Scent diffuser having an innovative structure and associated preparation method

Abstract

The present invention relates to a scent diffuser comprising a granular support with an innovative structure, capable of absorbing and diffusing fragrant essences into the surrounding environment with optimal diffusion capacity. The invention also relates to a process for the preparation of scent diffusers that involves modifying the physical structure of a vermiculite-based substrate so as to make it capable of absorbing and diffusing scent essences more effectively than existing commercially available diffusers.

Description

[0001] SCENT DIFFUSER HAVING AN INNOVATIVE STRUCTURE AND ASSOCIATED PREPARATION METHOD

[0002] DESCRIPTION

[0003] FIELD OF APPLICATION

[0004] The present invention relates to a scent diffuser comprising a granular support with an innovative structure, capable of absorbing and diffusing fragrant essences into the surrounding environment with optimal diffusion capacity.

[0005] The invention also relates to a process for the preparation of scent diffusers that involves modifying the physical structure of a phyllosilicate-based support so as to make it capable of absorbing and diffusing scented essences more effectively than existing commercially available diffusers.

[0006] PRIOR ART

[0007] It is known that some minerals belonging to the silicate family have great absorption capacity due to their porosity, partly due to the presence of silicon in silica form (SiO2).

[0008] Therefore, after being subjected to a crushing / grinding treatment and consequently obtaining granules of a suitable size, some of these porous minerals may be used as a support capable of absorbing one or more scented essences. The granular support, once impregnated with scents, can be placed inside containers called fresheners, which release the scented essence gradually over time into the surrounding domestic environment.

[0009] It follows that the porous granules contained inside air diffusers must not only have the capacity to absorb scents, but it is equally important that they have a physical-chemical structure that does not trap the molecules therein, preventing their gradual release into the environment. Therefore, the diffusive capacity of the granules that make up the support of the diffuser / freshener must be carefully assessed.

[0010] In addition, a granular freshener support must be completely odourless and avoid, from a chemical perspective, creating bonds with the scented substances with the risk of changing the olfactory result in an undesirable way. University studies have recently been carried out to identify porous mineral granules having the above-mentioned optimal characteristics. Research in this area has been directed at silicate minerals, particularly the phyllosilicate family.

[0011] Phyllosilicates are characterised by a layered structure with tetrahedral symmetry, in which each tetrahedron tends to bond with three other tetrahedral units via oxygen bridges. Phyllosilicates generally possess a lamellar or flaky appearance, with well-defined flaking: they are based on chains of S1O4 tetrahedra, extended and arranged side-by-side, joined together in the same plane to form a ring-hke mesh, generally with a pseudo-hexagonal symmetry. Rocks such as micas, chlorites, smectites belong to the phyllosilicate family.

[0012] Phyllosilicates generally have large planar interlayer surfaces and limited lateral or shear surfaces. A diagram of the structure of a phyllosilicate crystal, in particular the crosssection of the unit cell of the crystal is represented below:

[0013] In order to test a phyllosilicate porous stone, different types of sheets can be analysed, differing from each other in terms of the dimensions expressed by the distances between the individual sheets and the surface from which the scent is to diffuse.

[0014] The use of the terms “plane”, “sheet”, “layer” follows the recommendations of the Nomenclature Committee of the AIPEA (Association International Pour L'Etude des Argiles). The terms refer to increasing structural arrangements: the ion plane, the tetrahedral or octahedral sheet, the layer.

[0015] The sheet is a combination of planes and the layer is a combination of sheets. The layers can be separated from each other by interlayer materials such as cations, hydrated cations, organic molecules, groups and sheets of octahedral oxyhydroxide. A set of layers forms the crystal: the distance between a basal plane of one layer and the homologous plane of a subsequent layer is called the basal distance or identity period.

