Method to form a coating of a fabric free of fluorine and omniphobic

Abstract

A method for forming a coating of a fabric is described, said method comprising the steps of applying, repeatedly and alternately: a first aqueous solution or dispersion comprising anions and a first aqueous solution or dispersion comprising cations, in order to form a first stratified (LbL) coating of a surface of the fabric. On top of the first stratified coating there are further applied, repeatedly and alternately: the first aqueous solution or dispersion comprising anions or a second aqueous solution or dispersion comprising anions and a second aqueous solution or dispersion comprising cations, in order to form a second stratified (LbL) coating on top of the first stratified coating, these together forming the fabric coating. The first or second aqueous solution or dispersion comprising anions includes nanoparticles having a size within a first range; the second aqueous solution or dispersion comprising anions includes nanoparticles having a size within a second range, and the nanoparticles within the second range have a size smaller than the nanoparticles in the first range. The superimposition of the second stratified coating on the first stratified coating provides the fabric coating with a contact angle with any liquid greater than or equal to 90°.

Description

[0001] Title: Method to form a coating of a fabric free of fluorine and omniphobic

[0002] Prior art

[0003] In the textile sector, in particular the clothing sector, but also in other sectors, the usefulness of making a fabric hydro-repellent or oilrepellent is well-known, this in order to obtain not only a hi-tec article of clothing which is water-resistant, especially in the sports sector, but also a fabric which is substantially stain-resistant. Such properties are particularly appreciated not only in the automobile industry, for the upholstery of seats or other surfaces, but also in the furnishing sector, for the covering of sofas or furnishing accessories, to mention just a few examples.

[0004] Coatings designed to repel water, oil, as well as many other liquids normally comprise perfluorocarbons (PFC) and are also referred to as omniphobic coatings. Omniphobic coatings are able to repel almost any liquid, are characterized by a low surface tension (ySL < lOmN / m) and have a high contact angle (0 > 160°) with water and oil. Figure 1 shows in schematic form the contact angle of an omniphobic surface compared to the contact angle of a hydrophilic surface (which is also waterabsorbent) .

[0005] Although the aforementioned coatings have been used for a long time, their use is nowadays opposed by organizations which are responsible for ensuring better protection of human health and the environment against the risks posed by chemical compounds; there therefore exists an urgent need to provide a coating which is able to guarantee the same performance, but without using fluorine compounds or derivatives.

[0006] Fluorine-free coatings are currently known, but do not guarantee oleophobicity, only hydrophobicity. Numerous studies on the subject are cited in scientific literature. Methods for depositing on a fabric, by means of spraying or immersion, nanoparticles in combination with fluorine-free polymers have been studied, resulting in hydrophobic coatings and, in some cases, oleophobic coatings (Bibliographic references: 1. Journal of Colloid and Interface Science 296 (2006) 233- 241; 2. Journal of Colloid and Interface Science 574 (2020) 347-354; 3. Langmuir 22 (2006) 5660-5665; 4. RSC adv. 8, (2008) 27064; 5. Progress in organic coatings 97 (2016) 44-52; 6. Surface and coatings technology 438 (2022) 128406). However, the aforementioned technologies are unable to obtain an omniphobic coating, i.e. one which is able to repel essentially any type of liquid, and is therefore stainresistant.

[0007] Methods in which the Layer-by-Layer technique is adopted in order to provide oleophobic coatings based on a combination of nanoparticles and fluorinated polymer derivatives have been studied (Bibliographic references: 1. Applied Surface Science 263 (2012) 8- 13; 2. Surface and interfaces, 31 (2022) 102109). US patent 10,253,451 Bl describes an omniphobic coating with a hierarchical structure based on layers of nanoparticles with two different sizes combined with fluoropolymers or fluorine-modified molecules with a low molecular weight. As mentioned, these fluorinated polymer derivatives must now be avoided.

