabilizing electronic charges created during grinding is a solution aqueous alkali metal silicate.

6. A method according to claim 5, wherein the alkali metal silicate solution is a sodium silicate solution.

7. Composite material comprising zinc oxide crystals grafted onto the surface of diatomaceous earth particles, said grafted diatomaceous earth particles having an individual particle size ranging from 10 to 300 nm.

8. Composite material according to claim 7, wherein zinc oxide is present on the surface of diatomaceous earth particles at a concentration of 50% to 80% by weight, preferably 65% ​​to 75% by weight, preferably about 70% by weight.

9. Use of the composite material as defined according to claim 7 or 8 or prepared according to any one of claims 1 to 6 as an active ingredient for protection against UV radiation, particularly in cosmetic compositions.

10. Cosmetic composition comprising the composite material as defined according to claim 7 or 8 or prepared according to any one of claims 1 to 6.

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