[0016] Phyllosilicate granules are known to be used as an inert support to hold molecules of scented essences. For example, International Patent Application WO2024 / 028632 describes a process for the preparation of a scent diffuser, wherein mineral rock granules are used as a support to hold scents and subsequently release them into the environment. A number of phyllosilicates such as vermiculite, expanded vermiculite, perlite, expanded perlite, agri-perlite or a mixture thereof are listed as mineral rocks suitable to be used as inert supports. In particular, in the experimental tests implementing the described process, irregularly shaped perlite granules for agricultural use (hydroponic perlite) with a major diameter size in the range of 4-10 mm are used.

[0017] An object of the present Patent Application is to identify which phyllosilicate mineral is most suitable to be used as a granular support for the absorption and subsequent diffusion of a scented mixture into the surrounding environment.

[0018] Among the various phyllosilicate minerals, the structural properties of expanded vermiculite, a mineral with a lamellar appearance belonging to the mica family, attracted much interest. It is a natural product that expands when subjected to irreversible heat treatment at high temperature. After expansion, the product is carefully screened to obtain a product with a calibrated grain size. Expanded vermiculite is a lightweight, thermally- insulating and non-combustible product.

[0019] The internal structure of commercially available vermiculite may accommodate scented essence solutions, thanks to the characteristic structure of phyllosilicates. This absorption characteristic and ability to hold liquids therein may not, however, be effective for diffusing the scent outside as the granular support may not easily release the odorous substance outside.

[0020] The Applicant has experimentally verified that the use of commercially available expanded vermiculite granules gives good results in relation to the absorption of scented essences, however not optimal in relation to the diffusive capacity of the support.

[0021] The need perceived is therefore to make available to the concerned sector a method for preparing scent diffusers that is innovative if compared to those of the prior art. In particular, it would be desirable to make available a granular vermiculite support that is more effective in the step of diffusing the previously absorbed scented essences. The Applicant has surprisingly found an innovative method of treating vermiculite granules so as to achieve a structural modification of the granules and increase the diffusive capacity thereof after the absorption of appropriate amounts of scented essences.

[0022] A first object of the present invention is to make available to the concerned sector a scent diffuser based on a granular vermiculite support so as to improve the diffusion of scented substances into the environment compared to scent diffusers of the prior art.

[0023] A second object of the present invention is the preparation of a scent diffuser with a structure such that the quantity of scented essence absorbed can be minimised, with the same effectiveness in olfactory diffusion of the scent. This leads to a significant saving of raw materials (the essential oils) that are often expensive, resulting in an economic advantage in the preparation of the diffuser itself.

[0024] A further object of the present invention is to realise a simple and effective method for treating vermiculite granules in order to make them suitable for use in scent diffusers.

[0025] In order to overcome the drawbacks of the prior art and to achieve these and further objects and advantages, the Applicant has studied, tested and realised the present invention.

[0026] DISCLOSURE OF THE INVENTION

[0027] The present invention is expressed and characterised in the independent claims, while the dependent claims set forth other preferred and non-essential features of the present invention, or variants of the main solution idea.

[0028] A first object of the present invention consists in a scent diffuser comprising a vermiculitebased support capable of absorbing and diffusing a scent into the surrounding environment, said vermiculite support being impregnated with a solution of essential oils and being characterised in that:

[0029] - it comprises flattened vermiculite granules with an average thickness between 0.3 and 3.0 mm, preferably between 0.5 and 2.0 mm;

[0030] - said flattened vermiculite granules are made of lamellar structure crystals having a basal distance between adjacent layers between 0.1 and 1.3 nm, preferably between 0.3 and 1.0 nm.

[0031] Commercially available vermiculite comprises three-dimensional, irregularly shaped granules. In the present description, the term thickness is intended to mean the distance between the two outermost sheets of the vermiculite granule.

[0032] In accordance with an embodiment of the present invention, the vermiculite granules used in the preparation of the scent diffuser are preferably free of ferric oxide (Fe2O3) and potassium oxide (K2O).