[0008] Fluorine-free polymer formulations have also been developed in order to obtain anti-stain, hydrophobic, anti-corrosion coatings, to be deposited by means of impregnation or using a method known as SOL-GEL (Bibliographic references: 1. Progress in organic Coatings 174 (2023) 107254; 2. Progress in organic Coatings 163 (2022) 106671; 3. Progress in organic Coatings 174 (2023) 107227). However, these technologies are unable to obtain coatings which are oleophobic and therefore omniphobic.

[0009] WO2018 / 195119 claims a coating with a surface tension of 22 mJ / mm based on modified polydimethylsilicone with groups which may be crosslinked by means of polymerization in situ with radical initiators or catalysts of another kind. The coating is suitable for various types of substrates, but does not provide omniphobicity.

[0010] The technical problem underlying the present invention is to devise a method for coating a fabric which is able to provide the fabric with omniphobicity and therefore repellence against all types of liquids, being therefore stain -resistant, but at the same time avoiding the use of substances which are harmful for the environment, in particular perfluorocarbons (PFC), or which do not comply with the current regulations, thereby overcoming substantially all the drawbacks hitherto associated with the coating methods of the prior art.

[0011] Summary of the invention

[0012] The idea underlying the present invention is that of providing a coating for a fabric which is suitable for increasing the contact angle of a surface of the fabric with any liquid, in particular water and oil, but without using fluorine compounds or derivatives. The lined fabric is, among other things, oil-repellent.

[0013] The fabric coating is a multilayer coating. The plurality of layers of the multilayer coating is realized using an LbL (Layer by Layer) deposition technique. This technique chemically modifies the surfaces by means of the alternating deposition of positively charged polymers (polycations) and negatively charged ions (polyanions) in an aqueous solution or dispersion. The polycations and polyanions may also be replaced or combined with nanoparticles characterized by positive charges or negative charges on the surface. The polycation / polyanion deposition cycle is repeated until the characteristics of the surface are modified. The electrostatic interaction between the opposite charges of the different layers of the deposition causes crosslinking of the coating and ensures its growth on the surface of the substrate.

[0014] The parameters of the LbL deposition are controlled. In particular, the size of the nanoparticles forming the polyanions (below “anions”) is controlled. Said size is varied during at least two different steps of the method. In particular, where there is contact with the fabric, i.e. in the first deposited layers, larger-size nanoparticles are used, while in the following layers nanoparticles with a smaller diameter are deposited.

[0015] A first stratified coating obtained from the alternating deposition of nanoparticles with a partial negative charge and a weakly cationic thermal-crosslinking polymer is formed. An electrostatic interaction occurs between the alternately deposited layers (of nanoparticles with partial negative charge and weakly cationic polymer) and covalent bonds are formed, these resulting in the strong adhesion of the first stratified coating to the fibre (i.e. to the fabric to be coated) and its perfect washing resistance.

[0016] The first stratified coating is situated at the interface with the fabric, namely in direct contact therewith. As mentioned, it is formed by a plurality of alternating layers of the nanoparticles with a partial negative charge and the weakly cationic thermal-crosslinking polymer.

[0017] According to the present invention, in the multilayer coating the size of the nanoparticles gradually decreases as the deposition of the following layers is performed.

[0018] Therefore, below reference is also made to a second stratified coating, deposited on top of the first stratified coating and characterized by a smaller size of the nanoparticles compared to the nanoparticles of the first stratified coating.

[0019] In one embodiment, the difference between the first stratified coating and the second stratified coating consists in the size of the nanoparticles used for the negatively charged layer.

[0020] The alternating deposition of the layers with a positive charge and a negative charge is regulated so that, in the multilayer coating, the decreasing size of the nanoparticles in the upper layers (more distant from the fabric) results in a surface morphology or geometry of the fabric coating able to form a desired contact angle, in particular a contact angle greater than a given contact angle (for example 90°) with any liquid (oil, water, etc.) intended to come into contact with the coating.

[0021] In other words, the Applicant has studied the correlation between the contact angle and the nano-roughness of a superficial coating, for the surface tension values ySL<20mN / m, and has adopted the Layer-by- Layer (LbL) technique to deposit differently sized nanometric stratified coatings which impart to the surface a controlled roughness for the purposes of omniphobicity.

[0022] As final coating, a layer of molecules with a strongly apolar structure is applied on top of the multilayer coating obtained by the superimposition of the first stratified layer on top of the second stratified layer. These molecules belong, for example, to the family of fatty acids, triglycerides and paraffin waxes. The apolar molecules which interact with the first and second stratified coatings (in particular with the second stratified coating) help reduce the surface tension of the fabric, making it oilrepellent.

[0023] The Applicant has noted that the nanoparticles formed by colloidal silica and silica powder dispersed in a suitable concentration in water are particularly suitable for realizing the solution or dispersion with a negative charge. The size of the particles varies, for example, within the range of 7-500 nm, preferably within the range of 50-500 nm. The silica particles with partial negative charge are deposited on the surface alternately with a weakly cationic urethane-acrylate based polymer (for example Hydrosin NF- 16 or Hydrosin NF- 18) which crosslinks thermally, imparting to the fabric coating good adhesion and high wear properties.

[0024] The coating may be deposited by means of spraying or by means of immersion using aqueous solutions of the nanoparticles described and the polymer.

[0025] During the spraying deposition process the layers are deposited continuously without interruption and without intermediate washing and / or drying steps.

[0026] During deposition by means of immersion, instead, the immersion by means of deposition of the single layer may vary from 1 to 10 minutes (depending on the formulation), for example 5 minutes. In this case (immersion), washing with distilled water is performed between each layer.

[0027] The concentrations of the aqueous solutions may vary within the range of 0.5 - 10 g / L, for example typically 1-3 g / L.

[0028] The number of pairs of layers which form the multilayer coating may vary within the range 10-30 and is for example 20. The term “layer” is understood as meaning that coating part formed by the application (by a single application) of the first aqueous solution or dispersion comprising cations or that coating part formed by the application (by a single application) of the second aqueous solution or dispersion comprising anions; said application forms, respectively, a positively or negatively charged layer.

[0029] The expression “pairs of layers” is understood as meaning that coating part formed by a first layer (i.e. that coating part formed by the application of the first aqueous solution or dispersion comprising cations) and a second layer (that coating part formed by the application of the second aqueous solution or dispersion comprising anions); in other words, the first positively charged layer forms, together with a respective second negatively charged layer, a pair of layers.

[0030] Several pairs of layers are superimposed.

[0031] Each pair is realized by the superimposition of a first positively charged layer and a respective second negatively charged layer.

[0032] The terms “layer” and “pairs of layers” have the same meaning also where a second aqueous solution or dispersion comprising cations and a second aqueous solution or dispersion comprising anions is used to form the second stratified layer (which is also formed by a plurality of pairs of layers with a positive charge and negative charge, like the first stratified layer).

[0033] According to the aforementioned idea of a solution, the technical problem underlying the present invention is solved by a method for forming a coating of a fabric, comprising the steps which are summarised below and claimed in claim 1.

[0034] A first step involves applying onto the fabric, repeatedly and alternately, the steps a) and b): a) a first aqueous solution or dispersion comprising cations, in particular comprising a weakly cationic polymer; b) a first aqueous solution or dispersion comprising anions.

[0035] The steps a) and b) are repeated several times, obtaining a first stratified (LbL) coating of a surface of the fabric. A second step involves applying onto the fabric (i.e. on top of the first stratified coating already formed beforehand), repeatedly and alternately, the steps c) and d): c) the first particular solution or dispersion comprising the weakly cationic polymer, or a second aqueous solution or dispersion comprising cations, for example a different weakly cationic polymer and d) a second aqueous solution or dispersion comprising anions.

[0036] Steps c) and d) are repeated several times, resulting in a second stratified (LbL) coating on top of the first stratified coating, which together form the coating of the fabric.