[0033] In fact, the presence of ferric oxide (Fe2Ch) can be damaging, as, in the event of the presence and / or formation of water vapour and / or water, the chemical process originating iron hydroxide (Fe2C>3-nH2O) would begin, thus generating rust. The possible presence of rust would be an obstacle to the proper functioning of the scent diffuser.

[0034] The use of vermiculite granules with the presence of potassium oxide (K2O) was also found to be disadvantageous, as this is a basic oxide that reacts violently with water to produce the caustic potassium hydroxide. Since it is also deliquescent, it can react by absorbing water from the atmosphere.

[0035] Essential oils are natural compounds of plant origin, also referred to as “essences”, which are characterised by the presence of volatile substances at room temperature that give different odours and scents to the scent diffuser.

[0036] The presence of different essential oils gives rise to different olfactory families. The term olfactory families refers to the categorisation of scents based on the essential oils composing it. The following olfactory families have been tested in the present invention: citrus, flowery / floral, fougere, woody, chypre, oriental, musky, aromatic.

[0037] The olfactory families have different absorption times because the chemical substances present (from the more acidic ones of the citrus family to the more resinous ones as oriental and musky) have different molecular sizes and the penetration into the vermiculite granules is different. All the essential oils of the eight olfactory families were absorbed by the vermiculite without liquid release.

[0038] Compounds belonging to the glycol ether family can be used as solvents for essential oils. Dipropylene glycol (DPG) is preferably used.

[0039] The scent diffuser according to the present invention comprises a vermiculite-based support with an innovative structure if compared to commercially available supports. The basal distance between adjacent layers of a lamellar structure crystal is defined as the distance between a basal plane of one layer and the homologous plane of a subsequent layer. The vermiculite granules used in the present invention are flattened granules consisting of lamellar structure crystals having a basal distance between adjacent layers from 0.1 to 1.3 nm.

[0040] With regard to commercially available vermiculite, the basal distance between adjacent crystal layers is higher than the above-mentioned values and is generally in the range between 1.0 nm and 2.0 nm.

[0041] Commercially available vermiculite generally has a thickness / height between 1 and 20 mm: this is why vermiculite granules according to the present invention are flattened compared to commercial ones, having a thickness between 0.3 mm and 3.0 mm.

[0042] As will be apparent from the analysis of the experimental tests, the use of a commercial vermiculite-based substrate can give good results in relation to the absorption of essential oils, but not optimal in relation to the diffusive capacity of the substrate. In contrast, flattened vermiculite granules having the structural characteristics according to the present invention showed an improved diffusive capacity of scented essences.

[0043] Without being bound to any specific theory, the layered lamellar structure of commercial vermiculite crystals is considered to be capable of effectively absorbing the molecules of the essential oils, but the latter remain partially trapped in the space between the successive layers of the crystals, thus reducing the diffusive capacity of the commercial vermiculitebased granular support.

[0044] It was therefore envisaged to reduce the space (basal distance) between adjacent layers to prevent the absorbed liquid penetrated within this interlayer space from subsequently struggling to diffuse in olfactory terms. The basal distance between adjacent crystal layers was reduced, using the technique of pressing commercial vermiculite granules, from initial average values ranging from 1.0 nm to 2.0 nm to final values in the range from 0.1 to 1.3 nm. At the same time, the average granule thickness was reduced to values between 0.3 mm and 3.0 mm.

[0045] The pressing of the granules must be properly adjusted to flatten them without damaging their surface structure. In general, pressure values above an upper limit lead to damage to the granule structure, making them unable to absorb scented substances. On the other hand, pressure values below a lower limit do not lead to the desired reduction in the thickness of granules and to the above-mentioned optimal values of basal distance between adjacent layers in vermiculite crystals.