[0037] According to the present invention, the first and second aqueous solutions or dispersions comprising anions include nanoparticles of different sizes: the first aqueous solution or dispersion comprising anions includes nanoparticles with a size in a first range dl, d2, the second aqueous solution or dispersion comprising anions includes nanoparticles with a size in a second range d3, d4, and the nanoparticles in the second range d3, d4 have a smaller size than the nanoparticles in the first range dl, d2.

[0038] The superimposition (of the nanoparticles) of the second stratified coating on (the particles of) the first stratified coating provides the fabric coating with a contact angle with any liquid greater than or equal to 90°.

[0039] The multilayer coating obtained from the superimposition of the first and the second stratified coatings has a roughness which increases with the distance of the coating from the underlying fabric. Essentially the surface of the multilayer coating has peaks and troughs. The troughs have a maximum breadth where the distance of the coating from the fabric is greater, minimum or preferably zero breadth at the interface with the fabric, and a breadth essentially decreasing depending on the distance of the coating from the fabric. In other words, at the end of deposition of the first stratified coating, the fabric (only partially lined) has a given nano-roughness which is intended to increase following the application of the second stratified coating.

[0040] The step of applying the first or second aqueous solution or dispersion comprising anions or cations may be performed continuously or separately.

[0041] In the first case (continuous application) a flow of the solution with a positive charge is continuously alternated with a flow of the solution with a negative charge. The flow is for example obtained by means of spraying of the solutions.

[0042] In the second case (separate application) contact of the fabric with the solution with the positive charge is terminated before starting contact of fabric with a negative charge. The contact is for example obtained by means of immersion in tanks containing the solutions.

[0043] In the case of immersion of the fabric, immersion is performed for predetermined time period, preferably of between 1 minute and 15 minutes, even more preferably between 3 and 7 minutes, for example 5 minutes.

[0044] Still in the case of immersion, rinsing is performed between one of said steps for applying the first or second aqueous solution or dispersion comprising anions or cations and the following one of said steps for applying the first or second aqueous solution or dispersion comprising anions or cations.

[0045] Rinsing is for example performed for a time period of between 1 and 20 seconds, preferably 4 to 5 seconds, preferably in demineralized water.

[0046] It is further envisaged applying a surface layer or multilayer, below also called final layer, on top of the first and second already stratified coatings. The final layer is for example an emulsion of negatively charged stearic acid in a concentration of 3 g / 1 or a triglyceride-based layer. The final layer is subjected to heat-treatment at a temperature of between 110°C and 160°C, preferably 140°C, for a predefined time period, for example of between 30 seconds and 3 minutes, preferably 1 minute, and then left to cool in air down to room temperature.

[0047] Advantageously, the method according to the present disclosure may be applied to several different fabrics, for example a natural or synthetic fabric, including cotton, polyester, polyamides or aramid fibre fabrics.

[0048] Several characteristics are imparted to the fabric by the coating. The coating is breathable; therefore the fabric may also be breathable. The coating is omniphobic, i.e. is able to repel any liquid, including oil.

[0049] The fabric is free from fluorocarbons (PFC). The coating may be applicable or is applied to a fabric for technical or sports clothing, for furnishings, for example sofas, or for the transport industry, for example car seats, to mention just a few examples. In principle, there is no limit to the fabrics to which the method can be applied.

[0050] Brief description of the attached drawings

[0051] Figure 1 shows in schematic form a contact angle of an omniphobic surface and a hydrophilic surface.

[0052] Figure 2a shows in schematic form an omniphobic fluorinated surface according to the prior art and Figure 2b shows in schematic form a fluorine-free omniphobic surface which is coated according to the method of the present invention.

[0053] Figures 3 show in schematic form a step of the method according to the present invention;

[0054] Figure 4 is a different schematic representation of the omniphobic surface of Figure 2b.

[0055] Figure 5a shows in schematic form the ratio f between the surface of a hydrophilic coating and the total surface of the coating; Figure 5b shows in schematic form the ratio f between the surface of an oleophobic coating and the total surface of the coating.