[0046] A second object of the present invention is therefore a process for the preparation of a scent diffuser comprising the following steps:

[0047] A) placing commercial vermiculite granules having an average thickness between 1 and 20 mm on a flat surface;

[0048] B) overlaying the vermiculite granules with a metal film, preferably aluminium;

[0049] C) subjecting the vermiculite granules to pressing by sliding a roller over the metal film applying pressure values between 0.05 and 0.20 Pa, preferably between 0.08 and 0.14 Pa;

[0050] D) impregnating the pressed vermiculite granules with a solution of essential oils.

[0051] Step C) of pressing the granules allows to obtain a modified form of vermiculite that has an advantageous structure, both in terms of absorption of scented essences and their subsequent diffusion into the surrounding environment. As previously reported, the flattened vermiculite granules have an average thickness between 0.3 mm and 3.0 mm and consist of lamellar structure crystals of with a basal distance between 0.1 and 1.3 nm.

[0052] With regard to step D) of absorbing essential oils by the vermiculite granules, it can be estimated that a quantity between 0.5 ml and 1.0 ml of essential oil solution is absorbed for each gram of vermiculite.

[0053] According to a preferred embodiment of the process of the invention, during step C) the pressure is between 0.08 and 0.14 Pa, while the distance between the sliding roller and the metal film is between 0.8 mm and 2.2 mm.

[0054] The scent diffuser obtained by the preparation method of the invention has the following advantages:

[0055] 1) Improved diffusion capacity of scented essences compared to the case where the substrate consists of commercial vermiculite granules;

[0056] 2) Reduction in the required quantities of essential oils compared to commercial vermiculite support, with the same effectiveness in olfactory diffusion of the scent;

[0057] 3) The scent diffuser can also be used on a flat material and can be applied to a lying material, such as a reduced-surface ribbon. DETAILED DESCRIPTION OF THE INVENTION

[0058] The scent diffuser according to the present invention will now be described in detail with reference to the attached Figures 1-4, which are to be considered merely as exemplifying and non-limiting the subject matter of the present Patent Application.

[0059] Figure 1 shows a schematic cross-section view of two successive layers of a vermiculite crystal having a basal distance according to the teachings of the present invention.

[0060] Figure 2 shows a specific use of the scent diffuser of the present invention inside a small closed ribbon-shaped container.

[0061] Figure 3 shows the use of an adhesive strip that allows the scent diffuser of Figure 2 to adhere to a desired surface.

[0062] Figure 4 shows the use of the scent diffuser of the present invention inside small containers of variable geometry.

[0063] With reference to Fig.l, the layered lamellar structure of a vermiculite crystal C is shown with a cross-section view of the first two layers 1 and 2 in order to emphasise the “basal distance” parameter between adjacent layers of crystal C.

[0064] On the left-hand side of Fig. 1 crystal C and a separate view of the upper layers 1 and 2 of crystal C are shown, while on the right-hand side of Fig. 1 the composition of the layers is shown. Layers 1 and 2 consist of a sequence of three sheets and are separated from each other by interlayer material 3.

[0065] It can be noted that each layer 1, 2 consists of alternating tetrahedral or octahedral symmetry sheets. In particular, sheets 4, 6, 7 and 9 consist of side-by-side chains of (Si, AljCL tetrahedra, joined together in the same plane. The intermediate sheets 5, 8 of each layer 1, 2 consist of octahedral silicate-based chains containing magnesium.

[0066] The interlayer 3 material mainly consists of iron cations, magnesium cations, hydrated cations and organic molecules.

[0067] As well visible in Fig. 1, the basal distance is identified as the distance between the plane of sheet 4 of the first layer 1 and the plane of the homologous sheet 7 of the subsequent layer 2. As said, the vermiculite granules used in the present invention are flattened granules consisting of lamellar structure crystals having a basal distance between adjacent layers ranging from 0.1 to 1.3 nm.