[0056] Figure 6 is a diagram of the structure of the coating formed according to an example of implementation of the present invention. Figure 7 is a diagram of the structure of the coating formed according to another example of implementation of the present invention.

[0057] Detailed description of the invention

[0058] In the present invention, in order to achieve the oil-repellence as well as the omni-repellence of a fabric, without having to use the chemical element fluorine, a coating with a specific surface roughness has been devised, based on the assumption that a correlation exists between the contact angle (0*) of a rough surface and a factor f, which represents the surface fraction in contact with the liquid. cosff* = fcosQ + (1 — f) cos 180° (1)

[0059] In the case of oleophobic surfaces (with a contact angle 0* > 160°) a very small value of f is required, this being schematically shown in Figure 5b. As can be seen from Figure 5b, the surface of the coating in contact with the liquid (oil) with respect to the total surface is very small. By quantifying the factor f it has been possible to develop, using the LbL technique, an omniphobic nano-coating.

[0060] The deposition process may be performed by means of spraying or immersion depending on the type of substrate. Usually, deposition by means of spraying is faster and is used for flat, very large, non-porous surfaces, for example glass, polymer films, etc. The process by means of immersion, instead, requires longer times and is more suitable for substrates with complex and porous forms, such as wood, polymer foams, stones, etc.

[0061] In the case of both processes (spraying and immersion) it is envisaged operating at room temperature and pressure and using water as a solvent.

[0062] The chemical compounds used to modify the surfaces are chosen depending on the functions which are to be imparted to the surface, but in any case also their solubility or dispersibility in water. The aqueous solutions which are used for the deposition of the coating are very diluted and typically have a concentration of 1 g / L

[0063] The LbL coatings are molecular multilayers so that they have very small thicknesses, ranging from a few tens of nm to a micron, so that they are flexible and transparent, these being very important characteristics for very many substrates such as fabrics, polymer films, glass.

[0064] Below some examples of embodiment of the method for forming a coating according to the present invention are provided.

[0065] Example 1

[0066] In a first example, the nano-roughness of the surface of the coating is initially obtained by means of stratification on the fabric of nano particles of silica with a partial negative charge and different size, alternated with a urethane-acrylate based polymer (Hydrosin NF- 16).

[0067] The urethane-acrylate based polymer (Hydrosin NF- 16) has the characteristic that it is self-crosslinking following the application of heat and subsequent cooling.

[0068] In particular, in order to form the coating according to this example of embodiment of the invention, the following solutions were prepared using demineralized water as solvent (other solvents may however be used as a starting base).

[0069] 1) Hydrosin NF- 16, in a concentration of 1 g / 1, as a positive layer. Hydrosin NF- 16 in the concentration of 1 g / 1 is used as a first aqueous solution or dispersion, comprising cations.

[0070] 2) Silica with an average size of 200 nm, in a concentration of 3 g / 1, as negative layer, namely as a first aqueous solution or dispersion, comprising anions.

[0071] 3) Silica with an average size of 50 nm, in a concentration of 3 g / 1, as negative layer.

[0072] 4) Stearic acid emulsion, in a concentration of 3 g / 1, as negative layer.

[0073] The solutions were applied using LbL technology. A polyester fabric substrate was chosen as fabric to be coated. The polyester substrate is one example of a fabric, but other fabrics may be used.

[0074] Initially, the polyester substrate was immersed in the solution of Hydrosin NF- 16 for 5 minutes.

[0075] Then the polyester substrate was washed for 4-5 seconds in demineralized water and then immersed in the solution of silica with size 200 nm for 5 minutes.

[0076] This cycle was repeated 10 times, resulting in first stratification with 10 pairs of layers of type 1) and type 2).

[0077] Then the previously treated substrate was immersed in the solution of Hydrosin NF- 16 for 5 minutes.

[0078] Washing in demineralized water was performed for 4-5 seconds and then the substrate was immersed in the solution of silica with diameter 50 nm. In this case also, the cycle was repeated 10 times, resulting in a second stratification of 10 pairs of layers 1) and 3).