[0068] This is achieved by means of the process according to the present invention, which provides the use of commercial vermiculite granules that are spread out on a plane, preferably made of steel, covered with a metal film and then pressed by sliding a roller applying pressure values between 0.05 and 0.20 Pa, preferably between 0.08 and 0.14 Pa.

[0069] The flattened vermiculite granules obtained by the process of the invention have an average thickness between 0.3 mm and 3.0 mm. In the present description, the term thickness is intended to mean the distance between the two outermost sheets of the vermiculite granule. The flattened vermiculite granules acquire a structure that improves the diffusive capacity of the scented essences and makes it possible to reduce the required quantities of essential oils compared to the use of commercial vermiculite.

[0070] Figure 2 shows a first practical application of the scent diffuser of the present invention, which is used inside a ribbon-shaped container 10.

[0071] The container 10 comprises a flat filtering surface 11 provided with appropriate filtering characteristics to allow the release of scented essences. The flat surface 11 consists of a filtering material with a porosity between 40 and 60 microns.

[0072] The flat surface 12, on the other hand, consists of a non-filtering material, which must be chosen in such a way that it does not trigger any absorption of the essential oils to be diffused into the environment. In fact, on top of the flat surface 12, they are placed flattened vermiculite granules (not shown in Fig. 2) impregnated with the essential oil solution, the granules being obtained by the process of the present invention.

[0073] The flat surface 12 preferably comprises a material with an oily film base, so as not to encourage the absorption of essential oils. The two surfaces 11 and 12 are coupled to form a sort of a ribbon containing therein vermiculite granules impregnated with the essential oil solution.

[0074] The material constituting the filtering surface 11 will be able to undergo an antibacterial treatment thanks to the sputtering technology, which will increase the filtering characteristics thereof and will be able to be applied like a “cap” on some containers that can diffuse the scent contained inside thanks to the air suction or air diffusion therein, and make it flow out on the opposite side.

[0075] The materials that make up the non-filtering surface 12 can be made from food-grade compostable material of organic origin, such as rice husks, cellulose pulp, polylactic acid (PLA), maize starch, wheat, tapioca, potato starch, seaweed, milk processing residues, aseptic carton.

[0076] An adhesive material 13, shown in Fig. 3, can be applied to the external side of the non- filtering surface 12, so that the ribbon-shaped scent diffuser can be conveniently applied to any flat, rounded, curved, etc. surface to allow diffusing the scent that has been absorbed by the vermiculite support inserted therein. The result is a ribbon-shaped scent container that has both a filtering side and an adhesive side.

[0077] In summary, the ribbon-shaped container comprises: a flat non-filtering surface above which the scent diffuser having the innovative features of the present invention is evenly distributed; a flat filtering surface to close the ribbon; eventually an adhesive layer applied to the external side of the non-filtering surface.

[0078] Figure 4 shows the use of the scent diffuser of the present invention inside small containers with a different geometry. Containers 14A, 14B have a parallelepiped shape with different heights, container 14C has a cylindrical shape, and container 14D has a discoidal shape.

[0079] The containers of Fig. 4 contain within them flattened vermiculite granules impregnated with essential oils according to the teachings of the present invention.

[0080] Advantageously, the containers of Fig. 4 contain within them not only flattened vermiculite granules, but also perlite granules. Thus, in contrast to the examples of Fig. 2 and Fig. 3, the flattened vermiculite granules are separated from the perlite granules (which have the same inert, high-performance characteristics as vermiculite), thereby facilitating the passage of air.

[0081] Each container 14 comprises at least one side 15 made of a filtering material, which therefore constitutes the filtering surface, which can possibly be treated with the sputtering technique. At this side 15, air can either be blown out of the container, or sucked in and be released out on the opposite side of the container 14 allowing the scent to diffuse. The remaining sides or surfaces 16 of the containers 14 are made of non-filtering material, which must be appropriately chosen so as not to allow any absorption of the essential oils intended to be diffused into the environment.