[0079] Then a layer based on stearic acid was deposited. In this case, the previously treated substrate was immersed for 40 minutes in the solution of stearic acid and then heat-treated for 140°C for one minute and then left to cool in air down to room temperature.

[0080] The heat treatment with stearic acid is a final treatment which forms the outer surface layer of the coating.

[0081] Figure 6 shows a diagram of the structure of the coating realized in Example 1.

[0082] Example 2

[0083] In this example also, the nano-roughness of the surface of the treated fabric was obtained by means of stratification on the fabric of nano particles of silica with a partial negative charge and different size, alternated with an acrylic polymer (Hydrosin NF- 16) which selfcrosslinks thermally. The following solutions were prepared, again using demineralized water as starting solvent.

[0084] 1) Hydrosin NF- 16, in a concentration of 1 g / 1, for the positive layer. Hydrosin NF- 16 in the concentration of 1 g / 1 is used as first aqueous solution or dispersion, comprising cations.

[0085] 2) Silica with an average size of 200 nm, in a concentration of 3 g / 1, as negative layer, namely as a first aqueous solution or dispersion, comprising anions.

[0086] 3) Silica with an average size of 50 nm, in a concentration of 3 g / 1, as negative layer. The silica with average size of 50 nm, in the concentration of 3 g / 1, was used as second aqueous solution or dispersion comprising anions.

[0087] 4) Solution of triglyceride in heptane, in a concentration of 40 g / 1.

[0088] In this case also, a polyester fabric substrate was used, only by way of example.

[0089] The substrate was immersed in the solution 1) for 5 minutes, then washed for 4-5 seconds in demineralized water and then immersed in the solution 2) for 5 minutes. The cycle was repeated 10 times (obtaining 10 pairs of layers).

[0090] Then the substrate was immersed in the solution of Hydrosin NF- 16, washed in demineralized water for 4-5 seconds and then immersed in the solution 3). The cycle was repeated 10 times (obtaining 10 pairs of layers) .

[0091] The final step was deposition of the outer surface layer, this time based on triglyceride.

[0092] The substrate was immersed for 10 minutes in the solution of triglyceride.

[0093] The immersion cycle was repeated 3 times, followed by heat treatment at 140°C for one minute, and then cooling in air down to room temperature. Figure 7 shows a diagram of the structure of the coating realized in Example 2. As shown in Figure 6, the indication “xlO” is provided in order to specify where the cycle was repeated 10 times and the indication “x3” provided to indicate where the cycle was repeated 3 times. Obviously these factors (“xlO”, “x3”) are purely indicative and a greater number of cycles or a smaller number of cycles may be applied.

[0094] To summarise, the present invention offers many advantages.

[0095] Firstly, the coating of the fabric is omniphobic, but fluorine-free. The coating is multilayer and achieves omniphobicity as a result of the chemical synergy effect, obtained by means of LbL deposition, and the structural effect of surface roughness, obtained by means of specific parameters of the solutions used in the LbL process, thus achieving a significant reduction in the surface energy of the fabric.

[0096] The treatment developed does not use perfluorinated polymers (PFC) nor fluorinated molecules with a low molecular weight. The oil- repellence is obtained owing to the nano-rough hierarchical structure obtained by depositing in sequence two stratified coatings with different- size particles. The coating is suitable for the treatment of different types of natural or synthetic fabrics, such as cotton, polyester, polyamides, aramid fabrics. The fields of application are many, including ordinary clothing, technical sports clothing, furnishing fabrics, or fabrics for applications in the transport industry.