[0082] The present invention is not limited to the particular embodiments previously described and illustrated in the accompanying drawings, but numerous modifications can be made to it in detail, within the reach of the person skilled in the art, without thereby departing from the scope of the invention, as defined in the appended claims.

[0083] Further advantages and features of the present invention will be apparent from the following embodiments, which are to be understood as descriptive and not limiting the scope of the appended claims.

[0084] EXAMPLES

[0085] Characterization

[0086] The average thickness of the vermiculite granules was measured using an electron microscope and a millesimal gauge.

[0087] The basal distance between adjacent layers in a vermiculite crystal was measured using an electron microscope.

[0088] Example 1 (comparative)

[0089] Commercially available vermiculite granules with an average thickness of 6.5 mm and a basal crystal distance between 1.4 and 1.8 nm were used, subjected to scent absorption tests and to subsequent evaluation of olfactory perception.

[0090] The following olfactory families were considered: Citrus; Flowery / Floral; Fougere; Chypre; Woody; Oriental; Musky; Aromatic.

[0091] Each olfactory family corresponds to a mixture of one or more essential oils.

[0092] Dipropylene glycol (DPG) is used as a solvent of the essential oils to give rise to a solution of essential oils that is put in contact with the commercial vermiculite granules for the absorption step.

[0093] 1 gram of vermiculite granules is placed in contact with 1 ml of essential oil solution inside glass containers. Eight glass containers are used to absorb the eight olfactory families mentioned above.

[0094] Vermiculite samples were taken from each glass container after a residence time of 6 hours in contact with the scented solution and placed in another glass container. In this second container they were left to rest for 4 hours at a controlled temperature of 20 degrees and hermetically sealed.

[0095] After resting for four hours, the eight containers were individually opened and the olfactory performance of the family was evaluated.

[0096] The following can be stated:

[0097] - no variation in the odour was observed

[0098] - there was no release of excess liquids

[0099] - crumbling of the mineral did not occur

[0100] - no apparent foreign substances formed

[0101] In the following hours, the intensity of olfactory perception was assessed by providing reference values from 1 to 3, where value 1 indicates a poor perception, value 2 indicates a sufficient perception, value 3 a perception similar or equal to the liquid mixture.

[0102] Table 1 shows the results obtained:

[0103] TABLE 1

[0104] As it can be noted, with the exception of the aromatic family, which is diffusive as such, the results are not optimal. For the citrus olfactory family, the olfactory perception is poor, while for most of the other olfactory families it is barely acceptable. Example 2

[0105] Flattened vermiculite granules with the innovative structure according to the present invention (average granule thickness and basal distance of the crystals) are used as a support for impregnating essential oils.

[0106] Method of preparation of vermiculite granules

[0107] The flattened vermiculite granules were obtained from the commercial vermiculite of Example 1 by subjecting the granules to the pressing treatment by sliding a roller with an appropriate pressure, as claimed in the present Patent Application.

[0108] The pressing treatment involved the following steps:

[0109] - the granular material was distributed on a smooth steel plane, cleaned with odourless bicarbonate, and dried with an absorbent paper towel;

[0110] - the vermiculite layer was covered with an aluminium film;

[0111] - a steel roller was made sliding in a controlled manner, keeping the distance between the roller and the aluminium film constant: this distance is set at 1.5 mm;

[0112] - a pressure of 0.101 Pa, measured by means of a manual dynamometer, is applied by the roller to the vermiculite layer.

[0113] As a result of the pressing technique applied, the vermiculite granules are flattened and have an average thickness of 1.5 mm. In addition, the basal distance of some vermiculite crystals is measured using an electron microscope and found to be of the order of 0.4-0.8 nm.

[0114] The same olfactory families as in Example 1 were subjected to the absorption step by the vermiculite granules. Dipropylene glycol (DPG) is used as a solvent of the essential oils to produce a solution of essential oils that is put in contact with the vermiculite granules.