Claims

CLAIMS1. Method for forming a fluorine-free omniphobic coating of a fabric, comprising the steps of applying, repeatedly and alternately:- a first aqueous solution or dispersion comprising cations, said first aqueous solution or dispersion comprising a first cationic polymer and- a first aqueous solution or dispersion comprising anions, so as to form a first stratified (LbL) coating of a surface of the fabric, characterized by further applying, repeatedly and alternately, on top of the first stratified coating:- the first aqueous solution or dispersion comprising cations or a second aqueous solution or dispersion comprising cations, said second aqueous solution or dispersion comprising a second cationic polymer and- a second aqueous solution or dispersion comprising anions, so as to form a second stratified (LbL) coating on top of the first stratified coating, said coatings together forming the coating of the fabric, wherein- the first aqueous solution or dispersion comprising anions includes nanoparticles with a size in a first range,- the second aqueous solution or dispersion comprising anions includes nanoparticles with a size in a second range, and wherein- the nanoparticles in the second range have a smaller size than the nanoparticles in the first range, the superimposition of the second stratified coating on the first stratified coating provides the fabric coating with a contact angle with any liquid greater than or equal to 140°.

2. Method for forming the coating according to claim 1, characterized in that the first stratified coating has a nano-roughness smaller than the nano-roughness of the coating.

3. Method for forming the coating according to claim 1, characterized in that the first aqueous solution or dispersion comprising cations includes Hydrosin NF- 16 in a concentration of 0.5- 10 g / 1, preferably 1- 3 g / 1, even more preferably 1 g / L4. Method for forming the coating according to claim 1, characterized in that the first aqueous solution or dispersion comprising anions includes silica with an average size of 200 nm, in a concentration of 0.5- 10 g / 1, preferably 1-3 g / 1, even more preferably 1 g / L5. Method for forming the coating according to claim 1, characterized in that the second aqueous solution or dispersion comprising anions includes silica with an average size of 50 nm, in a concentration of 0.5- 10 g / 1, preferably 1-3 g / 1, even more preferably 1 g / L6. Method for forming the coating according to claim 1, characterized in that said first or second solution of anions or cations are formed using a starting solution of demineralized water.

7. Method for forming the coating according to claim 1, characterized by applying a final layer on top of the first and second stratified coatings and applying a heat treatment to the final layer.

8. Method for forming the coating according to claim 1, characterized in that said final layer is an emulsion of negatively charged stearic acid in a concentration of 3 g / 1 or a triglyceride-based layer, said final layer being heat-treated at a temperature of between 110°C and 160°C, preferably 140°C, for a time period of between 30 seconds and 3 minutes, preferably 1 minute, and then left to cool in air down to room temperature.

9. Method for forming the coating according to claim 1, characterized in that said step of applying the first or second aqueous solution or dispersion comprising anions or cations comprises the immersion of the fabric, respectively, in the first or second aqueous solution or dispersioncomprising anions or cations for predetermined time period, preferably of between 1 minute and 10 minutes, even more preferably between 3 and 7 minutes, for example 5 minutes.

10. Method for forming the coating according to claim 1, characterized in that rinsing is performed between one of said steps for applying the first or second aqueous solution or dispersion comprising anions or cations and the following one of said steps for applying the first or second aqueous solution or dispersion comprising anions or cations, said rinsing being applied for a time period of between 1 and 20 seconds, preferably 4-5 seconds, preferably in demineralized water.

11. Method for forming the coating according to claim 1 , characterized in that the fabric is either a natural or synthetic fabric, comprising cotton, polyester, polyamides or aramid fibre fabrics.

12. Method for forming the coating according to claim 1, characterized in that the coating is breathable.

13. Method for forming the coating according to claim 1, characterized in that the coating is omniphobic.

14. Method for forming the coating according to claim 1, characterized in that the coating and the fabric are free from fluorocarbons (PFC).

15. Method for forming the coating according to claim 1, characterized in that the coating and the fabric are free from fluorine- containing molecules with a low molecular weight, in particular free from fluorine-containing molecules with less than 6 carbon atoms.

16. Method for forming the coating according to claim 1, characterized in that the coating can be applied or is applied to a fabric for technical or sports clothing, fabric for furnishings, for example sofas, or fabric for the transport industry, for example for car seats.

17. Fabric, characterized in that it comprises a multilayer surface coating formed according to any one of claims 1 to 16.

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