[0115] The same method as in Example 1 was carried out using eight glass containers for the absorption of the eight olfactory families mentioned above.

[0116] 1 gram of flattened vermiculite granules are placed in contact with 1 ml of essential oil solution inside glass containers. Vermiculite samples were taken from each glass container after a residence time of 6 hours in contact with the scented solution and placed in another glass container. In this second container they were left to rest for 4 hours at a controlled temperature of 20 degrees and hermetically sealed. After resting for four hours, the eight containers were individually opened and the olfactory performance of the family was evaluated. The following can be stated:

[0117] - no variation in the odour was observed;

[0118] - there was a release of excess fluid, with the same ml of the previous test;

[0119] - crumbling of the mineral did not occur;

[0120] - no apparent foreign substances formed;

[0121] - there was a noticeable colour change in the appearance of the mineral on the surface that seems to be due to the colouring of the base of the olfactory family.

[0122] In the following hours, the intensity of olfactory perception was assessed by providing reference values from 1 to 3, where value 1 indicates a poor perception, value 2 indicates a sufficient perception, value 3 a perception similar or equal to the liquid mixture.

[0123] Table 2 shows the results obtained:

[0124] TABLE 2

[0125] As it can be inferred from the data in Table 2, there is a clear improvement in the intensity of perception of the different olfactory families compared to the data in Table 1. The following positive remarks can be made:

[0126] A) with a certain quantity of liquid remaining at the bottom of the glass containers, it follows that less than 1 ml of solution is absorbed for each gram of vermiculite: the intensity of perception is nevertheless improved if compared to the previous test;

[0127] B) for the same olfactory performance, a smaller quantity of granular material could be used if compared to the case of Example 1, resulting in cost savings in the raw material used as a support.

Claims

CLAIMS1. Scent diffuser comprising a vermiculite-based support capable of absorbing and diffusing a scent in the surrounding environment, said vermiculite support being impregnated with a solution of essential oils and being characterized in that:- it comprises flattened vermiculite granules with an average thickness between 0.3 mm and 3.0 mm;- said flattened vermiculite granules are made of lamellar structure crystals having a basal distance between adjacent layers from 0.1 nm to 1.3 nm.

2. Scent diffuser according to claim 1, characterized in that said flattened vermiculite granules are free of ferric oxide (Fe20s) and potassium oxide (K2O).

3. Scent diffuser according to claim 1, characterized in that said essential oils derive from different olfactory families selected from citrus, flowery / floral, fougere, woody, chypre, oriental, musky, aromatic.

4. Scent diffuser according to claim 1, characterised in that said average thickness ranges from 0.5 to 2.0 mm.5 Scent diffuser according to claim 1, characterized in that said basal distance ranges from 0,3 to 1,0 nm.

6. Process for the preparation of a scent diffuser comprising the following steps:A) placing commercial vermiculite granules having an average thickness between 1 and 20 mm on a flat surface;B) overlaying the vermiculite granules with a metal film, preferably aluminum;C) subjecting the vermiculite granules to pressing by sliding a roller over the metal film applying pressure values between 0.05 and 0.20 Pa;D) impregnating the pressed vermiculite granules with a solution of essential oils;7. Process according to claim 6, characterized in that during the step C) the pressure ranges from 0,08 to 0,14 Pa.

8. Process according to anyone of claims 6-7, characterized in that during step C) the distance between said roller and said metal film ranges from 0,8 mm to 2,2 mm.

9. Process according to any one of claims 6-8, characterized in that during step D) a quantity of solution of essential oils between 0.5 ml and 1.0 ml for each gram of vermiculite is used.

10. Ribbon-shaped container comprising:- a flat non-filtering surface above which the scent diffuser according to any one of claims 1-5 is uniformly distributed;- a flat filtering surface of closure of said ribbon;- eventually an adhesive layer applied to the external side of said non-filtering surface.

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